351 swap, Flexplate question?

1970 302 with c4, iam gearing up to swap in an early 80s 351w, what flex plate do I need? I cant use the the 302plate right? The 351 has a flywheel on it now.

Use the flexplate off the 302. It will work.

All 351 had the 28 oz-in external balance. 302 had that till 82, then went 50 oz-in.

If the 302 is from the 70's or 60's then that is the flexplate to use.
If someone put a newer (after about '82) 302 in it, you will need a new flexplate.

Now since a C4 was never offered in a '70 Bronco you will have to deal with what ever was swapped in in the past. With luck you got a Bronco C4. But there is a chance that it is a car C4 that was converted. The difference? case is a bit different (case fill/pan fill) bellhousing smaller (car usually 157 tooth, truck 164), few other odds and ends inside as well.

Best answer, what you have now works, you need the same thing. If it is bad you need to match the torque converter bolt circle (3 options but only 2 are common) and the number of teeth. As mentioned, balance on a 351 is always the 28 oz-in. Not the 50.

Yeah, what those guys said. Just thought I'd remind you that you need to remove the pilot bushing from the 351!

70_Steve said:

Yeah, what those guys said. Just thought I'd remind you that you need to remove the pilot bushing from the 351!

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Only if the 351 has one (was in front of a stick shift)

Broncobowsher said:

.....Now since a C4 was never offered in a '70 Bronco you will have to deal with what ever was swapped in in the past. With luck you got a Bronco C4. But there is a chance that it is a car C4 that was converted. The difference? case is a bit different (case fill/pan fill) bellhousing smaller (car usually 157 tooth, truck 164), few other odds and ends inside as well....

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Does the pan look difrerent? is there any easily noticible signs that I can ID a car C-4 from Bronco c-4?

I will have to remove the pilot from the 351 Crank.

1970excursion said:

Does the pan look difrerent? is there any easily noticible signs that I can ID a car C-4 from Bronco c-4?

I will have to remove the pilot from the 351 Crank.

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Pics in this thread showing a Bronco C4 next to a non Bronco C4. Hope this helps.

http://classicbroncos.com/forums/showthread.php?t=155209