I’m having a vibration that comes on at 2000rpm and gets worse above that. It’s not the drive train, because it does it in the garage when the car isn’t moving.

I bought a rebuilt ’88 305 engine with the one piece rear seal and I’m using a T-5 transmission. The engine didn’t come with a flywheel or harmonic balancer so I ordered a flywheel from JEGS which later after I bolted everything together, noticed it said it was an EXTERNALLY balance flywheel.

http://www.jegs.com/i/Exedy/317/FWGM13/10002/-1#moreDetails

The harmonic balancer I ordered said it was INTERNALLY balanced.

http://www.proformparts.com/mistore/productdisplay.php?sku=407647&hdwt=31101&loc=101&dealer=&company_id=100719

Since then I searched everything I could find on internal and external balanced flywheels and balancers and it’s starting to make my head hurt. I think the ’88 305 is supposed to be internally balanced. A friend who is a mechanic said that it doesn’t matter but I’m not sure I believe him. He thinks it is an ignition miss not the flywheel causing it, but I have replaced plugs, wires, distributor cap, checked timing and just about everything I can think of that would cause it to miss. I’ve read that the chevy 400 is externally balanced and just about every other sbc’s is internal.

Does this flywheel need a balance plate of some kind or am I screwed and need a internal balanced flywheel?

I’m confused.

 

no - I'm Confuzed...lol
Is that friend of yours really a mechanic? If so, then he/she should know it DOES matter. If you have a cylinder missing, any mechanic should be able to determine that along with which cylinder it is.
I can't understand why you didn't just get a '88-up stock T-5 flywheel in the first place. I know they sell counterweights that attach to the flywheel to turn a INTERNAL balanced flywheel into EXTERNAL - but not the other way around. The way it sounds to me, you'll need to remove the flywheel, take it to a machine shop to have it internally balanced. - Or get a stock WC T-5 flywheel and be done with it.

 

I really hate to just regurgitate stuff I have read. I usually only comment when the topic is something I know about firsthand. However, from looking at the description Jegs gives of the flywheel you bought, it is the correct one. This external/internal thing seems to make for tremendous confusion when it comes to 1 piece rear main stuff. Too bad Sofa hasn't been around - I've seen him explain it before. Look elsewhere for your vibration - I believe you have the correct flywheel.

 

Your engine is ALMOST internally balanced. ALL one piece rear main small blocks from 87-up use a very slight counter-weight on the flywheel/flexplate. The balancer on the front of the motor is truly neutral balanced, however, with no counterweight at all.

From you description and parts links, you have the proper flywheel and dampener on your engine.

 

On Summit's site they call them a "Counter Balance Plate".

http://store.summitracing.com/partde...5&autoview=sku

So if you have to add an offset weight to turn a internal into a external, doesn't that mean that an external flywheel already has that weight added to it? Making it not balanced for my engine.

Just trying to make some sense of this whole thing before I do anything major and waste any more money that doesn't solve my problem.

 

I explained it thoroughly in this thread:
https://www.thirdgen.org/forums/engi...nny-piece.html

 

That weight is NOT for the one-piece rear main seal 3.48" stroke balance. It is for the 3.75" stroke external balance use ONLY!

 

If it bolted up to your crank, its the right flywheel... unless of course you bought a flywheel from a clueless company like Fidanza that doesnt know how to counterbalance a SBC. Doesnt look like you bought one from them. Forget about all that internal/external nonsense. The older SBC's had the so-called counterweight cast into the rear flange of the crank where the flywheel bolted up. The newer ones have no such provision since the 1 piece rear main took up that space so they put the weight on the flywheel instead. If your flywheel came properly balanced, its not your issue, its something else.