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Chevy Small Block? Chevy V8 Specs & Options

Tech Q+A

Street and Performance Inc.
Dept. CC
1 Hot Rod Ln.
Mena, AR 71953-1169

Summit Racing Equipment
Dept. CC
P.O. Box 909
Akron, OH 44309-0909
330/630-0270 or 800/230-3030

IROC's Getting Ready to Roll
I need your expert opinion on the motor I'm building for my '86 IROC-Z. I plan to build a 350 bored 0.060-over with a torque plate. It'll have a balanced bottom-end with TRW forged pistons, LT1 rods, Air Flow Research 190cc heads, TPIS ZZ-9 cam, TPIS large-tube intake runners, TPIS baseplate, BBK throttle-body (58mm), and SLP headers (1 3/4 inch). My goal is to run in the 12s. The car weighs 3,350 pounds without a driver, has a 3.27:1-geared 9-bolt, and a 2,800 stall converter. I used forged pistons just in case I use (need) nitrous oxide, but I'm a little hesitant to use it.

Another question I have is, does anybody make ring-and-pinion sets for 9-bolts? I already shredded my 10-bolt with 3.45s, so I lost some launch with the 9-bolt.
Tim Casey
Mesa, AZ

According to TPIS (TPI Specialties), your well-planned combo should make about 430 lb-ft at 3,500 rpm, and 365 hp at about 5,000 rpm. With driver, the car should weigh just over 3,500 pounds. On street tires with a stock suspension, you're looking at 13.20s at around 108 mph. Hook it up and/or turn on the nitrous and you'll be well into the 12s. Invest in a set of 9-inch-wide slicks, and maybe a set of Air Lift's rear air-bags to preload the chassis. Fuel-injected, computerized engines are well-suited to mild nitrous oxide systems because the O2 sensor and the knock-sensor team up to act as a fail-safe.

The low-production Borg-Warner of Australia 9-bolt rearend uses a 7 3/4-inch ring-and-pinion compared to the 7 5/8-inch gears found in the more common GM F-car corporate 10-bolt. That makes the 9-bolt's potential tooth contact area only about 1/16-inch greater (diameter/2) than the 10-bolt. Both rearends' posi cases are weak, but if you need a new case for the 9-bolt, it's a $600 dealer-only item. I only know of one non-stock ring-and-pinion for the rare 9-bolt: U.S. Gear's 3.70:1 (PN 01878370BW). Assuming around a 26-inch-diameter tire is used, you'll turn better e.t.'s with the existing 3.27:1 gear (shift at 5,800 rpm).

AirLift Co.

Dept. CC
P.O. Box 80167
Lansing, MI 48908-0167
800/248-0892 or 517/322-2144

U.S. Gear
Dept. CC
9420 S. Stony Island Ave.
Chicago, IL 60617-3695

Mechanical Response Response
I thought I'd send a brief note on the installation of a mechanical fan on the LT1s (Ask Marlan, Sept. '98). This fan is a good setup; however, it will only work with B- and D-chassis engines. This is due to the longer crank hub on these vehicles compared to the F-bodies, as well as the accessory drives being different. This setup could possibly be used on an F-car accessory drive setup with attention to pulley-to-balancer spacing, and radiator hose and water pump clearances.
Al Hassenboehler Jr.
A C Engineering
Terrytown, LA

Thanks for the additional information. For those readers unfamiliar with the modern LT1 balancer, instead of slipping directly onto the crank like the classic style balancer did, the LT1 balancer bolts to a separate crank hub that in turn presses onto the crank. Because there's no keyway on an LT1 balancer, when removing it you need to make appropriate reference marks so it can be correctly reinstalled.

The B/D (full-size) chassis LT1 crankshaft balancer hub referenced by Mr. Hassenboehler carries GM PN 10168570; the F-car (Camaro/Firebird) accessory drive bracket is PN 10186132.

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