Subject: Re: [Fot] Intake manifold vacuum and no high RPM

From: John Styduhar <[email-masked]>
Date: Mon, 28 Nov 2016 17:03:31 -0500

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I had the same problem in my TR3 racer. I corrected the lean condition by
installing a stronger damper spring in the carb and oil in the piston. This
created more vacuum in the throat of the carb at the higher revs and caused
more fuel to be drawn through the jet via the venturi effect.  Choking the
carb does basically the same thing.

On Mon, Nov 28, 2016 at 4:23 PM, Mike Harmuth <[email-masked]> wrote:

> I'm tracking down a problem with the Spit race car (1296 Small Journal,
> 12;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported
> as per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles
> (manifold and carbs checked for vacuum leaks), Advanced Distributor for
> spark (34 degrees at full, mechanical only, advance @ 3.5K RPM)
>
> The problem I have has followed me on two different short blocks, I can
> easily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire
> case, 4th gear is 1;1,  4:11 locked diff ) gears. In 4th I'm struggling to
> get over 6K, no matter how long the straight. Just before the last race of
> the season, I installed an air fuel ratio gauge on the header (stahl) and
> found out I'm running (progressively)  very lean (19:1) in 4th over 5K. At
> 2K I adjusted it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I
> get over 5K when it really leans out. If I pull the choke to 1/2  full over
> 5K, I get a good ratio again, 13.5- 14%.
>
> To me that seemed like the carb pistons aren't pulling all the way up so I
> drilled and tapped the manifold to get a vacuum reading. It was steady but
> low at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped if
> I blipped the throttle. Under 6K, it was in the 15 inch range. Normal air
> filters are K&N with stub stacks but I get the same results with open carbs.
>
> Am I correct in assuming that the vacuum is too low or is it that due to
> overlap with a performance cam? Any ideas on where to look to get the ratio
> "normal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the
> engine compartment and steady through all revs.
>
> I have dyno time scheduled in a few weeks but I'd like to use that time to
> tune not debug things.
>
> thanks
> mike h
> 63 spitfire
>
> _______________________________________________
> [email-masked]
>
> http://www.fot-racing.com
>
> Donate: http://www.team.net/donate.html
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>
>

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<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-size:small">I h=
ad the same problem in my TR3 racer. I corrected the lean condition by inst=
alling a stronger damper spring in the carb and oil in the piston. This cre=
ated more vacuum in the throat of the carb at the higher revs and caused mo=
re fuel to be drawn through the jet via the venturi effect.=C2=A0 Choking t=
he carb does basically the same thing.</div></div><div class=3D"gmail_extra=
"><br><div class=3D"gmail_quote">On Mon, Nov 28, 2016 at 4:23 PM, Mike Harm=
uth <span dir=3D"ltr">&lt;<a href=3D"mailto:[email-masked]" target=3D"_b=
lank">[email-masked]</a>&gt;</span> wrote:<br><blockquote class=3D"gmail=
_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:=
1ex"><div dir=3D"ltr"><div><div><div><div><div><div>I&#39;m tracking down a=
 problem with the Spit race car (1296 Small Journal, 12;1 compression, APT =
TR74 cam 295 duration and 0.324 lob lift, head ported as per Kas&#39;s book=
). Rebuilt European SU HS4 carb setup with AAA needles (manifold and carbs =
checked for vacuum leaks), Advanced Distributor for spark (34 degrees at fu=
ll, mechanical only, advance @ 3.5K RPM)<br><br></div>The problem I have ha=
s followed me on two different short blocks, I can easily pull 7500RPM in 1=
st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4th gear is 1;1,=C2=A0=
 4:11 locked diff ) gears. In 4th I&#39;m struggling to get over 6K, no mat=
ter how long the straight. Just before the last race of the season, I insta=
lled an air fuel ratio gauge on the header (stahl) and found out I&#39;m ru=
nning (progressively)=C2=A0 very lean (19:1) in 4th over 5K. At 2K I adjust=
ed it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I get over 5=
K when it really leans out. If I pull the choke to 1/2=C2=A0 full over 5K, =
I get a good ratio again, 13.5- 14%. <br><br>To me that seemed like the car=
b pistons aren&#39;t pulling all the way up so I drilled and tapped the man=
ifold to get a vacuum reading. It was steady but low at 6K, ~20 Inches but =
would jump to ~28 briefly as the revs dropped if I blipped the throttle. Un=
der 6K, it was in the 15 inch range. Normal air filters are K&amp;N with st=
ub stacks but I get the same results with open carbs.<br><br></div>Am I cor=
rect in assuming that the vacuum is too low or is it that due to overlap wi=
th a performance cam? Any ideas on where to look to get the ratio &quot;nor=
mal&quot; at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the=
 engine compartment and steady through all revs.<br><br></div>I have dyno t=
ime scheduled in a few weeks but I&#39;d like to use that time to tune not =
debug things.<br><br></div>thanks<br></div>mike h<br></div>63 spitfire<br><=
/div>
<br>______________________________<wbr>_________________<br>
<a href=3D"mailto:[email-masked]">[email-masked]</a><br>
<br>
<a href=3D"http://www.fot-racing.com" rel=3D"noreferrer" target=3D"_blank">=
http://www.fot-racing.com</a><br>
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et=3D"_blank">http://www.team.net/donate.<wbr>html</a><br>
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et/mailman/<wbr>options/fot/johnstydo@gmail.<wbr>com</a><br>
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<br>
<br></blockquote></div><br></div>

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_______________________________________________
[email-masked]

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Archive: http://www.team.net/archive

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From: Rick Parent <[email-masked]>
Date: Mon, 28 Nov 2016 22:22:20 +0000 (UTC)

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Hi Mike,
If you have removed the springs for the pistons, reinstall them. If you sti=
ll have the springs purchase some heavier ones or stretch the ones you have=
 1" at a time and test. The pistons are most likely up all the way and they=
 need to be closed more to pull a better signal on the needle jet.=C2=A0
Just like pressing the easy button!=20

