Is my engine internally or externally balanced?

[Taylor1969]

Hi,

I need to buy a flywheel and didn't realize that there are two kinds: Internally or externally balanced.

How do I tell which one I should purchase?

The engine is a 383 stroker. Here are a few pics of it -


https://static1.pt-content.com/images/noimg.gif

https://static1.pt-content.com/images/noimg.gif

https://static1.pt-content.com/images/noimg.gif


Thanks in advance for all of the help.

Chris

[6'9"Witha69]

From the looks of the material removed from the balancer, it is external. Thing is, you can't really just buy a flywheel w/o having it balanced to the motor.

[Ricoch3T]

I agree with the above. Looks external to me.
Also agree with buying on that has not been balenced with the rotating assembly

[Taylor1969]

hmm...

So should i be purchasing a new balancer w/ flywheel? I am assuming that the rotating assembly is neutral balanced right?

If not, do I need to take the engine somewhere to have this worked on?

[6'9"Witha69]

The balancer and Flywheel need to be balanced to the rototing assembly. The internals are not neutral, otherwise it would be internally balanced.

Do you have the build sheet for the motor? Most good machine shops can use the balance card to balance a new piece w/o tearing down the engine.

[Taylor1969]

The balancer and Flywheel need to be balanced to the rototing assembly. The internals are not neutral, otherwise it would be internally balanced.

Do you have the build sheet for the motor? Most good machine shops can use the balance card to balance a new piece w/o tearing down the engine.

The engine came with the car when I bought it so I am not sure on specifics. It looks like I may have to track down the owner to find out more specific information. I assumed it was neutrally balanced because most engines are assembled that way these days.

If I end up with no information will the motor need a complete teardown to determine correct balancing?

[Taylor1969]

On a side note, is it possible that the harmonic balancer has the holes drilled in it to balance it neutrally?

[Adam's 55 Chevy]

010 engine number is a 4" bore which would be a 302 / 327 /350 which is internally balanced but to make it a 383 it has had a 400 crank fitted which is external balanced.

Therefore you will need an external balanced flexplate. Make sure the balancer has also been changed. It should have a balance weight on the rear (ie not be perfectly round on the inside edge).

[6'9"Witha69]

010 engine number is a 4" bore which would be a 302 / 327 /350 which is internally balanced but to make it a 383 it has had a 400 crank fitted which is external balanced.Just so the comment is not taken as a blanket statement, you can internally balance a 400 assembly. This is something you need to request to have done and costs a little more.


Therefore you will need an external balanced flexplate. Make sure the balancer has also been changed. It should have a balance weight on the rear (ie not be perfectly round on the inside edge).This is correct. Thanks for reminding me. Looking at the pic it almost looks like it is right on the top there.

[Taylor1969]

Ok... So all I need to do is buy an off the shelf externally balanced flexplate for a 400 crank, bolt it up and I am good to go right? I don't need to balance it all together.

[Adam's 55 Chevy]

Balancing the complete rotating assembley is always better just like blue printing an engine is better than a straight rebuild but no. While you are there you might as well get an SFI rated flex plate. One more thing, I do not know if the 400 flex plates are 168 or 153 tooth. Just make sure your starter is correct for the flex plate while you are in the shop or on the phone.

[6'9"Witha69]

One more thing, I do not know if the 400 flex plates are 168 or 153 tooth. Just make sure your starter is correct for the flex plate while you are in the shop or on the phone.If you run a 6" balancer then use the 153 tooth plate or an 8" balancer with the 168. I run the larger sizes as there is more leverage at the starter. Also, any externally balanced 400 crank is balanced better IME with the larger parts.


Ok... So all I need to do is buy an off the shelf externally balanced flexplate for a 400 crank, bolt it up and I am good to go right? I don't need to balance it all together.No, it should all be balanced to the rotating assembly.

[Taylor1969]

No, it should all be balanced to the rotating assembly.

I don't understand that... so if you need to replace a damaged flywheel down the road, the engine needs to be disassembled and completely balanced with the balancer and flexplate?

[6'9"Witha69]

That is where the balance card comes in. As I said, with that most good machine shops can set up a new balancer or Flexplate/flywheel. Without it, yes, you need to pull it out and get it redone. That is another reason I prefer internally balanced motors (besides the fact they come out better and work smoother).

[MonzaRacer]

oh PLEASE ITS NOT THAT CRITICAL HECK gRUMPY jENKINS USED TO OVER BALANCE HIS CRANKS AND THEY RAN FOR years IN HIGH RPM RACE ENGINES.
bUY A 400 FLYWHEEL AND RUN IT.
UNLESS YOU CAN SEE FRESH DRILL MARKS ON THE COUNTER WEIGHTS AOR PUSHED IN AND WELDED ROUND PLUGS IN THE COUNTER WEIGHTS ITS NOT BALANCED AND YOU MAY ALSO SEE A 4 OR 5 DIGIT STAMPED NUMBER ON THE FIRST THROW.
jUST INSTALL A 400 FLYWHEEL AND GO IF NO NUMBERS
LEE
PS SORRY FOR CAPS STUPID BUTTON IS STUCK