June 2012 Chevy High Performance Q&A

Chain Reactions

Kevin McClelland Apr 23, 2012 0 Comment(s)
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With your collection of components I would target the horsepower in the 600-pony range with open exhaust. Back in the day there weren’t the performance mufflers available to make good power through capped exhaust. This, coupled with your low rear gears and slicks, should have been able to slip into the low 11s at low 120s. If you had a really good run, the car stuck, and you hit every shift point, it may have tickled very high 10s! These cars were a blast to drive and row through the gears.

Things happen to us in our lives that make us do the responsible thing. Unfortunately, you lost your pride and joy. Hopefully sometime in the future you can relive your Nova passion. They are still available and not too expensive yet. Good luck!

P.S. We’ve all dropped something down the carb. Only real men step up to the plate and admit it!

Air Dyno Lives

Thanks for the great tech. I have a 350-bored 0.060 inches with 4340 crank, H-beam rods, Mahle flat-top forged piston, and the block has been decked to 0. The camshaft is a Crane Cams (PN 118911) mechanical roller with a duration at 0.050 inches tappet life of 252/260, 1.6 rocker arm, at 0.020 inches lash the max lift is 0.652 inches. I have a set of Airflow Research 220cc heads, a Victor Junior intake, Performer RPM nitrous plate, a Holley 750, with 1.75 inch Hedman headers. How much horsepower should I be making on the motor? I know I’m down on compression a little bit and these are big heads for a 360ci engine. I have plans for a 388 with 12.6:1 compression. How much horsepower do you think that would make, and how hard would I have to turn each engine for peak horsepower. I run this engine in a truck and it weighs about 3,200 pounds with a TH350 with 4,000-stall converter and 4.88 gears, with Mickey Thompson 31s. I have not run the engine since the new cam and heads were installed.

John Parker
Via email

Boy, I haven’t officially fired up the Air Dyno in quite a while. Most readers I’m sure know what I’m talking about. The Air Dyno is when I pull power numbers out of thin air. I hope that my numbers are closer than the keyboard dyno operators on the Internet! Just ask anyone on a message board. If you don’t like the numbers I give you, I’m sure that there is someone out there who would give you the numbers that would make you happy!

Luckily, the air dyno should be pretty close; I ran a very similar combination before as a dyno mule. It was an original ’71 LT1 block, pistons, crank, and rods. It had the exact same camshaft that you’re running, flat-tops, Dart 220cc heads, Dart single-plane manifold, 4779 Holley 750-cfm carb, and 13/4- inch headers. We ran this engine on pump gas and it pushed out 540 hp all day long. It would make peak horsepower around 7,200 rpm. I didn’t like taking it that high with an all-stock rotating assembly so I would usually limit the high side of the test to 7,000 rpm. Now, on the torque side of things it was quite weak. It only kicked out 440 to 450 lb-ft and this happened at a high 5,600 rpm; the only thing that this engine had going for it is that it would carry the torque and make good horsepower.

For your high- compression 388, I would think that the power is going to be up about 70 hp for the added cubic inches and compression. This should put you in the 610 range. The peak power rpm should drop slightly too around 7,000 rpm and I would expect the torque to come up nicely into the low 520 range. The torque will be helped by the added inches, but the compression will give the engine more personality.


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