Something isn't right with this...

Well I raced the maverick with the new setup. track was shit and couldn't make a good pass. But it ran like azz... I ran it with the 600 cfm holley, then with the 750 proform my buddy had, now I just messed with it in the garage with the 600 holley now with a blocked of powervalve and rejetted. What its doing is it runs fine and revs up, but when revved past say 5,500-6,000 it runs like crap almost like an engine with a miss, no compression, or a cam installed a tooth off. Not the best way to describe it but in short, it runs real crappy for a couple seconds, clears out, then its fine until I rev it past that point again.

Cam was degreed, and installed straight up. Timing has been at 16* and 12*, no difference in how it runs. Heads were assembled with the same valvesprings that were with the old setup (which reved to 7,200 with ease). Could I be loading up on fuel? Could I be floating the valves now because of the higher lift? Heck, could this be because my spark plugs are gapped tight at 25? (I was told to run at 20 by a racing buddy)

I wanted to race tomorrow, and I'd be running t&t basically. This is my last chance to race for the year. Any ideas what it could be? could it be the lifters not bleeding off? (I now think it might be that plus not enough spring pressure)

think a bigger carb needed, ive got a 800 double pumper on ma pop for racing & 750 vac for street use . cheers jonny

Crap I forgot to mention, its the small block. Anyways, I got new springs, retainers that work (they were wrong) and hardened keepers. Putting them in tonight, I will let everyone know if that fixed it.

And thank you for the advice, nice car by the way That's my dream car

sorry justin, thought u were running a big block m8. jonny

Justin, IMO I would replace the power valve. Depending on the displacement of your engine and you mentioned previous engine speed was considerably higher then now, if the same carburetor was in use, I'd look elsewhere for the problem. Sure a carburetor will become a restriction at high engine speed if incapable of meeting the engine's demands. If the tune up is correct, I would look at the valve springs condition. The first part of your "crappy run" is IMO due to an over rich mixture of fuel and air, probably due to no power valve. The second part of your "crappy run" could be fuel, carburetor or/and valve springs.

Just an opinion,
Dave.

Justin did the springs work what you was describing sound like my 351w back years ago.I was running a crane cam with .488 lift and switched to the comp 280h with .512 lift. I had lot quicker response out of the hole but up in rpm it would float the valves.I changed my valve spring and the valve flow went away I went from running low 8s in the 1/8 tp high 7s with the cam swap.

Valve springs were the problem. Doesn't have any issues with it running crappy anymore. I made 24 passes tuning it, I had the powervalve blocked off and kept rejetting it and got it dialed in but the poor lil 600 wasn't enough. Buddy brought the 750 proform out, big difference (ran a little rich though) and with that I was able to cross the line at 7,500 one pass and shift at 7,000 for the others. It really helped it breathe.

All in all I still need a torque converter. 2.0 60ft stalling @1500. Once I pass 60ft it takes off, and I was squeeking the 12" slicks going into 2nd and the ass end moved over a few times. I was told my 107 mph was consistant with a 12 second car. And I may need a bigger intake, like a windsor intake. not this little 302 one. Also I think the 12" tire is too much, but they were free

jonny z racing wrote:sorry justin, thought u were running a big block m8. jonny

Hey, it is a BIG BLOCK forum I forgot to specify