Shurshot

Hi

I was wondering about the claims of the manufactures of direct fans of 25 plus HP?

Or just how much the difference in running temperature would there be with two pull fans and an aluminum radiator if I went the route of a direct fan? (plus an overdrive transmission although I suppose the difference is more down low in the rpm and speed range).

Any thoughts other than try and and find out?

Thanks in advance

Doug

gonefishn

Other then try and find out my Pontiac GTO has a clutchless fan by GM design and works very well. The metal blades flex as RPMs increase thereby reducing the drag (ie HP increase). The air flow increase sthrough the radiator at speed which is enough without the contribution from the fan. They called this a "flex fan".

Maybe the aftermarket setup your looking at incorporates this concept.

babbah

I run a 7 blade clutchless stainless steel flex fan on mine and it works perfectly also

Allcoupedup

If you use a high flow air filter +10 HP, flow master mufflers+ 10 HP, the clutchless fan +25 HP, octane booster +5HP, that tornado thingy +5HP, underdrive pulleys +10HP, racing stripes +15 HP, super duper elctrokilovolt whiz bang blamo coil +10HP, splitfire spark plugs +10 HP, you will have an extra 100HP!!!!!

Sarcasm aside, I don't think you'll ganin any significant HP as a properly functioning clutch fan will not match engine RPM 1:1 at higher RPM. It does the same thing as the flex fan.

brian

Shurshot

I know a place that has better racing stripes then you have.

Seriously how much does air flow over the motor help? What about an electric water pump and no fan.

Illl bet if it works though it cost to much for me. The only things that work for me are wwwwaaaaaayyyyyyy expensive

Doug

avideo

and by changing out the stock fan and replacing it with some spacers; (so it is closer to the radiator) my engine now runs about 10 degrees cooler on the highway. Also, I can idle for long periods of time in parades and similar situations and the temp stays in the 200-210 degree range. This was not possible prior to the fan and spacer install. It also helps if you have a Dewitt or BeCool Radiator.

ghostrider20

A solid mounted stock fan (if your's is stock) will rob 25-35 HP at 3500 RPM and hurt economy.

The stock clutch limits the rpm to 3500 (I think) and disengages when not needed, like when going down the road.

Mark

Shurshot

Hi

There has been some good feed back on this thread and I am going to make a change in my stock setup. It seems to me through looking at Jegs that the flex lite line with their spacers is the better way within the products that they offer.

I just got my car back on the road again but another problem has shown up that needs to be addressed first

Either my electric fuel pump or fuel regulator or both are dying

Isn't this about par for the course?

Doug

wmf62

i think the 'best' fan choice would be an electric puller fan; but i am a really big fan of the solid hub flex type fans.



Bill

JohnZ

The fan's distance from the radiator isn't important - what matters is that the fan is properly positioned fore-aft at the rear of the shroud, with the blades half-in and half-out of the rear edge for maximum air movement through the core at idle and low traffic speeds. The fan contributes virtually nothing to highway-speed cooling; the ram air through the core over 30-35 mph is far in excess of anything the fan can supply, and a fixed fan can actually reduce ram airflow - that's why the production fan clutch nearly free-wheels at normal temperatures and disengages over 3500 rpm.

It's hard to improve on the original factory radiator/shroud/clutched-fan design, if the components are up to snuff; if you have more motor making more heat (like Shurshot), leave the factory setup as is, but add more radiator.

lovevettes

I met a guy at a cruise nite that use to have a fan that was a flex
type and he won't use them any more because the blade got metal fatigue [from flexing too many times] and snapped off and got embedded in his fiberglass hood. And if you think about it, at highway speeds the fan flattens out to be a wall , not letting the air pass directly thru the radiator this might be o.k. if you have overdrive , most of us don't.

wmf62

think about it this way... a 'wall' is a 'wall'... the fan blades on a windmilling clutch-type fan present a somewhat solid face to air flow too.. (and that same air has to turn the fan too, rather than the engine turning it)
Bill

avideo

To John Z: Just to be clear about things, the original clutch fan on my 1966 convertible was spaced at least 1-2 inches away from the shroud. The newer flex fan now sits much closer with about half of the fan's blades siting within the shroud. As for cooler temps at highway speeds; that's my real life experience with this new set up. The temps are confirmed both by the dash temperature gauge and a temperature measuring cap on my surge tank. (Readings taken just after stopping at a highway rest stop.)
Perhaps best of all, I no longer have high temp issues when driving in parades or idling for any period of time.

