too much RPM for waterpump ???

[v8zed]

Hey Guys,

I am having a small problem with water loss in my 240 with a 355 Chevy . I love the performance and am overall happy with the car. I shift at 6200 to 6400 when accelerating hard and at 2600 when driving normally . Whenever I have made a long hard run I find my 1qt catch can full and the same gone from my radiator. Regular (below 5000) driving doesn't make this happen.

What is the top rpm a stock water pump should see? I am thinking maybe trying to find a smaller pulley but I have serpentine drive .

Thinkin I may need to remove every other vane in the pump if I can,t slow it down.

Any one else have this type problem?

355 chevy block

sr torquer 2.02 heads bowl ported 67cc chamber

forge crank

hp618 .125 dome hyperu pistons

1968 Z28 3030 cam solid lifters 513 lift at valve installed 4 degrees advanced 114* lobe center 254 duration at .050 in w crane roller tip rockers

chromoly pushrods

Victor jr 1 in taller than std with Holly 750 vac secondary carb

petronix module in acell hei dizzy recip assembly balanced to 8000

I would also ask if Grumpyvette or some one with a dyno program could give me a horsepower and torque estimate.

I do know the 240 weighs 2680 with me and 10 gallons of fuel and was still pulling hard at 5000 in high ( .73 OD ) with 3.54 gears.

Calculated at 145 mph with 25.. in tall tires.

What hp does this take??

Thanks for taking time to read,

Dennis

AKA V8ZED

IZCC #1390

Heart of America Z-Car Club # 13

[Guest Anonymous]

I'd hazard a guess its more than likely just the extra heat put in the motor from the extra RPM thats causing it to just heat the water up when you turn it off and the water expands and gets sent out of the radiator. I'd put a catch can that can allow it to be sucked back into the radiator when it cools down. Just a idea anyway, I know my car won't even go to 180 this time of year unless I get into it through a few gears, it'll stay about like 165-170.

Not sure on the RPM thats safe at the pulley, but I don't recall anyway mentioning blowing up water pumps here and I know several that shift at those RPM's.

 

Regards,

 

Lone

[Guest greimann]

You wouldn't be running without a thermostat would you? If you are, it needs to go back in because it serves as a metering orifice that limits the filling pressure in the radiator. Also, the radiator cap is only a pressure relief valve. It does not know how hot the water is, all it knows is that at X psi it will open and send excess pressure down the little tube. When the water pump is spinning at high RPM, a system without a thermostat will send the pump pressure directly to the top of the radiator and blow out the cap. If you have a thermostat in, try a higher pressure rated cap. I would not alter the pump vanes in any way because you will sacrifice low speed cooling.

[BLKMGK]

I'm using one of the catch cans made of aluminum with the drain in the bottom. Rather than use that drain as a drain I hooked up my vent hose to the BOTTOM. This way when the radiator cools it won't suck air it'll suck the water back in. Air vents from the top where the hose would normally go...

[v8zed]

Thanks for the replies,

I am running a 165 degree thermostat it also has a 1/8 inch hole to prevent air embolism.

I notice the water going into the can before the motor is shut off. I also observe no spike in temp after a run other than to about 180 . After a couple minutes normal running it goes back to 165,170 .

I am not really worried about blowing up the pump but rather about blowing water past the pressure cap due to high pressure from a pump spinning too fast. Although it seems that it should be able to go through the Griffin and back to the block as fast as the pump can move it. Sometimes I can smell the water hitting the engine while driving if the can gets full to fast.

I am going to replace the cap and thermostat as a start and hook the hose to the drain on the can to try to recover the water. Second I would really like to get a horse power estimate. Did I give enough detail in the above post to run on a dyno program?

Thanks, Dennis

[Guest JAMIE T]

It sounds like you might have an air pocket in the cooling system. My Z28('94 LT1/6spd) had a problem with pushing coolant into the over flow while the engine was running. The LT1's are notoriously hard to purge the air out of the system. I know yours is not a LT1, but you might try purging the system. You might have to make a fitting with a bleed or even a air valve(like a valve stem) at the highest point of your cooling system.