    On Monday, November 28, 2016 4:57 PM, Mike Harmuth <[email-masked]> =
wrote:
=20

 I'm tracking down a problem with the Spit race car (1296 Small Journal, 12=
;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported a=
s per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles (man=
ifold and carbs checked for vacuum leaks), Advanced Distributor for spark (=
34 degrees at full, mechanical only, advance @ 3.5K RPM)

The problem I have has followed me on two different short blocks, I can eas=
ily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4=
th gear is 1;1,=C2=A0 4:11 locked diff ) gears. In 4th I'm struggling to ge=
t over 6K, no matter how long the straight. Just before the last race of th=
e season, I installed an air fuel ratio gauge on the header (stahl) and fou=
nd out I'm running (progressively)=C2=A0 very lean (19:1) in 4th over 5K. A=
t 2K I adjusted it rich, to 12;1 and it keeps in the 13.5- 14.5 range until=
 I get over 5K when it really leans out. If I pull the choke to 1/2=C2=A0 f=
ull over 5K, I get a good ratio again, 13.5- 14%.=20

To me that seemed like the carb pistons aren't pulling all the way up so I =
drilled and tapped the manifold to get a vacuum reading. It was steady but =
low at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped if =
I blipped the throttle. Under 6K, it was in the 15 inch range. Normal air f=
ilters are K&N with stub stacks but I get the same results with open carbs.

Am I correct in assuming that the vacuum is too low or is it that due to ov=
erlap with a performance cam? Any ideas on where to look to get the ratio "=
normal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the e=
ngine compartment and steady through all revs.

I have dyno time scheduled in a few weeks but I'd like to use that time to =
tune not debug things.

thanks
mike h
63 spitfire

tt.net

  =20
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<html><head></head><body><div style=3D"color:#000; background-color:#fff; f=
ont-family:HelveticaNeue-Light, Helvetica Neue Light, Helvetica Neue, Helve=
tica, Arial, Lucida Grande, sans-serif;font-size:13px"><div id=3D"yui_3_16_=
0_1_1480371071095_21108"><span id=3D"yui_3_16_0_1_1480371071095_21292">Hi M=
ike,</span></div><div id=3D"yui_3_16_0_1_1480371071095_21108"><span><br></s=
pan></div><div id=3D"yui_3_16_0_1_1480371071095_21108" dir=3D"ltr"><span id=
=3D"yui_3_16_0_1_1480371071095_21293">If you have removed the springs for t=
he pistons, reinstall them. If you still have the springs purchase some hea=
vier ones or stretch the ones you have 1" at a time and test. The pistons a=
re most likely up all the way and they need to be closed more to pull a bet=
ter signal on the needle jet.&nbsp;</span></div><div id=3D"yui_3_16_0_1_148=
0371071095_21108" dir=3D"ltr"><span><br></span></div><div id=3D"yui_3_16_0_=
1_1480371071095_21108" dir=3D"ltr"><span id=3D"yui_3_16_0_1_1480371071095_2=
1524">Just like pressing the easy button!</span></div> <div class=3D"qtdSep=
arateBR"><br><br></div><div class=3D"yahoo_quoted" style=3D"display: block;=
"> <div style=3D"font-family: HelveticaNeue-Light, Helvetica Neue Light, He=
lvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 13px;=
"> <div style=3D"font-family: HelveticaNeue, Helvetica Neue, Helvetica, Ari=
al, Lucida Grande, sans-serif; font-size: 16px;"> <div dir=3D"ltr"><font si=
ze=3D"2" face=3D"Arial"> On Monday, November 28, 2016 4:57 PM, Mike Harmuth=
 &lt;[email-masked]&gt; wrote:<br></font></div>  <br><br> <div class=3D"=
y_msg_container"><div id=3D"yiv1750785075"><div dir=3D"ltr"><div><div><div>=
<div><div><div>I'm tracking down a problem with the Spit race car (1296 Sma=
ll Journal, 12;1 compression, APT TR74 cam 295 duration and 0.324 lob lift,=
 head ported as per Kas's book). Rebuilt European SU HS4 carb setup with AA=
A needles (manifold and carbs checked for vacuum leaks), Advanced Distribut=
or for spark (34 degrees at full, mechanical only, advance @ 3.5K RPM)<br><=
br></div>The problem I have has followed me on two different short blocks, =
I can easily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfir=
e case, 4th gear is 1;1,&nbsp; 4:11 locked diff ) gears. In 4th I'm struggl=
ing to get over 6K, no matter how long the straight. Just before the last r=
ace of the season, I installed an air fuel ratio gauge on the header (stahl=
) and found out I'm running (progressively)&nbsp; very lean (19:1) in 4th o=
ver 5K. At 2K I adjusted it rich, to 12;1 and it keeps in the 13.5- 14.5 ra=
nge until I get over 5K when it really leans out. If I pull the choke to 1/=
2&nbsp; full over 5K, I get a good ratio again, 13.5- 14%. <br><br>To me th=
at seemed like the carb pistons aren't pulling all the way up so I drilled =
and tapped the manifold to get a vacuum reading. It was steady but low at 6=
K, ~20 Inches but would jump to ~28 briefly as the revs dropped if I blippe=
d the throttle. Under 6K, it was in the 15 inch range. Normal air filters a=
re K&amp;N with stub stacks but I get the same results with open carbs.<br>=
<br></div>Am I correct in assuming that the vacuum is too low or is it that=
 due to overlap with a performance cam? Any ideas on where to look to get t=
he ratio "normal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PS=
I at the engine compartment and steady through all revs.<br><br></div>I hav=
e dyno time scheduled in a few weeks but I'd like to use that time to tune =
not debug things.<br><br></div>thanks<br></div>mike h<br></div>63 spitfire<=
br></div></div><br>_______________________________________________<br><a ym=
ailto=3D"mailto:[email-masked]" href=3D"mailto:[email-masked]">fot@=
autox.team.net</a><br><br><a href=3D"http://www.fot-racing.com/" target=3D"=
_blank">http://www.fot-racing.com</a><br><br>Donate: <a href=3D"http://www.=
team.net/donate.html" target=3D"_blank">http://www.team.net/donate.html</a>=
<br>Archive: <a href=3D"http://www.team.net/archive" target=3D"_blank">http=
://www.team.net/archive</a><br>Forums: <a href=3D"http://www.team.net/forum=
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<a href=3D"http://autox.team.net/mailman/options/fot/[email-masked]" t=
arget=3D"_blank">http://autox.team.net/mailman/options/fot/rick.parent@att.=
net</a><br><br><br><br><br></div>  </div> </div>  </div></div></body></html=
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From: Jason Sukey <[email-masked]>
Date: Mon, 28 Nov 2016 18:10:46 -0500

