TNTS70STANG

I have a70Mustang coupe,351W with a C4 Automatic.

My questions are...

1.) By looking at the flexplate, how do you determine whatthe balance weight is? (Considering there are no numbers)
2.) Can I use a 302 flexplate on a 351W? Are the weights interchangable?
3.) Can I use a 302 Torque Convertor on a 351W?
4.) Whats the balance weight difference for a torqueconvertorbetween a 302 and a 351W?

Ihave the 302 flexplate and torque convertor in my garage but before Iinstall them on the 351W, I wanted to make sure. I'm sure that I shoulduse the appropriate flexplate and torque convertor for a 351W but I'm just curious if the car will run and drive accurately and smoothly with a 302 flexplate and torque convertor. I don't want any vibrations due to the balance difference.

wrenchturner75

you have 2 different balances(thanx ford) early 28 oz and late 50 oz, i believe the 28 oz stopped in the early eightys, 50 oz came after that. the 28 oz weight will be small and of course the 50 will be twice as large. the 302 flexplate will bolt up. as long as the weights look similar in size youll be ok. this is where things get sticky! ford blessed us with 2 different size flexplates and about a hundred different bellhousings for the c4, if the 351 windsor has a 157 tooth count then the converter should fit, if it has a 164 tooth count it probably wont. the bellhousing youll need is #c5op-7976-a. and a 157 tooth flexplate. check the part # on the bell if you got that # and a 157 tooth flexplate your in luck cause it will allwork. yes you can usea 302 converter behind a 351 windsor

TNTS70STANG

Thank you wrenchturner75. I really appreciate the information. Well, I did a "test bolt-up" without starting it and every thing fits with perfect clearance. I counted the teeth on the flexplate and I counted 157. So it looks like I'm in good shape on the teeth count. So your saying that the 351W and 302 torque converter is interchangable, correct?

The only thing I can see doing is going to the local parts store, having them pull a flexplate for a 351W (in which they told me they have it in stock over the phone) and compare the size of the flexplate balance weight that I have with the one at the parts store. Your saying that if the weights looks similar in size, I'm ok to use it on the 351W, correct? Thank you again for you all your help.

JMD

WrenchTurner pretty much nailed it, 1985 and later 302/5.0 flywheels,flexplates, and harmonic balancers are 50oz imbalance, while earlier ones are 28.

All torque converters are "zero balanced", they don't care what balance your engine is...

tyler72

351s and 302s are the same balance as long as they are both before 85. They should be 28 oz. But, if the 302 was say a 75 block and the 31 was a 95 block they woulnt be interchangable b/c of the balance. Basically, if both of them are pre-85, then you will be A-OK!

JMD

Hey Tyler!

It is my understanding that....

1. All 351W's are 50oz imbalance

2. All 289's andall all 1984and older302/5.0's are 28oz imbalance..

3. All 302/5.0 1985 and newer are 50oz imbalance.

Non stock engines can be different, my son's 408 is neutral balanced.... Balance can change with stroker kits, so you need to verify balance on your 347!!

<<EDIT... Tyler,, you got me thinking, were 351s 28oz instead of 50oz?

I checked my interchange book to check my memory, it does not directly address the issue, but it points to the 351 being a 50oz imbalance in the caption for a picture of a harmonic balancer. This caption indicates that a 351 balancer is interchangeable with late 5.0's... = 50oz, so I think I was right!!

TNTS70STANG

Well, I went to the parts store today with my flexplate to compare the weight difference between my 302 flexplate and a 351W flexplate and physically, the weights were the same size but the actually flexplate diameter of the 351Wwas1/2 inch larger. Thus; making the weight differ. Soooo........it looks like I'm gonna have to buy a 351W flexplate. Even though you guys are wondering if the 302 has a 50oz. imbalance weight and the 351W has a 28oz. imbalance weight, or the other way around; the 351W flexplate is bigger in diameter than the 302 flexplate. So, I have to buy it.

I don't want to pay $55 bucks for it at the parts store, so...does anybody have a 351W flexplate that they can spare under $55 bucks? I would really appreciate it.

PetesPonies

Old thread, but bad info here. First, all 351s were 28 oz balance, not 50. Second, 50 oz started in '82, not '85. For reference reasons, wants to keep the info accurate.