Reply to "New engine/low HP"

Art,

the dyno is the best place to diagnose a problem. I have more questions than answers at this point.

First, my random observations. Your motor is making about 407 bhp at the flywheel, which is about all you're going to make using the cast iron 4V heads without porting & a good valve job (multi angle). Although the cam is rated for power out to 6000 rpm by Comp Cams, thats with a 351 cubic inch motor, the extra displacement of your stroker moves the power band lower in rpm, I would have guessed power to 5750 rpm, but 5650 is close enough. David Berman had his motor dyno tested with an Edelbrock Performer adapted to work with his Blue Thunder heads, that motor made a tad more than 500 bhp, at around 6000 rpm, feeding a 408 cubic inches. I never liked the Performer myself, but David's dyno results has given me a new found appreciation of that intake, you can make more power at the upper rpm with other intakes for sure, but I do not believe the intake is what is "choking" your motor. It may very well be the characteristics of that cam to drop off like a brick above the powerband, rather than the torque curve tapering downward at a slower rate, which is why sports car guys normally want a wide flat torque curve, rather than an upward tilted one. The upward tilted ones drop off faster beyond peak torque. When all is said and done, you may very well need a custom ground cam to get the characterisitcs you want.

Having written all that, I myself would not be satisfied with the performance of your motor either. I would expect it to perform better too.

OK, here's my questions:

Do you have assurance that the person who built your short block did a good job with the rings as far as getting them to seal well in the cylinders?

Did the dyno operators run any air/fuel ratio numbers while your motor was on their dyno? If so, what were the numbers like between 4000 & 6000 rpm?

What components is your ignition composed of, and how old are they?

What is your ignition timing specs?

What parts are your fuel delivery system composed of & how old are they?

What make & size is your carburetor?

What are you using for an air filter and was it installed during dyno testing?

What size are the exhaust pipes of the mind train system, and what type mufflers does it use?

Have your heads been ported and had a multi angle valve job?

How do the specs of the Isky 8005A springs compare to the springs recommended by Comp Cams?

your friend on the DTBB