It revs higher than 6000 no problem, but noticeably less acceleration rate above 6000.

Does it have mufflers on it?

If so, have you tried uncorking it?

I agree think it is running out of air or fuel--pumps need 12 volts to do the job--I have seen many run without relays and correct voltage --they just will not do the job

would also be interested in what timing is doing--have seen Mopar ECU's that really retard and move timing and limit RPM

whopping spring pressure just leads to dead lifter wheels and bearings all over the place
I have a small block with 230/550 pulls 7800 RPM with ease and parts look great so.....

More pressure helps our heavy Mopar valve trains COPE with stuff better but it is easy to put together a combo that simply looses control of the entire valve train I see it happen on the dyno all the time--get to a certain RPM and thing just dies right in front of you Does it have Titanium retainers?
IMO any race engine should have them they work miracles and we consider them a 100% Must for any race engine--they are best $ spent on any engine in Cost vs. results

+ 3/8" x .120"-wall pushrods, FWIW...

I think he's running out of fuel. My solid flat tappet cam It'll go to 7400 with no problem.

It has 2"x4" headers, dual 4" exhaust with crossover, flowmaster 40 series, 4" all the way to the bumper. I told him to pull the exhaust and put 18" extensions on and try it.

It has relays for all systems, relay for the fuel pump is in the trunk with the fuel tank, pump, and dual Optima D35 yellow top 620CCA batteries wired in paralell properly with 1/0 cable all around. MSD 140 amp alternator with 3:1 pulley ratio, 4 gauge charge wire. MSD Digital 7 plus ignition box and HVC 2 coil.

Titanium retainers and Smith Bros 5/16" x.116" wall pushrods.

He did say that on the weekend he noticed that when the dual cooling fans were on, the fuel pressure would jump around, and drop. The regulator is mounted on the front of the engine, and the fan on that side blows hot air right on it. When he cooled the car down between rounds more, so the fans didn't come on during a run, or in the staging lanes, the pressure stayed solid. So he is moving the regulator to the fender, and wrapping all the fuel lines under the hood with foam pipe insulation. But, the performance didn't change even when the pressure was moving around.

I’m going with this:



Had a customer with a low deck 511 with a .640 roller and 943 springs at 1.900.
Ended up dropping an exhaust valve.
Sent me the heads to repair.

There were witness marks 1/4” away from where the exhaust pushrods passed through the heads!!!
All the areas near where the pushrods passed through the heads showed that there was a ton of pushrod flexing going on. Enough so that there was not only a witness “mark”, but it had actually pounded a raised lip at the deck of the head.
Again..... that was 1/4” away from the pushrod.
The intake pushrod tunnels were closer to the pushrods, which limited the amount they could deflect, but the area around the exhaust pushrods was much more spacious, allowing for much more flex. The severe flexing is just another way to lose valvetrain control...... and the result was a dropped valve.

They were heavy wall heat treated 5/16” in that motor.