DIY TH350 Governor Calibration

[SkinnyG]

Lots of talk of doing this online. VERY few pictures. Here's what I did to my '77 Silverado....

I finally bought the MSD Tach adapter (8920) to make my tach work with an MSD box, and discovered WOT shifts were occurring at about 3800rpm. I knew it was shifting early, but wow. The cam should be good to 6000rpm (231°@050", 0.470", 108°LSA, 104°ICL, 10.9:1). Gotta change the governor weights.

Governor came out, and I bought a small box of 6d nails. These nails were just a tick too big in diameter, so I drilled the holes #40 so the nails would fit dandy. This is just a baby fart larger. Wonderful manufacturer's tolerances.


OEM Weights are 0.062" thick.


I removed the governor weights and marked them 1/2" from the end, and 1/16" off each side. Ron Sessions' TH350 book says grind no more than 1/2" down, and 3/16" in. I figured I'd do this in stages - it's harder to put metal back.


Then ground them down, and de-burred.

I didn't even install them yet. I decided to get more aggressive.


This is now 5/8" off the end, and 3/16" off the sides.

This brought the shift point to about 4800rpm. More grinding is in order.

I did not change any springs - most folks online have had the best success using the original springs.