Rotating assembly has been internally balanced. I was told I need a "350" flexplate. So I have a few questions... 1. Does tooth count matter? At the moment I haven't decided on a starter. 2. Any advantage to a lightweight flexplate? 3. Converter bolt pattern, Do aftermarket converter manufacturers stick to a certain diameter, if so, what is it? I see theres a 10.75" and a 11.5". Thanks

theres a large and a small converter bolt pattern, stock plates have both sets of holes


th400 tended to be the opposite of the other tranny models

usually



lightweight would technically rev up quicker but not have as much rotational mass to keep the bottom end going for low end torque(bad explanation)

large diameter= staggered starter nose bolt patten

small diameter= straight across nose bolt pattern

1. Yes it matters. Your car came with a 12.8" flex plate (153 teeth). Some exhausts WILL NOT clear the starter for the 14" (168 teeth) version. However, few 400 blocks have the bolt pattern for the starter for the smaller flex plate. I recommend that you get that hole drilled in your block while it's at the machine shop.

2. Not really.... they already weigh basically nothing, like about 10% as much as the thing they're bolted to (the converter)

3. Yes it matters. Those are the 350/PG size, and the 400 size. The 700 uses a metric version or something of the 350 size, the same except on just a slightly smaller circle. As long as the flex plate is equipped with that pattern, at most, you'll have to elongate the bolt holes toward the center of the flex plate. Some flex plates will fit fine as they are.