I recently purchased a 1977 El Camino. It has the original 350 4bbl with 94,000 miles on it. Bought it from the original owner and based on its overall condition I'm inclined to believe the mileage. Engine bay looked as if it had never been cleaned since it left the showroom.
It had a miss under acceleration when I bought it and I can't seem to get rid of it. I have checked the compression (135-145 all around - cold) and replaced the plugs, wires, cap and rotor.
It still has a miss under load, idles perfectly, cruises fines, but runs rough as soon as you accelerate. I checked the plugs after driving it a few hundred miles and they're all identical and a normal light brown color.
Beyond what I've already done, I'm out of ideas to get it to run right. Any suggestions will be appreciated.

Considered replacing the ignition module?

Not yet, although I'm looking for the next choice.
I have an 86 Camaro with a 305 that can act as a donor car for most pieces. Changed the coil between the two cars last night and that made no difference, so I can try the module tonight and see what that does.

The module will be different, the Camaro is Computer controlled.

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Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction.
Maryland Chevelle Club (http://www.chevelles.net/mcc/mcc.htm)

Another possibility is the pickup coil wiring going bad. When the vacuum advance moves the stator, the wires flex and may give an intermittent connection if damaged. Try cycling the vacuum advance unit while at idle and see if you get the misfire. I suspect that your vacuum advance does move a bit when you accelerate.

Thanks for all the suggestions, they all make good sense to me.
This evening I took the entire distributor off my Camaro, which runs perfectly and put it on the El Camino. It runs exactly the same, still misses under load.
I still have myself convinced its an ignition problem, but about the only thing left is the voltage to the distributor. Is there any reason not to try connecting a jumper cable from a full 12 volt source and connecting it to the battery connection on the distributor? Any better ideas?

This is sounding like a small vacuum leak that's hiding from you. Or a fuel delivery problem. I had a customer's Chevy pickup in my bay (back when I used to work for a dealer) that acted similar to what you described. I ended up pulling the carb and when I pulled the top off the float bowl (Q-jet also), I found a pair of insect wings down in one of the main jets. Some sort of bug managed to get into the float bowl through the bowl vent and his remains were partially plugging one side of the carb. It was most noticeable under a load. It idled fine and ran okay at steady throttle.

I've also found cracked vacuum hoses that would cause one or two cylinders to lean out under a load, and this is what I would check first. You need to give all the vacuum lines a good, thorough inspection. Move them around and feel for stiff and brittle hoses. Look on the bottoms of the hoses that are hidden from view.

If these two things check out, you may have to move on and check other things that will require you to start popping the valve covers and checking the valvetrain, but let's get the easy stuff checked first.

[This message has been edited by Randy Mosier (edited 09-06-2002).]

I vote for cam going flat. Those years were the worst. Take off valve covers and see if any of the rocker arms don't look like they are moving enough.

My '76 has the same problem. I've already been through the vacuum lines. I second the vote for the flat cam. Thats where I look next!

EGR? could be the vacuum can has a leak.

K

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64 2 Door 400SB/TH350 (actually IN the driveway!)
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This is getting frustrating!
Today I rebuilt the carb, looked OK, but cleaned everything up anyway, no dead insects or anything simple like that.
Checked the plugs again all 8 the same light brown color. EGR moves properly, or what seems to be properly. Still has the miss.
I never got any comment yet an my idea of hooking a 12 volt jumper wire directly to the Batt post of the coil. Any risk in trying this?
I haven't removed the valves covers to check for poor rocker arm movement, although with the mileage etc I'm thinking a worn cam is unlikely. But I'm also running out of ideas so need to try something.

Ummmm
When i bought my 77 Elky with 105,000 miles on it THE cam was flat ! Many lobes barely moved so just pop off the covers and take a peak.

Jim