Technical Overdrive water pump

Is it a bad idea to consider over driving the water pump? SBC in a model a gets hot at idle over 85 degrees ambient. 32 grill shell and aluminum radiator with a shroud. Fan is HD 6 blade flex fan. Medium size thermostat disc. ( no thermostat) Runs 170-180 all day until you stop at a light. Thinking if I spin the fan faster maybe that would help. My concern is, speeding up the water flow. Trying everything to avoid a pusher fan.

 

What is 85 degrees ambient?

 

That's what I ended up doing and works great for me in the 100+ AZ heat. I run a rigid blade fan. Was able to find where I wrote my pulley part numbers down. Crank pulley is GM # 3850838, bigger than a standard SBC pulley at 7 1/4". Water pump is Ford # D8AE 8509 AA and a bit smaller than a standard SBC pulley.

These are both for short pump only and may or may not need slight shimming to get alignment perfect. I've also found that a proper overflow bottle, not just a "catch can" helps too. Keeping tubes full and preventing air bubbles from getting pulled through the core.

 

Don't overdrive it too much, and make darned sure your fan is good and doesn't show ANY sign of flex cracking. High RPM's can make the blades separate if they are weak, and wreak havoc on many hard and soft parts. They have been known to slice right through a hood, and I assume at some point in time a stray fan blade has met human flesh.

 

Using a smaller w/p pulley on a Yblock is a common solution to idle overheating problems.
Search “flex blade fans” here. Not good in most cases. A buddy in Tucson uses a Hayden clutch, a 16” a/c fan from a junkyard, and a smaller pulley on a Yblock in Tucson. He can idle at up to 105 degrees in a 56 bird. Proof enough for me.

 

I would go to a 7 blade flex fan and open up or remove the restrictor plate first before I overdrive the water pump. It sucks power and may cause cavitation.

 

A SBC shouldn’t need a restrict plate for a non-race kinda car. What Al radiator do you have? Personally I feel you can’t “circulate the coolant” too fast, others have a different view.
May want to mention your engine build, base timing specs as well.
And finally, how hot is it at idle?

 

The days when it reaches 85 degrees F outside, but I know you knew that

 

So that’s just a fancy way to say it 85 degrees outside.
Well I be. We don’t talk that than in Bama. I’d probably get called a yankee.
Wonder how hot the engine actually gets?

 

How hot does it get?
Ya left that part out
Why no thermostat?
How does it do with a thermostat?

 

I have had good results with Flow Kooler brand water pumps....Generally when doing engine swaps we need to consider radiator size and capacity when in the stock vehicle....If it ran okay in them it should be okay in a hotrod...

 

As far as fans go I had cooling issues in my Chevy II and a flex fan and a rigid fan with a "super heavy duty" clutch were a tie. A rigid solid mounted fan did the best and can be had in a lot of diameters with aluminum blades and a steel hub. My Vicky has a smallish diameter all steel rigid fan, was blown and revved to 6200 here and there without incident even with the funky pulley setup and had 20,000 or so miles on it before I yanked it for to put in another car. I do usually opt for the "heavy duty" water pump but still a parts store brand.

Also, having a shroud is a big help but it has to be made right. Perimeter should seat tight to the radiator and not too small of a fan. Can't believe the stuff I see sold usually for electric setups that are 1/2" or less deep and choke off most of the core with a round hole or two for fans. Gotta repeat the need for a proper overflow bottle with a siphon tube. Have had 3 or 4 cars with cooling issues helped by adding one. Either running a little warmer, usually cross flow radiators as whole tubes go empty with low water or wild temperature cycling on either type core.

 

I put an adjustable washer in mine.
It opens and closes and keeps the engine at a constant temp

 

Thanks, those are all great suggestions especially the coolant resivoir. Currently I have a catch can type. Never gets much in it though. I’ve seen it get just under 210 at a light. I’ve never let it get any hotter than that. The Block is .060 over bored which doesn’t help. Timing is 12 deg base and 38 total. Problem is..... I’m limited to a 13 inch fan. At a light it goes from 180 to 200/205 within a few min. I assume it will keep climbing.

 

You mean... like a... thermostat?

 

Cavitation is what I was concerned about. I did not know how that may enter into the conversation.

 

Mine is a long water pump but they do make kits out there to overdrive them.

 

I remember in the late 70s Ford had problems with their flex fans. They would pretty routinely come in with one sticking out of the hood!

 

210 is perfect for a 350.
I ran mine 210-215 for 4 years. .060 over.
A vapor lock issue would sometimes occur in traffic at 215, other than that, it’s fine.

 

If I remember correctly, it’s about the same temp with a thermostat, without a thermostat or with the restrictor. Doesn’t really seem to matter.

 

I would remove the flex fan and replace it with a rigid steel fan that has a known RPM rating. I would install a thermostat and drill it for three air bleed holes. Double check the fan to radiator core clearance and shroud to fan clearance. If all of that is where it should be you should not need to change the Water pump drive ratio.

 

You mention a "proper overflow bottle", sounds good, but how much coolant should be int the bottle?

 

Pop the hood on a modern vehicle. Seems about 75% full when “hot” and around 60% full when “cold”.

 

most serpentine belts have a larger crank pulley and a small WP pulley

 

You need to see water movement at idle for proper cooling. I never worry about increasing the rpm of a water pump because I’ve made it a practice not to drive with my engine at 5000 rpm for a constant time. Today with higher rear gears and OD transmissions the high rpms at freeway speeds are a thing of the past as we modernize our vintage cars.

 

Whatever it takes to keep the siphon tube covered and not pouring out the vent tube. Somewhere in the middle, not too much science involved.

 

Yep. Did some calculations with my combo described above and think with my 6" pump and 7 1/4" crank pulley the pump/fan is at around 7,500 with the crank at my 6200 rpm limit. Think the solid fan is rated at 8,000 and rarely saw those speeds. Increased fan speed really helped at idle sitting in traffic though.

 

I've never been able to figure out why guys shit their pants when temp of a SBC gets up above 200 in a hot rod when it ran at or over 200 for the whole time it was in the donor rig it came out of. the Oh crap it's in an old car and It scares me nonsense.

Still air flow is the issue most of the time and when the engine is idling air doesn't flow good without a lot of help. I had the "hot rod fan" on top on my 48 for years and in the summer the temp went up at every stop light but dropped right back down as soon as the truck was moving over 20 mph. That bugger doesn't take many horse power to turn it at speed but doesn't move air worth squat. It didn't help that half the radiator was not getting any air flow from the fan at all as I had no shroud on it. It's getting replaced with the one below it with about twice the blades and a shroud.

 

I think something is wrong with my 500 caddy. It never gets past 185. Traffic or climbing hills. Maybe I need a warmer thermostat.

 

Texas in Jan?

BEN