October 2011 Chevy High Performance Q & A

Scales are for Fish

Kevin McClelland Sep 1, 2011 0 Comment(s)
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A: Good luck with your schooling, and congrats on a great field. We need more young people in engineering fields.

As for your Vette, you’ve really taken your ’81 to a new level. From your list of components, the 650-cfm carburetor is slightly on the small side. However, this will give you outstanding driveability and will only lose a few ponies right at the top of the rpm range. We’d start with your carburetor and the factory-installed jets. You may need to slightly richen the jets after you get the car running and can determine if it needs more fuel.

The clutch you use to mate your power to the transmission can really affect the car’s personality. If your clutch is too aggressive it can operate like a light switch—either it’s disengaged or it’s locked. This can be very annoying for street driving but just what you need for track days. We’ve had very good luck with a compromise; the Centerforce Dual Friction clutch will give you the best of both organic clutch application and metallic segmented torque-holding capacity. The Dual Friction technology pairs organic lining on the pressure plate side of the friction disc and segmented carbon composite pucks on the flywheel side. This clutch will give you the ultimate in street/strip holding power and performance without sacrificing pedal effort and driver control. We’d go with a 10.4-inch disc clutch, which will allow you to run the smaller and lighter 153-tooth flywheel. The clutch is offered in 10-spline disc (PN DF271675) and 26-spline disc (PN DF161675). The 10-spline is for the earlier Muncies, and the 26-spline should be for the ’71-and-up transmissions. The matching Steel Billet Centerforce flywheel (PN 700100) is a 153-tooth, 30-pound wheel. This clutch will give you years of trouble-free service and will take whatever your 350 will throw at it.

A common theme going through the car community is “save the manuals.” If you go to buy a new car today, it is virtually impossible to find a manual trans in anything except what manufacturers consider a “performance” car. Swapping out your lethargic TH350 trans that was equipped with a torque converter will completely change the manners of your Vette. Great find picking up all the swap parts from that ’73. Your Vette is equipped with a very unique Dana 44 centersection. It is an aluminum case with an aluminum posi carrier, really trick parts for a ’81 passenger car. The factory gears for an automatic trans-equipped, federal-emissions Vette was 2.87:1. If it was equipped with a manual trans or sold with California emission requirements it would have 2.72:1 gearing. Luckily, Dana 44 gears will swap out into this specialized Corvette carrier. Check with Randy’s Ring and Pinion for all your parts needs. Randy’s offers gearing for this differential from 2.73 all the way up to 5.89 gears. We’d go with 3.54-3.73:1 gears based on your 2.52:1 First in your wide-ratio Muncie. This will give you great acceleration without killing the streetability and highway cruising.

No matter how much your projects pull you away from school, finish your degree. You will have that for life. Cars come and go, but your education will be in your toolbox forever!

Sources: centerforce.com, ringpinion.com

Blown Rod

Q: I’m building a 372-inch aluminum block with AFR 195cc aluminum heads, a 6-71 blower (8 pounds boost, 9:1 initial compression), and electronic fuel injection. Do I use straight or angle plugs, or does it matter? I am thinking 75cc chambers to keep compression down. I am having custom headers made; what length primary header tubes should I run and what diameter? Finally, I will be running a built 200-4R to a 9-inch rear with 3.70 gears. What stall converter should I use? This is strictly a street engine, and all this goes into a ’31 (gulp) Ford weighing approximately 2,700 pounds. Thank you for your help—you’re the man!

Rick Carpenter
Via email

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