June 2011 Chevy High Performance Q&A

Love It When a Plan Comes Together, Part II

Kevin McClelland May 3, 2011 0 Comment(s)
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My son and I built a ’73 Camaro and have a current best time of 12.69 in the quarter-mile. We are running P255R50-16 Mickey Thompson Drag Radials on heavy steel rims. We bought some much lighter alloy rims in 15x8 with a 4.5-inch backspace. I am focusing on 275R50 or 275R60 drag radials. Which will give us the best bang for the buck, the taller 60 series or the wider 50 series? Or do you have a better pick based on the following information?

The car is close to stock weight and has a stage three TH350 transmission with a 3,000-stall converter, 8.5-inch 10-bolt with 3:73:1 Richmond gears, factory Positraction, and West Coast Machine lift bars. The motor is a BP 383 with 405 hp and 440 lb-ft of torque. This is all topped with a 770-cfm Street Avenger, DUI distributor, and COMP Pro Magnum roller rockers. The long-tube 5/8 headers had open cutouts during the best time and isolated cold air intake on the cowl-induction hood.

Since this is not a forged motor, and we want to drive home from the track, we want to limit the revs to fewer than 6,000 rpm. If you can expand on your answer and give us your estimated potential for the car, what you would do next? Also, what’s the best tire selection?

Walter Drysdale Via email

A: Thank you for a very good analogy on the fuel and pollution issue. The SEMA Action Network is a national partnership of car clubs and individual enthusiasts (like you) who work together to impact legislation that affects car and truck hobbyists of all kinds. SAN is a very good way to make a difference. Speaking with Jim McFarland, one of the writers of the SAN article (Dec. ’10), he tells us that more than 6,000 people joined the cause after the story ran. Writing to our elected officials, letting them know that we are not going to stand for them taking our sport and livelihood away, is one of the very strongest tools we have. Check out the latest movement that SEMA is supporting to keep our hobby alive on the website and link to the SEMA Action Network page.

Normally, we’d recommend going with the taller 60-series tire to gain more sidewall in the tire. However, with your 3.73 gears, go for the shorter tire to gain a gearing advantage; we’re going to assume you’re having traction issues with your current combination. The 12.69 e.t. isn’t all bad for a dual-purpose street/drag car. We wish you would have given a few more pieces of information, such as your quarter-mile speed, and we’re going to guess that your 60-foot is in the 1.80 range.

After figuring out what a BP 383 was, we found that this is a crate small-block offered by Summit Racing. It’s dressed with a Professional Products dual-plane similar to the Edelbrock RPM Air-Gap. The engine is topped with iron Vortecs with 2.02/1.60-inch valves installed in them. Our experience is that stock 1.94/1.50-inch valves with the factory valvejob are very hard to beat. Also, Summit doesn’t offer up the camshaft specs for this engine. We guess it’s somewhere in the mid 220-duration range at 0.050-inch lift, based on the power curve of the engine. Our next step would be to install a set of aftermarket aluminum cylinder heads in the 180-190cc range. Also, mill the heads to reduce the combustion chamber size down from 64 cc to raise the compression over the current build of 9.5:1. With a cylinder head and compression change, your power could go from the 405 to the 440 range and the torque up around 460 lb-ft. This would give you several more tenths on the track without changing the manners of the engine.

I hope this helps with a direction for your son’s Camaro. Keep instilling the proper values into your son and his friends. Fewer of us are passing our knowledge down to the young people. Also, please check out the SEMA Action Network and join. It is free and it helps keep our passion alive.

Source: semasan.com, summitracing.com


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