Hey guys, I purchased a band new 383 short block from a member here not too long ago. The engine was balanced, came with a dampener and flexplate. I then realized the flexplate is useless to me since I'm running a manual transmission and actually need a flywheel. I have a flywheel attached to an older block, but I'm pretty sure the older two piece rear main has a different flywheel bolt pattern into the crank. Can I buy a new flywheel and bring it and the previously balanced flexplate to a machine shop and have them then balance the flywheel?

Other related question, but probably a dumb one. Balancing only needs to balance the centripetal forces of the crank right? So I shouldn't have to put on a different front balancer just because the rear flywheel is going to be much more weight cantilevered off the back of the rear main bearing.

Thanks for your help

 

Did he internal balance the short block or externally? If he internal balanced the short block you just buy a neutral or internal balanced flywheel. Same thing for externally.

 

We're having to read a lot into what you're giving us, so please clarify some details.

One-piece rear main seal crank, right? If so, they are often internally balanced, especially if the crank is forged. However, even an externally balanced crank can be turned into an internally balanced unit.

Can you tell if the damper that came with the engine has a weight on it? It's typically on the back side of the damper. If it does, then you need an external balance flywheel (and they are available). If it doesn't have the weight, then you can use a flywheel for the '86-'92 f-body V8 application (assuming it is a one-piece rear main seal crank).

 

Thanks for the help. It is a one piece rear main seal (87-95 350 block). Sorry I left that out.

Reading over the build sheet for the short block, it does say balanced. However it doesn't specify externally or internally. Looking at the flexplate that was included with the motor, there is a good size weight on it. The balancer does not have a weight on it, however it does have one or two 1/2" deep holes. Probably about 7/16" in diameter hole. So I think it may be externally balanced because of the drilled holes? Any thoughts? I can take pictures of it. If I see lead (not exactly sure what they use) in the crank then does that mean it is definitely internally balanced?

Of course the company is out of buisness (motor was built a year ago) so I can't just call them and check

I don't want to start a new thread so I'll throw this one out there too while it's on my mind. Switching from a 2 piece rear main block ('83) to this one piece rear main block, it doesn't change the location of the pilot bushing right? My old manual transmission will bolt right in right?

I like this section of the forum. Thanks for the help.

 

Those holes in the damper are normal for final balance of the unit. If it was external balance, it would be obvious. Any chance of getting a pic or two of it to post here? One each front and back would be good.

Sounds like it's internally balanced. There is a weight on one-piece rear main seal flexplates that takes the place of the weight on the back of a two-piece rear main crank. This is different than the weight for an externally balanced engine.

With the proper flywheel, there aren't any other issues using your existing manual transmission.

 

Shoot, wish I read this before going to work. I'll snap a picture or two of it tomorrow once I get to work.

Thanks for the help.

 

Here we are...

 

That's internally balanced stuff. Just get a flywheel for one-piece rear main seal.

 

kick ***. So I don't need to worry about finding a 400 one piece flywheel and having it balanced? I can just get a 350 flywheel from the one piece rear main? Thank you so much.

Have you ever came across an aftermarket crank that didn't have the final machining for the the pilot bushing? I have came across a stock one that was just a rough cast hole, so when you pounded in the pilot bushing it actually shrunk the ID of the bushing down so the input shaft wouldn't go through...

 

This site is amazing, thanks five7kid... 4 years later and I'm finally moving forward with this. Life is crazy...

Now just looking for a flywheel for an internally balanced 350, 1 piece rear main

 

make sure you get a 153 tooth flywheel for your engine, I believe the 168 tooth will be to big in diameter for your bellhousing, incase you didn't know this.

auto parts store should ask year make and model so there shouldn't be any confusion!

 

Maybe this will help?

http://www.eaglerod.com/index.php?op...d=27&Itemid=25

 

My 588 BBC is internally balanced. Only the 396/402 BBC came from the factory as internally balanced. The 454's are externally balanced like the 400's. I needed to buy a special internally balanced crankshaft that has an extra counterweight to compensate for the missing balancer and flexplate/flywheel weight.

Not a big deal until I took the rotating assembly to get balanced for the pistons, rods etc. The extra counterweight was in the way of where they had to drill to add heavier weight. The guy who does my balancing knows his stuff and was able to relocate weight to an area that was more accessible.

The nice thing about having an internally balanced engine is that the balancer and flexplate/flywheel are standard neutral balanced pieces. Nothing special required.

 

And the only drawback I had with an internally balanced 400 sbc, was the size of the rear counterweight. It actually cuts into the oil pan gasket sealing rail, so only "stroker" pans will fit it.

But it is nice to buy any neutral balance flywheel.

 

On my Howards crank,I-Con pistons,Scat stroker clearanced rods,with king bearings,nothing special ring pack,we found the rotating assembly to be 180 grams light in the front and 200 grams light in the rear.I seriously considered adding Mallory metal to it for a internal balanced assembly.But I'm not going to spin this up very high and maybe,just maybe,it's going to see some limited track time to get a tune done on it.I wanted a neutral balance on it because I figure I'll start off with a auto tranny and at some point swap in a T56 or some variation of a stick shift.

So what I ended up doing was Pioneer H/B'er with has the etched timing marks on it(nice) and a balance plate on the rear.That way I can swap to any flexplate or flywheel that is a neutral balance.Done and done.

 

I just bought a 383 and glad I found this thread because I was asking the same thing!

The one I bought is a 350 with a 400 crank; old school.

The guy I got it from said it has a special harmonic balancer on it; now I have an idea about what he was talking about!