What does the flex plate do for engine perfomance? I need to buy one...

If I understand correctly, it is just the gear that the starter makes connection with and also is what your torque converter is bolted to...

I can buy a stock one at Autozone for around $45 and it looks like one of the cheapest aftermarket ones from the parts catalogs will be at least $120...Why so much difference and why would the aftermarket ones be so much better if they are?

I am going to install it in my CJ C6 behind my 521 stroker with D0OE-R heads if that makesd a difference

Thanks

Odds are, the AutoZone flexplate isn't SFI approved. If you are going faster than 10.00 seconds in the 1/4 mile you need an SFI approved flexplate. At that point you would also need a SFI flexplate shield and a transmission shield as well. If it's only going to be a street car, you're probably fine with the AutoZone piece. If you have aspirations of going into the 9's or quicker, you might want to step up to the SFI approved pieces.

A guy on the 460Ford forum gave me a link to a PRW flex plate for $80 so I'll probably just get that one!

Make sure you get the right one, there is different tooth ratios, and some are internally , and externally balanced.

My engine is a 429 CJ being stroked to a 521 and the tranny is a CJ C6 with R servo...I wasn't sure what tooth count I needed and not sure what the pilot size is for my tranny? Thanks

And make sure the bolt circle (the holes for the torque converter bolts) is the same. Count up the teeth and measure the distance between the two farthest converter bolt holes (bolt circle).

Scat sfi flexplates are like 56 bucks call Lem at BF Evans ford he has both internal and external sfi flexplates and even if its a street car why not go better for only 10 to 15 bucks. And they are stronger (more welds)