Vette Rookie

Finally getting around to putting the motor together for my 73 rebuild. Can anyone give me a little information on which bolt pattern to look for in a flex plate? Basically is there a preference between the 10.75 and 11.5 inch torque converter bolt patterns. The motor is a 427 and trans will either be a TH400 or 700R4. Will this change anything?

TimAT

You can get a flexplate that is "double drilled" meaning it will fit the 350/400 convertor bolt pattern or the metric 200/700R4. Other than that, the 427 is internally balanced, so the new flexplate will not have an additional weight on it and be neutral balanced.

Vette Rookie

So the different sizes relate to the transmission size 350 or 400?

TimAT

Sort of. Chevrolet used 2 different diameter 'wheels depending on application. 153 or 168 teeth. (counting the teeth on the flywheel/flexplate ring gear.

Read this- it may shed some more light for you. This was written thinking of the SBC, and you have a BB 427. Pretty much the same except for application.
http://www.speedwaymotors.com/small-...-flexplate.dlp

Vette Rookie

Thanks, that did help, now all I have to do is decide which starter bolt pattern is better, and the diameter of the torque converter will be.