C-3 AC fan clutch

[D S.]

1970 454 with AC if that matters. Who was the original manufacturer and what was the part number of the fan clutches? What does the NCRS recognize as correct and/or acceptable replacements in lieu of the original ones?

Thanks,
Scott

[John H.]

Re: C-3 AC fan clutch

Schwitzer (rectangular bi-metallic plate) and Eaton (bi-metallic coil) were the original manufacturers; your Judging Guide will describe them. GM service replacements were made by the original manufacturers, and will get deductions based on the degree to which they deviate from the originals. Parts-store replacements (Hayden, etc.) will most likely get total deductions.

[Jack H.]

Re: C-3 AC fan clutch

I don't have a 1970 AIM to consult, but the '71 AIM says the LS5 engine used the 3937771 fan clutch until AIM date 8-18-70 and the C60 option (A/C) does NOT call out a different fan clutch when A/C was installed, only a different fan blade. The '71 SB with A/C option continued to use the 3937771 fan clutch and I know this to be 7-inch, Schwitzer, bar-type clutch with HI RISE center cooling fins.

Your copy of the '70 AIM may call out two BB fan clutches (prime and second source suppliers) with the other PN specified for the application being an Eaton coil-type clutch...

As far as what NCRS recognizes as an 'acceptable substitute' for the factory original part, the answer is nothing. Flight Judging is a sport/hobby with the objedctive being to make the car appear to have rolled off the assy yesterday.

So, to the extent a replacement fan clutch differs from known factory original units along the lines of Finish, Date, Installation, Configuration and Completeness, the car loses 20% of the originality points allocated for the fan clutch based on each axis the replacement fan clutch violates in comparison to a true original part.