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--001a1140f6cef67e080542649430

Mike,
    Sure sounds very similar to tuning issues with my dad's small journal.
Make your adjustments so that the mixture is optimum at racing RPM (5k plus
rpm).  13.5 - 14.5 is still too lean for power, that's a good economy
cruising mixture on the street.
Pay no attention to mixture at lower RPM - doesn't matter in a race car.
You might have to change needle profiles also.
You don't want much vacuum in the intake manifold at wide open throttle.
It's the velocity of the airflow thru the bridge in the carb that creates
the vacuum to lift the dampers, not the vacuum in the manifold runners.

Jason

On Mon, Nov 28, 2016 at 4:23 PM, Mike Harmuth <[email-masked]> wrote:

> options/fot/[email-masked]
>
>
>
>

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<div dir=3D"ltr">Mike,<div>=C2=A0 =C2=A0 Sure sounds very similar to tuning=
 issues with my dad&#39;s small journal.=C2=A0 Make your adjustments so tha=
t the mixture is optimum at racing RPM (5k plus rpm). =C2=A013.5 - 14.5 is =
still too lean for power, that&#39;s a good economy cruising mixture on the=
 street.</div><div>Pay no attention to mixture at lower RPM - doesn&#39;t m=
atter in a race car.=C2=A0 You might have to change needle profiles also.</=
div><div>You don&#39;t want much vacuum in the intake manifold at wide open=
 throttle.=C2=A0 It&#39;s the velocity of the airflow thru the bridge in th=
e carb that creates the vacuum to lift the dampers, not the vacuum in the m=
anifold runners.</div><div><br></div><div>Jason</div></div><div class=3D"gm=
ail_extra"><br><div class=3D"gmail_quote">On Mon, Nov 28, 2016 at 4:23 PM, =
Mike Harmuth <span dir=3D"ltr">&lt;<a href=3D"mailto:[email-masked]" tar=
get=3D"_blank">[email-masked]</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex"><div dir=3D"ltr"><div><div><div><div><div><div>I&#39;m tracki=
ng down a problem with the Spit race car (1296 Small Journal, 12;1 compress=
ion, APT TR74 cam 295 duration and 0.324 lob lift, head ported as per Kas&#=
39;s book). Rebuilt European SU HS4 carb setup with AAA needles (manifold a=
nd carbs checked for vacuum leaks), Advanced Distributor for spark (34 degr=
ees at full, mechanical only, advance @ 3.5K RPM)<br><br></div>The problem =
I have has followed me on two different short blocks, I can easily pull 750=
0RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4th gear is 1=
;1,=C2=A0 4:11 locked diff ) gears. In 4th I&#39;m struggling to get over 6=
K, no matter how long the straight. Just before the last race of the season=
, I installed an air fuel ratio gauge on the header (stahl) and found out I=
&#39;m running (progressively)=C2=A0 very lean (19:1) in 4th over 5K. At 2K=
 I adjusted it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I g=
et over 5K when it really leans out. If I pull the choke to 1/2=C2=A0 full =
over 5K, I get a good ratio again, 13.5- 14%. <br><br>To me that seemed lik=
e the carb pistons aren&#39;t pulling all the way up so I drilled and tappe=
d the manifold to get a vacuum reading. It was steady but low at 6K, ~20 In=
ches but would jump to ~28 briefly as the revs dropped if I blipped the thr=
ottle. Under 6K, it was in the 15 inch range. Normal air filters are K&amp;=
N with stub stacks but I get the same results with open carbs.<br><br></div=
>Am I correct in assuming that the vacuum is too low or is it that due to o=
verlap with a performance cam? Any ideas on where to look to get the ratio =
&quot;normal&quot; at higher revs? Fuel pump is Holley Red, adjusted to 3 P=
SI at the engine compartment and steady through all revs.<br><br></div>I ha=
ve dyno time scheduled in a few weeks but I&#39;d like to use that time to =
tune not debug things.<br><br></div>thanks<br></div>mike h<br></div>63 spit=
fire<br></div>
<br>______________________________<wbr>_________________<br>
<a href=3D"mailto:[email-masked]">[email-masked]</a><br>
<br>
<a href=3D"http://www.fot-racing.com" rel=3D"noreferrer" target=3D"_blank">=
http://www.fot-racing.com</a><br>
<br>
et=3D"_blank">http://www.team.net/donate.<wbr>html</a><br>
Archive: <a href=3D"http://www.team.net/archive" rel=3D"noreferrer" target=
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mailman/<wbr>options/fot/[email-masked]</a><br>
<br>
<br>
<br></blockquote></div><br></div>

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From: Mike Harmuth <[email-masked]>
Date: Mon, 28 Nov 2016 18:58:31 -0500

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--94eb2c05c184c2d8040542653f64

Thanks for the replies, here are the answers to some of the questions:

Valve springs, - Dual springs with alloy retainers. The engine builder
tested and shimmed them to a uniform pressure but I don't know the number
off the top of my head. I'll ask him tomorrow

Silver springs in the carbs, the lightest they make I believe. I have a set
of heaver ones (red I believe) that I can try. The pistons are filled ~ 3/4
of the way,  up with SU branded oil and the dampers are in place.

The fuel pump, Holley red, all the lines, micron filter before the pump and
the regulator were changed last winter because I didn't know how old they
were. I had the problem then as well, before and after the replacement. I
opened the cell up two weeks ago. The foam is in great shape, the pickups
and intake line look to be solid as well. The ATL cell is 6 years old.

