dual disc clutch special flywheel identification?

[Warren F.]

When hunting for one of these, either the 427 or 454 version, what identifying numbers or marks are on them to be sure what it is? Thanks.

[Joe L.]

Re: dual disc clutch special flywheel identificati

Warren-----

I don't have casting numbers for these flywheels. However, the PART number for the 427 MA-6 was GM #3955151. The PART number for the 1971 LS-6 flywheel was 3992094. It's possible that the casting numbers for the flywheels are "closely related" to these numbers. However, I think that it may be that the flywheels were manufactured from the same castings used for the "standard" 14" flywheels. I believe that the primary difference is the pressure plate bolt pattern.

[Wayne M.]

Pics of "151" in How to Hotrod BB Cheys

1971 edition, pgs 126,127. Whether 396/427 or 454 useage, they're 14" dia, 168-tooth. I differ in LS6 (externally balanced) dual disc flywheel from the part # given by Joe L., though. My Jan '70 Corvette P & A 30 parts book shows # 3963541, which agrees with the "How-to" source.

[Warren F.]

Re: dual disc clutch special flywheel identificati

Joe:

Thanks, for what information you could get. I see many flywheels at the various swap meets across the land, was just hoping for some way to identify. I have an extra complete assembly ie; pressure plate, floater plate, and clutch discs. I just don't have a regular pressure plate set-up to compare it to.

[Warren F.]

Re: Pics of "151" in How to Hotrod BB Cheys

Wayne:

My Corvette P&A 30B catalogue, effective October 1972 shows part number 3992094, same as Joe stated.

Crane Corvettes apparently has manufactured this flywheel, all that is stated is that this special flywheel is thinner than the normal 454 unit.

[Joe L.]

Re: Pics of "151" in How to Hotrod BB Cheys

Wayne-----

GM #3963541 was a predecessor part number for the 3992094. At least, it was "sort of". GM #3963541 was removed from SERVICE without supercession in April, 1970 and it was not available as a SERVICE part after that time except to the extent that stock existed. After that time, the GM #3992094 became the externally balanced dual disc flywheel.

In February, 1973 GM finally got around to officially superceding the 3963541 and GM #3992094 became the supercessive part number. However, the 3992094 was available well before then. It's hard to say, for sure, which of these flywheels were actually used on 1971 LS-6 applications. IF a special casting was used for the dual disc flywheels, I would expect that the casting number was the same for both flywheels. It's hard to imagine that GM would have had 2 different castings for a flywheel used for an application with miniscule demand. Likely, there is some machining difference between the 3963541 and the 3992094.

[Mark #28455]

look at the spacing of the press plate bolts

The garden variety flywheels have all 6 pressure plate bolt holes evenly spaced. The pressure plate for the dual disc clutch has the pressure plate bolt holes in three groups of two bolts each.

Imagine a clock face and put the bolt holes at 1&2, 5&6, 9&10 o'clock.

Good luck,
Mark

[Warren F.]

Mark, thanks for that tell tale sign!!! *NM*