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Obviously you have hydraulic lifters..
If original Mopar OE stockers 5K or a little over is all you will get...

Just my $0.02...



My 383 had a 292/509 old school purple shaft with stock springs and rockers, and Summit hyd lifters. It would pull hard up to 7200 and would keep going if I didn't shift or back off.

Previous owner used it for bracket racing and would hold it to 8000 on the shifts.

When I first installed the engine it would fall flat at about 4800-5000, mine ended up being a bad carburetor. I switched from the Holley it came with to a new Eddy 750 and wow, that woke it up.

Latter added the tunnel ram and a second Eddy 750 and I couldn't stop giggling.

But it seems the OP had determined its not a fuel issue.



The usual.. mopar valve spring bashing
I ran the same set of mopar "purple stripe" springs for 4 seasons, 3 or 4hundred runs. Shifted the Hemi at 6200 and trap rpm was about 7200! oh, rear gear ratio was 5.50
I still have those spring and they carry the same pressure 35 years later. Also a few more new sets and I compared seat and open pressures on every set. They were indentical.
I guess I bought the only good sets that came out of Performance Parts.

I had a 383 built by Mid West Balancing(Performance Research now) in the early 70s and it would tach over 8,000 with the magnum "red springs". The bad thing is the valves couldn't take it and I broke a few... my bad

My roadrunner.. same set of MP street Hemi springs since 1988 and its still pulling hard at over 7,000rpm.

Last edited by 52savoy; 07/28/13 05:51 AM.