Fuel pressure is measured by a gauge at the regulator 2 feet from the carbs.

I'm not sure that the problem isn't electrical but the car runs with a
alternator (confirmed working). The distributor was built with a profile to
match my engine by Jeff at Advanced Distributors. I've changed the points
(using his high speed set), rotor, cap, wires and capacitor over the
summer, just in case, but with no affect. Timing is steady, double row
timing chain.

thanks for all the info.

mike h

On Mon, Nov 28, 2016 at 5:05 PM, Sam Halkias <[email-masked]> wrote:

> What are you running for valve springs? Sounds like valve float to me.
>
> Sam
>
> *Sent from my Verizon Wireless 4G LTE DROID*
>
>
> Mike Harmuth <[email-masked]> wrote:
>

--94eb2c05c184c2d8040542653f64
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div><div><div><div><div><div><div>Thanks for the replies,=
 here are the answers to some of the questions:<br><br></div>Valve springs,=
 - Dual springs with alloy retainers. The engine builder tested and shimmed=
 them to a uniform pressure but I don&#39;t know the number off the top of =
my head. I&#39;ll ask him tomorrow<br><br></div>Silver springs in the carbs=
, the lightest they make I believe. I have a set of heaver ones (red I beli=
eve) that I can try. The pistons are filled ~ 3/4 of the way,=C2=A0 up with=
 SU branded oil and the dampers are in place.<br><br></div>The fuel pump, H=
olley red, all the lines, micron filter before the pump and the regulator w=
ere changed last winter because I didn&#39;t know how old they were. I had =
the problem then as well, before and after the replacement. I opened the ce=
ll up two weeks ago. The foam is in great shape, the pickups and intake lin=
e look to be solid as well. The ATL cell is 6 years old.<br><br></div>Fuel =
pressure is measured by a gauge at the regulator 2 feet from the carbs.<br>=
<br></div>I&#39;m not sure that the problem isn&#39;t electrical but the ca=
r runs with a alternator (confirmed working). The distributor was built wit=
h a profile to match my engine by Jeff at Advanced Distributors. I&#39;ve c=
hanged the points (using his high speed set), rotor, cap, wires and capacit=
or over the summer, just in case, but with no affect. Timing is steady, dou=
ble row timing chain.<br><br></div>thanks for all the info.<br><br></div>mi=
ke h<br></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On =
Mon, Nov 28, 2016 at 5:05 PM, Sam Halkias <span dir=3D"ltr">&lt;<a href=3D"=
mailto:[email-masked]" target=3D"_blank">[email-masked]</a>&g=
t;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0=
 .8ex;border-left:1px #ccc solid;padding-left:1ex">

<div>
<div>
<div>What are you running for valve springs? Sounds like valve float to me.=
</div>
<div><br>
</div>
<div>Sam</div>
<div><br>
</div>
<div><font style=3D"color:#333333"><i>Sent from my Verizon Wireless 4G LTE =
DROID</i></font></div>
</div><div><div class=3D"h5">
<br>
<br>
Mike Harmuth &lt;<a href=3D"mailto:[email-masked]" target=3D"_blank">ofr=
[email-masked]</a>&gt; wrote:<br>
<br>
<div>
<div dir=3D"ltr">
<div>
<div>
<div>
<div>
<div>
<div>I&#39;m tracking down a problem with the Spit race car (1296 Small Jou=
rnal, 12;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head =
ported as per Kas&#39;s book). Rebuilt European SU HS4 carb setup with AAA =
needles (manifold and carbs checked for
 vacuum leaks), Advanced Distributor for spark (34 degrees at full, mechani=
cal only, advance @ 3.5K RPM)<br>
<br>
</div>
The problem I have has followed me on two different short blocks, I can eas=
ily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4=
th gear is 1;1,=C2=A0 4:11 locked diff ) gears. In 4th I&#39;m struggling t=
o get over 6K, no matter how long the straight.
 Just before the last race of the season, I installed an air fuel ratio gau=
ge on the header (stahl) and found out I&#39;m running (progressively)=C2=
=A0 very lean (19:1) in 4th over 5K. At 2K I adjusted it rich, to 12;1 and =
it keeps in the 13.5- 14.5 range until I get
 over 5K when it really leans out. If I pull the choke to 1/2=C2=A0 full ov=
er 5K, I get a good ratio again, 13.5- 14%.
<br>
<br>
To me that seemed like the carb pistons aren&#39;t pulling all the way up s=
o I drilled and tapped the manifold to get a vacuum reading. It was steady =
but low at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped=
 if I blipped the throttle. Under 6K,
 it was in the 15 inch range. Normal air filters are K&amp;N with stub stac=
ks but I get the same results with open carbs.<br>
<br>
</div>
Am I correct in assuming that the vacuum is too low or is it that due to ov=
erlap with a performance cam? Any ideas on where to look to get the ratio &=
quot;normal&quot; at higher revs? Fuel pump is Holley Red, adjusted to 3 PS=
I at the engine compartment and steady through
 all revs.<br>
<br>
</div>
I have dyno time scheduled in a few weeks but I&#39;d like to use that time=
 to tune not debug things.<br>
<br>
</div>
thanks<br>
</div>
mike h<br>
</div>
63 spitfire<br>
</div>
</div>
</div></div></div>

</blockquote></div><br></div>

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---

From: [email-masked]
Date: Mon, 28 Nov 2016 17:43:57 -0800

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	charset=us-ascii
Content-Transfer-Encoding: quoted-printable

Make sure the bowl vents are clear and working properly.  I don't know much a=
bout SUs, but how about float level?  Is it simply running out of gas the lo=
nger you drive it?

I've also seen this happen when a coil goes bad.  You might just switch out t=
he coil first to see if things improve.

Good Luck!

