I am in the process of relplacing a 302/C4 combo in my 58 with a 351W/T5 combo. While I save the money to have the T5 rebuilt, I'm going to bolt the C4 to it to get around. I know that Ford used two different weight flexplates and harmonic balancers (28 oz and 31 oz) on the 302. They apparently only used one (28 oz) on the 351W. So, while pulling the flywheel today, I noticed that it is considerably heavier than the flexplate I'm putting on in it's place. Like several pounds heavier. When I put the 28 oz flexplate on, should I use the 28 oz balancer from the 302 also? Will this have any ill effect on the rotating assembly? Can I just use the balancer that's on it now? Thanks, Black58

 

They can also use a 50oz.

 

the 351 or the 302

 

Either one can depending on year I do believe. But I have been doing HW all day so maybe I am off. I am building a 351w for my truck and I believe we are using a 50oz. And my buddy has a 90 something mustang with a 302 that I think also is using a 50oz, off the top of my head.

 

I think it was late 80's that 302 went to a 50oz, the 351W stayed at 28oz.

Not sure if you can change to 28oz balancer and flywheel if you have a 50oz to start with. I would think the crank would be balanced for the 50oz.

 

I think that depends what it is out of, the mustangs I believe, could have the 50oz back in 65+.

 

Not real sure but I think the 302 engine balance change over was in 1980/1?
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W) forum: Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W) - Ford Truck Enthusiasts Forums
On edit/From that forum a great thread: https://www.ford-trucks.com/forums/4...confusion.html

 

get with it folks its not wise to spit out information that your not sure of

all 351w's regardless of year 69-97 were all 28.8oz external balance
302s up until 80 were 28.8oz external as well then ford changed it to 50oz from 81+ when it got the name "5.0"

NO YOU CAN NOT USE A 50oz BALANCED BALANCER OR FLYWHEEL/FLEXPLATE ON A 351w. You will throw bearings in no time and have a serious balancing problem resulting in severe vibration problems.

to the OP... I don't see any problem using the balancer you have on there now, but thats only all fine and dandy on paper. NO telling what ford did when they balanced the engine. Not only that ford isin't known for doing to well of balancing jobs to begin with. I'd recommend leaving the balancer you have on there now and feeling the engine. If it vibrates then I'd swap out the balancer and hope for the best.

Is it possibly that the new balancers pulley won't line up with the rest of the belts? If thats the case swap the pulley from the old balancer on the new and be done with it.

That is of course IF you have a balance problem with the balancer you have now.

 

Well, we'll all try to shape up Mr. Decipha!

First there are two issues here and the way you posted this will furhter the confusion on one of them.

There are "Flywheels", and there are "Flexplates" - and they are two entirely different pieces of gear. And they are already balanced. The purpose of the Harmonic balance is to counter eccentricities in the crankshaft, so the two are not related. You would use the same balance irregardless of whether you swap the flex plate with flywheel of vice versa.

Flexplates are used in conjunction with Automatic Transmissions for the purpose of providing a connection from the crank shaft to the torque converter of the automatic transmission. It also provides a geared edge to engage the starter. It is lighter than a flywheel because it serves functions entirely differently that a flywheel. It is usually of stamped construction with the starter ring welded on. It may be solid or have a "Scarf Ring" configuration. Flexplates can ONLY be used on an engine carrying and Automatic Transmission.

A "Flywheel" is used with a "Manual Transmission." It is a thick heavy solid cast wheel which is also bolted to the back of the crankshaft. It has a solid machined surface that serves to hold a manual clutch plate pressed to it by heavy spring force of the clutch pressure plate (which is bolted to it). Thus it is an integral part of the clutching aparatus of the vehicle; carries the weight of the clutch; and, absorbes/distributes substantially more mulitdimensional stress and heat than a flexplate. Flywheels can only be used on vehicles with Manual Transmissions.

That's why the big difference in weight.

