Race Fan

**hucktyson** · 10-27-2019, 09:35 AM

Has anyone done CFM testing between a 4 or 6 blade 19” “ race fan “ and the old school GM 442 fan ? I’m finally out of the good original GM ones and looking for something that moves as much or more air. I know 4 blades used to move more air than 6 but has race fan figured out a way to change that ?

**billetbirdcage** · 10-27-2019, 10:19 AM

This probably ain't gonna help you.

Back story: Years ago, I wanted to test fans and 2 blade vs 4 blade. The only way I had to do this was to use the Air flow hats for the Carb that measures CFM (I have 2, one for a Dominator and one for a 4150 carb sizes). One was 1000 cfm and the other was 1400 CFM max, so I made a box to go on a shroud that attached both Air flow meters. The problem was I didn't have enough CFM to measure at a very high RPM, but ran up until it maxed out both flow meters. I had to make an educated guess from the limited data, but the more blades pulled more air at low RPM and as the RPM increased the numbers came closer together. I would have to look it up, but I think I maxed out the air flow meters at around 2500 RPM fan speed

So going off that data, it appeared as at lower RPM the 4 blade would cool better and at higher RPM the 2 blade may get close to the same cooling yet use less power. Just wasn't enough data to make an accurate decision.

That being said, a 2 blade GM fan (4 blade with 2 removed) doesn't seem to cool as well on a crate engine as the 4 blade does on the track, when it's really hot outside in the summer. Now while that could be from RPM not always at max or a number of other factors.

Like everything, that is my experience and I'm sure others have different experiences

**fastford** · 10-27-2019, 11:49 AM

we run 2 blade on alky and the old 4 blade on gas...

**Jking24** · 10-27-2019, 08:05 PM

We run the four blade configuration and have run it on a crate aswell as a 440 wide bore cornett with no issues. From what i have seen it's close to or as good as a gm

**billetbirdcage** · 10-28-2019, 12:38 AM

Misread your question, sorry.

Anyways, everyone I know that runs the racefan uses either 3 or 4 blades with an open engine. I've never seen anyone run more then 4, but obviously not something you typically look at.

**hucktyson** · 10-28-2019, 04:07 AM

Yeah the question was really does a 6 blade race fan move more air than a 4 blade race fan , because years ago the 6 blade steel stuff usually ran hotter than 4 blade steel stuff but I’m thinking it might have been because the 4 blades usually had a much steeper pitch than the 6 blades

**MasterSbilt_Racer** · 10-28-2019, 04:31 AM

There are always diminished returns of more blades with increasing speed. I have serious doubts spinning a 6 blade fan at 8000 rpm is going to be a winner.

**JustAddDirt** · 11-05-2019, 10:06 AM

Allstar Performance has a new 19 inch GM fan they just released. 60º pitch.
Hard to tell from the photo if the tip of the blades are the same as the factory GM. That is were a lot of the magic happens on the old GM blade.

part # ALL30099