Took my car to the dyno the other day and I was a little disapointed with the results. It lost a lot of power after 5500 rpm but started to mount a comeback after 5800. Any suggestions as to why? Is this normal? I am thinking ignition or valve train. All advice is greatly appreciated. Here are is the specs on the motor.

Stroked 340 (418 ci)

Mild Ported Eddy Heads

Hydraulic Comp. Cam: Lift Intake .534 Exhaust .520. Duration (.050) Intake 242 Exhaust 250. Lobe Center 112. Instaled @ 108.

Facory Chrysler Electronic Ignition with chrome ignition box.

Pro Systems 837cfm carb.

Anyone?

I'd be a little concerned with that A/F dip and slow recovery at the bottom.

Try a different ignition box ?

That's what I see too. Take some of that pump shot out and watch the lean out on the top end.

What intake is on the engine?

Engine dyno or chassis dyno?

The intake is an RPM Air Gap and it was a chasis dyno.

Make sure your not dropping fuel pressure at the high end. if it is ok, you may want a smaller high speed air bleed so the A/F ratio won't lean out as much at higher RPMs. The dip looks like a rich pump shot as mentioned earlier.

Just an observation - Don't be too disappointed - I'd have thought 390 RWHP (470-500 crank) was pretty good for that cam and mild Eddie heads.

What's the advertized RPM range of that cam? it drops off at 5800 for sure, is that the cam's design? or are you getting valve float or ignition problems preventing you from turning more RPM?

FWIW, my comp XE275HL is similar to your specs... I've got .525 lift, 235 degrees at .050" and mine starts to die after 5800 as well. but then again, they advertize a power band of 1800-5800 rpm.

You may have the pre load too tight. try backing it off to the bare minimum. Light ticking hurts nothing and will give the most RPM. Many people way over tighten the lash on a new build.

The sharp power drop at 5600 does not seem right for that cu.in. displacement and that cam. As others mentioned - check fuel pressure during entire pull, valve train, maybe ignition.

I had an external fuel pressure gauge the whole time. Never dropped below 6 psi.

Without knowing all the details, my first thought is valve train crash due to aggressive cam lobes w/ hydraulic lifters. It wouldn't be the first time that Comp's Xtreme hydraulic lobes have done this.

Jeff you took it to the wrong dyno(LOL) Jake

The XE extreme energy comp cams have an aggressive lobe design and need extra seat pressure and open load pressures to sustain high rpms. Even though a cam may be design to make power up to a certian rpm the engine make up will determine it's over all out put. Valve train weight etc plays a roll as well, thus the extra spring load to go along with the aggressive lobe design.

logan426

Jake, I will stop by your shop in a few days. I would like your opinion.