A few months ago in your column a gentleman wrote in about his El Camino (I think it was) with a 1970s 454 2-bolt truck block and 1960s closed chamber heads. A few years ago I purchased a ‘66 Impala that I believe also has a ’70s 454 truck block (T1115TRH, 3999289) with late ’60s closed chamber heads (3917215, E27, GM4T). I’m curious, since his setup seems to be similar to mine, is this combination a common “old school” attempt to improve performance on the ’70s 454 smog engines prior to all the new performance stuff out there now? My engine has flat top pistons, a modest Comp cam upgrade with stock hydraulic lifters and rockers, a 750 Holley carburetor, and an aluminum Edelbrock Performer 2.0 intake. I’m running stock exhaust manifolds and 2.5-inch Flowmaster mufflers. Can you please hazard a guess at what kind of HP and torque this setup makes?
You have your info slightly off regarding the previous column’s particulars, but I’ll address your question as it stands. Sure, putting on better stock heads was, and still is, a good way to wake up a choked down piece. Your block is a ’72-78 454 2-bolt casting that came in both cars and trucks. The heads are an oval port, closed chamber that came on a ‘67-69 396 or 427 of varying hp ratings. With the upgrades that you’ve installed, I will make an educated guess that your motor makes around 350hp and 400 lb-ft of torque. I do know this much for certain, you don’t have any problems doing nice, long smokey burnouts, lol.
What’s The Diff?
I own two Chevy Caprices, a ’94 and a ’95, both with the police package and an LT1 engine. I’d like to know what the difference is between my rides and a ’94-’96 Impala SS. I’d also like to know what type of upgrades you would suggest for 300-400 horsepower for street/strip. And lastly, what is the difference between a limited slip and Posi?
I’m no expert on Caprice police packages, otherwise known as the 9C1 option, but I can do research with the best of them, and sometimes I even come up with the right answers. I wound up on a forum dedicated to the car, and a moderator there spoke to this exact topic. There are a number of outward aesthetic differences, like moldings, trim, badges, etc.; the Impala SS has a different grille, while the 9C1 has a unique front spoiler. Mechanically, the 9C1 has more body mounts than the Impala SS and different windshield wipers, while the Impala SS has a unique width rear end different from the 9C1s and normal Caprices. The SS also sits lower and has bigger tires and wheels.
As for horsepower upgrades, the LT1 in your cop mobile was rated at 260hp, and you can probably approach the 300hp mark with the typical bolt-on type upgrades, ie: CAI, headers, exhaust, underdrive pulley, thermostat/fan control, etc. If you want to make the hurdle above 300, I’d advise a camshaft and associated valvetrain upgrade. If you want to keep reaching for the stars, you’re looking at a cylinder head upgrade, more rpm, and most likely a bottom end rebuild to go with it. Edelbrock and Trick Flow Specialties have top-end kits for your exact combination that will net you major horsepower improvements—like put you in the 430 horsepower range with one phone call.
And the difference between limited slip and Posi? Nothing really, it’s just vernacular. Positraction is simply Chevrolet’s brand name for its version of a limited slip rear.
What Wheels Fit?
I have a 1968 Camaro with 2-inch lowering coil springs in the front, stock control arms, and stock multi-leaf springs in the back with air shocks. I have been thinking about installing the Hotchkis TVS 2-inch front, 1.5-inch rear drop Stage 1 kit. My question is, what size tire and wheel do you think I can use in the 17- to 18-inch range, including back space? I have a stock style Flowmaster exhaust. Can I fit 8-inch rims in front and 9- inch rims in the back? Thank you for any help you can give. I have read your magazine for years.
Simple enough question when you have a tire and wheel guy like I do. A quick discussion with Don Raiser at TCT in Buffalo, New York, netted the info you need to go with the Hotchkis lowering kit on your ’68 Camaro. The recommendation is 7- and 8-inches, not 8 and 9. Upfront, go with a 215/40x17 tire on a 17x7 wheel (4-inch back space). On the rear, go with a 255/50x17 tire on a 17x8, 4.50-inch back space wheel. This selection will give the car a pretty mean stance, and you shouldn’t have any problem regarding the exhaust.
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