[Hooter]

After sitting several years, finally working on the '71 455 for my '74 Firebird. I haven't worked on a stick car for 30 years, so needing some guidance.

The motor was rebuilt back in 2003 by a previous owner. I have the receipts showing the engine was balanced. At that time, it had a flexplate in the receipt, so the 5 speed trans was added later. Started disassembling the motor and noticed it has a stock style cast flywheel(pic). I believe these were externally balanced from the factory. My assumption is this flywheel was neutral balanced when the 5 speed swap occurred a few years later? I need to replace it since the teeth on it are pretty chewed up, so my gut says to order a internally balanced flywheel?

Last question, I'm looking at the RAM billet flywheel. Do I go with the lighter weight 29lb or the regular 35lb. Car is strictly a street car with no plans to take it to the track. 74 Firebird with a TKO500 5 speed. 3.73 gear. 455 with e heads and small hydraulic cam. Old dyno sheet showed 500hp and 550tq. I purchased the motor and trans several years ago from a guy who went LS in his 78 TA.

[firechicken]

Factory flex plates were external balance as well so hard to assume the factory flywheel was neutral balanced. It could be external as well.

You could just change the ring gear.

[Mr Twister]

+1 on changing the ring gear only.

[Murf]

I think I’d take it to a shop & have them check it before I made any plans.

Murf

[Hooter]

Forgot that changing the ring gear was an option. I"m fine running this stock type flywheel since not a race car. Any ring gears better than others? Looks like RAM has these for around $30.

Still curious if I would need internal or external flywheel if decided to upgrade to a better billet.

[track73]

If you change flywheels I wouldn't be afraid of the 29 pound flywheel. The rotating assembly and crank weigh enough to get the car rolling. I have an aluminum flywheel on my 455 and I really can't feel the difference.

[Schurkey]

Originally Posted by Hooter

Still curious if I would need internal or external flywheel if decided to upgrade to a better billet.

There's NO WAY for us to know how that engine was balanced.

Look at both sides of the flywheel, see if it's got drillings indicating a deliberate out-of-balance. Otherwise have it checked by a balance shop.

[Hooter]

Originally Posted by Schurkey

There's NO WAY for us to know how that engine was balanced.

Look at both sides of the flywheel, see if it's got drillings indicating a deliberate out-of-balance. Otherwise have it checked by a balance shop.

I hear what you're saying, just curious if by looking at the pic that indicated anything. In the pic, there are complete drilled holes in the 4 and 5 o'clock position. Around the 7 o'clock position, there is a partially drilled hole. Not having any old flywheels around from a point of reference, wasn't sure if these were factory or possibly the partial hole was added later to balance it.

The clutch face side has nothing drilled in it.

I've already ordered another starter ring so that will be the fix for now.

[25stevem]

Pontiac motors from the factory go thru two balancing procedures.

The final very fine one is done by spinning up the assembled short block and then the last bit of metal is taken out of the flexplate or flywheel.

[Schurkey]

Originally Posted by 25stevem

Pontiac motors from the factory go thru two balancing procedures.

The final very fine one is done by spinning up the assembled short block and then the last bit of metal is taken out of the flexplate or flywheel.

Buick final-balanced the engine by dicking with the flywheel and damper. I have numerous Buick flexplates, no two of which have drill holes in the same locations and the same amount. But then, the entire Buick balance philosophy was goofy as a fresh-fooked sheep. The eight connecting rods in a Buick engine may all weigh the same (within production tolerance) But they make ZERO effort to match the big-ends and match the small ends. The balance pads aren't where they belong--on the big end cap and the small end above the pin. Nope, they're in the middle of the rod at the "center of mass". Who cares about center of mass?

The Pontiac video showed 'n' told about them initially drilling the counterweights when the crank was first machined, then again drilling the crank counterweights for final balance (1/2 inch-ounce!!! 14 inch-grams. No mention at all about "front" and "rear" of the crank, or getting the rods 'n' pistons to weigh the same. Not all that "fine", but probably adequate given the typical RPM and usage of a production engine.) after the assembled short-block was spun-up, starting at 9:39. Right after the sound comes back.

Do any of you see oil being flung off, or visible lube on the cylinder walls of that short-block as it's spinning? So much for the need to prime the oil pump, turn the crank a quarter-revolution, prime the oil pump, turn the crank...making sure to get oil to every moving part in the engine before start-up.

https://www.youtube.com/watch?v=9LuX...oPonchosGarage

[Kenth]

Originally Posted by 25stevem

Pontiac motors from the factory go thru two balancing procedures.

The final very fine one is done by spinning up the assembled short block and then the last bit of metal is taken out of the flexplate or flywheel.

Source on that?

[Tom Vaught]

Originally Posted by Kenth

Source on that?

Agree what is the source?

Moldex crankshaft has done balancing for me for 40+ years and I have observed the balancing of the crank assy with the "Bob Weight" several times.

It differs from your post QUITE A BIT.

Tom V.

[25stevem]

In the film I mentioned in a post I made yesterday they explain the first normal step in balancing the rotating assembly, then later in the film its said , and they also show that they do the final balance adjustment by spinning the built up short block ( pan on and no heads)
And then another procedure is done at the rear of the motor.

My guess is that Engineers did this for a reason.

[will slow gto]

re-ringing a cast flywheel on a 500 horsepower engine doesn’t make any sense. Ram makes a very nice, balanced steel flywheel for about 300 bucks.

[Kenth]

Originally Posted by 25stevem

In the film I mentioned in a post I made yesterday they explain the first normal step in balancing the rotating assembly, then later in the film its said , and they also show that they do the final balance adjustment by spinning the built up short block ( pan on and no heads)
And then another procedure is done at the rear of the motor.

My guess is that Engineers did this for a reason.

How would they do the final balance adjustment drilling the counterweights with the pan on? Take a look again, 9:45 - 10:15 in the film.

NO other procedure done, and certainly no extra drilling in flexplate or flywheel.

[64speed]

I am not an expert but the only aftermarket flywheel I know of that is externally balanced is the Centerforce one. I found that out when I bought it and had a vibration in the first 100 or so miles. Ended up having to take it off and buy a Ram

[Skip Fix]

I think there is a PRW that has a bolt on weight also.
https://store.prw-usa.com/1645573-po...lbs-166-teeth/

[Hooter]

I found a local shop that does balancing. Stopping by there tomorrow to spin up the flywheel to see what I’ve got. Being in the anal camp, I’d still like to buy one of the RAM units.

[GTOLou]

Really enjoyed that old poncho video. Not sure I can parse a ton of info about balancing from the narrator.

Here's a tiny bit of help: https://butlerperformance.com/n-1349...k-balance.html

I've used Hays/centerforce/ram flywheels before - would trust any of them. PRW - i've used some of their stuff. Some parts (rocker arms, etc) - I've not sure I'd trust. JMHO.

[MarkS57]

Many years ago I swapped in a 61 389 A1 short block that came from probably a Cat for a 62 389 Bonneville. The A1 had what I believe was a some sort of monster flexplate / flywheel used with a slimjim. The Bonneville, a superhydramatic flexplate that was much more conventional. The result was nasty vibrations from the A1 swap. From that point on, I always tried to the keep original flexplate or flywheel to the engine it came from. A one point, I was gong to swap in a 4spd into my current Tempest. If I did, I would have had the new flywheel match balanced to the original flexplate just to be sure.