350 running on 7

[dotgone]

last night i was driving my 57 with a 350 mild cam
edlebrock manifold and carb 240 hp on pump gas
i stoped at a stop sign the idle droped to 350 rpm
and is running on less tha 8 probably 7 cilynders
the engine has 3500 miles and has been perfect
up to now.i changed the plugs they all looked good
i also changed the inline fuel filter and checked the
filter screen in carb. it still sounds like its running on
7.when i give it a littlle gas it sounds like the other
cylinder or cylinders try to kick in the only thing i
did not change are the plug wires also the carb
is geeting plenty of gas. the distributer is new
with 3500 miles on it.

[southerner]

Might be a vacume leak

[dotgone]

southerner

i have a composite plate 5/16 thick that the carb
sits on inplace of a gasket i never liked the plate the carb
sits on maybe i should try gasket only like most engines
i have seen. when i first put this 5/16 spacer on it did
have a vaccum leak so i tightened it down but i think
one gasket between manifold a carb sounds better.

[southerner]

Yeah its a process of elimination finding vacume leaks, I would get a tuners vacume guage and it will pretty much confirm a vacume leak, but if your in a hurry check all your vacume line plugs. As a thought did you have a serious backfire recently ?, it could of blown off one of your vacume lines , port plugs, or part of thet composite gasket. Good hunting and let us know how you got on.

[dotgone]

i found a vaccum gage in my tool box the one i
used on my 327 which i blew up last summer.
i can connect it direcly to the intake manifold or the front
of the carb where i hook up vaccum advance,do you
know what i should look for?

[Chevytu]

I had a vac leak in my 350 Nova and the reading was a little erratic, also been told to spray the suspected area with carb cleaner and see if the idle goes up?

[southerner]

Originally posted by dotgone
i found a vaccum gage in my tool box the one i
used on my 327 which i blew up last summer.
i can connect it direcly to the intake manifold or the front
of the carb where i hook up vaccum advance,do you
know what i should look for?

OK hook the guage up to the manifold so you have aconstant vacume sorce. Start engine and have it idle see what the needle is doing. If it is below stock vacume it shows a vacume leak, if it bounces all over the place it shows a broken valve spring

If thats ok rev the engine up to 2000 rpm the vacume should drop smoothly on the guage. Let the throttle snap back to closed the vacume should come right up and settle down again. Do all this and if thats ok we start looking at the ignition.

[dotgone]

vaccum at idle reads 15 on gage at about 750 rpm
vaccum at 2000 rpm reads 21 on gage
at 2000 rpm vaccum remains at 21 it did not drop it just
stays at 21 at 2000 rpm

the needle doe's not bounce around at any rpm
the gage is hooked directly to manifold.

[dotgone]

techinspector

i also think its the plugwires,i just replaced and checked
the plugs they all looked good,the wires are about 2 years
old i did not replace them when i replaced the engine,also
the wires are not mallory and i have a malory ignition i
just priced some mallory wires 8mm for 83 bucks. the plugs
are under the ram horn exhaust manifold to get to them
i slide under the car. the mallory ignition is also new. when
i run the engine it sounds like the piston or pistons are trying
to fire. anyway i will change the plugs.

[dotgone]

Just want to let all of you who responded to this thread
know what the problem was,(dirt in the carb) after i pulled
the carb and took it apart i found dirt or what ever in the
bottom of the bowls,also the primarys and secondarys
were clogged, thats what happens when you drop below
1/8 of a tank of gas and put the peddle to the mettle.
thanks for your response.

[shawnlee28]

Sounds like its time fer a new tank , or a good flush.