wmf62

i've never seen a temperature reading cap. who makes it, and do you have a picture?
Bill

00fxd

I had a flex fan in a street rod years ago. Everything was adjustable. There was no shroud so I adjusted the flex fan to about 1/2" away from the rad. When I got out on the hiway and got the rev's up the flex fan flexed into the rad

waynec

I can't really comment on the physics involved, but considering that auto companies bend over backwards to save pennies on every car they produce ($0.01 is $10,000 saved on a million cars)... do you really think they'd have gone to the expense of specifying a clutched fan if the simpler (and much cheaper) flex fan was a better choice, considering airflow capacity, safety, durability, and engine noise?

Seems intuitive to me that whatever HP is required to drive a flex fan at the speed that the blades are fully flexed, will continue to be required (and more) at speeds above that, whereas the clutched fan disconnects and is no longer a drag on the engine at the higher speeds.

wmf62

my personal opinion...

i think the parasitic losses due to engine fans are exaggerated...

and, most clutch type fans are thermostatically controlled, not rpm controlled (you know, the flat bar or coil spring on the front)

that having been said, i believe the primary reason the manufacturers went to a clutch-type fan is to cut down on engine compartment noise. even if you've never heard a solid hub, non-flex type a/c (6 or 7 blade) fan at high speed, you'll know in a heartbeat what it is.
Bill

Plasticman

GM did not have flex fans in their choice bucket (at that time). But when good flex fans became available, GM was one of the first to use them on many big car/big engined AC vehicles. They also came out with a huge flex fan that they installed as a dealer TSB fix for overheating AC 454 Vettes in the early 70's. Somewhere I have that info, and will dig it out. I used one on my daily driven 70 Vette (SBC 350/350 with AC) after my 2nd dealer supplied clutch fan went belly up. NEVER had a heating issue and it lasted forever! And I swear (seat of pants) that power did not change one iota, but it was certainly louder at idle!

Been using the GM flex fans ever since, with no issues whatsoever.

Plasticman

avideo

I'm not sure who the manufacturer is of the cap. But I bought it through Summit Racing. If you go to the Summit website I suspect you will find it pictured there. It looks pretty neat, since you don't expect to see anything under the hood to measure temperatures.

Shurshot

I started thinking about the flex fan after being told my double pulley on the water pump was hitting the screws on the face plate of the certified harmonic balancer. Not able to wear my hearing aids around the car I took the guy's word for it and spaced the fan further out on the shaft.

Because that resulted in less support for the fan and not being too keen on the idea of it coming off at 7000 rpm I started rethinking that decision and started this thread.

It seems that many of you are happy with your flexible fans (other than the one that flexed into the radiator ) but I do question the overall claim in HP increase. Maybe there is a increase below 3500 but for me personally with 4:11 and a 5 speed the only time I am that low is in 5th gear when HP is not needed .

I do not do parades or traffic and so far ( I have only been back on the road for short time) my temp with a Dewitt is right at 195 and matches the thermostat.

Meanwhile I drove by a friends place today and he hears the ticking still happening but locates it in the rockers and low valve covers still hitting even with shaft rockers (680 inch lift). So knowing that I will remove the spacers and retain the integrity of my fan mount and not have to stress whether it will remain put

What works for me may not work for someone else but I do agree with the following posts as examples in dealing with my situation. However there were many other good posts

WMF62 said
I thought Wayne brought a real good point up

However I believe John Z has the record here for steering more of us to happy motoring then any magazine or product tech ever will and his post sealed my choice
Soooo the fan stays (without the spacers) and I fixed the fuel pump problem (my bad, to fine a filter before the pump) and I am ready to go do some driving and enjoying God willing

However as I speak we are having our first real rain here in over 4 months

But for the better of others I can wait another day or two

Thanks for all the replies

Doug