Quite awhile back I put on a March under drive pulley setup on my '88. I've been happy enough with it but need better cooling for road course racing. There are a few options, go back to a stock crank pulley, use a smaller water pump pulley, or go to a whole new setup.

I'm going to try an early water pump pulley which is smaller diameter. Because for my track car the charging seems fine, and the power steering is alright. So I don't want to waste HP driving them faster.

Here is a bunch of info on diameters and pulley ratio.

1.2 to 1.35 :1 waterpump to crank speed ratio. Example, use a 6.25" wp pulley and a 7.75" crank pulley to get a 1.24:1 ratio.

If your water pump pulley is LARGER than your crank pulley, then your waterpump is UNDER DRIVEN, meaning that the water pump will spin slower than the crank.

Griffin radiator site:
5. Thou shall use the proper water pump pulley ratio.
To obtain the maximum operating efficiency rate for your water pump at highway speeds, you should overdrive the pump by 30-35%. Check your pulley selection. Most after market pulleys are a 1:1 ratio. For a 30-35% overdrive, the crank pulley should be approximately 7 7/8" and the water pump pulley approximately 5 3/4". This overdrive provides proper coolant flow from the engine and through the radiator.

Stock pulley dia. - March 4425 kit:

Crank 7-1/4 - 5-5/8
WP 5-3/8 - 6-15/32
Alt 2 - 1-5/8

I also removed the fan for better high speed airflow. Hopefully temps are good next year! They were especially bad drafting another car. It will be awhile till a report back.

 

It may not apply to Your exact High Speed Road Racing application & usage........

But I like to under drive the water pump impeller Vs the crankshaft RPM's.

Its done that way on most dirt track cars & UMP Super Late Models, and NASCAR running at speeds over 190 MPH.
At continuous High RPM's from 6,000 to 9,000 RPM's +,
the water pump moves so much water volume that it does not have adequate time to conduct engine created thermal heat to the radiator cooling tubes, into the external cooling fins, and thermal heat dissipated to the air.

6 inch crankshaft pulley & a 7" to 8" inch water pump drive pulley typical.

Under driving the water pump on my 70 T/A took water temps of 200 to 210 F down to 160 F continuous driving down the highway.
Nothing else done or changed.

Have to experiment & see what works best for you.
Results will vary for each more than likely.

BR

 

i agree with with brian but us road racers do need more cooling than most all u have to do is make sure the water coming out of the radiator is preportionally cooler than water entering at any given flow rate. for instance if your at idle use a pyrometer to check the inlet , outlet hose then check water temp at guage. then run a few laps hard and test again. note the difference in water entering and exiting the rad when you get your over drive pully on repeat the process. when u .compare the temps to make sure water has time to cool in the rad....i have found that completely sealing the air intake to the rad with sheet metal and expandable foam. so air is forced through rad and the addition of heat extractor vents in the hood or just removeing the upper wheel well to let hot air out helps alot...if you dont see a good drop in temp beween inlet and outlet more flow isnt going to help. i use a dual 1 inch core rad with a sealed intake and am finally getting to the bottom of my cooling issues......

 

One problem with under driving the water pump on our C4's is that no one makes it for a serpantine drive belt setup to my knowledge.
All available aftermarket pulley kits do not have a larger diameter water pump driven pulley.
They are all geared for street & strip performance.

Currently available undrive water pump pulleys are in old school "V" Belt configuration.
Water pump pulley must be a larger diameter than the crankshaft pulley to possible gain coolant reduction temps under steady state high RPM operation of 6k to 9K + .

If you have a Master Machinist bud that has access to a MAZAK 4 or 5 axis CNC machining center & handy yourself of drawing up Blueprints,
he can easily make you a custom Under Drive Serpantine water pump driven pulley & matching crankshaft drive pulley.
Billet aluminum pulleys then should be heat treated to T6 Areospace standards afterwards for long term high RPM durability.

I have my bud MOPAR Bob to make the serpantine underdrive water pump pulleys for me in the near future for my own C4.

