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Re: [oletrucks] Carb Questions

To: "Tony D'Angelo" <tonyd3@earthlink.net>,
Subject: Re: [oletrucks] Carb Questions
From: "Allen Jones" <jonesal@u.washington.edu>
Date: Tue, 11 Apr 2000 08:47:15 -0700
Tony,  tuning the dual Rochesters is going to be fun.  I installed the exact
setup on a 261 and am still working on getting it the way I want.  You might
check for a leak in your exhaust first...?  Second, which tech article?
There are 3.  Did you (or your rebuilder) rebush the throttle shafts (per
the tech article)?  This is important as these old carbs (even rebuilt ones)
are going to have worn shaft holes in the carb body.  Are you absolutely
sure that the internal parts of the carbs are a matched set (jet stand, U
link on accel pump, etc.)?  This is usually a big problem.  Did you modify
the off idle circuit per one of the articles?  This made the most, and best,
difference for me.  Do you have the dual linkage set so the each carb is
actuated about the same (maybe one carb is partly on when the other is off
on decel)?  The Offy linkage (IMO) is kinda cheesy...  Did you "reset" the
throttle plate per the article?  What cam are you using (and what are your
valves set at?)?  This will definitely make a difference as the vacuum will
drop with these carbs.  Your jets sound about right.  I think I ended up
with 52s after trying 56s (?) and 58s.

Good luck.

Allen in Seattle
'50 3100

----- Original Message -----
From: "Tony D'Angelo" <tonyd3@earthlink.net>
To: "Oletrucks" <oletrucks@autox.team.net>
Sent: April 10, 2000 11:43 PM
Subject: [oletrucks] Carb Questions

I have a 235 with a 2x1 Offenhauser manifold and and Fenton headers.  I
finally replaced my warped and leaking carbs with a pair of rebuilt
Rochesters. Following the tech article on the Inliners site, I added
insulators at the same time.

The truck idles fine.  however, when I took it out for a drive, I was
getting rapid backfiring on foot off throttle deceleration.  This got worse
the longer I drove.  Based on my limited knowledge, this would indicate a
lean burn condition, right?  I checked the carbs and they have 52 main jets
in them.  Based on the Inliners article, I wouldn't think that the jets are
too small.  Or could they be?  Could this condition be caused by an air
leak?  If so, I would assume that at idle there isn't enough air being
pulled into the system to cause a problem.  If this is true, then under
acceleration the fuel compensates for the leak.  Does this sound right?
What else would I have missed?

Tony D.

oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959

oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959

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