What would cause every other cylinder not to fire on a big block chevy? Answered

The truck had been running fine and ignition is not my strong spot. The ignition module has been replaced but like I said the truck was running fine up until now. Do you think that the ignition module has gone bad again?

Thats where I'd be looking, it doesnt really sound like a mechanical problem, more like electronic related.

So I had the ignition module tested and it passed so still not sure what it is now. Is there a chance it could be the coil?

There is only 3 or four things to check, compression, fuel, spark and timing. It not likely to be compression, if you have a timing light you can check spark at each lead, or pull off a dead lead and put a spark plug in the end of it to check. which leaves fuel, its possible that one side of the carb is blocked, check the runners on the manifold do 2, 3, 5 and 8 all go to one side of the carb?

You are 100% correct on the carb. I have a dual plane intake and left side of the carb feeds 2,3,5,and 8 I am not sure what caused it but the left float was not lowering all the way and not getting fuel to that side I fixed that and it works fine. not going to lie I feel kinda dumb that I didn't notice that I thank you for the answer very much.

good to know it helped you out

Most cars have a single coil feeding the distributor, in the unlikely event you have dual coils, its possible one of them isnt firing.

Another thing I seem to recollect is dual points in the distributor of some V8's, so you could check to see if you have such a beast, it might need new points of have a condenser shorting out one set.

It should be a simple matter to trace out one of the offending cylinders spark plug leads to see which set of points is triggering it, and then sand/clean points or whatever is necessary.

So I feel a little dumb I figured out what was wrong and it had nothing to do with the distributor. I have a dual plane intake on my truck so the right side of the carb feeds cylinders 1,7,4 and 6 and the right side feeds cylinders 2, 3, 5 and 8. the left side float was messed up I fixed it and it works perfectly now. So what I thought was no spark was actually no fuel. I thank you for all of your advice

Ok thank you I will pull it off and have it tested. That is kind of what I was thinking it was.

On my distributor the cap and rotor only go on in one position and the distributor is turned to set timing. That may be true about diffrent position on some distributors but thank you for the answer.

Ignition is not my strong spot. all I can tell you is that it is an MSD HEI distributor.

Well the truck had been running fine all week and out of nowhere this happened so I am sure the cap and wires are right. Thanks for the answer tho

I'm sorry I forgot to say that there is a new cap on it, that was the first thing I replaced when I got the misfire.