I have a 66 mustang, with a c4 transmission. I just put a 1980 302 rebuilt engine into it. I am having problems working out which flexplate to use. I know i need a 157 tooth butnot certain of the balance weight 50oz or 28oz. I think itshould be 28 oz but i have tryed that and get a wicked vibration so i shut it down straight away. I was told i may have to get the crank number and search that way but i dont know if this is true. I think i have right flexplate but maybe wrong harmonic balancer but again not sure how to know which one to get. Pleae someone save me

 

thought that was the other way around the older cars were 157 28oz and the 70's something plus was 157 50oz. Net should be able to tell you for sure. You need to use the flex plate for the motor and what it was balanced for not the year of car im almost sure 60s was 28oz so you should use the 50oz.

 

1982 is the year the balance changed....if its 81 and earlier you need 28oz 1982 and newer you need 50oz

 

ok but heres the problem. What if, during an engine rebuild they put a new or reco crank into my 1980 motor and the crank was say made after 1981 so now im geussing i would need to use 50oz flexplate and balancer would I not

 

Sure, but that would also means they are idiots. What makes you think they did something that dumb?

 

The short answer is YES.

Summit has a generous return policy.... and Jeg's ships super fast...

Seeing that you have a severe vibration with the 28 oz balance, try the 50 and see if this cures the issue.

It will suck having to switch the stuff out, but not so much as switching the stuff out AND dropping the pan.

There are three possible scenarios, 28 oz, 50 oz, and neutral balance, with neutral being highly unlikely, 28 oz does not work try 50. (Jim's 408 is neutral balance...)

It may be that the engine builders were idiots, or they might have made a mistake when they selected the crank during rebuild, or the sales person did not read the footnote stating that this is a 50 oz engine.... **** happens.

 

i put a 28oz flexplate (new) and that I know for sure due ease of telling them apart however i was sold a damper that looks totally differerent to the damper that came with the engine however the original damper says its a D5AE-BA and cant seam to track what that one is for sure. Now if its a damper then great but not sure how to tell the weight or compatibility of the damper

 

D5 means 1975.....