Help!! Engine Miss

[Ben Kallies]

Adger,

I've tried 3 different distributors,each with their own new cap and rotor, so I believe I've eliminated that possibility. I've also replaced the coil, plug wires, plugs, MSD box, battery, and rerouted and insulated the MSD connectors, double-checking the polarity of each. I appreciate the encouragement and continued support.

Randy,

Thank you for your input.

FED 387,

Thanks for your input. Pulling the engine is the last resort, but I've been considering it.

buzzinhalfdozen,

I believe that I've eliminated the "insufficient voltage to the ignition system" by installing the HEI with a single wire direct to the battery. However, this does still leave the door open to a possible ground issue elsewhere in the vehicle. I've also tried a second carb, eliminating that possibility. The new switches are definitely on my list of things to eliminate. Perhaps I'll disconnect them, and hardwire the components one by one. Thank you for your input.

-Ben

C

[buzzinhalfdozen]

Ben, is the battery for this vehicle in the trunk or under hood ? If in the trunk how is it grounded ? If it's in the trunk and grounded somewhere in the trunk area do you have a dedicated ground wire to the front of vehicle? Also you stated that you "hard wired" an HEI unit direct to the battery with the same results which would nearly eliminate the switch as being the issue as you have bypassed it alltogether, we still have the question of sufficent voltage. From rereading your posts I'm starting to believe you have a mechanical problem assuming your voltage is sufficent to operate the vehicle. Have you performed any mechanical diagnostics, compression test, leak down, checked spring pressures, checked valve action while rotating engine with valve cover off? just some thoughts. Joe

[mtkawboy]

Ive had a broken valve spring cause a similar problem

[Ben Kallies]

Joe,

The battery is in the factory location behind the driver's seat ('71 Corvette), and the negative cable goes through the floor and grounds directly to the frame. I've got an additional ground wire from the cylinder head to the front of the frame.

I haven't performed any mechanical tests yet. I've had the valve covers off, and reset the valves, but it's worth a second look.

-Ben

[P Bailey]

Originally Posted by Ben Kallies

Joe,

The battery is in the factory location behind the driver's seat ('71 Corvette), and the negative cable goes through the floor and grounds directly to the frame. I've got an additional ground wire from the cylinder head to the front of the frame.

I haven't performed any mechanical tests yet. I've had the valve covers off, and reset the valves, but it's worth a second look.

-Ben

Ben,You might want to check the ground at the frame. We have had problems with the connector on the end of the cable inside the rubber cover.Good Luck with your problem. Phil

[Tony Curcio]

It sounds like you've isolated everything external to the engine- after 67 posts it's hard to take it all in.

As you said, the valve train is your next suspect. You've had the valve covers off- did you run the engine while they were off? This is a quick way to see if a lobe is flattened, a pushrod bent, a stud pulled out of its threads, or a broken valve spring. You'd probably be able to spot these things even if you just cranked it with the covers off. Any of these will make a popping sound in a consistent rhythm.

An overtight valve just sounds like crap, hard to describe, but a valve is not closing, so it's just weak and shakey.

One more thing I remember chasing long ago- a head gasket that is blown between two cylinders. Spits out the exhaust and intake of the two affected cylinders.

All of the above have a distinctive sound. If it was possible to post an audio file, many here would probably recognize it.

Hope you solve it soon, and hope you'll post it when you do.

[Ben Kallies]

Adger,

I can see the fuel sender and sock very easily looking through the filler neck. I didn't blow it out, but it looks very clean. I'll consider this.

Tony,

I was just talking with my dad about mocking up a set of see-through valve covers to watch the valve train. I couldn't run the engine with the valve covers off - I'm too much of a neat freak. I spun it with the covers off, and didn't see anything, but again, it's worth a second look.

I'm running MLS head gaskets, so I'd be really surprised (and disappointed) to find something wrong with them. I leave it open as a possibility though.

I will certainly post whenever I find the source of my frustration. If I have any money left, I may even throw a party.

-Ben

[junior barns]

Originally Posted by mtkawboy

Ive had a broken valve spring cause a similar problem

This is what I would check