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Excellent write-up Tony!
Glen
=20
-----Original Message-----
From: Tony Drews via Fot <fot@autox.team.net>
To: Alec Buchan <agb@compsnw.com>; fot@autox.team.net <fot@autox.team.net>
Sent: Mon, Jan 18, 2021 5:20 pm
Subject: Re: [Fot] Weber help and/or advice
Alec, in my experience (also a TR-4), you can make just as much power=20
with a well tuned set of SU's as with Webers.=C2=A0 My dad (Jack) ran SU's,=
I=20
have Weber 42's (came with the car).=C2=A0 We were virtually the same speed=
/=20
power.=C2=A0 Took us both a while to get there and required running on the=
=20
Dyno to dial them in.
From what I understand, the "Cannon" intake manifolds are considered=20
the best.=C2=A0 I discovered that the 42's (which are rare as hen's teeth)=
=20
take the same internal bits as the 40's, so I think the advantage is=20
more psychological than anything over the 40's.=C2=A0 I ended up with the=
=20
biggest chokes (venturi) that would fit - I think 36 mm was as big as I=20
could go.=C2=A0 I do have a set of 45's that I keep threatening to spiff up=
=20
and try.=C2=A0 I suspect that going to a 38 mm choke would be the hot ticke=
t=20
for my engine.=C2=A0 Depending on the build, 40's work pretty well.=C2=A0 B=
ig=20
bore, billet crank, hairy cam, high RPM would probably benefit from 45's.
What I found on the Dyno is that there's a ton of power in just getting=20
the mixture right across the rev range.=C2=A0 I ended up with pretty small=
=20
air correction jets to keep it from going lean at high RPM's.=C2=A0 I=20
probably gained around 20 HP just by tuning the carbs.
From what I understand, comparing jetting from one engine build to=20
another is pretty haphazard, it's best to tune it to the specific engine=20
rather than just copy someone else's jetting. Also, I believe the=20
emulsion tube can make quite a bit of difference, so just comparing main=20
/ air jet sizes if you're not running the same emulsion tube kinda=20
invalidates the comparison. In my case I just used the emulsion tubes=20
that came in the carb's and didn't try alternates.=C2=A0 I believe the big=
=20
differences in those is more for part-throttle driveability which I=20
generally ignore. If I can drive it to the grid it's fine, otherwise=20
it's pretty much just wide open or closed, not a lot of part throttle.=C2=
=A0=20
But other drivers may use more part throttle and so the emulsion tubes=20
would be of greater importance.
I love the looks of the webers, but Jack was able to get decent mixture=20
control with SU's and some slighly custom needles - I think he took RB's=20
and skinnied down the tips to be more of the RA needle profile there.=C2=A0=
=20
He also ran 0.104" jets to get enough fuel out (stock is 0.100").=C2=A0 We=
=20
would draft each other at Road America, so were pretty close in overall=20
power.
I'm not quite sure what kind of advice you're looking for - should I do=20
it or not?=C2=A0 What specific setup should I get?=C2=A0 What carb settings=
should=20
I start with?=C2=A0 None of these have cut and dried answers in my opinion.
Should I do it?=C2=A0 Maybe, but you can also get similar results with good=
=20
well tuned SU's.=C2=A0 The webers look awesome though.
Which setup to get?=C2=A0 Partially depends on the engine build.=C2=A0 I su=
spect=20
you'd be happier with 40's on a decent manifold with a decent linkage.=C2=
=A0=20
If you have a monster motor you'll want 45's.
Starting setup?=C2=A0 If 40's, 36 mm chokes, possibly 150 mains with about=
=20
130 airs is roughly where I ended up (need to dig through the expensive=20
box of brass bits to verify).=C2=A0 No idea what emulsion tube or accelerat=
or=20
pumps I'm running.
One advantage of the webers is that they DO have accel pumps, so getting=20
the engine started on a cold day without the choke is easier than with=20
the SU's.
I found the tuning of SU's to be more obvious than the Webers.=C2=A0 I used=
a=20
couple of books and Teri Ann's website to get a good understanding of=20
what I was doing with the Webers.=C2=A0 The big aha for me was understandin=
g=20
that the main jet affects the mixture across the entire rev range while=20
the air correction affects high RPM mixture more than low RPM mixture.=C2=
=A0=20
Changing the air correction does also affect lower RPM mixture so they=20
need to be tweaked in combination with each other.=C2=A0 Getting the air=20
correction small enough that it didn't lean out at high RPM but big=20
enough so it didn't richen at high RPM was my key, then I tweaked the=20
main jets for max power and maybe went a step richer to keep the pistons=20
un-molten.
Regards, Tony Drews
On 1/18/2021 2:54 PM, Alec Buchan via Fot wrote:
> It looks like I am moving up a group and in order to not maintain my=20
> 'blue caboose' moniker, I am looking at converting to Webers. Moss and=20
> Pierce sell a 2 x 40 DCOE kit but I've also located a 2 x 45 DCOE kit=20
> (not from Moss or Pierce). looking for recommendations, if you might=20
> be so kind.
