Muscle Car Tech Tips - What's Your Problem?

This is a common problem with many small- and big-block engines. Especially when you get into aftermarket cylinder heads, some manufacturers are moving the position of the intake and exhaust valves in order to improve flow. When this happens, the position of the valve in relation to the rocker stud has now changed. This means that when you bolt on a typical guideplate, it may not position the rocker arm directly over the valve as it should. Until recently, small-block Chevy engine builders were forced to cut the guideplate down the center to allow independent positioning of both rockers and then weld the plate back together. Isky has come up with an adjustable small-block Chevy guideplate that has overlapping slots to allow lateral positioning of the pushrods. Then you just lock the plates down with the rocker studs (PN 200-AGP for 51/416-inch pushrods, 300-AGP for 31/48-inch pushrods; both are $55.99 at Summit Racing). The plates can also be welded for a more permanent solution. We've had to deal with this misalignment situation as well on small-block Fords and big-block Chevys. Dart recently introduced an adjustable guideplate for the Rat motor that is incredibly simple and effective. A small nut and bolt can be loosened, and then the spacing can be adjusted to line up the rockers with the valves. Dart sells this under PN 27001230-4 for a set of four for $33.69 from Summit Racing. The only thing we've noticed is that these adjustable guideplates occasionally hit the cylinder head on some aftermarket heads, which might require some grinding on the head to make them fit, but it's still a great idea.

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As for your question concerning valvesprings, the camshaft you refer to is a GM hydraulic roller cam used in HT383 crate engines with iron Vortec heads and a 1.250-inch-outside-diameter valvespring. The cam makes great torque and will extend the rpm a little bit for a 350ci engine. If you wanted to stick with a GM spring, the PN 10134358 spring is rated at 110 pounds of load at a 1.70-inch installed height, which would generate roughly 260 pounds of force at max intake lift, slightly more on the exhaust. This is more than enough spring to control that cam. You can buy the spring at any GM dealership, but we priced it through Scoggin-Dickey at $3.75 each or $60 for a set of 16. Just make sure you have plenty of retainer-to-seal clearance, but there should be enough room because of the limited lift. One thing to consider when adding stiffer springs to older iron heads is that the additional spring load may just begin pulling the studs out of the heads. Most production iron heads use press-in studs that pull out rather easily with stiffer springs. The best solution is to machine the heads for screw-in studs and guideplates. But be careful. By the time you've added quality screw-in studs and guideplates, rebuilt the guides, and added new springs, you've got almost as much invested in these old iron heads as a new set of aluminum heads would cost. So we recommend doing your homework first and then deciding.