a friend of mine said that he has a 9.5 inch stall converter and i was wondering what flexplate that would bolt up to? i was looking online and all i could find were ones with 10.5,10.75, and 11.5 bolt pattern. i know that the bolts hang out father then the size of the converter but would that bolt up to either of those flexplates? thanks, Ty.

 

All converters "stall". The 9-1/2" converter will probably have a stall speed much higher than what your engine wants.

The majority of all the GM converters use the same 3 bolt pattern on the flexplate. The smaller than stock converters use the tabs off the housing to bolt to the flexplate. Instead of bolts going into threaded holes in the converter, the converter is bolted to the flexplate with 7/16" grade 8 bolts with stover or nylock nuts. Don't use grade 5 bolts and don't use lock washers with plain nuts. I don't even like recommending nylock nuts.

A TH400 specific converter has a slightly different bolt pattern but aftermarket flex plates will have a dual bolt pattern to accept all GM converters. Many truck converters use a 6 bolt pattern.

The stall speed of the converter depends mostly on your camshaft. Knowing the total duration (advertised) of the camshaft is easy to determine the best stall speed.