I recently picked up a car with a 360 in it. I have never had a 360 motor before and do know they are externally balanced. Question is are the flex plates different between 360 and 340 motors? I know the converters are weighted for the 360. I have a stack of flex plates here and know there is the small hole for 1/4" torq converter bolts and 3/8" hole for some other converter bolts.

The reason I am asking is the car had an issue where 3 bolts backed out of converter where they bolt to the flex plate and was making one hell of a noise. Of course there were several issues I discovered, like bolts too long so someone used washers to take up space, no lock tight, and 1/4" bolts used on a 3/8" hole flex plate. The guy I got the car from showed me his receipt where he just had a new tranny put in and was not a cheap job. Needless to say some real shade tree mechanics was going on.

I want to put it back together correctly and want to use the correct flex plate, so is there any difference?

Thanks

Either the flex plate or the converter need to be offset balanced for a 360. B&M and others offer flex plates that are balanced or neutral balanced and drilled for both 5/16 and 3/8 bolts.

http://www.manciniracing.com/search-resu...p;Submit=Search

there is no difference in the flexplate , they are all neutral balanced , the external weighting is on the converter.

Your holes sizing is off , 5/16 or 7/16 I don't recall ever seeing a 6 bolt factory flexplate with 7/16 (hemi) size holes ... but I haven't seen every plate made for production line cars ... maybe a Direct Connection/MP flexplate has a 6 bolt crank flange and 7/16 holes ??

Sounds like whoever put the trans in didn't know the converter has an offset in the pattern.

All 426 M.W. motors and maybe the 413 M.W motors had them with stock 11 inch converters, maybe some other later ones had them OEM like the 1969 440 A and B body M code motors, maybe not