Engine Guru's, I need help
 

I have a dead cylinder (#3), and #2 seems to cut in and out. I have a detailed account in the technical Q & A but basicly I have spark (most of the ignition is new), 160 psi compression, great leak down, fuel (plug is black), valve springs are unbroken, cam lift is equal to other cylinders when measured @ pushrod w/no rocker arm, exhaust port and manifold (stock) show no discoloration to indicate reversion. The miss seemed to start after I lost the sea water pump on that motor, but the water temp gauge never went above 210, so it may be unrelated.
Oh yeah, its a 97 454 mag carbeurated all stock, 200 hrs.
I am open to any and all suggestions!!:confused:

Did you replace the plug wires?

Yup, new plugs, wires, caps, rotors, f. filters, swapped coils and hall effect switches from the other motor. No effect.
All the details are in the technical Q&A.
Thanks Biggus!

Anyone have any suggestions? I'm at a loss.:mad:

did you verify that you have good connections on both the plug and dist.? Also did you check to make sure you have no play in the dist. I've heard that when the bearings go they will cause some problems.

Sounds like a good reason to go out and get that 672 you've been dreaming about.

Distributor?
 

Can you swap distributors between engines?

Do these engines have an ignition box?

That may be going bad.

Crazy horse, you have the answer!!!!:D
Tonight I'm going to swap #1 and #3 valve springs to see if the skip follows.

Have you done a vacuum test at the intake manifold?

BT :cool:

Good luck Chris!!

I can't believe it is a valve spring if your compression is good check for a vacume leak at the intake where it meets the head posibly causing a lean misfire. Is it a dead skip?

BN thanks!
Blue Thunder, I haven't checked vac leaks because the plug is black, not lean.
Cartman, yup its a dead skip. Weak springs can give normal compression when cranking, then float the valves when running.
I swapped the springs but I can't fire it up because I creased the exhaust gasket and have to get another today.:mad:

GO4Broke,

Vacuum testing is not necessarily to look for vacuum leaks, it is to diagnose engine conditions. Particularly good for sticky valves and other top end problems. Look into it.

BT :cool:

Double or triple check the plug wires/ firing order it sounds like ignition.

I will triple check all the ignition because I too lean that way. Blue thunder, thanks for the reminder about vacume testing, your right thats a powerful tool, I just don't use it often. I'll be finishing reassembly tonight and inspect the ignition, then tomorrow I'll fire it up and see what happens. I'll keep you posted...

I rechdecked all the ignition, still NPF. The motor is together and I will run it tomorrow and see what happens.

Well I ran it and the damn thing finally gave me a hint as to the problem. It blew black smoke. I think the port float is sinking and flooding out #2 and #3 which are the front 2 cylinders fed by the upper plenum. I knew it would be something stupidly simple!! I'll be pulling the carb after work tomorrow. This would have been much easier if it had smoked for me before!!