I worked in the same machine shop as him in the 1990's.
It can be easily done & completed there by him.

A science experiment to see how it works on my own 410 ci stroker small block transplant into my '87 Vert.

Brian

 

I ended up replacing the March under drive water pump pulley of 6 15/32" from their under drive pulley set 4425 with an early year pulley 5.375" part MCH-4132. Losing an inch in diameter, and being slightly larger than the crank pulley now (5 5/8" crank pulley).

Heat transfer through the system works by convection. You cannot flow it to fast. It's a long standing myth that can be debunked by the other side of the coin. If the water was flowing to fast to cool off, it would also be moving to fast to get hot. You can't have it both ways. The myth came about I believe from cavitation.

 

Yes & No.

Pressurize Your cooling system & Feed it 2,000 gallons per minute coolant flow.

Likely flow too much.......LOL

Have to experiment as you are doing right now by over driving the water pump impeller.

I am going the opposite route of You.
Under drive the water pump impeller.
Larger diameter water pump pulley than crankshaft pulley.

Smokey Yunick is smarter than You & me and anyone else here on C4 or rest of Corvette Forum.

Look at his Book Smokey's Power Secrets.......

The front cover............

Way larger diameter crankshaft pulley than crank.
Custom billet machined pulley set he made.
Smokey was not wrong.
His engines won many races.
He built more than his fair share of race winning SBC & Vintage Pontiac V8's.

BR

 

Looking to sell this larger pulley if you want it.

This setup worked well for drag racing but in hindsight an electric setup would have been better. It didn't cool all that well at idle.

 

Suggestions from a track guy who is **** about track engine cooling.

Stock water pumps have paddle wheel type tin fins that will cause cavitation at high rpm.
Get a pump with a cast curved vane impeller. Moroso used to make them.

Under drive the pump 30% of crank rpm.

Remove thermostat, install a water restrictor washer in its place. A restrictor washer with a 3/4" hole should get you real close if not right on the money.

If you do not already have one build a front air scoop to direct air up into the radiator. Style it like the Vette big mouth air dam. Measure the radiator area, the intake area of the scoop needs to be no less than 40% or larger than 50% of the radiator size.

If your car still runs hot you need a good radiator.

An electric fan mounted on the engine side of the radiator will not reduce much air flow through the radiator & should only be used when putting around the pits. The fan blades will spin freely when the vehicle is at track speed.

Luck with your project.

Here's a link to a track parts supplier near you:
https://www.lefthanderchassis.com/v2...idcategory=261

 

The scoop when done right will grab as much air as possible yet not create drag when its reinforced from behind so it cannot fold downward too much. Angle is everything. Use the 2 rails as a guide to width.

I was going to suggest that (pump type) as the simple/obvious answer...

just use a REAL water pump impeller, often referred to as a "cast" impeller that has more efficient vanes to move water easily at low rpm. It equates to high vol at low speed.

By doing this you can underdrive the pulley system all you want and apply that parasitic HP to the wheels (gain of 5-10 mebbe) and still have cooling from water flow. IF there is cooling issue from too fast flow, meter that down with an orifice or adjustable orifice somehwere in the system. Your car came from the factory with orifices in the cooling system to cause water to get backed up in the heads so they stayed full of liquid to collect as much heat as possible and to prevent hot-spotting and spikes.

Get an efficient water pump and under drive the pulley. I know from experience that a good pump moves as much water at idle as a stock pump and stock ratio does at 3500 rpm. Easy to figure that an under drive is well within the safe range.

Electric fans do not restrict airflow at high speed. They spin assisting the flow. Taking the fan out....poor engineering.

The goal here is to achieve the best cooling thru efficiency. That means water pump type, the radiator (larger capacity and higher efficiency) and air flow thru air scoop and fan. Taking any of these things OUT forces the other remaining componants to do more, which they cannot. They can only do what they were designed to do.