Chuck

> On Nov 28, 2016, at 3:58 PM, Mike Harmuth <[email-masked]> wrote:
>=20
> Valve springs, - Dual springs with alloy retainers. The engine builder tes=
ted and shimmed them to a uniform pressure but I don't know the number off t=
he top of my head. I'll ask him tomorrow
>=20
> Silver springs in the carbs, the lightest they make I believe. I have a se=
t of heaver ones (red I believe) that I can try. The pistons are filled ~ 3/=
4 of the way,  up with SU branded oil and the dampers are in place.
>=20
> The fuel pump, Holley red, all the lines, micron filter before the pump an=
d the regulator were changed last winter because I didn't know how old they w=
ere. I had the problem then as well, before and after the replacement. I ope=
ned the cell up two weeks ago. The foam is in great shape, the pickups and i=
ntake line look to be solid as well. The ATL cell is 6 years old.
>=20
> Fuel pressure is measured by a gauge at the regulator 2 feet from the carb=
s.
>=20
> I'm not sure that the problem isn't electrical but the car runs with a alt=
ernator (confirmed working). The distributor was built with a profile to mat=
ch my engine by Jeff at Advanced Distributors. I've changed the points (usin=
g his high speed set), rotor, cap, wires and capacitor over the summer, just=
 in case, but with no affect. Timing is steady, double row timing chain.
>=20
> thanks for all the info.
>=20
> mike h
>=20
>> On Mon, Nov 28, 2016 at 5:05 PM, Sam Halkias <[email-masked]> wrot=
e:
>> Sent from my Verizon Wireless 4G LTE DROID
>>=20
>>=20
>> I'm tracking down a problem with the Spit race car (1296 Small Journal, 1=
2;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported a=
s per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles (mani=
fold and carbs checked for vacuum leaks), Advanced Distributor for spark (34=
 degrees at full, mechanical only, advance @ 3.5K RPM)
>>=20
>> The problem I have has followed me on two different short blocks, I can e=
asily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4=
th gear is 1;1,  4:11 locked diff ) gears. In 4th I'm struggling to get over=
 6K, no matter how long the straight. Just before the last race of the seaso=
n, I installed an air fuel ratio gauge on the header (stahl) and found out I=
'm running (progressively)  very lean (19:1) in 4th over 5K. At 2K I adjuste=
d it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I get over 5K w=
hen it really leans out. If I pull the choke to 1/2  full over 5K, I get a g=
ood ratio again, 13.5- 14%.=20
>>=20
>> To me that seemed like the carb pistons aren't pulling all the way up so I=
 drilled and tapped the manifold to get a vacuum reading. It was steady but l=
ow at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped if I b=
lipped the throttle. Under 6K, it was in the 15 inch range. Normal air filte=
rs are K&N with stub stacks but I get the same results with open carbs.
>> Am I correct in assuming that the vacuum is too low or is it that due to o=
verlap with a performance cam? Any ideas on where to look to get the ratio "=
normal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the en=
gine compartment and steady through all revs.
>>=20
>> I have dyno time scheduled in a few weeks but I'd like to use that time t=
o tune not debug things.
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/chasgee22@gm=
ail.com

--Apple-Mail-EA71D618-CC73-4F59-9D2D-8D67234ED50C
	charset=utf-8
Content-Transfer-Encoding: quoted-printable

<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div>Make sure the bowl vents are clear and=
 working properly. &nbsp;I don't know much about SUs, but how about float le=
vel? &nbsp;Is it simply running out of gas the longer you drive it?</div><di=
v id=3D"AppleMailSignature"><br></div><div id=3D"AppleMailSignature">I've al=
so seen this happen when a coil goes bad. &nbsp;You might just switch out th=
e coil first to see if things improve.</div><div id=3D"AppleMailSignature"><=
br></div><div id=3D"AppleMailSignature">Good Luck!<br><br>Chuck</div><div><b=
r>On Nov 28, 2016, at 3:58 PM, Mike Harmuth &lt;<a href=3D"mailto:ofracer@gm=
ail.com">[email-masked]</a>&gt; wrote:<br><br></div><blockquote type=3D"c=
ite"><div><div dir=3D"ltr"><div><div><div><div><div><div><div>Thanks for the=
 replies, here are the answers to some of the questions:<br><br></div>Valve s=
prings, - Dual springs with alloy retainers. The engine builder tested and s=
himmed them to a uniform pressure but I don't know the number off the top of=
 my head. I'll ask him tomorrow<br><br></div>Silver springs in the carbs, th=
e lightest they make I believe. I have a set of heaver ones (red I believe) t=
hat I can try. The pistons are filled ~ 3/4 of the way,&nbsp; up with SU bra=
nded oil and the dampers are in place.<br><br></div>The fuel pump, Holley re=
d, all the lines, micron filter before the pump and the regulator were chang=
ed last winter because I didn't know how old they were. I had the problem th=
en as well, before and after the replacement. I opened the cell up two weeks=
 ago. The foam is in great shape, the pickups and intake line look to be sol=
id as well. The ATL cell is 6 years old.<br><br></div>Fuel pressure is measu=
red by a gauge at the regulator 2 feet from the carbs.<br><br></div>I'm not s=
ure that the problem isn't electrical but the car runs with a alternator (co=
nfirmed working). The distributor was built with a profile to match my engin=
e by Jeff at Advanced Distributors. I've changed the points (using his high s=
peed set), rotor, cap, wires and capacitor over the summer, just in case, bu=
t with no affect. Timing is steady, double row timing chain.<br><br></div>th=
anks for all the info.<br><br></div>mike h<br></div><div class=3D"gmail_extr=
a"><br><div class=3D"gmail_quote">On Mon, Nov 28, 2016 at 5:05 PM, Sam Halki=
as <span dir=3D"ltr">&lt;<a href=3D"mailto:[email-masked]" target=3D"=
_blank">[email-masked]</a>&gt;</span> wrote:<br><blockquote class=3D"=
gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-l=
eft:1ex">

