The Stovebolt Site Forums The Shop Area Engine Shop Engine miss on a 61 Apache with a 235

I guess the subject line summarizes the problem. At idle, especially when hot, the engine has a slight miss. Not a steady miss, but an erratic poofing type miss that you can hear when standing by the exhaust pipe. The truck starts and runs very strong. We have just completed a rebuild. All new plugs, points, plug wires, coil, etc...We have hydraulic lifters and adjusted the valves after running the truck for about an hour so it was good and hot. We adjusted down to just where they stopped clicking and then 3/4 turn beyond. We then adjusted again taking only about 1/4 turn with no difference. We have carefully checked the points, and adjusted and re-adjusted the timing. Carburator has been rebuilt. New gas tank and gas lines. The truck continues with this slight miss at idle. What are we missing? Any input or thoughts would be appreciated.

Just moving this up in the hopes that somebody has some ideas.

Apache61: Have you checked and made sure all the caps to the plugs, and dist. cap are good and tight fitting? Possible exhaust leak also. popcorn The Truth is Out There (Ok you 6 cyl. guru's help)

I'm just interested also my truck has same eratic miss always has but runs great tried different things but just got used to it mines a 66 with a 292

Thanks for the response. I replaced the condenser, points and rotor button, but not the cap because it looked like it was fairly new and recently replaced. I will probably just replace it to rule that out. The exhaust leak is a good point. When reassembling the engine we had a hard time getting the old manifold to seat correctly. I see a very small area that appears as if it might be a slight leak, but it is not enough to notice by the sound. Would a very small breach in the exhaust manifold be enough to cause this miss?

Run a compression check. It,s easy on these 6,s.
You can buy a gauge pretty cheap at one of the
DYI auto stores. You may have an exhaust valve
leaking.

Also check for a leak at the intake manifold, which will cause the two closest cylinders to run lean.

This is an intresting topic...

I too have this same problem and did not have it before.
New plugs,points,cap,rotor wires, and rebuilt carb. I have taken a compression test and I'm at 75psi give or take a few on all cylinders. Mine has solid lifter and the intake is at .008 and exhaust .010 that is .002 larger than specs on both. I can feel the miss more when hot that cold.

I have put a vacuum gauge on and set the timing with the best vaccum, but notice a little flicker in the gauge that coresponds to the miss. I thought for sure that would indicate a compression problem but I don't see it of the readings I took. What is the specs for compression on 235's anyway. Should it be read with wide open throttle etc...

Mine is very similiar to the popping sound described. Car runs strong, can't find any vacuum leaks and the idle circuit on the carb seems to be adjusted correctly.

More than an anoyance than anything.

Brent

Take some carb spray and start looking for vacuum leaks,especially where the intake mates to the head. Also check the carb mounting flange and throttle plate area. Pinch off any vacuum hoses like the dist. advance, brake booster, PCV, etc., and listen for a RPM change. A slight miss is usually a vacuum leak and can vary according to engine heat.
Good luck and hope it's simple,
Scott

i second the compression tester.i checked my 61 apache 235 and it has a burnt # 2 exaust valve.

Thanks for all the tips--------I'll get on it this weekend.

A check for leaks this weekend disclosed a small leak in the center top portion of the exhaust manifold. There is a small black smudge on the gasket and I can feel a slight leak there. Could this be the culprit, or should I continue to search? If it is the problem, has anyone had any luck using sealant between the gasket and manifold? I would like a temporary fix until I can replace or reface the manifold. Thanks.