Here it is, the September 2006 issue of GMHTP, and our project 2001 Trans Am is eager to have an engine back under its hood--this time with 383 cubic inches of brawn. Having run the gamut of parts selection, block machining and cleaning, preassembly checks and part fitment, and finally the actual bolting-in of our Lunati rotating assembly in Part 1 of this series ("My First Stroker," August 2006), we probably fried a lot of readers' brains with information overload. Completing the short-block was a very time- intensive process, with lots of test fitting and dimension checking; fortunately, the hard stuff is basically over.
Hopefully, eager-to-learn do-it-yourselfers have had enough time to think over and digest all 18 pages of our last issue and are ready for more. If you're up to the challenge, follow along as we continue the assembly--bringing us ever closer to firing and testing our garage-built Gen III.
Like nearly all small-block GM engines produced in the last half century, the LS1 continues the tradition of a cam-in-block, pushrod-actuated valvetrain. While viewed by many techno-freaks as "old school" and dated, this setup yields dividends of increased durability, decreased engine mass, and lower center of gravity over an overhead-cam style engine. It also allows for a lower hoodline and therefore increased aerodynamic efficiency of the vehicle. Arguments of pros and cons of the design aside, what we're really interested in here is how to put such a valvetrain together, and we begin with the heart of it: the camshaft. In the interest of not inadvertently skipping any steps, we're going to continue to follow our GM service manual as closely as possible. Our machine shop had installed new cam bearings for us, and you should insist the same be done for your block. Just prior to installation, clean the cam using mineral spirits and coat all the cam bearings in the block (those you can reach anyway) with SAE 30 oil. Unlike earlier in the install, where too much oil could be a bad thing on some of the smaller engine parts (piston rings, for example), there's no harm in using large amounts of oil from here on out. So as we continue with the build, feel free to lube away!
Degreeing the Cam
We've just gone through what's known as installing the cam "straight up," with the crank keyway in the "0" position and the marking on the camshaft sprocket aligned with the "0" on the crank sprocket. Normally, cam manufacturers design their cams to be installed just this way, and it should yield the proper timing of valve opening and closing events with respect to the position of the piston in the cylinder. However, if you're a professional engine builder with a custom application for a specific cam, you may wish to second-guess the cam designers' choices and have valve events occur sooner, or in the alternative, delay them. By "advancing" or "retarding" the cam in this manner, one can alter characteristics of the engine's powerband. As mentioned earlier, SLP's timing chain makes this adjustment easy.
This author is not a professional engine builder, however, and wants to stick with Lunati's recommendations as to valve events. And theoretically, we've already done that. Nonetheless, it's common practice to degree the cam; that is, double-check that the timing of all valve events with respect to crank (and hence, piston) position match up to the specs provided on the cam manufacturer's cam card. This verifies that all parts have been manufactured correctly (highly unlikely with quality components from Lunati and SLP), but more significantly, the degreeing process ensures that the installers haven't made any errors of their own. This is a far more likely scenario--though we'd like to think not that likely!
We'll need some special tools to degree the cam, but in the interest of showing you how to avoid spending money on duplicate tools, don't be shocked when you see some tools we used earlier in the build in addition to a few new ones.
OILING SYSTEM INSTALLATION & MODIFICATION
The LS1's oiling system is fairly decent from the factory, although the stock oil pump can benefit from some improvement in capacity. To that end, we'll be swapping to a high-volume unit from SLP. Beyond this, minor modifications will be required to adapt the stock oil pickup tube and crankshaft oil deflector to our stroker crank and new pump.
ENGINE COVERS AND OIL PAN INSTALLATION
Older versions of the small-block Chevrolet (many still refer to the Gen III as a Chevy as a nod toward its ancestry, though it has very little in common with the original) had thin, stamped-steel engine covers and oil pan. But with the deep-skirt design of the Gen III, these items are stressed, machined-aluminum members that add to block rigidity. The oil pan also doubles as a mounting point for the clutch housing, so precise alignment of all components is critical for sealing as well as structure of nearly the entire driveline. The steps of installing these covers, while somewhat involved, are quite manageable if you get ahold of the right tools.
Front and Rear Cover
Before installing the front and rear engine covers, the crankshaft oil seals need to be replaced. Though GM designed these seals to last at least twice as long as those of previous generation small-blocks, there's no sense in reusing the stockers--particularly when you've already put thousands of miles on them. They're a press-in design, and as such a bit of care and some specialized tools are required. Their PTFE-coated sealing lips mean the areas of these seals that ride on the crankshaft should not be oiled; GM found that on past engines, oil breakdown would cause the crankshaft seals to become caked with degraded oil and additives over time, destroying the ability of the seals to maintain proper contact with the crank surface. The switch to PTFE coating means no more reliance on oil for lubrication and the elimination of this problem.