I just got a LT4 timing set and have heard that getting the larger crank sprocket to help with less slack in the chain. My question is won't that change your valve timing? Won't it spin the cam faster than before and possible cause some issues with piston to valve timing/clearance? Do you just fix it by degreeing the cam to compensate? It's just a thought I had and didn't see anything when I did a search.

Thanks
Anthony

 

With a chain or toothed belt, the speed ratio is exactly proportional to the numbers of teeth on the sprockets. For a given chain pitch and tooth count, there is an ideal diameter (called the pitch diameter) that gives the correct center-to-center distance of the sprockets.

Now, you can "cheat" that pitch dia. a little bigger to tighten up the chain for a decked block. .010 larger diameter would be equivalent to tightening or shortening the chain approx. .011. The pitch will still be the same because the number of teeth is the same.

Any cam drive has a tight side and a loose side of the chain. The tight side drives, and as the chain stretches or wears the timing retards. With a 5-1/4 in. pitch diameter on the cam sprocket, each degree is about .046. IOW, the chain would have to stretch (or center to center distance would have to change) about that much to retard the cam 1 degree.

Perhaps one could use chain or belt inertia or dynamic stretching to effectively change the length of the chain or belt with high rpm. Dynamically retarding a few degrees might help high rpm power without changing low rpm power.

Hey, it ain't VVT, but it could be used I suppose. It would be pretty simple to check that on a Spintron.

 

Actually by definition that would be variable cam timing!

 

That would be illegal in organizations like NASCAR or NHRA wouldn't it?

 

NASCAR??? Who the hell cares!