Internal or External balance

[Michael Homan]

Having a brain freeze.

Is a stock 302 in a EB with a C-4 trans of the INTERNAL or EXTERNAL balance.?

Reason for asking is so that I get the proper Flexplate for the C-4. (is the trans different than the motor?)

New B&M torque converter and rebuilt C-4 trans, might as well get a flexplate and have new stuff in the same place,less likely to cause problems in mt experience!

Thanks for any and all input or advise towards a certain brand of flexplate for the C-4

Mike Homan

 

[BlackHills4X4]

I am going to preface my answer saying I think it is External. Many moons ago, I changed the tranny in my mustang (302 equiped) from a 4-speed to an auto. I obviously had to change from a flywheel to a flex plate. I got a horrible shake at about 3500 RPM. I could not find the problem. I eventually took the block in to have it rebuilt and explained my issue. They informed me they needed the flex plate to balance the motor and changing from a flywheel to a flexplate put the motor out of balance.

 

[73azbronco]

All the ford motors we talk about here (302, 351, 5.0) are external balance from the factory, unless someone has zero balanced them.

 

[DirtDonk]

And for your stock engine, it should have a 28 oz imbalance value. Newer 5.0's use a 50 oz rating. Numbers aren't exact (like 28.2 or something like that), but you get the idea.

Paul

 

[motoman]

Have a question along those same lines.... noticed my harmonic balancer is wobbling so I need a new one.

I have a 1973 Stock Bronco 302 w/ C4...... my choices seem to be the following:

Internal
External, 28 oz. imbalance
External

Which is correct?

And 3 hole or 4..... not around the Bronco right now to check.

TIA
Moto

 

[DirtDonk]

A stock 73 will always be a 28oz externally balanced damper.
You don't have to separate the internal from the external. Anything with an imbalance factor rating, whether 28 or 50, is by definition "externally balanced".
All EB engines would be external with the 28 imbalance factor.

Now, as to whether 3 or 4 holes, you're going to have to look at where your pulley attaches to the damper and see how many bolts. Ford changed from 3 to 4, but if I'm not mistaken, it was right around your year.
My '71 was 3-bolts. Not sure what your '73 would be.
Maybe someone knows for sure when the exact changeover was, but in lieu of that info, gotta take a peek.

Paul

 

[ilovemaui]

My 408 is internally balanced. My flexplate and balancer are zero balanced. My flexplate which was supposed to be zero balanced needed a little work to make it truely balanced.

 

[DirtDonk]

When you install a crank like that, does it just drop right in or is this one of the kits that requires some internal block machining?

Paul

 

[motoman]

A stock 73 will always be a 28oz externally balanced damper.
You don't have to separate the internal from the external. Anything with an imbalance factor rating, whether 28 or 50, is by definition "externally balanced".
All EB engines would be external with the 28 imbalance factor.

Now, as to whether 3 or 4 holes, you're going to have to look at where your pulley attaches to the damper and see how many bolts. Ford changed from 3 to 4, but if I'm not mistaken, it was right around your year.
My '71 was 3-bolts. Not sure what your '73 would be.
Maybe someone knows for sure when the exact changeover was, but in lieu of that info, gotta take a peek.

Paul

Thank you!!!! I will get one ordered asap!

 

[Broncobowsher]

Maybe someone knows for sure when the exact changeover was, but in lieu of that info, gotta take a peek.

Paul

For most cars the changeover to 4-bolt balancers was '70.
But Broncos (and maybe econolines?) kept the 3-bolt longer. For the Bronco it was until the end of '77.

 

[Quick & Dirty]

The 3 bolt balancer was used with the passenger side inlet water pump, the 4 bolt with driver inlet. The timing marks are in a different location, so the bolt change makes it more difficult to accidentally swap the wrong one on. Most cars changed sides, but the Bronco kept the passenger inlet because of the location of the steering box.

 

[ilovemaui]

When you install a crank like that, does it just drop right in or is this one of the kits that requires some internal block machining?

Paul

Sometimes you have to do a little grinding to get clearance. You have to make sure the rods don't hit. In my case I had the machine shop clearance and internally balance the entire rotating assembly.

 

[motoman]

Clarified when I got home.... 3 hole on my 1973...... thanks for all the help! Looking at this:

http://www.summitracing.com/parts/PIO-872008/Application/?query=Year|1973|Make|FORD|Model|BRONCO&prefilter=1