See Ebay description below:

"You will be bidding on an 10.5" or 11" - it will fit EITHER size Clutch. It is a BRAND NEW Pontiac 166-tooth flwheel. This is for INTERNALLY balanced motors -- 350 - 455 Engines - 1964 to 1976 with the 2 3/4" crank shaft hole."

I've seen this comment before - whats the meaning/definition of "internally balanced" with relation to our FGF engines?

All stock Pontiac V-8 except 301 and maybe 303 and maybe a couple of other rare exceptions are internally balanced. Rods and pistons are also balanced by matching for weight. Holes are drilled in the counterweights, or weight added, to balance the rotating assembly. That means the balancer and flywheel are neutral balanced, they should not affect the balance of the rotating assembly.

As opposed to a few engines like the Chevy 400 and 454 that need weights on the fly wheels to balance the rotating assembly. They are called externally balanced.

interesting- never knew that. When I rebuilt my engine, I just balanced everything internal and external; crank, pistons, flyweel, clutch, valve covers, etc. The machine shop was happy to comply.

I bet they were!

Yeah, they always seemed to be extra happy when they saw me coming...really friendly folks. And, they gave me a 3% discount on balancing the valve covers.....

LOL...

Where can I get a set of balanced valve covers?

I'll be happy to media blast, balance and paint a nice set of MTs...the raised ribs are ideal for the task.

Yeah, balanced valvecovers keeps the engine from leaning too far to either side. Great for handling. They also cross-drilled my air cleaner for better air flow.

Technically, A Pontiac is not an internal balanced engine from the factory. The front balancer is neutral, but the rear flexplate (flywheel) is not. Pontiac used the rear flexplate as part of the balancing. It is not a “neutral” flexplate, so if you are talking a stock engine, you need a flexplate designed for the std. Pontiac engine.

Problems arise while engines are rebuilt and balanced. It is more of how it is balanced.
If the internals are neutral balanced, then you need a neutral balanced flexplate. If your engine guy used the flexplate to help balance the assembly, then you need to keep that flexplate with the engine.

You should not use a neutral balanced flexplate on an original engine, which is what I think he is trying to say.

Brian

Agree in theory, but how could you order replacement flywheels and flexplates without rebalancing the entire engine?

The welded tabs are on the flexplates, NOS in the box...that may make them specific for Pontiac V-8, but not for any individual engine.

Cross drill your brake lines for far better cooling efficiency on those hard braking situations!!

So, back to John's question, that flywheel isn't going to work on your stock(factory unaltered rotating assembly) Pontiac engine. It would be for a pontiac engine that was altered to be internally balanced.

Vikki:
The factory flexplates/flywheels are all balanced to the same specification, but not neutral. (That is why they only go on one way). Consequently, the factory engines are balanced to work with the factory flexplate.

When you have an engine builder balance an assembly, you should tell him what you want.
1) A neutral balance assembly without the flexplate or balancer. (now you need a neutral flexplate)
2) Balance it with factory flexplate, but do not let him touch the flexplate. (Now you have an engine balanced with all factory flexplates)
3) Worst case is he thinks too much like the Chevy guys and asks you for the flexplate and balancer, then modifies them during the balancing. Now you have to keep those components together.

Aftermarket companies will usually list in the specs if the flexplate is neutral balanced or offset balanced for the factory engine. If the company is not sure, stay away.

Brian

When I took my engine down for the machine work the mech(chevy guy) told me to bring everything so it could be all balanced together. As far as I know he balanced weight on all the pistons and rods and then mounted the flywheel and balancer on the crank to spin them together. At least that's how I thought he said he would do it. Now that I think about it there's no gaurantee that you would install the balancer in the same position so that wouldn't make any sense. Guy's probably laughing all the way to the bank at guys like me. Think it was an extra $90 to balance.

Robert

I had wondered about this question myself. Thanks for asking, Nash. And to those who answered this question as well.

Well, at least I'm not the only one. Did you get the valve covers done also?

Lemme see if I understand correctly.. when I (we) balanced all the internals, we changed the engine from externally balanced to internally balanced, but we compensated for it by balancing the flywheel also?

I'm now sorry I asked the question. I know plenty of FGFers have done all this before many times, and never had balancing issues. I meant to ask last year when I had my original flywheel resurfaced.

A month later a good Ford Fairlane friend of mine stopped by, and I explained my recent work on the bird (new clutch, rebuilt tranny, resurfaced flywheel). Well, he immediately acted very concerned about the whole job. "Did the machine shop balance the flywheel to the engine?" he asked.

Uh, "no, I just dropped the flywheel off and picked it up a few hours later", I responded. That left him very concerned about the internal/external balances between the engine, tranny and flywheel/clutch. I tried to calm him down with talk but finally had to offer him a few dark German brews to get him back down to earth.

I was using all original FGF parts and pieces to the bird, so I wrote it all off as "FGF pontiacs don't have that concern".

When I sent my 350 to S&S, they asked about balancing and said if I wanted it balanced to sent the flexplate. It came back with a small weight welded to the flexplate. That completes what I know about balancing - seemed similar to balancing a wheel I figured.

Now you have me worried. My flexplate went in with the engine, but came back loose. I merely bolted it on and assembled the rest. I don't recall seeing any marks on the mating surfaces, but I don't believe I paid to have my engine balanced, per se.

???

Dave, if you have a true Pontiac engine you are most certainly fine, 99 percent accurate. Your builder would have pointed out otherwise.

Vikki,

Will you sell a set of M/T's without the balace job? I'd like a set.

I should explain my original post a little better. It certainly was not by intention to cause anyone concern.

The reason I said "technically" was by the correct definition, a true internally balanced engine is a neutral balanced engine using no external components to correct an imbalance.

Because a factory Pontiac engine used the flexplate to correct the imbalance, it is by correct definition an externally balanced engine.

However, because all normal factory Pontiacs (sorry 301 guys) where internally balanced to a specified spec vs. most other manufactures, it is generally referred to as internally balanced. Don’t quote me, but I believe the unbalance was 7 or 8 in-oz. (1 ounce of unbalance at a 1-inch radius). All factory flexplates were then manufactured to offset this.

A balanced engine is a balanced engine. Makes no difference how it got there. For high performance engines, a neutrally balanced is usually preferred because most of the aftermarket components are neutral balanced. (Although a true race high RPM engine should still have all components checked.)

Any reputable engine builder should certainly know what they are doing, or they would not be in business very long. My pet peeve on this subject is when shops modify the flexplate to balance the engine without informing the customer that they have to keep the componts together to keep it in balance. (Exception is when a shop modifies the factory flexplate to neutral balance it)



Brian

Nash, mine is the original 400 for the car, as it came from Ohio.

Whew!

Good topic. Learn something new every day...

Very good posts and topic! Somebody rate it high, as I can't since I'm the one that started it.

Warpath threw in some great insight and info, and I just now realized who he is! I've bought a few parts from him recently and he is a straight up guy. He has great Pontiac knowledge, but not the pushy type.

Make use of him here and be glad folks like him hang around this website. Thanks Brian and best wishes to you my friend.

Yes. Excellent info. Deserves the 5 stars! Thanks Brian.