<div>
<div>
<div>What are you running for valve springs? Sounds like valve float to me.<=
/div>
<div><br>
</div>
<div>Sam</div>
<div><br>
</div>
<div><font style=3D"color:#333333"><i>Sent from my Verizon Wireless 4G LTE D=
ROID</i></font></div>
</div><div><div class=3D"h5">
<br>
<br>
Mike Harmuth &lt;<a href=3D"mailto:[email-masked]" target=3D"_blank">ofra=
[email-masked]</a>&gt; wrote:<br>
<br>
<div>
<div dir=3D"ltr">
<div>
<div>
<div>
<div>
<div>
<div>I'm tracking down a problem with the Spit race car (1296 Small Journal,=
 12;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported=
 as per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles (ma=
nifold and carbs checked for
 vacuum leaks), Advanced Distributor for spark (34 degrees at full, mechanic=
al only, advance @ 3.5K RPM)<br>
<br>
</div>
The problem I have has followed me on two different short blocks, I can easi=
ly pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4th=
 gear is 1;1,&nbsp; 4:11 locked diff ) gears. In 4th I'm struggling to get o=
ver 6K, no matter how long the straight.
 Just before the last race of the season, I installed an air fuel ratio gaug=
e on the header (stahl) and found out I'm running (progressively)&nbsp; very=
 lean (19:1) in 4th over 5K. At 2K I adjusted it rich, to 12;1 and it keeps i=
n the 13.5- 14.5 range until I get
 over 5K when it really leans out. If I pull the choke to 1/2&nbsp; full ove=
r 5K, I get a good ratio again, 13.5- 14%.
<br>
<br>
To me that seemed like the carb pistons aren't pulling all the way up so I d=
rilled and tapped the manifold to get a vacuum reading. It was steady but lo=
w at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped if I b=
lipped the throttle. Under 6K,
 it was in the 15 inch range. Normal air filters are K&amp;N with stub stack=
s but I get the same results with open carbs.<br>
<br>
</div>
Am I correct in assuming that the vacuum is too low or is it that due to ove=
rlap with a performance cam? Any ideas on where to look to get the ratio "no=
rmal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the engi=
ne compartment and steady through
 all revs.<br>
<br>
</div>
I have dyno time scheduled in a few weeks but I'd like to use that time to t=
une not debug things.<br>
<br>
</div>
thanks<br>
</div>
mike h<br>
</div>
63 spitfire<br>
</div>
</div>
</div></div></div>

</blockquote></div><br></div>
</div></blockquote><blockquote type=3D"cite"><div><span>____________________=
___________________________</span><br><span><a href=3D"mailto:[email-masked]=
.net">[email-masked]</a></span><br><span></span><br><span><a href=3D"htt=
p://www.fot-racing.com">http://www.fot-racing.com</a></span><br><span></span=
><br><span>Donate: <a href=3D"http://www.team.net/donate.html">http://www.te=
am.net/donate.html</a></span><br><span>Archive: <a href=3D"http://www.team.n=
et/archive">http://www.team.net/archive</a></span><br><span>Forums: <a href=3D=
"http://www.team.net/forums">http://www.team.net/forums</a></span><br><span>=
[email-masked]">http://autox.team.net/mailman/options/fot/chasgee22@gmail.=
com</a></span><br><span></span><br><span></span><br></div></blockquote></bod=
y></html>=

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---

From: Jack Brooks <[email-masked]>
Date: Tue, 29 Nov 2016 03:10:54 +0000

Push through a filter, never pull through a filter. That could be a fuel flow issue. .  

Jack

---

From: Mike Harmuth <[email-masked]>
Date: Tue, 29 Nov 2016 18:19:57 -0500

--===============7213736232740160539==

--001a11452d14adb60d054278d385

I measured fuel flow at the tee feeding the carbs, and I got 2 quarts in 31
seconds or roughly 60 GPH. The pump is rated for 97 GPH,unregulated, so 60
seems reasonable and able to meet demand.

thanks
mike h

On Mon, Nov 28, 2016 at 10:59 PM, Kas Kastner <[email-masked]> wrote:

> Duh!!!  have your measured the flow of the pump to the carbs? Do you get
> 15 gallons per hour? You don't get fuel Mr. you do not get power.
>
> *Never be beaten by equipment.*
>
> On Mon, Nov 28, 2016 at 3:58 PM, Mike Harmuth <[email-masked]> wrote:
>
>> Silver springs in the carbs, the lightest they make I believe. I have a
>> set of heaver ones (red I believe) that I can try. The pistons are filled ~
>> 3/4 of the way,  up with SU branded oil and the dampers are in place.
>>
>> The fuel pump, Holley red, all the lines, micron filter before the pump
>> and the regulator were changed last winter because I didn't know how old
>> they were. I had the problem then as well, before and after the
>> replacement. I opened the cell up two weeks ago. The foam is in great
>> shape, the pickups and intake line look to be solid as well. The ATL cell
>> is 6 years old.
>>
>>> To me that seemed like the carb pistons aren't pulling all the way up so
>>> I drilled and tapped the manifold to get a vacuum reading. It was steady
>>> but low at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped
>>> if I blipped the throttle. Under 6K, it was in the 15 inch range. Normal
>>> air filters are K&N with stub stacks but I get the same results with open
>>> carbs.
>>>
>>> I have dyno time scheduled in a few weeks but I'd like to use that time
>>> to tune not debug things.
>>>
>>> thanks
>>> mike h
>>> 63 spitfire
>>>
>>
>>
>> options/fot/[email-masked]
>>
>>
>>
>>
>

