November 2012 Chevy High Performance Q&A

Power Tour Leaves

Kevin McClelland Sep 20, 2012 0 Comment(s)
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Fuel-Sipping Elky

Hi! We just got a subscription to your magazine at our office, and it is great! I have a question for you: I have a ’72 El Camino with a 307 engine and a TH350 transmission. I have an early ’90s 350 block (one-piece rear main seal) bored 0.060-inch over with flat-top pistons and a 700-R4 transmission to put in it. I’m not sure what gearing I have in the rearend, but it is a 10-bolt.

My heads are camel-hump 462s that sat unused for 30 years and are in pristine shape. I’ve had hardened seats added on the exhaust for unleaded fuel. The intake is factory, and my planned carb is a Quadrajet with Cliff’s high-performance rebuild kit.

I want to get 300-plus horsepower from this engine with good torque, and achieve in the 20-mpg range for fuel efficiency. This will be my daily driver. I do not have a cam selected yet, or my rocker arms and springs. Can you recommend an appropriate cam to achieve this? If it is not possible with this setup, can you recommend a cam, intake, and carb that would let me achieve this? Would I do better by using Vortec heads? This is my first engine build so any help is much appreciated!

Via email

How many people in your office read one issue of our rag? We need to add your office count to our pass-through readership and figure out how to charge you guys! Just kidding, and glad to be of service. Let’s go over the finer points of your engine build.

Starting with a one-piece rear main seal Gen 1 small-block gives you a ton of options for camshaft selection. The block will accept either a standard flat tappet–type arrangement, or you can slide a hydraulic roller camshaft in, as the block is machined for the anti-rotator plates for the lifters and the block has the bosses for the spring spider that holds them down. To use the hydraulic roller you’ll need to scrounge up a set of lifters and hardware from the lifter valley. Good news is there are a ton of Gen 1 small-blocks in the wrecking yards that are just waiting to be snatched up.

If you decide to go with the roller selection, we’d recommend a very short camshaft to build tons of slow-speed torque with your 700-R4 and its 0.70 overdrive and lockup torque converter. The factory gearing in your ’72 El Camino is probably 3.08. With a standard 25-inch-tall tire, these gears and trans, cruising down the freeway at 65 mph, your engine will be loafing along at 1,900 rpm! Give the HT383 camshaft from Chevrolet Performance (PN 14097395) a look. It specs out at 196/206 duration at 0.050-inch tappet lift, 0.435/0.460-inch max lift, and is ground on a tight 109 separation angle. All of this will add up to great slow-speed torque and fuel economy. If you don’t want to dig around the wrecking yards for the lifters and hardware, they are offered by Chevrolet Performance as a kit (PN 12371042). Finally, you will need a camshaft retainer (PN 10168501) to set the camshaft endplay. Go on Chevrolet Performance’s website for more information and a dealer near you.


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