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Tech Questions Answered in CC's What's Your Problem?

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The Comp Cams camshaft you bought has the old-style mount, which is why the Cloyes gear you mentioned won't work-it's designed for the later-model roller cam with the stepped snout and smaller bolt pattern. All you have to do is convert to an early style timing-chain setup. You mentioned that the gear you tried hits the block. This happens from time to time and may occur because you're using an aftermarket dual-roller timing set that is slightly wider. Often, the cam gear will hit a non-machined portion of the block, such as around the oil galleries where they protrude through the block. All you have to do is trim this area with a die grinder and you're home free. The correct Cloyes timing set for the early style cam is PN C-3023. This will bolt up to the early style camshaft. Be sure to use the matching crank gear in the timing set. Never mix and match cam and crank gears, especially used crank gears with a new chain. The thrust plate is not required with the old-style cam.

As a quick aside, many car crafters may want to go the opposite direction by using a later-style hydraulic-roller cam with its stepped nose in an early non-roller block. The trick there is to trim the bolt holes off the factory roller cam's retainer plate and use it as a spacer to correctly position the late-model-style cam sprocket relative to the crank gear. This is a slick little move that will allow you to run, for example, a GM Performance Parts Hot cam in an earlier non-roller cam block.

Learn to Be FlexibleChris Murphy, Dayton, OH: In your April '05 article about the 383 LT1, you stated that the "combo also required internal balancing because we were running the stock front damper." I was wondering where you found an internal balance flexplate that fits a one-piece rear-main-seal crankshaft, and if it was an SFI-approved unit.

Jeff Smith: We caused some confusion here, Chris, so it's up to us to straighten it out. In the original, '55-'85 two-piece rear-main-seal small-block Chevy cranks, GM internally balanced these engines by placing a small offset weight on the flywheel end of the crankshaft while leaving the harmonic dampener "zero" balanced. This also meant that the flexplate/flywheel on these early engines were also zero balanced.

Starting with the '86-and-later small-block Chevys, which includes the LT1 and LT4 engines, GM switched to a one-piece rear-main seal. This one-piece seal left no room for that "external" balance weight on the crank flange, so GM moved that weight to the outer rim of the flywheel/flexplate. This made these one-piece rear-main-seal flywheels/flexplates externally balanced components even though the damper is still zero balanced. On the LT1 383ci small-block buildup we followed, the Scat crank assembly is officially an internally balanced system just like the factory crank. Where we messed up was referring to the flexplate as an internally balanced flexplate. In reality, it is an externally balanced piece with the stock weight in the OE location. The flexplate used in the buildup was a B&M SFI-spec, 168-tooth, one-piece rear-main-seal unit (PN 20239, $89.99, summitracing .com). We don't know of any SFI-spec, one-piece, zero-balanced flexplates. If necessary, the weights could be removed, but this would require more weight to be added internally to the crankshaft to make up the difference.

You Got Problems?We've Got Answers!CarCraft@primedia.comCarCraft.comCar Craft Mag6420 Wilshire Blvd.Los Angeles, CA 90048

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