C3: LT1/ZR1 fan - 5 or 7 blade?

[Dan Pepper]

Did 1970 LT1's and ZR1's use the same cooling fan? Where these 5 blade or 7 blade? Since the ZR1 has the 436 HD radiator, would the 7 blade fan be a possiblility?

What is the Part number for the standard 5-blade fan, and were these date coded?

TIA

[Jack H.]

Re: C3: LT1/ZR1 fan - 5 or 7 blade?

I don't have a '70 AIM book, but my copy of the '71 AIM shows both the LT1 fan and clutch annotated with a mark. The annotation reduces to 'Production Parts' which indicates they were the same as those used on the base SB engine...

5-blade fans were NOT stamped with PN or date code. Fan clutches are often seen with date codes on the drive hub, but not universally so. If memory serves, the base SB 5-blade fan was PN 3770529 and, with the exception of the style of rivets used to attach blades to the center spyder, was the same part for mid-year cars as well as early Sharks....

[Terry M.]

Re: C3: LT1/ZR1 fan - 5 or 7 blade?

Dan,
Too bad you wern't at the National Convention. Sal had his 1970 ZR1 there -- complete with 5-blade fan. You could have taken all the pictures you wanted for days and days.

[Joe L.]

Re: C3: LT1/ZR1 fan - 5 or 7 blade?

Jack------

The GM #3770529 was not used for any C3. The 5 blade fan used for 1970 was first used for certain 1966 applications and has a greater blade pitch than the 3770529. I don't recall the complete part number, but the last 2 digits are 66 and the first 3 digits are 388.

[Jack H.]

Thanks, Joe...didn't have a '70 AIM... *NM*

[Dan Pepper]

Re: C3: LT1/ZR1 fan - 5 or 7 blade?

Terry-

Yeah, I would have taken a few hundred pics. This being only my 2nd C3 I have a lot of general questions RE the details on this car. All the major ZR1 components are there, so it's a matter of looking at wire & hose routing, fittings, connectors, etc. Luckily, most of this stuff is standard LT1 fare and is fairly easy to reference.