I've got a slightly different over-heating problem. This is in an American Sedan race car (91 Camaro). I recently put in a professionally built race enging (305) and have since been over-heating when I push the new engine.

I've got a Griffin race radiator and I run a restrictor instead of a thermostat. I also took out most of the plastic duct-work from in front of the radiator, but have blocked off the top and the sides - but I still have an opening in the bottom just in front of the airdam.

I've got dual electric fans - they work, and they're pulling the right way.

The new engine can easily pull 6500 RMP or more. But, I'm still running my stock water pump and pulleys (the serpentine type).

A couple laps pushing near red-line and the water temp is approaching 230 and oil is about 310...I back off to a couple laps at a max of 5,000 RPM and things start cooling down right away.

But this same cooling configuration worked fine with my old stock 305 - with a rev limiter at 5,500 RPM. Could the new engine just be putting out that much more heat over 5,500 RPM??

I'm currently toying with two theories:

Theory 1: I'm just not flowing enough air thru the radiator...I'm thinking of blocking off the bottom area in front of the air dam. This would force all the air to come in thru the grill and then thru the radiator. I'm thinking that perhaps the perssure is building up and the air is swirling around and then going out the bottom in front of the radiator. My thought is to block it off, but to include a small "scoop" to also direct air in from below the bumper - just those two holes in the grill don't seem like all that much air inlet.

Theory 2: Could it be that the water pump is spinning too fast above 5,000 RPM? Could I be getting cavitation and just creating turmoil in the water flow - essentially degrading overall flow? And then, when I back off, it returns to normal? If so, would going with under-drive pulleys help? If so, does anyone know where I can find a water pump under-drive pully that's compatible with my serpentine belt system? (I'd prefer a single pulley swap rather than re-working the entire belt & pulley system to the "old fashioned" style...

Any thoughts??

 

Did you remove all of the plastic pieces before the new engine or after? If nothing has changed besides the rpm I would tend to go with theory 2, march makes underdrive pulleys but another solution would be to replace the stock pump with a stewart.

 

I assume the Stewart water pump is designed to handle the higher rpms?

I'm also wondering if a smaller restrictor would help any...I'm running a 1" restrictor now, but I'm not sure...the threads on slowing down the water flow helping or hurting seem inconclusive...seems like many conflicting opinions there...

I guess I'll call Stewart and ask their experts...

(That's right, I have the same basic cooling configuration as I did before with my stock 305 engine, so the only change is the new engine, more HP, and higher RPMs...)

 

The guys at stewart are great, excellent customer service.

 

By all means , PUT THE DUCT WORK BACK IN!!!

I raced roundy rounds for years and was head wrench on a sprint car for 3 years and faced similar problems.

1--check with some others that U race against and see what size restrictor they run.
2--Look at their air flow ducting.
3--Make sure the hoses are good and not collapsing under pressure!!!
4--Look at their overall cooling system.

Remember that making more horsepower means making more heat!

I know U said you have an air dam/air deflector, is it the stock air dam like comes from the factory? In good shape? If not put one back on ---QUICK!!!

 

That was going to be my suggestion...Being that this engine can pull to 6500RPM and it has a high volume water pump. There is a very good chance your lower rad hose is collapsing on you, causing it to overheat.

 

It might be a combination of both pump and air flow.

The pump does need more suction head at high revs and it could easily cavitate in hot coolant, because the temperaure rise increases the vapor pressure and effectively reduces the suction head seen by the pump.

The impellor might be spinning in steam.

Is the overheating associated with speed or only rpm. The Camaro requirement for the air to divert up into the radiator could mean that the faster you go, the air flow under the car could get to such a high speed and low pressure that the air flow to the radiator stalls and you get no flow. This depends so much on the air dam and the channelling of air to the radiator

 

I talked to the guys at Stewarts and they said it sounded like cavitation - the stock pumps aren't intended to go past 6,000 rpm.

I can't really say if airflow is dropping off at higher speeds...I've not tried running a lower gear but keeping the revs up.

I'm going to tackle both - seems safest...

I've ordered the Stewarts Stage 2 water pump.

I'm also fabricating some new ducting for the inlet to the radiator...

I've blocked off the top - where the stock air filters used to be (I did that a long time ago).

Air can come straight in thru the two bumper openings to the radiator...but I had it opened below that (in front of the air dam under the radiator).

I'm going to make a sort of scoop that'll go down underneith also...I'm hoping that will help force more air in and it'll then have nowhere to go except thru the radiator.

I won't know until my next race on Labor day...

Stewart's also recommended no restrictor (or thermostat)...they said maximum water flow is what they recommend.

I hope this does the trick! If I wanted to run below 6,000 rpm, I'd have kept the stock engine!

 

Sounds like cavitation is the problem because it comes on so suddenly which is what happens in a pump.

If you have the air dam nearly scrapping the ground you should be sure of the air going into the rad and reducing drag under the car.

A hood air outlet at the low pressure area part way up the hood might also help.

Good luck

 

I guess this too late, since you ordered the stage 2 pump, but an undersize probably would have solved the problem IF it is cavatation. Unless they are doing things different than when I was roundy round racing, the "racing pump" is the same as what you have now, with every other impeller removed inside the pump.

 

Martin..what car number are you?

DM

 

I'm Number 98, White 91 Camaro...I just run the regionals around Atlanta (Rd Atlanta, CMP, Roebling...)

Solved the over-heating problem, I think...turned out that the Griffin Radiator was only flowing about half of what it was supposed to. Swapped out a new radiator and it made a huge difference...it still ran hot after about 10 laps, but would cool right down if I just backed off about 500 RPM for a couple laps. So, I fattened up my jets - secondaries most - and that seems to have given me tolerable temps... I don't know if I clogged up the Griffin with something at one point, or if the first major over-heating problem - which was probably due to a pinhole in the radiator - may have collapsed some passages. I heard someone say that if you overheat a Griffin they can do that...I cut it open to look, but really couldn't tell...

And, as soon as I declared my over-heating problem solved, I broke something in the tranny during my last race...that's racing...