[Not a Y88 T/A]

I am putting a new clutch in my 1978 T/A with the original (400) engine and transmission and I need a new flywheel.

Does this car have an external or internal balanced flywheel? Looking at several sights (such as Summit) they show flywheels that are supposed to be correct but some say external balance and some say internal.

Last, is there any prep that needs to be done with the new flywheel before installation, other than wiping it clean with brake cleaner?

Thanks in advance for advice given.

[Skip Fix]

Factory are external balance. Look at a factory flex plate. Holes are not symmetrical all around.

[78w72]

hays billet steel is a great flywheel & what i used on my 78 W72 400, no prep before installation.

traditional pontiac v8's are considered neutral balance & most pontiac flywheel/flexplates ive seen are referred to as neutral or internal balance. the flywheel/flexplate comes pre-balanced & aren't part of the engine balance like a chevy or the 301 that use the damper & flexplate/flywheel as part of the balance, those are what i always considered external balanced. might be wrong on the terms or maybe people just confuse them?

https://www.jegs.com/i/Hays/490/13-1...SABEgLSBfD_BwE

[Singleton]

Factory flywheels are not neutral balanced.https://forums.maxperformanceinc.com...99#post5855699

Also, if buying a new flywheel, don't assume that it is machined flat. I bought a brand new Hayes about 7 years ago, and the machined clutch disc surface was not flat. Short story, I had issues with the clutch not fully releasing, as last resort took the new flywheel to local machine shop to have it checked and they confirmed that it was way off. Solved my clutch issue.

[78w72]

Originally Posted by Singleton

Factory flywheels are not neutral balanced.https://forums.maxperformanceinc.com...99#post5855699

Also, if buying a new flywheel, don't assume that it is machined flat. I bought a brand new Hayes about 7 years ago, and the machined clutch disc surface was not flat. Short story, I had issues with the clutch not fully releasing, as last resort took the new flywheel to local machine shop to have it checked and they confirmed that it was way off. Solved my clutch issue.

again i think its a confusion of the term, pontiac engines are internal or neutral balanced & most pontiac flywheel/flexplates ive seen refer to that term in their advertising.

yes the flexplate itself is balanced "externally" but its for an engine that is balanced internally or neutrally. look at the description in that jegs link for the hays flywheel, it calls it internal balanced & further down says "engine balance: neutral"

my hays flywheel bought about 10 years ago was confirmed flat & had no issues you described. but i agree its good to have it checked out.

[Skip Fix]

There are Pontiac flywheels that have an add on balance weight for factory balance not "neutral" PRW for one. Most SFI flexplates do not have the missing hole external balance like a stock flex plate also. To me "Internal"," neutral" means flywheel has no external to it and is totally neutral. Might all be semantics but the flywheel manufacturers other than PRW with the weight do not make it real clear.