 

I've had a good water pump on the car since soon after I bought it. There was a drop in cooling ability with the UD pulleys when I put them on, even with the better pump.

Many road course cars don't have a fan. Less weight and better airflow through the radiator. Recently I removed all of the shroud behind the radiator, it made a noticeable difference in lower temp.

I've been tempted to use a restrictor in place of the 'stat but spring/fall events are just to cold.

 

Yep, Do not need the rear fan shroud.

BTW, I used the Howe track radiators. They are cost effective & work well.

Here is a size chart, something should fit a Vette.

https://www.lefthanderchassis.com/v2...dgroup=2512623

 

Andy, this write-up is on the money, do not overdrive your water pump, that is part of the problem with your overheating issue. You need to address all of the other issues and even then I suppect your radiator is too small. You are making at least 400 HP and running at WOT for long distances on RA.

 

Suggest looking at the impeller blades on the water pump. Many "high flow" pumps are nothing more than a stock pump with a round sheet metal plate pop rivited to the engine side of the impeller. They do work well for low rpm vehicles but not for track cars.

BTW another cooling solution is to build or modify a radiator so that it is a double pass unit. You will need a metal or aluminum radiator.

Locate both inlet & outlet on the same side. Midway up between the inlet & outlet install a plate in the side tank from the core out.

The coolant will flow across, drop down then flow across again.

Suggest moving the lower hose fitting. Plumb it back to the pump with as much metal tube as possible. Rubber hose will suck shut when the pump is running @ high rpm.

 

For ANYONE thats skeptical about what both Church and I are speaking about....

Look at your alternator.

That "fan" that you see around the alt pulley is the exact same thing thats used for the impeller in common and even many performance water pumps ! A stamped impeller is just that, a stamped piece of steel thats as efficient as a styrofoam hammer. It moves water...it will not push water...

The type of impeller that you NEED to move water at under drive speeds looks more like a boat propeller. Curved to capture fluid and move it with minimal rotation. Efficient. Its called a "cast" impeller.
Do as you wish, but the way out is to spend the money ( and yes, cast impellers DO cost more) and end the problem.
Edlebrock makes a nice one.

 

Good with the discussion guys. If my ideas don't work I'll keep trying different things. Something has got to do better, it is painful having to slow down because of temps.

I took apart a stock water pump a long time back:

Attachment 48183263

I had an Edlebrock on there but switched to a normal rotation Weiand. 9208 model http://www.holley.com/9208.asp It sounds like the good type?

I do have a double pass radiator on there now. It helped a little but I was hoping for more out of it. It is 3" with dual 1" tubes.

I think things will improve with the changes to the thermostat. With the miniram it is very shallow there so I'm changing that. Also I'm considering machining grooves in the water pump pulley.

 

Might take a look at the "features" of that pump.

"Six-blade stamped steel anti-cavitation impellers for maximum water flow necessary on street applications"

 

[QUOTE=Churchkey;1579106340]Suggestions from a track guy who is **** about track engine cooling.

Remove thermostat, install a water restrictor washer in its place. A restrictor washer with a 3/4" hole should get you real close if not right on the money.

warning not lt1s
i was told this too u cant do it on a lt1 motor the water pump has a hot water mix hole in it the thermostat closes when it opens.. a restrictor dosent allow this hole to close and the result is hot water gets pushed back into the motor over and over and dosent even get to the rad instant overheat!!! if using a restrictor block the lower hole in waterpump visiable through the thermostat housing

 

[QUOTE=TRACKMAN2;1579121690]I watched some of your racing Videos George You sent me.
I have been busy much lately.
Should go back and watch some more of them.

I want to see You holding the Checker Flag taken from the Flag Man & waving it to the crowd cheering for Your RACE WIN.
MAIN FEATURE WIN.
HOT LAP TIME OF THE YEAR WOULD BE AWESOME TOO.

You can drive a Road Race Car.
I knew that all along.

Will work out as it should this time with your SBC LT-1 race Engine for You.



BR