>
> On a side note, the few of us here in the PNW are looking forward to=20
> seeing all you 'front of the packers' in Portland this summer.
>
> Kindly,
>
> Alec Buchan
> Bellingham, WA
> '62 TR4 #5 (aka the Blue Caboose)
> _______________________________________________
> fot@autox.team.net
>
> http://www.fot-racing.com
>
> Donate: http://www.team.net/donate.html
> Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
> Unsubscribe/Manage:=20
> http://autox.team.net/mailman/options/fot/tony@tonydrews.com
>
>
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
m
------=_Part_2061178_1064468414.1611062254416
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<div style=3D"color:black;font: 10pt Arial, Helvetica, sans-serif;">
<div> <font size=3D"2">Excellent write-up Tony!</font><br>
</div>
<div> <font size=3D"2">Glen</font><br>
</div>
<div> <br>
</div>
<div style=3D"font-family:arial,helvetica;font-size:10pt;color:black">-----=
Original Message-----<br>
From: Tony Drews via Fot <fot@autox.team.net><br>
To: Alec Buchan <agb@compsnw.com>; fot@autox.team.net <fot@autox.t=
eam.net><br>
Sent: Mon, Jan 18, 2021 5:20 pm<br>
Subject: Re: [Fot] Weber help and/or advice<br>
<br>
<div dir=3D"ltr">Alec, in my experience (also a TR-4), you can make just as=
much power <br clear=3D"none">with a well tuned set of SU's as with Webers=
. My dad (Jack) ran SU's, I <br clear=3D"none">have Weber 42's (came =
with the car). We were virtually the same speed / <br clear=3D"none">=
power. Took us both a while to get there and required running on the =
<br clear=3D"none">Dyno to dial them in.<br clear=3D"none"><br clear=3D"non=
e"> From what I understand, the "Cannon" intake manifolds are considered <b=
r clear=3D"none">the best. I discovered that the 42's (which are rare=
as hen's teeth) <br clear=3D"none">take the same internal bits as the 40's=
, so I think the advantage is <br clear=3D"none">more psychological than an=
ything over the 40's. I ended up with the <br clear=3D"none">biggest =
chokes (venturi) that would fit - I think 36 mm was as big as I <br clear=
=3D"none">could go. I do have a set of 45's that I keep threatening t=
o spiff up <br clear=3D"none">and try. I suspect that going to a 38 m=
m choke would be the hot ticket <br clear=3D"none">for my engine. Dep=
ending on the build, 40's work pretty well. Big <br clear=3D"none">bo=
re, billet crank, hairy cam, high RPM would probably benefit from 45's.<br =
clear=3D"none"><br clear=3D"none">What I found on the Dyno is that there's =
a ton of power in just getting <br clear=3D"none">the mixture right across =
the rev range. I ended up with pretty small <br clear=3D"none">air co=
rrection jets to keep it from going lean at high RPM's. I <br clear=
=3D"none">probably gained around 20 HP just by tuning the carbs.<br clear=
=3D"none"><br clear=3D"none"> From what I understand, comparing jetting fro=
m one engine build to <br clear=3D"none">another is pretty haphazard, it's =
best to tune it to the specific engine <br clear=3D"none">rather than just =
copy someone else's jetting. Also, I believe the <br clear=3D"none">emulsio=
n tube can make quite a bit of difference, so just comparing main <br clear=
=3D"none">/ air jet sizes if you're not running the same emulsion tube kind=
a <br clear=3D"none">invalidates the comparison. In my case I just used the=
emulsion tubes <br clear=3D"none">that came in the carb's and didn't try a=
lternates. I believe the big <br clear=3D"none">differences in those =
is more for part-throttle driveability which I <br clear=3D"none">generally=
ignore. If I can drive it to the grid it's fine, otherwise <br clear=3D"no=
ne">it's pretty much just wide open or closed, not a lot of part throttle.&=
nbsp; <br clear=3D"none">But other drivers may use more part throttle and s=
o the emulsion tubes <br clear=3D"none">would be of greater importance.<br =
clear=3D"none"><br clear=3D"none">I love the looks of the webers, but Jack =
was able to get decent mixture <br clear=3D"none">control with SU's and som=
e slighly custom needles - I think he took RB's <br clear=3D"none">and skin=
nied down the tips to be more of the RA needle profile there. <br cle=
ar=3D"none">He also ran 0.104" jets to get enough fuel out (stock is 0.100"=
). We <br clear=3D"none">would draft each other at Road America, so w=
ere pretty close in overall <br clear=3D"none">power.<br clear=3D"none"><br=
clear=3D"none">I'm not quite sure what kind of advice you're looking for -=
should I do <br clear=3D"none">it or not? What specific setup should=
I get? What carb settings should <br clear=3D"none">I start with?&nb=
