[Gator67]

I had planned to use a factory appearing v belt driven clutch fan and shroud for my 535ci pro-touring '70 Formula. Installed everything (factory shroud, 19.5" 7 blade fan 9796134, Hayden 2797) and noticed that the fan sits just at the edge of the shroud opening. Did not consider that the engine is set back 1.5" from factory (DSE subframe). Am I going to have a problem, and if so, what's my best option (other than electric cooling fans)? 1" spacer with existing clutch & fan, flex fan & 3" of spacers, or maybe there's a longer fan clutch or something else I haven't considered?

[TxSportCoupe]

I like the spacer idea. I think you’ll pull plenty of air at speed as is. But I’d like to see that fan just a little forward for idle cooling. Flex fans are a power robbing, screaming joke IMHO. No need for fancy stuff if your set up and timed correctly. I think you’re on the right track.


Sent from my iPhone using Tapatalk

[Hikin Mike]

I'd be cautious about adding a spacer. I did that years ago and the fan impaled the radiator in short order. The spacer I used was larger than 1" though.

[78w72]

could try a longer factory spacer? later 2nd gen birds & other cars came with the longer 2" aluminum spacer on the fan, one like this. i have a bunch of nice used ones id sell for cheap or let you try one out if you covered shipping of a few bucks.

https://www.firebirdcentral.com/Pont..._p/rad-742.htm

[srmmmm]

I would recommend first evaluating your operating temps with the configuration the way it is. I think you'll find the fan pulls air through the shroud just fine the way it is. I would not recommend a spacer more than 1" in thickness because of the weight of the fan/clutch assembly. The least imbalance will be amplified and lead to premature bearing failure in the water pump.

The primary concern is safety - you've got significant exposure to those spinning blades anytime you're working under the hood on a running engine. It's obvious you're maintaining a pristine factory appearance, but I would consider extending the shroud rearward with a nicely formed aluminum ring, solving both issues.

[Murf]

I think Hayden says not to do that. I’ve never seen a factory clutch fan with a spacer. I will admit I haven’t seen everything tho. ��

[78w72]

Originally Posted by srmmmm

I would recommend first evaluating your operating temps with the configuration the way it is. I think you'll find the fan pulls air through the shroud just fine the way it is. I would not recommend a spacer mare than 1" in thickness because of the weight of the fan/clutch assembly. The least imbalance will be amplified and lead to premature bearing failure in the water pump.

The primary concern is safety - you've got significant exposure to those spinning blades anytime you're working under the hood on a running engine. It's obvious you're maintaining a pristine factory appearance, but I would consider extending the shroud rearward with a nicely formed aluminum ring, solving both issues.

GM used the longer 2" spacer on lots of cars... but maybe not with clutch fans, there shouldnt be a safety or imbalance/bearing failure issues using a facotry 2" spacer.

GM put the fan about 1/2 to 2/3rds into the shroud on their cars for maximum air flow, it may work like it is but its not ideal & with a big 535 it may need all the help it can get for good cooling, although if everything is set up right the factory fan/clutch/shroud should be sufficient.

[srmmmm]

They didn't use a spacer with clutch fans.

[78w72]

Originally Posted by srmmmm

They didn't use a spacer with clutch fans.

right, the one thats in the clutch fans are probably shorter than the 2" spacers.

[grivera]

Try Hayden 2731 - it has same spec's as the 2747 but has a longer shaft so will be closer to radiator: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[78w72]

Originally Posted by grivera

Try Hayden 2731 - it has same spec's as the 2747 but has a longer shaft so will be closer to radiator: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

that looks like a good option.

but curious why its OK to use a 1" longer shaft vs using a spacer to account for the extra length to space the fan further into the shroud?

[grivera]

Educated guess is due to it being an engineered part vs cobbled together as spacers are not recommended for fan clutches that I’m aware of.

[78w72]

makes sense

[Formulabruce]

Take a look at a 1970 Grand Prix. Pontiac installed a factory " wind tunnel " behind the fan shroud to remedy distance to shroud. A shorter version would work ( trim down a GP wind tunnel ) This would avoid a longer clutch fan if that option is risky out that far. The GP wind tunnel will fit right up to the factory shroud opening.

[OG68]

Just throwing this out there;
How about a deeper shroud from another GM product?
I think by extending the fan shaft out too far your water pump may fail.

[OG68]

Ack, FB beat me to it.

[Gator67]

Thanks folks. It will be another week or two before she's up and running, so we'll see soon enough if there's an issue. I think plan B will be the Hayden 2731...that should put the fan about 3/4" closer to the radiator...definitely inside the existing shroud. The extreme duty 2797 on there now was kind of an experiment anyways...That clutch calls for a fan pitch of 2.5+ and I believe the pitch on my 9796134 is only 2.25. I'll have to do more research on the GP wind tunnel...that might be plan C.

[Formulabruce]

The GP Wind tunnel. This looks like 1 piece, and could be trimmed? The fan placement of the blade is critical to air turbulence at the edge impending the efficiency.

[grivera]

[QUOTE=OG68;635181
I think by extending the fan shaft out too far your water pump may fail.[/QUOTE]

I’m curious on what outcome would be. Looking at the application chart for the 2731 fan clutch shows numerous Cadillac models. So I looked at relevant waterpumps on line and don’t see what makes them different from a Pontiac water pump in the snout and how it could lead to bearing failure.

https://www.go-parts.com/ps-mmp.php?...ine+Water+Pump

[OG68]

I'm curious too. I'm just thinking that having the weight of the fan and clutch extended further out than normal can't be helpful for longevity of the pump unless it was designed for it. Does the Cadillac pump have a bigger bearing or greater support? I don't know, just thinking out loud.