M117 adjustable timing gears

[Tony H]

I have been long toying with the idea of adjustable timing gears to correct the extremely retarded smog cam timing in most of the available cams for the M117 engines. Ever wonder why cars got such horrible fuel economy in the 70’s and 80's? A lot of it is the retarded cam timing used as an attempt to reduce emissions before technology caught up. I noticed several SBF-SBC timing sets have multiple keyways in the cam gear so you can set your cam timing by installing the gear in the appropriate keyway. Instead of messing with offset woodruff keys and custom gears why not cut new keyways with the cam timing in the desired position? The stock gears are inexpensive enough to experiment with. Just a thought…

[Frank Reiner]

Good thought on the cam gears Tony, each one could accommodate 4-5 keyways in different steps of advance/retard positioning.
Re: SBC/SBF gears. It seems to me that the timing sets I've seen had multiple keyways in the crank gear, rather than the cam gear. Cam gears have been supplied with provision for an offset bushing at the dowel between gear and camshaft.

[Tony H]

Correct on the crank gear-my bad. Anyway something for me to ponder in the couple years my project is going to be in storage while we move.

[rwd4evr]

I like that idea. The cam gears should be able to be machined for at least a few different Timing settings without removing too much of the bore. What is the gear bore size?