When replacing head gaskets in the L98 aluminum-headed engines and the ZZ small-block family of crate engines, you must be very careful. The Fel-Pro head gasket has a diameter of 4.166 inches. This large diameter gets very close to the water jacket feed on the spark plug side of the cylinder head deck. With this gasket, you have less than 0.050 inch of sealing surface! It's very easy to knock the gasket out in this area. This is why we recommend sticking to factory head gaskets that have a diameter of 4.100 inches. The production gaskets are 0.052 inch thick for the aluminum heads, and 0.026 inch thick for the iron heads. I use the 0.026-inch-thick gasket exclusively for my performance street buildups. Most of the GM short-blocks have the pistons somewhere around 0.020 down in the hole. The iron gasket at least gets you in the ballpark for a decent quench. Pick up a set of the iron gaskets under PN 10105117.
The L98 TPI engines have been pushed to the side by both the LT and LS engine families. The long-runner TPI system will pull your truck around quite nicely. Good luck with your swap and enjoy the great gas mileage.
Source: gmperformanceparts.com
Take The Boat
Q I have a '69 SS Chevelle with a '70-model 408. It has closed-chamber heads with recommended valvesprings and about 9:1 compression. Now my problem: I have put two Xtreme Energy flat tappet cams in that went flat. Then I went with a 270 Magnum cam, which also went flat. The last cam was installed by a professional mechanic, the engine was pulled and all the metal cleaned out. This cam lasted less than 500 miles. Now I am going with a hydraulic roller. It has a performer intake and a Q-jet carb. I would like to get about 400-425 hp. I don't mind changing intake and carb. I have also bought a TH700-R4 core. What are your thoughts on this trans with a Corvette converter to put in place of the TH400? The rearend is a 3.31:1 posi. Any help in cam selection and trans selection would be appreciated. Also, I may have the opportunity to buy a rebuildable marine 454ci long-block for $1,000. Would this be a better alternative to the 408? This car is driven on weekends, weather permitting, with some freeway trips.
J. WhiteBenton, AR
A OK, where did all the boat parts come from? If you can scoop them up, go for it. The marine components take way more of a beating than standard passenger-car or truck parts do. They are tested to a much higher durability level than the production stuff. The 454 marine short-block should have four-bolt mains, a forged steel crankshaft, and possibly forged pistons, based on the power level of the original engine. Another added benefit would be the almost 50hp/ci bump.
Sorry about the camshaft pain. You can thank all the new emissions regulations that have taken the zinc and phosphorus out of our engine oil. The sliding contact of a flat tappet lifter to the lobe is the highest sheer contact in the whole engine. Without these additives in the oil, the lifters and camshaft really don't have much of a chance. Comp and all the other camshaft manufacturers offer oil additives to fortify the current engine oils, but they still come up a little short. Some of my dyno buddies have told me about Joe Gibbs racing engine oil, with two products that really help out with our flat tappet dilemma. First is a petroleum-based break-in oil, which isn't under the DOT regulations that kill our oil. Next is a synthetic engine oil specially blended for older engines, sold as Hot Rod engine oil for hot rods, street rods, and classic and vintage cars built before 1997.