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Re: [Mgs] MGB Ignition Idle

To: MGs <mgs@autox.team.net>
Subject: Re: [Mgs] MGB Ignition Idle
From: Richard Lindsay via Mgs <mgs@autox.team.net>
Date: Tue, 8 Oct 2019 06:37:57 -0500
Delivered-to: mharc@autox.team.net
Delivered-to: mgs@autox.team.net
References: <mailman.2.1570471202.5536.mgs@autox.team.net> <1706026489.3353033.1570529924196@mail.yahoo.com>
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   Good advice Joel, and congratulations on your long ownership! Here are a
few more hopefully helpful ideas now surrounding your words. You wrote,

> I\we installed a Petronix's ignition...

   I did the same on both my TD and TR3b, and plan to do so on my TR6. The
issue with all of these cars was unstable slow idle timing. No electronic
trigger system alone would solve that problem.
   My original assumption was wear and therefore slop in the distributor
bushings, but that was not the case. The bushings were fine. The bits that
were worn out were the pivot holes and posts in the centrifugal advance
mechanisms. I observed the same problems in all three cars. There was
nothing for it but to replace the distributors. Okay, perhaps some of the
worn out bits could have been replaced if parts could have been sourced,
but since the holes AND posts were worn, I bought new.
   Like Joel I opted for Pertronix brand but purchased the whole
distributors. What an incredible improvement! I know owners often change to
electronic ignition trigger modules for reliability but I changed the
complete distributors for ignition timing stability. After upgrading, my
TR3b would idle smoothly at 500 rpm! (But I set it as per the manual.) The
TD would actually idle below 1500 rpm, which it wouldn't do before. :-P
   As I implied above, my next upgrade will be for the TR6, but that has to
wait until after paint. The coin chest is running way too low. Joel also
wrote,

>...and had Mr. Johnson rebuild the HIF4 carbs replacing the throttle
> body shafts.

   Yet another wise choice. Joel went on to say...

> To determine if your throttle shafts are leaking, start car and at
> operating temp, spray some carb cleaner around shafts.
> Any change in idle RPM'S indicate shafts are leaking air.

...and that is a good test. Now allow me to offer yet another tip.
   Should one determine that air is being sucked in between the shafts and
the bodies, here is a temporary BandAid fix while the owner saves up for a
proper repair. Saturate snug fitting felt washers with vacuum grease and
place them on the throttle shafts adjacent to the carb bodies. Use the
linkage to hold them snugly against the bodies, or add a washer or two, as
required.
   Vacuum grease is the stuff used in chemistry labs to seal glassware
fittings. It is designed specifically to not migrate into the experiment,
even under moderate heat. The same characteristic will keep it in place
while sealing air from leaking into the gap between the worn throttle
shafts and bores. Yes, it's a BandAid fix, not a proper repair, but it does
do two valid things: It validates the problem identification, and it buys
the owner time to save up for a proper repair.

   Thank you again Joel for reminding me to check my TR6's timing stability
and throttle shafts for vacuum leaks!

Rick

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Content-Transfer-Encoding: quoted-printable

