Years ago, I put a 4-speed on a re-built 302. I had not used this block before. I had terrible clutch chatter. When coasting, it would pop out of 3rd gear. I think I changed the clutch twice in 6 months.

I then slid the tranny back and put a dial indicator on the pressure plate so it would indicate on the bellhousing bore. Turning the crank with a wrench, I found that the bore was .020 or .030 out of alignment with the crankshaft. The bellhousing bore was higher then the crank centerline. Since I had used this bellhousing before with no problems; I realized the dowel pins in the block were not in the correct location.

I found out that you can buy dowel pins with different amounts of offset. I got what I thought would be the correct amount of offset. Put them in the block and installed the bellhousing and dial indicator. The dowels have a screwdriver slot so you can turn them. I rotated the crank and kept adjusting the dowels until the dial indicator read 0 as the crank made a complete rotation.

You should also make a check with the indicator on the bellhousing surface that the tranny bolts up to. Shims between the engine and bellhousing can correct any error here. Fixing the bore alignment totally cured the chatter problem. I also found out that the chatter caused the thrust bearing to wear, had to replace it. Whenever I put in a new engine/bellhousing combo, I always check the alignment. Much easier to check out of the truck.