You're probably on the right track in questioning the valvesprings, based on the information you provided. If your cylinder-head guy is sharp, he would have checked the spring pressures at the installed height, which would have revealed the lower pressure that could have been caused by the longer valve-stems. However, if this guy is a production shop employee rather than a performance shop technician, chances are also good that his idea of acceptable seat pressures are not sufficient for your application. That's a pretty healthy cam, and the fact that it's a solid-lifter setup just contributes to the extra load placed on the valvesprings at high rpm. If your head guy set up those springs for 100 pounds on the seat, which wouldn't be unheard of for a regular production valve job on a small-block, you'd almost certainly be experiencing valve float at high rpm. There is another factor to consider, though: The "Z28" valvesprings you refer to are common machine-shop items, and are only marginally better than standard replacements. For a typical engine, they make a nice upgrade from stock, but for a high-winding small-block with a lumpy solid cam, they're really inadequate. The tech guys at Lunati agree, and recommend upgraded springs to accompany that cam. Check the valvesprings for seat pressure and pressure at maximum lift-in your case, 0.500-inch. You should see 125-140 pounds on the seat and somewhere over 300 pounds (but not more than 400) at max lift. The Lunati guys feel this should allow you to rev well into the 6,000-rpm range with no problem.
Crossmember SolutionsI have a '79 Chevy Malibu with a 305. I put headers on my engine and want to put dual exhaust on as well. The problem is the transmission crossmember-it's designed only for single exhaust. Is there a double-hump crossmember I can use that will accommodate true dual exhaust, or do I just have to modify the stock one? If modification is the answer, do I need to be concerned about weakening the crossmember?Ken SpearAlbuquerque, NM
You could modify the existing crossmember to clear duals, and there are several ways to do it. The crudest we've seen entails heating the side that needs clearancing with a torch and bashing it with a hammer, which will still require the pipe bender to dip the pipe underneath the crossmember on that side.
A more enlightened approach involves "notching" the crossmember by cutting out a section for clearance and then welding in another piece to reinforce the area. Of course, if you're handy with a welder, you could probably fabricate a completely new crossmember with the proper exhaust humps. However, when we faced the same challenge with our '78 Malibu project, we simply obtained a new crossmember from G-Force Performance.
The G-Force piece is far stronger than the stocker, yet maintains excellent ground clearance and features exhaust humps that are nice and large to accommodate variations in pipe routing. The price at the time (about a year ago) was $189, and was well worth it, since anything we would have fabricated wouldn't have been as nice, and attempts to modify the original would surely have resulted in a mangled mess.
Light 'Em UpCould you explain how a Line-Loc works? I know it locks the front wheels, but that's about it. How do you install one, and is it worth the time? If I did install one on my car, would I still be able to use the stock brakes to stop?Gavin ThorpeEugene, OR