If you are taking the flywheel off your 302, and it is of the same physical dimensions (diameter at the geared teeth, and crank shaft bolt pattern) and is properly balanced, it will work just fine on your 351W if you were putting the T-5 on that set up. But those physical dimensions remain to be seen. Since it is "balanced," it presents no eccentricities to the bearings. Since you are installing a C4 though, you will need to get a flexplate designed for the 351W/C4 combo (and there should be a million of them out there).

Getting the correct balance of a 351W should be no problem as well. It does need to be of the correct weight because of it's balancing properties in relation to the crank shaft. The overall weight of the balance is irrelevant as long as the "counterweight" portion of the balance is correct for the crank shaft in the engine. If that were not true, you would have to have separate balances for each of the single, double or triple groove pulleys used on that engine. Physical dimensions with the large pulleys may be a problem in an engine swap depending on how you are cross membered.

It kind of sounds like an input on the balances and flexplates from Number Dummy would be helpful in finding the right ones.

That 351/C4 is a great combination for your truck. And, parts for it are readily available.

Have a great time with the swap.

Julie

 

OIW, if you are pulling the T5 w/flywheel off the 351W, and installing the C4 w/flexplate, and the flexplate is the same physical dimensions as the flywheel (diameter and bolt pattern,) You can use it on your 351W and you won't have any problems. Use the 28 Oz balance.

J!

PS I didn't get the edit in within the one hour limit.

 

I think Black58's actual OP question is, does it affect the engine to replace a heavy flywheel with a light flexplate? The answer is No, because the torque converter makes up the rest of the weight difference (and the t.c. is neutral balanced).

The only other question I see as potentially open is the harmonic balancer to use. The answer there is, these are designed for a specific engine/crankshaft, unrelated to what trans is on the back end. Use the 351's h.b. with the 351, period.

I'd check the tooth count and diameter of the flexplate first thing!

 

A very good point, be sure to check that plus the bell housing size. Not knowing this yeas ago I put this together on my 65 Mustang 289 and had no contact with the starter drive and the flywheel. I had the larger diameter bell housing with the smaller diameter flywheel.

 

tooth count and bolt circle diameter are different among various 302's as well. So if you had the 302's 28 oz flexplate, you should be able use that flexplate with the same starter and C4. Only the engine itself would change. Until you get the T5 ready, then you'll have to get the proper flywheel to match the T5, and the matching starter as well. At that time you'll need the 28 oz flywheel regardless.

If your 302 was a newer version with the 50 oz flexplate, then you need to match that one with a 28 oz. flexplate with the exact diameter and tooth count from the local part store.

Now with all that being said, If it were me, I would just leave the 302 and C4 in as is, until the T5 is done, and then drop the 351W and T5 in at once. Less work, and the same result.

 

I agree 100%.

Some of the info bandied about in this thread is far from correct.

Remember fellow members, the topic refers to C4's, not C6's.

Ford parts catalogs do not list ounces, all I can go by are part numbers.

1968/80 302 C4: There are two different flexplates (exc. Bronco's **)

1968/76: C3AZ6375L which has 157 teeth.

1968/80: EOAZ6375A (which replaced [1/1980] C5AZ6375T) which has 164 teeth.
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1981 302 C4: EOSZ6375A .. 164 Teeth
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1969/81 351W C4: There is one flexplate.

EOAZ6375A (replaced C5AZ6375T).

This is the same 164 tooth flexplate used with the 302.
------------------------------------------------------
** 1973/77 Bronco 302 C4 without a smog pump used EOAZ6375A.

1973/76 Bronco 302 C4 WITH a smog pump used D3OZ6375A, a totally different flexplate.

 

157 teeth = 10.5" diameter
164 teeth = 11.5" diameter (or 11.440")

And if I remember right, Ford never offered the 157 tooth flexplate in a 50 oz. 164 tooth could be either or.

Not to mention Inline 6's getting a zero balance, lol.