This is what your completed...
This is what your completed engine could look like. We took the time to make some billet inserts for our valve covers and paint the engine a nice shade of sinister-looking gloss black.
For those just joining the fray, we are knee-deep in the teardown of a GTP and are looking to increase horsepower to 400 at the flywheel by installing a set of Thrasher heads that flow 211 cfm on the intake side, and 182 cfm on the exhaust side, and a bumpy Comp Cams stick featuring .520/.536 lift with 1.6:1 roller rockers, duration of 212/224 at .050 and a lobe separation angle of 116. The Other Guys Performance headers with 1 5/8-inch primary tubes will also be installed and topping it all off will be custom programming to make the most of the new parts.
So read along as we plod through the nuts and bolts of this top-end buildup. In our next installment, we'll tackle dyno tuning and making this engine live in a restrictive OBD2 environment.
| PARTS LIST |
| Component | Part Number |
| Thrasher Engineered Performance ported/polished heads | N/A |
| Comp Cams camshaft "X-P Hot Cam" | 76-000-9 3312S/3314S HR116+2 |
| Comp Cams LS1 valve springs (105 lbs.) | 26915-12 |
| Comp Cams steel LS1 valve spring retainers (12 needed) | 744-1 |
| Comp Cams chromemoly pushrods | 7937-12 |
| The Other Guys L67 FWD headers | 380021 |
| Front cover gasket | GM P/N 12539092 |
| Supercharger gasket | GM P/N 24503911 |
| Balancer to crankshaft bolt | GM P/N 24504736 |
| Cam to sprocket bolt | GM P/N 24501366 |
| Upper head bolts (8 needed) | GM P/N 25533811 |
| Lower head bolts (8 needed) | GM P/N 25527831 |
| Head gasket set | GM P/N 12539091 |
| Rocker arm bolts (12 needed) | GM P/N 24503515 |
| GM Assembly Lubricant | GM P/N 1052367 |
Special thanks to Tim Cole from Comp Cams, Bob Weiland from Motorsports Performance and last but certainly not least, Duane Dodson from The Other Guys Products.
With both cylinder heads and...
With both cylinder heads and associated hardware off, the fun begins, installing the camshaft. First remove the lifter retainers and lifters, checking them for wear and placing them aside in order.
Next, with the cradle supported...
Next, with the cradle supported by a jack on the passenger side, remove the passenger side tire and strut. Then take out the passenger side cradle bolts and loosen the driver's side bolts, and gently lower the cradle on the passenger side. This is a good time to refer to HPP June 2002 for the intricate steps, in "Bent Six Bumpstick Boogie," the cam swap story.
Remove the front engine cover,...
Remove the front engine cover, balancer, timing chain and miscellaneous other components and install the Comp Cams camshaft, per the instructions from Comp. Reverse the procedure to reinstall the front cover and associated parts. Part II of "Bent Six Bumpstick Boogie" in the July 2002 issue will provide all of the particulars for this.
With the cradle bolted securely...
With the cradle bolted securely back in place, now is the perfect time to set your rear The Other Guys header into the exhaust channel in the firewall. This will save you time over trying to put it in with the engine assembled.
Before we go ahead and bolt...
Before we go ahead and bolt down the fresh Thrasher cylinder heads, we need to swap the stock L67 valve springs for our higher seat pressure Comp Cams springs and new retainers. This can be done with a regular valve spring compressor and about 15 minutes time.
Be sure to tap the finished...
Be sure to tap the finished assembly lightly with a non-metallic hammer to make sure the locks are seated.
fter cleaning the block and...
fter cleaning the block and removing all old gasket material, place a new gasket on the block surface. Make note that the arrows point to the North side of the engine (passenger side). You may now mount your new cylinder heads and start all the bolts and tighten them down, just until they barely stop turning.
This step is extremely important....
This step is extremely important. Using new fasteners, per the factory service manual, torque all head bolts to spec. in sequence, also per the manual.
You can now go ahead and install...
You can now go ahead and install your Comp Cams one-piece pushrods.
With all of the major overhaul...
With all of the major overhaul done, start reassembling the engine. Reverse the disassembly procedure and put your car back together, taking care to align your new headers correctly. Torque the rocker bolts to 11 lb.-ft.; rotate them an additional 90.