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Discussion Starter · #1 ·
For ITB racing:

What water pump do I want to use, and who carries it?

Should I underdrive the pump, or the pump and the alternator?.

Is it necessary to clip any of the pump fins on the pump impeller to prevent cavitation?

Should I use a standard thermostat to regulate temperature or a restricted orifice?
 

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IT Manta said:
For ITB racing:

What water pump do I want to use, and who carries it?

Should I underdrive the pump, or the pump and the alternator?.

Is it necessary to clip any of the pump fins on the pump impeller to prevent cavitation?

Should I use a standard thermostat to regulate temperature or a restricted orifice?
Get a German 'reinforced' or heavy duty pump. It has larger bearings and holds up to rpms better.

Stock pump turns faster than the engine. Assuming 7000 rpms for the engine, you will spin the pump at about 7700 rpms.....too fast, it will cavitate. Slow it down as much as possible, I used to use a 4" crank pulley (illegal for ITB unfortunately), and a 6" water pump pulley for street use, reduced pump speed by 34%. Always ran cool, except at idle in traffic it would 'creep' a bit. Largest diameter for the water pump pulley with a stock crank pulley is about 5.5" I think...can't recall exactly. Any bigger and they hit.

No reason to clip fins if you have a good pump. Cast iron impeller with a full 'face' is the best. An open-faced stamped steel impeller sucks. Most aftermarket cheapie pumps use this type.

Use a 7/8" restrictor, works well.

Bob
 

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Rally Bob,

Could you tell us more about the Heavy Duty water pump. I'd like to know where to get one. I would guess it is made to fit the 74 and earlier style fan & pulley??? Sounds like it would be a good fit with an electric fan if one has to ditch their 75 style fan clutch/fan.

Thanks for the great information!!!
Paul
 

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That's it, nothing else to tell. Has the good impeller, and has better bearings. Don't know where to get them these days, when I was in business I had the option to buy the 'normal' or 'reinforced' pumps from Germany. Probably OGTS can get them though. They definitely last longer, stock pumps never lasted long with race engines (bearing failure), the stronger pumps never got changed at all.

Bob
 

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Do not run a fan at all. At racing speeds the fan slows down / blocks air flow through the radiator. You need all the air flow through the radiator you can get.

No fan can create a problem on the grid if you start the car too early, or start out "hot". I always wait until the "one minute" board to start the car. If the engine was fairly cold to start with, that gives you a few minutes even if they hold for something.
 

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Discussion Starter · #6 ·
So TGSI would you agree with the 7/8" restrictor? I may need to run an electric fan due to the fact that I will be driving the car approx. ten minutes to PIR. I see no room behind the radiator to fit even the slimmest Spal fan, and I really do hate to partially block the front and center of the radiator. I may not have a choice.
 

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It would not matter what side you put the fan on, it will still block air flow. However, I had assumed that you would be trailering your car. So, just drive at about 70MPH and you should havel have no problem.

If you are going to routinely drive the car on the street, then just run the stock fan. Un-bolt it when you get to the race, and bolt it back on when you go home.

No thermostat nor restrictor for racing.
 
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