sp; None of these have cut and dried answers in my opinion.<br clear=3D"non=
e"><br clear=3D"none">Should I do it? Maybe, but you can also get sim=
ilar results with good <br clear=3D"none">well tuned SU's. The webers=
look awesome though.<br clear=3D"none"><br clear=3D"none">Which setup to g=
et? Partially depends on the engine build. I suspect <br clear=
=3D"none">you'd be happier with 40's on a decent manifold with a decent lin=
kage. <br clear=3D"none">If you have a monster motor you'll want 45's=
.<br clear=3D"none"><br clear=3D"none">Starting setup? If 40's, 36 mm=
chokes, possibly 150 mains with about <br clear=3D"none">130 airs is rough=
ly where I ended up (need to dig through the expensive <br clear=3D"none">b=
ox of brass bits to verify). No idea what emulsion tube or accelerato=
r <br clear=3D"none">pumps I'm running.<br clear=3D"none"><br clear=3D"none=
">One advantage of the webers is that they DO have accel pumps, so getting =
<br clear=3D"none">the engine started on a cold day without the choke is ea=
sier than with <br clear=3D"none">the SU's.<br clear=3D"none"><br clear=3D"=
none">I found the tuning of SU's to be more obvious than the Webers. =
I used a <br clear=3D"none">couple of books and Teri Ann's website to get a=
good understanding of <br clear=3D"none">what I was doing with the Webers.=
The big aha for me was understanding <br clear=3D"none">that the mai=
n jet affects the mixture across the entire rev range while <br clear=3D"no=
ne">the air correction affects high RPM mixture more than low RPM mixture.&=
nbsp; <br clear=3D"none">Changing the air correction does also affect lower=
RPM mixture so they <br clear=3D"none">need to be tweaked in combination w=
ith each other. Getting the air <br clear=3D"none">correction small e=
nough that it didn't lean out at high RPM but big <br clear=3D"none">enough=
so it didn't richen at high RPM was my key, then I tweaked the <br clear=
=3D"none">main jets for max power and maybe went a step richer to keep the =
pistons <br clear=3D"none">un-molten.<br clear=3D"none"><br clear=3D"none">=
Regards, Tony Drews<br clear=3D"none"><br clear=3D"none">On 1/18/2021 2:54 =
PM, Alec Buchan via Fot wrote:<br clear=3D"none">> It looks like I am mo=
ving up a group and in order to not maintain my <br clear=3D"none">> 'bl=
ue caboose' moniker, I am looking at converting to Webers. Moss and <br cle=
ar=3D"none">> Pierce sell a 2 x 40 DCOE kit but I've also located a 2 x =
45 DCOE kit <br clear=3D"none">> (not from Moss or Pierce). looking for =
recommendations, if you might <br clear=3D"none">> be so kind.<br clear=
=3D"none">><br clear=3D"none">> On a side note, the few of us here in=
the PNW are looking forward to <br clear=3D"none">> seeing all you 'fro=
nt of the packers' in Portland this summer.<br clear=3D"none">><br clear=
=3D"none">> Kindly,<br clear=3D"none">><br clear=3D"none">> Alec B=
uchan<br clear=3D"none">> Bellingham, WA<br clear=3D"none">> '62 TR4 =
#5 (aka the Blue Caboose)<br clear=3D"none">> __________________________=
_____________________<br clear=3D"none">> <a shape=3D"rect" ymailto=3D"m=
ailto:fot@autox.team.net" href=3D"mailto:fot@autox.team.net";>fot@autox.team=
.net</a><br clear=3D"none">><br clear=3D"none">> <a shape=3D"rect" hr=
ef=3D"http://www.fot-racing.com/"; target=3D"_blank">http://www.fot-racing.c=
om</a><br clear=3D"none">><br clear=3D"none">> Donate: <a shape=3D"re=
ct" href=3D"http://www.team.net/donate.html"; target=3D"_blank">http://www.t=
eam.net/donate.html</a><br clear=3D"none">> Archive: <a shape=3D"rect" h=
ref=3D"http://autox.team.net/archive"; target=3D"_blank">http://autox.team.n=
et/archive </a><a shape=3D"rect" href=3D"http://www.team.net/pipermail/fot"=
target=3D"_blank">http://www.team.net/pipermail/fot</a><br clear=3D"none">=
> Unsubscribe/Manage: <br clear=3D"none">> <a shape=3D"rect" href=3D"=
http://autox.team.net/mailman/options/fot/tony@tonydrews.com"; target=3D"_bl=
ank">http://autox.team.net/mailman/options/fot/tony@tonydrews.com</a>
<div class=3D"yqt9723289551" id=3D"yqtfd55788"><br clear=3D"none">><br c=
lear=3D"none">><br clear=3D"none">______________________________________=
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eam.net" href=3D"mailto:fot@autox.team.net";>fot@autox.team.net</a><br clear=
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g.com/" target=3D"_blank">http://www.fot-racing.com</a><br clear=3D"none"><=
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rget=3D"_blank">http://autox.team.net/archive </a><a shape=3D"rect" href=3D=
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