Hi HAMBers - I recently dropped a 1966 289 rebuild into my 63 Comet, and also pulled the 63 Merc-o-Matic 2-speed tranny for an early 70s C4. I ordered a new flexplate off Jegs for a 1966 Mustang. I assume that a 1966 289/C4 combo is pretty common, but when I went to bolt up the transmission, the new flexplate did not match the torque converter and also wouldn't even fit in the bell housing (about 3/4 of an inch too big). I started wondering if maybe I got the wrong flexplate, since I am guessing C4 bellhousing size didn't get smaller over time, but I'm not sure about that. The real question is: I realized that the original flexplate from the 260/merc-o-matic combo fit perfectly, so I put it in. Is there any reason this is a bad idea? Will I potentially have starter gear compatibility issues? Thanks as always. RNY
A 280 and a C4 was pretty common in the late 60's. I see no reason not to use the old flex plate if it was in good shape.
There are different ones, 157 tooth is 10.5" & 164 tooth is 11.5" then there's 28oz or 50oz. I didn't think the fordomatic flexplate fit the c4 torque converter? The drain plug fit? C4's can have different bellhousings. Sent from my SM-G973U using The H.A.M.B. mobile app
Johnboy 34 is correct and just ordering for a '66 Mustang with a C4 will not guarantee that you got the correct one. Call Jegs and talk with them and they can set you straight and exchange for the correct one.
You shouldn't have any issues with the starter as the SBF was the first V8 adopter of Ford's new-design starter; the rest of the line used the old bendix design until '65. There is a 'automatic' starter and a 'manual' starter, with a very slight difference in the snout length. IIRC, the manual is the longer one but it's been a long time since I've looked. The flexplate isn't so clear-cut. It sounds like you got the wrong new flexplate first off. Second, the difference between some flexplates is how they position the torque convertor in relationship to the trans. If the torque convertor is too close to the block, you may not have full engagement in the trans. Too far away from the block, possible internal binding. It's not always easy to check...
This maybe what you need.: https://www.classicindustries.com/product/6375f.html There are 2 c4 bellhousings.
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