--001a11452d14adb60d054278d385
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div><div>I measured fuel flow at the tee feeding the carb=
s, and I got 2 quarts in 31 seconds or roughly 60 GPH. The pump is rated fo=
r 97 GPH,unregulated, so 60 seems reasonable and able to meet demand.<br><b=
r></div>thanks<br></div>mike h<br></div><div class=3D"gmail_extra"><br><div=
 class=3D"gmail_quote">On Mon, Nov 28, 2016 at 10:59 PM, Kas Kastner <span =
dir=3D"ltr">&lt;<a href=3D"mailto:[email-masked]" target=3D"_blank">k=
[email-masked]</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quo=
te" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"=
><div dir=3D"ltr">Duh!!! =C2=A0have your measured the flow of the pump to t=
he carbs? Do you get 15 gallons per hour? You don&#39;t get fuel Mr. you do=
 not get power.</div><div class=3D"gmail_extra"><span class=3D""><br clear=
=3D"all"><div><div class=3D"m_5493796194784360336gmail_signature" data-smar=
tmail=3D"gmail_signature"><p><strong><font color=3D"#000099">Never be beate=
n by equipment.</font></strong></p></div></div>
<br></span><div class=3D"gmail_quote"><div><div class=3D"h5">On Mon, Nov 28=
, 2016 at 3:58 PM, Mike Harmuth <span dir=3D"ltr">&lt;<a href=3D"mailto:ofr=
[email-masked]" target=3D"_blank">[email-masked]</a>&gt;</span> wrote:<b=
r></div></div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;=
border-left:1px #ccc solid;padding-left:1ex"><div><div class=3D"h5"><div di=
r=3D"ltr"><div><div><div><div><div><div><div>Thanks for the replies, here a=
re the answers to some of the questions:<br><br></div>Valve springs, - Dual=
 springs with alloy retainers. The engine builder tested and shimmed them t=
o a uniform pressure but I don&#39;t know the number off the top of my head=
. I&#39;ll ask him tomorrow<br><br></div>Silver springs in the carbs, the l=
ightest they make I believe. I have a set of heaver ones (red I believe) th=
at I can try. The pistons are filled ~ 3/4 of the way,=C2=A0 up with SU bra=
nded oil and the dampers are in place.<br><br></div>The fuel pump, Holley r=
ed, all the lines, micron filter before the pump and the regulator were cha=
nged last winter because I didn&#39;t know how old they were. I had the pro=
blem then as well, before and after the replacement. I opened the cell up t=
wo weeks ago. The foam is in great shape, the pickups and intake line look =
to be solid as well. The ATL cell is 6 years old.<br><br></div>Fuel pressur=
e is measured by a gauge at the regulator 2 feet from the carbs.<br><br></d=
iv>I&#39;m not sure that the problem isn&#39;t electrical but the car runs =
with a alternator (confirmed working). The distributor was built with a pro=
file to match my engine by Jeff at Advanced Distributors. I&#39;ve changed =
the points (using his high speed set), rotor, cap, wires and capacitor over=
 the summer, just in case, but with no affect. Timing is steady, double row=
 timing chain.<br><br></div>thanks for all the info.<br><br></div>mike h<br=
></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Mon, No=
v 28, 2016 at 5:05 PM, Sam Halkias <span dir=3D"ltr">&lt;<a href=3D"mailto:=
[email-masked]" target=3D"_blank">[email-masked]</a>&gt;</spa=
n> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;b=
order-left:1px #ccc solid;padding-left:1ex">

<div>
<div>
</div><div><div class=3D"m_5493796194784360336h5"><div><div class=3D"m_5493=
796194784360336m_-9144502024920502084h5">
</div></div></div></div></div>

</blockquote></div><br></div>
<br></div></div><span class=3D"">______________________________<wbr>_______=
__________<br>
<a href=3D"mailto:[email-masked]" target=3D"_blank">[email-masked]<=
/a><br>
<br>
<a href=3D"http://www.fot-racing.com" rel=3D"noreferrer" target=3D"_blank">=
http://www.fot-racing.com</a><br>
<br>
et=3D"_blank">http://www.team.net/donate.htm<wbr>l</a><br>
Archive: <a href=3D"http://www.team.net/archive" rel=3D"noreferrer" target=
=3D"_blank">http://www.team.net/archive</a><br>
Forums: <a href=3D"http://www.team.net/forums" rel=3D"noreferrer" target=3D=
"_blank">http://www.team.net/forums</a><br></span>
[email-masked]" rel=3D"noreferrer" target=3D"_blank">http://autox.team.=
net/mailman/<wbr>options/fot/[email-masked]<wbr>om</a><br>
<br>
<br>
<br></blockquote></div><br></div>
</blockquote></div><br></div>

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---

From: "Marcel Van Mulders" <[email-masked]>
Date: Wed, 30 Nov 2016 09:11:48 +0100

This is a multi-part message in MIME format.

--===============4468293077501743378==
	boundary="----=_NextPart_000_0010_01D24AE9.C7E08060"

This is a multi-part message in MIME format.

------=_NextPart_000_0010_01D24AE9.C7E08060
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

In 4th gear, the combustion chamber has more time to get too hot. What =
about
trying say 30=B0  maximum advance to check if detonation has something =
to do
with it?
Marcel

  _____ =20

Van: Fot [mailto:[email-masked]] Namens John Styduhar
Verzonden: maandag 28 november 2016 23:04
Aan: Mike Harmuth
CC: FoTTriumph
Onderwerp: Re: [Fot] Intake manifold vacuum and no high RPM

I had the same problem in my TR3 racer. I corrected the lean condition =
by
installing a stronger damper spring in the carb and oil in the piston. =
This
created more vacuum in the throat of the carb at the higher revs and =
caused
more fuel to be drawn through the jet via the venturi effect.  Choking =
the
carb does basically the same thing.

I'm tracking down a problem with the Spit race car (1296 Small Journal, =
12;1
compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported =
as
per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles
(manifold and carbs checked for vacuum leaks), Advanced Distributor for
spark (34 degrees at full, mechanical only, advance @ 3.5K RPM)

The problem I have has followed me on two different short blocks, I can
easily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire =
case,
4th gear is 1;1,  4:11 locked diff ) gears. In 4th I'm struggling to get
over 6K, no matter how long the straight. Just before the last race of =
the
season, I installed an air fuel ratio gauge on the header (stahl) and =
found
out I'm running (progressively)  very lean (19:1) in 4th over 5K. At 2K =
I
adjusted it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I =
get
over 5K when it really leans out. If I pull the choke to 1/2  full over =
5K,
I get a good ratio again, 13.5- 14%.=20

To me that seemed like the carb pistons aren't pulling all the way up so =
I
drilled and tapped the manifold to get a vacuum reading. It was steady =
but
low at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped =
if I
blipped the throttle. Under 6K, it was in the 15 inch range. Normal air
filters are K&N with stub stacks but I get the same results with open =
carbs.

Am I correct in assuming that the vacuum is too low or is it that due to
overlap with a performance cam? Any ideas on where to look to get the =
ratio
"normal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at =
the
engine compartment and steady through all revs.

