Corvette Engine Build - The Power Principal, Part 2

We continue with our Econo 383 build

Chris Petris Dec 7, 2009 0 Comment(s)
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On the first installment of our 383 engine build, we covered the rotating assembly. Now we'll put the finishing touches on the engine assembly so we can install it. we wrapped up Part 1 by handling the clearance issues with the cam and rods. Now the cam timing should be checked. We're concerned with maximum power potential, and cam timing is critical.

Most things in life are a balance-when you make a performance gain you lose somewhere else. Cam timing is no different. Retarding the cam typically makes more power at high-rpm and makes the idle choppy. Advancing the cam allows better low-rpm throttle response and hurts horsepower at the big end. This is where our Virtual Engine dyno software came in handy. We could advance or retard the camshaft to see power gains and losses. Be careful to look over the entire rpm band, watching for the changes in horsepower and torque when cam timing is adjusted.

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We lubed our Comp Cams retro-fit hydraulic roller lifters with our Royal Purple assembly lube before installing them into the lifter bores. We didn't soak the lifters before installing them per Comp Cams recommendations. In the old days, you had to soak the lifters in oil overnight to let them fill up but no more. We plan on priming the oil system before installing the distributor to ensure complete system oiling before start-up.

To start, you need to be sure the cam timing is correct according to the camshaft manufacturer, then make changes if desired. There are many informative web sites that discuss cam timing. Take the time to read the theory and then put it into practice. Today's cam manufacturers have precise equipment that is rarely incorrect, but a slight indexing error will make cam timing off. It could be multiple things, including crankshaft index, cam gear, crank gear, or even timing chain variations, causing cam timing errors.

There are also other factors to consider. For instance, in our engine build, the Keisler-supplied, Tremec five-speed with 3:27:1 First gear, along with 10.4 compression, and the 3:73 rear axle ratio allows us to benefit from some cam retard to help top-end power. If we had an automatic transmission with a 1,400-rpm stall speed torque converter and 2:59 rear gear, advancing the cam would be in order to give some off-the-line zip. To ensure our cam would stay in perfect timing for many hours of engine operation, we used a Comp Cams High-Tech Roller Race timing set; Comp Cams pushrods and rocker arms actuate the valves with precision at high rpm.

Now the timing chain cover is on we could cover up the bottom end, but we had concerns about oil capacity. There aren't many alternatives when it comes to extra-capacity oil pans, especially in the '84-'86 Corvette cast-iron cylinder head engines. These early C4 engines have the two-piece crankshaft rear main seal, leaving these engines in an oil-pan quagmire that no one wanted to deal with. That is until Canton Racing Products stepped up and custom-built a Road Race oil pan with adequate ground clearance. The Canton oil pan has an 8-quart oil capacity and a built-in windage tray with the same 7-inch depth as the original GM pan. Canton now offers the oil pan in one- and two-piece rear seal versions with the dipstick on the right or left side. For those of you that have the later '91-'96 L-98 and LT engines, you can also use their pan since they provided a provision for the oil level sensor. The original clunky Delco starter can also be used.

Moving on to the valvetrain-smallblock cylinder head design has become huge over the last few years. We all know that combustion engines are air compressors. Efficient air flow equates to power gains. Edelbrock Performer RPM aluminum cylinder heads (PN 60999) completely assembled had been purchased previously for this project, so all we had to do was clean them for installation. The Edelbrock cylinder heads have 64cc combustion chambers with 2.02-intake and 1.60-exhaust valves, allowing .575 valve lift, so an aggressive lift camshaft can be used. GM D-port heads will coil bind at .495 valve lift in most cases when using stock components. Always check for valvespring coil bind and piston-to-valve interference, no matter what the numbers say.




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