I am having a small issue with my 440 missing above 5000 rpm. It is in a 67 GTX with a 5 spd tranny. I have 10 3/4:1 comp, a solid cam with 242/252@ .50, heddman headers, performer RPM, 750 holley with proform main body, pertronix ignition and flamethrower coil. I just recently had the motor out doing some detail work and the only thing i did with the engine was adjust the valves. It seems to run hard up to 5k and then acts almost like a rev limiter and misses. Once I shift it seems to be fine. I have checked the carb and the secondarys seem to be working fine. i guess my question is, is this an ignition issue (double checked and the pertronix is getting 12v)or could a valve be hanging open or floating? I'm pretty sure it didn't do this when I pulled it out last fall. thanks for any help you might provide.
-karl

hi
just a guess cloged fuel filter / bad /week fuel pump can not deliver volume at hi rpm !

Sounds like valve float. I think you can confirm or rule it out on a vauum gauge if you try.

Run it out the from under the hood, to under the wiper, and tape it down. (sounds a little hill billy, I know ...)

If you see it really bounce down on the miss (like a big drop) it's likely because the intake valves are floating and burbing compression back into the intake.

No matter what the miss is, it will move, but the affect will be dramatic with a valve float/bounce.

rotor phasing or fuel starvation

Did you reinstall a block to chassis ground? My sons high rpm miss was because he failed to do so.

Double checked the ground and we are good there. I have felt fuel starvation before and this is a lot different. It would fall flat on it's face when I had fuel starvation, right now it just misses a little (even in first gear) at 5k and then will not pull anymore. I guess I am leaning at gettting some new valve springs, thanks for the help. BTW, what is rotor phasing? thanks
-karl

if the valves adjustment was all you did, and you're a competent wrench, thats the problem.

maybe try to back off the preload on the adjuster. try to undo what you did.

I would look at the valve springs. I had a 340 doing that one time above 4K rpm and it was a broken valve spring. Fortunately, the inner damper spring kept it from doing any damage but below that rpm it ran fine.

rotor phasing is when on some dist's vac & centrifugal adv & stackup of factory tolerances has the rotor tip so far away from the terminal on the underside of the cap that it is firing to that the spark cant jump that far & it starts to miss. you could drill a 3/8" or so hole in the dist cap between the center terminal & #1 terminal rev the eng up to the offending rpm & shine your timing light straight down in there & see how far off the rotor is from being close to the underside of the #1 terminal. easier would be to advance your initial 5 degrees & rev it up to the problem rpm then retard it 5 degrees(10 degree change) & rev it up there again. one of these 2 actions will move the rotor closer to the terminal & if phasing is causing your problem it will get better.If so holler