I have dyno time scheduled in a few weeks but I'd like to use that time =
to
tune not debug things.

thanks

mike h

63 spitfire

html
Archive: http://www.team.net/archive
<http://autox.team.net/mailman/options/fot/[email-masked]>
options/fot/[email-masked]

------=_NextPart_000_0010_01D24AE9.C7E08060
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content=3D"text/html; charset=3Diso-8859-1" =
http-equiv=3DContent-Type>
<META name=3DGENERATOR content=3D"MSHTML 11.00.10570.1001"></HEAD>
<BODY>
<DIV dir=3Dltr align=3Dleft><FONT color=3D#0000ff size=3D2 =
face=3DArial><SPAN=20
class=3D610360508-30112016>In 4th gear, the combustion chamber has more =
time to=20
get too hot. What about trying say 30=B0&nbsp; maximum advance =
to&nbsp;check=20
if&nbsp;detonation has something to do with it?</SPAN></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><FONT color=3D#0000ff size=3D2 =
face=3DArial><SPAN=20
class=3D610360508-30112016>Marcel</SPAN></FONT></DIV><BR>
<DIV lang=3Dnl class=3DOutlookMessageHeader dir=3Dltr align=3Dleft>
<HR tabIndex=3D-1>
<FONT size=3D2 face=3DTahoma><B>Van:</B> Fot =
[mailto:[email-masked]]=20
<B>Namens </B>John Styduhar<BR><B>Verzonden:</B> maandag 28 november =
2016=20
23:04<BR><B>Aan:</B> Mike Harmuth<BR><B>CC:</B> =
FoTTriumph<BR><B>Onderwerp:</B>=20
Re: [Fot] Intake manifold vacuum and no high RPM<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=3Dltr>
<DIV class=3Dgmail_default style=3D"FONT-SIZE: small">I had the same =
problem in my=20
TR3 racer. I corrected the lean condition by installing a stronger =
damper spring=20
in the carb and oil in the piston. This created more vacuum in the =
throat of the=20
carb at the higher revs and caused more fuel to be drawn through the jet =
via the=20
venturi effect.&nbsp; Choking the carb does basically the same=20
thing.</DIV></DIV>
<DIV class=3Dgmail_extra><BR>
<DIV class=3Dgmail_quote>On Mon, Nov 28, 2016 at 4:23 PM, Mike Harmuth =
<SPAN=20
dir=3Dltr>&lt;<A href=3D"mailto:[email-masked]"=20
target=3D_blank>[email-masked]</A>&gt;</SPAN> wrote:<BR>
<BLOCKQUOTE class=3Dgmail_quote=20
style=3D"PADDING-LEFT: 1ex; BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px =
0px 0.8ex">
  <DIV dir=3Dltr>
  <DIV>
  <DIV>
  <DIV>
  <DIV>
  <DIV>
  <DIV>I'm tracking down a problem with the Spit race car (1296 Small =
Journal,=20
  12;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head =
ported as=20
  per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles =
(manifold=20
  and carbs checked for vacuum leaks), Advanced Distributor for spark =
(34=20
  degrees at full, mechanical only, advance @ 3.5K RPM)<BR><BR></DIV>The =
problem=20
  I have has followed me on two different short blocks, I can easily =
pull=20
  7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4th =
gear is=20
  1;1,&nbsp; 4:11 locked diff ) gears. In 4th I'm struggling to get over =
6K, no=20
  matter how long the straight. Just before the last race of the season, =
I=20
  installed an air fuel ratio gauge on the header (stahl) and found out =
I'm=20
  running (progressively)&nbsp; very lean (19:1) in 4th over 5K. At 2K I =

  adjusted it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I =
get=20
  over 5K when it really leans out. If I pull the choke to 1/2&nbsp; =
full over=20
  5K, I get a good ratio again, 13.5- 14%. <BR><BR>To me that seemed =
like the=20
  carb pistons aren't pulling all the way up so I drilled and tapped the =

  manifold to get a vacuum reading. It was steady but low at 6K, ~20 =
Inches but=20
  would jump to ~28 briefly as the revs dropped if I blipped the =
throttle. Under=20
  6K, it was in the 15 inch range. Normal air filters are K&amp;N with =
stub=20
  stacks but I get the same results with open carbs.<BR><BR></DIV>Am I =
correct=20
  in assuming that the vacuum is too low or is it that due to overlap =
with a=20
  performance cam? Any ideas on where to look to get the ratio "normal" =
at=20
  higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the engine=20
  compartment and steady through all revs.<BR><BR></DIV>I have dyno time =

  scheduled in a few weeks but I'd like to use that time to tune not =
debug=20
  things.<BR><BR></DIV>thanks<BR></DIV>mike h<BR></DIV>63=20
  =
spitfire<BR></DIV><BR>______________________________<WBR>________________=
_<BR><A=20
  href=3D"mailto:[email-masked]">[email-masked]</A><BR><BR><A=20
  href=3D"http://www.fot-racing.com" rel=3Dnoreferrer=20
  target=3D_blank>http://www.fot-racing.com</A><BR><BR>Donate: <A=20
  href=3D"http://www.team.net/donate.html" rel=3Dnoreferrer=20
  target=3D_blank>http://www.team.net/donate.<WBR>html</A><BR>Archive: =
<A=20
  href=3D"http://www.team.net/archive" rel=3Dnoreferrer=20
  target=3D_blank>http://www.team.net/archive</A><BR>Forums: <A=20
  href=3D"http://www.team.net/forums" rel=3Dnoreferrer=20
  target=3D_blank>http://www.team.net/forums</A><BR>Unsubscribe/Manage: =
<A=20
  href=3D"http://autox.team.net/mailman/options/fot/[email-masked]" =

  rel=3Dnoreferrer=20
  =
target=3D_blank>http://autox.team.net/mailman/<WBR>options/fot/johnstydo@=
gmail.<WBR>com</A><BR><BR><BR><BR></BLOCKQUOTE></DIV><BR></DIV></BODY></H=
TML>

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