IH 345 idle on 4 cylinders-need more help

[semn john]

So - on to the 345. Has (I think) a 2300 Holley carb. Has a governor on the carb. Good runner, always strong on power. Problem is some times it will decide to idle on four cylinders and will produce a backfire and very poor power coming out of idle. The start of the run up in a gear is very unpredictable, some times after a backfire it will even die.

When this engine is running right it is so smooth-- I swear it must be balanced and blueprinted!

Any Ideas on this one ? ?

Thanks in advance.

[Allan E.]

Depends completely on which cylinders as to what is the problem.

1 x
x 4
x 6
7 x

The intake manifold feeds the cylinders marked X from one side of the carb, and the numbered cylinders from the other.

If it's that pattern, either side, you have a jet not feeding fuel.

If it's a different pattern, you have a distributor problem, most likely.

I would bypass the vacuum advance and see what effect it has. An intermittent vacuum leak on that circuit would cause similar problems.

[semn Dad]

Ya, I'm guessing it's the carb too. I've gone thru this twice before, but it always winds up coming back later after a carb kit is put in. Other times it seemed if you could get it to backfire real bad, or cross the plug wires it would clear up the 4 cylinder idle. I hate to intentionally backfire a motor cause it's got to be hard on carb gaskets. I hadn't thought about pulling plug wires to identify the cylinders. Thanks I really appreciate the help. (previous post 304 backfire) : It was the vacuum advance on the 304! not a one available anywhere ! ! found a rebuilt Dist. with one one at Advanced Auto parts

[BeJimmieEvive]

its not a graphic problem its a memory problem. sro is popular with memory leaks not much you can do about it. you can increase your virtual memory to see if that works free or buy more ram might need to get new OS for 64 bit