302 flexplates
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Senior User
Joined: Oct 2005
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From: Kalamazoo
302 flexplates
Probably an obvious question, but then agian, sometimes my wife refers to me as Captain Obvius!!!!
Switching out a worn out tired '76 302 in our old F100 with a '90 302. THe truck has a C4. The '90 had had a AOD on it. IN checking the AOD flexplate and the C4 convertor, the both have the 11 7/16" bolt pattern. Am I correct in assuming that I can just use the flexplate that was on the '90 motor and just bolt the C4 convertor right up without a problem??
Switching out a worn out tired '76 302 in our old F100 with a '90 302. THe truck has a C4. The '90 had had a AOD on it. IN checking the AOD flexplate and the C4 convertor, the both have the 11 7/16" bolt pattern. Am I correct in assuming that I can just use the flexplate that was on the '90 motor and just bolt the C4 convertor right up without a problem??
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From: Delta B.C.
as long as it bolts to the torque converter then yes...
you CAN NOT use the one off the 76 as that and the 90 have different imballance on the crank... that said... make sure you keep the 90 ballancer on the front too....!!!
this is off the FAQ page on the FRPP site:
<TABLE cellSpacing=0 cellPadding=0 width="100%"><TBODY><TR><TD class=std-text-large vAlign=top width=30>Q.:</TD><TD class=std-text-large>What is the crankshaft balance factor of my 302 or 351W/C engine?
</TD></TR><TR><TD class=std-text-large vAlign=top width=30>A.:</TD><TD class=std-text-large>1968-80 302 engines were built with a 28-ounce imbalance factor.
1981-2001 302 engines were built with a 50-ounce imbalance factor.
1969-97 351W engines were built with a 28-ounce imbalance factor.
</TD></TR></TBODY></TABLE>
you CAN NOT use the one off the 76 as that and the 90 have different imballance on the crank... that said... make sure you keep the 90 ballancer on the front too....!!!
this is off the FAQ page on the FRPP site:
<TABLE cellSpacing=0 cellPadding=0 width="100%"><TBODY><TR><TD class=std-text-large vAlign=top width=30>Q.:</TD><TD class=std-text-large>What is the crankshaft balance factor of my 302 or 351W/C engine?
</TD></TR><TR><TD class=std-text-large vAlign=top width=30>A.:</TD><TD class=std-text-large>1968-80 302 engines were built with a 28-ounce imbalance factor.
1981-2001 302 engines were built with a 50-ounce imbalance factor.
1969-97 351W engines were built with a 28-ounce imbalance factor.
</TD></TR></TBODY></TABLE>
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From: Kalamazoo
Just out of curiousity.....While I intend the use the '90 parts on the '90 motor, In checking the bolt pattern on the flexplates because I understood the C4 cnvertors had several bolt diameter patterns, I could not detect any visible differences. COnterweight location appeared the same and looked to be about the same dimensions. For the heck of it, I weighed the two with a digital 0-50lb scale and they came out within an ounce of each other.
I have read elsewhere that Non-HO 302's did come witha 164t-28oz flexplate up to at least 1990, but that all 302HO engines did indeed have the 50oz flexplate. The engien we have is a non-HO engine out of a Merc Gan Marquis.
I have read elsewhere that Non-HO 302's did come witha 164t-28oz flexplate up to at least 1990, but that all 302HO engines did indeed have the 50oz flexplate. The engien we have is a non-HO engine out of a Merc Gan Marquis.
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Joined: Jul 2005
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the counter weight on the 28 oz system is about 4 inches long, 1 inch wide and 7/16 inch thick. the 50 ounce is quite a bit larger. other than that i have no explanation. the total weight of the flywheel or flex plate is imaterial. the off balance is what counts. if they look the same, i would bet they are.
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From: Kalamazoo
kemical................just what is it I am chancing here anyway???
I've already said a couple of times I am using the '90 flexplate on the '90 motor, I only asked to verify that so long as the C4 convertor had the same bolt pattern as the AOD flexplate it was ok to go ahead and use the AOD-'90 flexplate. Never said a word about using the old '76 flexplate.
I borught up that the flexplates appear to be identical , as I said out of curiosity, as most sources claim all these later 302s shuold have the 50oz imbalance. I have run across some sources that do state that the later *NON-HO* 302s continued to use the 28oz imbalance.
According to teh dimensions of teh counter weight that steve gave, then these are both indeed 28oz flexplates, as the weights on each are within less than 1/8in of the measurements given.
Based on that, I would surmise that making the assumption that *all* later 302 had the 50 oz flexplate is not 100% accurate and that indeed some non-HO cars did indeed continue to use the 28oz imbalance. What it boils down to from what I can tell, is that with a late 302, you need to positvely identify your flexplate and not make assumptions as to it being a 50oz.
I've already said a couple of times I am using the '90 flexplate on the '90 motor, I only asked to verify that so long as the C4 convertor had the same bolt pattern as the AOD flexplate it was ok to go ahead and use the AOD-'90 flexplate. Never said a word about using the old '76 flexplate.
I borught up that the flexplates appear to be identical , as I said out of curiosity, as most sources claim all these later 302s shuold have the 50oz imbalance. I have run across some sources that do state that the later *NON-HO* 302s continued to use the 28oz imbalance.
According to teh dimensions of teh counter weight that steve gave, then these are both indeed 28oz flexplates, as the weights on each are within less than 1/8in of the measurements given.
Based on that, I would surmise that making the assumption that *all* later 302 had the 50 oz flexplate is not 100% accurate and that indeed some non-HO cars did indeed continue to use the 28oz imbalance. What it boils down to from what I can tell, is that with a late 302, you need to positvely identify your flexplate and not make assumptions as to it being a 50oz.
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From: Troy,NY
Charlie, You can definately use the AOD plate on a C4. I have one on mine and it works fine. There are a few oddball 90 cars that had a 5.8. If yours is one of them it could explain the weight thing. The only other thing I can think of is the bottom of your F100 motor already has a newer 5.0.
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