Is this flywheel OK to use.

[Donald H.]

[Mark M.]

Re: Is this flywheel OK to use.

Don from what I've seen it should be ok as long as it hasn't been machined too thin or overheated. There's many of that flywheel out there and it was often used in OMC boat engines were it used a coupler and not a clutch as then there would be no wear. It's weight if I remember right is around 25-30 lb. About the same as the 67 327 original. I pulled one out of a 65 that was there many years with no problems. The N stands for nodular iron which is better (safer) then non ductile flywheels. For hi rev. engines I would only use SFI steel flywheel.

[Joe L.]

Re: Is this flywheel OK to use.

I need a flywheel for a 67 small block. From research on this forum, I understand the original would have a casting of 3791021. I found a 366861N on eBay. From my research this is a later casting for small blocks. It is dated C 15 5.

assuming it’s in good condition, is this flywheel OK for my 327?

Thanks,
Don

Don------


GM says that the GM #366860 flywheel (casting #388681) will replace the original 1963-68 Corvette 12-3/4" flywheels GM #3791022 (casting #3791021).

Would I use a USED flywheel? Only if there were NO other options. But, there is another option---a NEW LUK or Sachs replacement flywheel.

You could also use the "lightweight" version of this flywheel, currently GM #14085720 and still available from GM. The predecessor of this flywheel was originally used for 1965 L-78, 1967-69 L-88, and 1970-72 ZR-1. It's a little expensive, though, at 250 bucks, GM list.

[Donald H.]

Re: Is this flywheel OK to use.

Don------


GM says that the GM #366860 flywheel (casting #388681) will replace the original 1963-68 Corvette 12-3/4" flywheels GM #3791022 (casting #3791021).

Would I use a USED flywheel? Only if there were NO other options. But, there is another option---a NEW LUK or Sachs replacement flywheel.

You could also use the "lightweight" version of this flywheel, currently GM #14085720 and still available from GM. The predecessor of this flywheel was originally used for 1965 L-78, 1967-69 L-88, and 1970-72 ZR-1. It's a little expensive, though, at 250 bucks, GM list.

Thanks Joe.

Yes, I was considering a LUK flywheel. What I find at various suppliers if the

LUK part number LFW131. That's the one that comes up at RockAuto and Summit. However, the specs say its 18 lbs. I've seen a lot of comments on various threads that its best to stay with something closer to the stock 28-30 lbs.

[Larry M.]

Re: Is this flywheel OK to use.

Whatever you buy, have it checked for both flatness/distortion/runout and also for balance. This is for both new or used. Too many horror stories over at CF C2 Section lately about issues. These issues are from both NEW and used units. Apparently no one is safe anymore.

FWIW.

Larry

[Joe L.]

Re: Is this flywheel OK to use.

Whatever you buy, have it checked for both flatness/distortion/runout and also for balance. This is for both new or used. Too many horror stories over at CF C2 Section lately about issues. These issues are from both NEW and used units. Apparently no one is safe anymore.

FWIW.

Larry

Larry------


Any flywheel and any clutch assembly should always be checked for balance and corrected if necessary before installation.

[Duke W.]

Re: Is this flywheel OK to use.

Thanks Joe.

I've seen a lot of comments on various threads that its best to stay with something closer to the stock 28-30 lbs.

Depends on the engine and gearing... SHP/FI with a CR trans and a 4:11 gear is okay especially if your driving territory is relatively flat...3.70 is iffy, and anything taller should use the OE flywheel. Medium performance engines work best with the OE flywheel.

Duke

[Joe L.]

Re: Is this flywheel OK to use.

More information:

The original flywheel used for all 1963-68 Corvette small blocks was GM #3791022 (cast GM #3791021). This is a 12-3/4" OD, 153 tooth ring gear flywheel. I believe it is cast of GRAY cast iron. It weighs 30 pounds.

The above-referenced flywheel was replaced by GM #3973452 in December, 1971. I know nothing about this flywheel except that it was discontinued in 1978 and replaced by GM #366860 (casting GM #366861N).

