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Author Topic:   Racing T-stats and underdrive pulleys
o5racer
Dirt Freak

Total posts: 402
posted April 10, 2005 08:35 AM  
What is everybodys opinion on racing thermistats? We had practice yesterday and the car ran warm all day. Even at idle it would get up to 210 on a 75 degree day and after a 5 lap seesion it was almost 230. Last year it would come off after a heat race and features around 210. In the really hot months it might get to 220 or so. This is the same combo that I have been running for years. 28 inch alum radiator, 17 inch plastic fan with a good shroud, stock cast short waterpump, angle milled cammelbacks that I have had been running for 9 years now. The short block is a 360, last year it was a 358 but that shouldnt make a difference. Compression is a little over 11-1, same as last year. The only other thing that changed is I went to serp belts instead of v-belts. The crank pulley is now a 35% underdrive. I really wanted to go with the 15 percent but they didnt have it on hand. In the past I ran 1to1 with a 6 inch crank and waterpump pulley. I have a feeling that the underdrive has something to do with my heating problem. Then it comes down to is the water flowing too slow(too small of a restrictor) or is it flowing too fast. Thats why I thought of a t stat. Any ideas? Thanks
Nick

dm3
Dirt Full Roller

Total posts: 40
posted April 11, 2005 07:07 AM  
First, the .060 makes a difference - a small one in causing it to overheat, a big one in it surviving an overheat. The racing thermostat I don't know about. But a 35% underdrive will definitely bring up your water temp, especially at low RPM. I would try removing the T-stat to improve flow and see if that brings it down to a livable temp.

powerglides
Dirt Freak

Total posts: 374
posted April 11, 2005 09:32 AM  
Ya can't move the water too fast. go to a 1-1 system and it will probably solve your problem

o5racer
Dirt Freak

Total posts: 402
posted April 11, 2005 03:27 PM  
The late model guys are running the 35% with no restrictor. That might be fine for moving water but it doesent speed up the fan. I am probably going to change to a 15% crank pulley and if it doesent help enough I will go to a aluminum 6 blade fan.
Nick

Ego Racing
Dirt Forum Champ
Total posts: 724
posted April 11, 2005 08:29 PM  
You should get your water pump to around 6000 rpm. If you are turning the motor at 7800 then the 30's are ok. We are running a 604 crate motor this year in our late model and went to a 1:1 because we are only turning 6600. It solved all of our problems.

racer17j
Dirt Forum Champ
Total posts: 5390
posted April 11, 2005 10:27 PM  
Get one of those four blade fans...they move more air.

J3
Dirt Maniac

Total posts: 188
posted April 12, 2005 09:18 AM  
I switched to a 25% underdrive pulley this year and my temps run only about 5 degrees higher than last year. So I would say that the underdrive pulley isn't your problem, I would look for other things.

BCracing
Dirt Full Roller

Total posts: 32
posted April 13, 2005 10:01 PM  
on my last two cars I have run stock pulleys 1 to 1 (6")and got a Robert Shaw thermostat--in my opinion this is the only way to get have NEVER had a overheating problem the hottest I have ever gotten is 200 deg. usually run about 190 on the track and when I pull in it goes up to 200 but thats to be expected--hope this will help everyone--I also run a good shroud a 31" alum rad. and a 17" alum fan or steel fan

powerglides
Dirt Freak

Total posts: 374
posted April 14, 2005 04:44 AM  
BC I went to the exact same setup couple of seasons ago and my water temp dropped 30 degrees. This exact setup is the best way to go!

o5racer
Dirt Freak

Total posts: 402
posted April 14, 2005 08:44 PM  
I switched the crank pulley to bring it up to 15% and went from the 3/4 inch restrictor that I dont remember putting in there to a gutted stock t-stat. I had it running for about a half an hour with a piece of cardboard blocking the front of the radiator before it finally got up to 200 and when I pulled the cardboard out it dropped right down to 180. The fact that it took that long to warm up and that cooled down right away makes me feel a little better. The rear test will be saturday.
Nick

    

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