351w flexplate with C4

I am planning to do an engine swap on my 1969 Cougar and would like to know if anyone has a 351w with a C4 with a 28oz 157 tooth flexplate. I know most 351w’s came with the 164 tooth, but the bellhousing I have is for the 157 tooth. It seems since they are both 28oz, they should be interchangeable, assuming the correct bellhousing is used. Is that correct?

Correct. The bellhousing determines the tooth count, and generally the starter depth as well (though the separator plate matters here too).

If you are running a C4, it’s most likely going to be 157 tooth, and of course for your engine, you need the 28 oz external balance.

For FMX or AOD, you’d run the larger diameter 164 tooth flexplate. The number of teeth really has little to do with the engine itself, and everything to do with the transmission/bellhousing. All Windsors have the same transmission pattern, except for the early 5 bolt.

Believe it or not, Ford made some weirdo C4 transmissions with more or less teeth, just to mess with everyone. In the early Mustangs, I think they used 160 teeth for example, but the diameter and starter are exactly the same as the later 157 tooth flexplates. Interchangeable. Some later C4s with Pintos and Mustang IIs also used less teeth, just to make things difficult.

But for the average 60s Windsor with a C4, you want 157 teeth, and match the balance to suit your crank. =)

Thanks Grim - that is what I was hoping to hear. So I can use my 289 157 (actually 160)tooth flexplate 28oz and all should be fine.

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You will also need the starter / engine spacer plate to go with that 157 tooth flexplate.

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I’ve done this swap several times with the 351W going into a 67 or 68 that previously had a 289 or 302 with C4. I did nothing to modify anything on the transmission or torque converter. Just bolted it together and it worked perfectly. Used the flex plate from the 289 or 302.

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Thanks for all your replies - I always appreciate the help I get on this forum!