Chevy Car Questions & Answers - Performance Q&A

Kevin McClelland Sep 1, 2009 0 Comment(s)

Quicker on the Cheap!
Q: I've got a '91 Chevy shortbed pickup with a Chevy Fast Burn 385 crate engine with the Hot Cam kit. It is carbureted with a Quadrajet and has a TH700R-4 transmission with a 2,500-stall converter, a 12-bolt rearend out of a 454 SS pickup, and 3.73:1 gears. It also has a B&M Mega shifter. I raced it in a bracket series about seven years ago and it was running mid-13s at 100 mph. I went through the traps at 4,200 rpm and I would like to be around 6,000. I want to get back in racing, but I want to go faster. I've got a TH350 trans with a TCI 3,000-stall that I was thinking about installing. I need advice on what to install that will be cheap-I have a baby on the way. Much appreciated.
Stephen Swartzman
Topeka, KS

A: It may be tough building up your racer with a child on the way, but we've got a few inexpensive tricks up our sleeve to bring the engine closer to its powerband. We'd stick with the TH700R-4 trans for the streetability aspect of the truck. Going to the TH350 would require a lower rearend gearing to get the truck to accelerate in First gear. The TH700R-4 has a 3.06:1 First gear as compared to the TH350's 2.52:1. That half point of gear ratio is huge when you're trying to get a heavy vehicle moving. From the information you've given us, we're assuming that you're running 30-inch rear tires. This works out the 4,200 rpm at 100 mph and 3.73:1 gears. You could purchase a set of 26-inch-tall M/T ET Streets that would dead hook your truck on the starting line. This would also bring the engine speed up to around 5,000 rpm at about 103 mph. This is where we think the speed would come up to with the engine running longer in its powerband. Now, to bring the engine up to 5,500 rpm, you'd need to swap out for 4.11:1 rear gears. This would be a good compromise between keeping the truck on the street and making it more of a race truck. If you made your ratio change with both the gear and the tire diameter, it would give you the ability to swap back to the 30-inch street tires for everyday driving.

If you want to go with the tire swap idea, we'd use a set of Mickey Thompson ET Street tires. These are purpose-built, DOT-legal, bias-ply racing tires. They give you outstanding traction and decent tire life, but we would only run these at the track. If you pick up an extra set of rear wheels that are 10 inches wide and get a set of 26x11.50-15LT tires, these have a section width of 12 inches and a tread width of 9.8 inches. These will fit well in the wheelhouse of your '91 pickup and take all the power that your 385 can throw at them.

Try the tire swap first. This may give you the performance change you're looking for. Keep your spending to a minimum until you know how much it costs for formula and diapers for the new little Chevy fan. Good luck and congrats!
Source: mickeythompsontires.com

I Hear You Coming
Q: I hope you can help me out with this one. I just had a shop install a 350 small-block in my '72 Chevelle and I'm very disappointed with the performance of this engine, which was supposed to see 440 hp at 5,900 rpm and 450 lb-ft at 4,400 rpm. The engine specs out at 10:1 compression, a 230 duration at 0.050-inch tappet lift, single-pattern camshaft with a max lift of 0.512 inch, and it's ground on a 108 separation angle. The cylinder heads are Pro Topline angle-plug with 210cc inlet runners, 2.02/1.60-inch valves, roller rockers, and an Edelbrock RPM Air-Gap with a Barry Grant 650-cfm Speed Demon, lit by an MSD distributor and a 6AL box. The engine is backed up with a TH350 trans and a 3,000-stall converter.

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