<div dir=3D"auto"><div>=C2=A0 =C2=A0Good advice Joel, and congratulations o=
n your long ownership! Here are a few more hopefully helpful ideas now surr=
ounding your words. You wrote,</div><div dir=3D"auto"><br></div><div dir=3D=
"auto">&gt;=C2=A0<span style=3D"font-family:sans-serif">I\we installed a Pe=
tronix&#39;s ignition...</span></div><div dir=3D"auto"><span style=3D"font-=
family:sans-serif"><br></span></div><div dir=3D"auto"><span style=3D"font-f=
amily:sans-serif">=C2=A0 =C2=A0I did the same on both my TD and TR3b, and p=
lan to do so on my TR6. The issue with all of these cars was unstable slow =
idle timing. No electronic trigger system alone would solve that problem.</=
span></div><div dir=3D"auto"><span style=3D"font-family:sans-serif">=C2=A0 =
=C2=A0My original assumption was wear and therefore slop in the distributor=
 bushings, but that was not the case. The bushings were fine. The bits that=
 were worn out were the pivot holes and posts in the centrifugal advance me=
chanisms. I observed the same problems in all three cars. There was nothing=
 for it but to replace the distributors. Okay, perhaps some of the worn out=
 bits could have been replaced if parts could have been sourced, but since =
the holes AND posts were worn, I bought new.</span></div><div dir=3D"auto">=
<span style=3D"font-family:sans-serif">=C2=A0 =C2=A0Like Joel I opted for P=
ertronix brand but purchased the whole distributors. What an incredible imp=
rovement! I know owners often change to electronic ignition trigger modules=
 for reliability but I changed the complete distributors for ignition timin=
g stability. After upgrading, my TR3b would idle smoothly at 500 rpm! (But =
I set it as per the manual.) The TD would actually idle below 1500 rpm, whi=
ch it wouldn&#39;t do before. :-P</span></div><div dir=3D"auto"><span style=
=3D"font-family:sans-serif">=C2=A0 =C2=A0As I implied above, my next upgrad=
e will be for the TR6, but that has to wait until after paint. The coin che=
st is running way too low. Joel also wrote,</span></div><div dir=3D"auto"><=
br></div><div dir=3D"auto">&gt;...<span style=3D"font-family:sans-serif">an=
d had Mr. Johnson rebuild the HIF4 carbs replacing the throttle</span></div=
><div dir=3D"auto"><span style=3D"font-family:sans-serif">&gt; body shafts.=
</span></div><div dir=3D"auto"><span style=3D"font-family:sans-serif"><br><=
/span></div><div dir=3D"auto"><span style=3D"font-family:sans-serif">=C2=A0=
 =C2=A0Yet another wise choice. Joel went on to say...</span></div><div dir=
=3D"auto"><font face=3D"sans-serif"><br></font></div><div dir=3D"auto"><spa=
n style=3D"font-family:sans-serif">&gt; To determine if your throttle shaft=
s are leaking, start car and at</span></div><div dir=3D"auto"><span style=
=3D"font-family:sans-serif">&gt; operating temp, spray some carb cleaner ar=
ound shafts.</span></div><div dir=3D"auto"><span style=3D"font-family:sans-=
serif">&gt; Any change in idle RPM&#39;S indicate shafts are leaking air.</=
span></div><div dir=3D"auto"><span style=3D"font-family:sans-serif"><br></s=
pan></div><div dir=3D"auto"><span style=3D"font-family:sans-serif">...and t=
hat is a good test. Now allow me to offer yet another tip.</span></div><div=
 dir=3D"auto"><span style=3D"font-family:sans-serif">=C2=A0 =C2=A0Should on=
e determine that air is being sucked in between the shafts and the bodies, =
here is a temporary BandAid fix while the owner saves up for a proper repai=
r. Saturate snug fitting felt washers with vacuum grease and place them on =
the throttle shafts adjacent to the carb bodies. Use the linkage to hold th=
em snugly against the bodies, or add a washer or two, as required.</span></=
div><div dir=3D"auto"><span style=3D"font-family:sans-serif">=C2=A0 =C2=A0V=
acuum grease is the stuff used in chemistry labs to seal glassware fittings=
. It is designed specifically to not migrate into the experiment, even unde=
r moderate heat. The same characteristic will keep it in place while sealin=
g air from leaking into the gap between the worn throttle shafts and bores.=
 Yes, it&#39;s a BandAid fix, not a proper repair, but it does do two valid=
 things: It validates the problem identification, and it buys the owner tim=
e to save up for a proper repair.</span></div><div dir=3D"auto"><span style=
=3D"font-family:sans-serif"><br></span></div><div dir=3D"auto"><span style=
=3D"font-family:sans-serif">=C2=A0 =C2=A0Thank you again Joel for reminding=
 me to check my TR6&#39;s timing stability and throttle shafts for vacuum l=
eaks!</span></div><div dir=3D"auto"><span style=3D"font-family:sans-serif">=
<br></span></div><div dir=3D"auto"><span style=3D"font-family:sans-serif">R=
ick</span></div></div>

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