I think I forgot to mention I can recreate the problem just sitting still in neutral. If I hold it at the right RPM, it'll break up just as it does cruising about 50mph.
Junior Member
Still running the stock Stromberg Aerotype AAV-16.Originally Posted by 322bnh
Junior Member
I think I forgot to mention I can recreate the problem just sitting still in neutral. If I hold it at the right RPM, it'll break up just as it does cruising about 50mph.
Member
What burned the valves?
1979 TRegal
Junior Member
Not too sure. The exhaust valves were all heavily coked up, but only number 4 and 6 were burned up (both cylinders were putting out about 45 psi compression, the rest were from 80-100). I'd guess I've put less than 1000 miles total on the car since I got it road worthy a couple years ago, so it's possible they were burnt out before I picked the car up. Or maybe it's possible that driving the car with the breaking up is what wiped the valves out. The first compression check I ran on the car was maybe 6 months ago.. which is what lead me to pulling the head and pistons.
Last edited by agraz400; 11-08-2016 at 04:58 PM.
Senior Member
Check that the power piston is not stuck in the up or high vacuum position and that you have the correct valve in the bottom of the bowl. If this system is not working it will lean out under higher demand.
Also verify that the machine shop that did your valves set the proper guide to stem clearance. If they set it like all the chivvy engines they do, the tighter clearance will start binding when hot.
Junior Member
Sounds like a good possibility. I'll have to break open the manual and see where in the carb that is exactly. I did notice the "high heat" paint I originally sprayed on the exhaust manifold began turning white.. wonder if that's another indicator of burning lean and hot.
I replaced the two exhaust valves (and lapped the rest of them) myself. Really just didn't want to dump a ton of money into machine work. Water tested before and after to confirm they're seated with no leak through. Guides had enough slop they should never bind, but not enough for me to be concerned about oil leak through.
Senior Member
couple guesses, acc pump or. I'm too lazy to read. had a vaccum gauge on it? spray manifold, carb base, fuel/ vac pump and vac wiper motor with carb cleaner to check for vac leak.
52 Special.
Tin Militia CC
Member
Check the two valve springs for proper tension. May float at said RPM
Very possible the Pertronix is bad. Had almost the same thing happen on many cars installed into. DON'T use them any longer.
Tom Telesco
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Junior Member
Acc pump appears to be working. The rod and seal assembly were replaced during the rebuild awhile ago. Sprayed down all possible intake/vac leak areas.. no leaks found.
Valve float did cross my mind. I visually inspected the springs and they looked like they held the same height as all the other ones. I'm not sure how else to check for proper tension.
Part of the reason for me installing the pertronix was in an attempt to fix this issue. I've heard of similar problems with pertronix from a local buick guy that I had rebuild my vacuum advance.. I suppose I could throw the points back on real quick and see if it's any better.
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