Reply to "New engine/low HP"

Art,

Thanks for providing the info, sorry for the third degree.

have you spoken to Russ about this? I know who Russ is because other Pantera owners like Dennis A speak very highly of him. I would expect him to have built you a top notch motor, and am surprised to read you're having trouble with it knowing he's the builder. There's a mechanics code of honor by the way, one mechanic doesn't criticize or second guess the work of another, at least not publicly, ahem.... Mechanics are all a very highly opinionated bunch, become irritated easily. If we went around second guessing each other, we'd end up throwing burning carburetors through each others windows in the middle of the night. You've never heard of a "Holley-tof cocktail"?

Shame on your dyno operators for not taking A/F ratio readings! That would have provided you with very critical info (1) you have an air/fuel problem, or (2) you don't have an air/fuel problem. At least you would know to concentrate on other areas.

I wish your problem could be solved as easily as with a manifold swap too. You can always borrow one from somebody & give it a try, but I wouldn't go out & buy one until after I tested the theory with a borrowed manifold. If we lived closer I'd let you borrow my Holley Strip Dominator. Surely one of the OC guys has a torker you can borrow.

We are talking about 2 "possibly" unrelated issues, so lets make that clear, (1) your motor is not producing the power that we expect from it (2) your motors torque curve drops like a brick above 5650 rpm. Your peak torque, at 4000 rpm, is not what I would expect, which is why I say the issues "may" be unrelated.

Regarding issue #1, ring seal is very important, if they don't seal properly, then you'll never achieve the bhp numbers you are expecting. On the other hand, Russ is quite capable of building a good short block, so I would lean towards ruling that issue out. If fixing problem #2 doesn't resolve problem #1, a leak down test may be called for. I can also guarantee you that your heads need some porting to achieve the numbers you and I both expect for your motor. The exhaust port demands most, but not all, of the attention. The roof of the exhaust ports has a bump that needs removal, and a flat surface that requires blending out to the exhaust flange. The whole exhaust port (sides, floor) also needs to be blended and "straightened out" dimensionally. I would also like to see at least 2 1/2" tubing between the collectors and the mufflers. I have no experience with the mind train exhaust system, if it will support more than 400 bhp or not. I like the Magne Flo muffler, like those sold by PI Motorsports, better than the dual glass pack systems I've seen. But liking something, and having actual dyno experience with it, are 2 completely different things.

Regarding issue #2, while a single plane intake WILL make bigger bhp numbers for you, I don't expect the Performer intake manifold to affect the motor the way you desribe, i.e. the drastic drop in torque above 5600 rpm. It will roll the curve off, but not that drastically. Thats more of a symptom I would expect from a fuel problem, an ignition problem, or a camshaft design issue. I'm just not familiar with the Comp retro-fit roller cam, so I am unable to say if that's normal for that cam or not. Dennis A's engine has the next size bigger Comp Cam and pulls to the mid 6000 range just fine. He's running C302 heads of course.

I've had engines exhibit similar charactersitics before, once it turned out to be a lifter had partially come apart, the push rod was still in place, it wasn't making any noise, but the guts of the lifter were laying in the lifter valley, that lifter wasn't opening it's valve! That one busted my balls for several days. More common was the old Holley running too rich syndrome. A rich carb will make the motor drop off like that. I've seen a 351C that wouldn't rev beyond 4800 rpm for that reason. But I wouldn't expect that from your "tuner" carb.

I would also not discount the older ignition coil, performance of coils does taper off with age & use, and aftermarket parts quite often do not have the longevity of oem parts. The MSD box could have a defect also. Ohming the spark plug wires would also be a good idea, especially the wire between the coil & distributor. You may want to monitor the voltage supply to the coil or ignition box while its being run on the dyno, the Pantera electrical system may simply just be dropping the voltage to the coil or MSD box as the current draw increases. A method to diagnose that issue is to install a direct jumper between the battery & ignition using a heavy gage (12 gage) length of wire with alligator clips on both ends. Ignition issues are also something that can be easily diagnosed on a dyno with an engine analyzer.

One test you can run is to rev the motor in the driveway & determine if the motor hits a brick wall under those conditions (unloaded) or only on the dyno.

It's getting late Art, I'm running out of steam. I hope I've given you some ideas. Perhaps some of the other guys have ideas.

Your friend on the DTBB