GM #366860 (casting GM #366861N) is a 12-3/4" OD, 153 tooth ring gear flywheel. It is cast of NODULAR iron. It weighs 23-1/2 pounds. It was discontinued without supersession about 10 years ago.

GM #3866735 (cast GM #3856579N) is a 12-3/4" OD, 153 tooth ring gear flywheel. It is cast of NODULAR iron. It is considered a "lightweight" flywheel and weighs about 16 pounds. It was originally used for 1965 L-78, 1967-69 L-88, and 1970 ZR-1. It was discontinued in October, 1971 and replaced by GM #3991406.

I do not know the casting number of th 3991406 flywheel but it is otherwise similar to the 3866735.

The 3991406 was discontinued and replaced about 1986 by GM #14085720 (casting #14085721N). It is similar in all respects to the 3991406. It remains available from GM.

The LUK LFW 131 is a 12-3/4", 153 tooth ring gear flywheel. It weighs about 18 pounds. As far as I know, it is cast of nodular iron.

[Donald H.]

Re: Is this flywheel OK to use.

Thanks all, I think I have enough information now to make a decision

[Gary B.]

Re: Is this flywheel OK to use.

So am I correct that no one sells a nodular iron flywheel for the application in question that weighs in the range of 25 to 30 lbs?

Gary

[Joe L.]

Re: Is this flywheel OK to use.

So am I correct that no one sells a nodular iron flywheel for the application in question that weighs in the range of 25 to 30 lbs?

Gary

Gary------


No one that I know of.

[Donald H.]

Re: Is this flywheel OK to use.

Obviously I don't know enough, but here are some I have found. I don't know the good or bad about any.

McCloud - one suggestion from a friend of mine. Material is noted as Steel (so I assume it is cast steel). Weight 28 lbs. 55-85 small block.
Hayes - Billet steel, weights 30 lbs. Listed as for 63-85 small block.

What I don't know for a flywheel, is how does nodular iron compare to cast steel or to billet steel?

Don

[Joe L.]

Re: Is this flywheel OK to use.

Obviously I don't know enough, but here are some I have found. I don't know the good or bad about any.

McCloud - one suggestion from a friend of mine. Material is noted as Steel (so I assume it is cast steel). Weight 28 lbs. 55-85 small block.
Hayes - Billet steel, weights 30 lbs. Listed as for 63-85 small block.

What I don't know for a flywheel, is how does nodular iron compare to cast steel or to billet steel?

Don

Don------


gray iron------good

nodular iron-----better

cast steel-----about the same as nodular iron, maybe a bit better

billet steel-----the best

What is the OD of the flywheel you mentioned above?

[Donald H.]

Re: Is this flywheel OK to use.

Don------


gray iron------good

nodular iron-----better

cast steel-----about the same as nodular iron, maybe a bit better

billet steel-----the best

What is the OD of the flywheel you mentioned above?

I can't find the OD. I even looked on Mcleod's (corrected spelling) website. The specs just state for 10.5" clutch and 153 teeth. There is quite a difference in pricing between these 'racing' flywheels in cast or billet steel and one like the LUK LFW 131, which is $53. The cast or billet ones all seem to be in the $300 range.

Do you really get what you pay for here? I'm not building a racing engine, but would like to have something within recommended specs, i.e. weight.

[Joe L.]

Re: Is this flywheel OK to use.

I can't find the OD. I even looked on Mcleod's (corrected spelling) website. The specs just state for 10.5" clutch and 153 teeth. There is quite a difference in pricing between these 'racing' flywheels in cast or billet steel and one like the LUK LFW 131, which is $53. The cast or billet ones all seem to be in the $300 range.

Do you really get what you pay for here? I'm not building a racing engine, but would like to have something within recommended specs, i.e. weight.

Don------

If they are 153 tooth ring gear, that answers the OD question. 153 tooth = 12-3/4" OD.

I'm not surprised, at all, about the prices. Steel flywheels are usually expensive.