First off it takes a lot more fuel to run at idle than to run at
speed proportionally to the amount the throttleplate is open ie at
idle it is almost closed except for a few thousands.... Checking the
plugs at idle is not the way to do it ... Find a straight flat road
and take it up to 3 to 4 thousand rpm and hold it there MPH doesn't
matter ...release peddle and shut it off and depress clutch at the
same time... stop the vehicle on the side of the road and pull the
plugs (All of them as the ones closest to the carb will be different
than the ones on the ends.) Examine and determine condition. You said
you checked all the things on your list and they appear fine??? Are
these all new??? Has the carb been rebuilt with new gaskets???Has it
been taken off and the bowl filled to proper level and checked for
cracks or leaks? Backfiring upon acceleration indicates timing is out
or accelerator pump is malfunctioning. Fuel filter would have no
effect unless its clogged then it would seem to run out of gas. Air
filter New? or Oil bath if so clean and rinse several times before
reinstalling and be sure oil level is correct. Points, cap and wires
should be ok unless its skipping under hard acceleration. Check
mechanical and vacuum advance operation with timing light. Disconnect
vacuum and test mechanical by holding at about 3000rpm make a note
where it is then reattach vacuum and rev it up and watch the
operation of the lever to see if it moves or bring it to 3000 rpm
again and see if it has increased. Look for the simplest thing as
that is usually what it is. good Luck
Rogerg
51-3100 AD huckster
> From: MKlepp4335@cs.com
> Date: Wed, 13 Sep 2000 22:00:14 EDT
> Subject: [oletrucks] Too Rich
> To: oletrucks@autox.team.net, old-chevy-truck@egroups.com
> Reply-to: MKlepp4335@cs.com
> Help gang,
> I am experiencing another problem with my rebuilt 235 engine. It drinks
> gas and runs very rich! Plugs get super sooty after only a few minutes of
> idle time. Tailpipe sooty also, smells of rich mixture while running.
> Engine stumbles and wants to pop (backfire) when accelerating. Here's what
> I've checked and all seems good: Float level, choke (manual) accel pump,
> fuel filter, air cleaner, points, wires, cap, plugs, timing, valve lash,
> mechanical advance, vacuum advance, compression, carb (rebuilt recently), and
> even tire pressure! I changed the main fuel jet down to a 46 and it seemed
> to have no effect.
> I know it is either too much gas or too little air causing the imbalance,
> but can't find anything to save my soul. Any ideas/experiences?
>
> Mike Klepp
> '48 3100
> Wichita Falls, TX
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
Roger Gleason
Uconn U-38
Office of Architectural and Engineering Services
Storrs, Connecticut 06269-3038
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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