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Author Topic:   radiator cap pressure
Dirt Freak

Total posts: 334
posted July 20, 2005 12:10 PM  
Lots of overheating questions on here, it must be summer!

My car will run 180 - 190 the entire race, heat race or feature. On the way in to the pits, it starts heating up. I usually get to my pit stall by 210 - 215 degrees. When I shut it down, it gets up to 230 - 235.

Before the heat and feature, I pop off the cap, fill it full of water, rev it up some to get the maximum amount of water, and then go run the race. On the track, some of my crew can see some water coming out the back out the overflow. So when I idle in, I don't have as much water in the radiator and it starts getting hot.

The cap was brand new at the beginning of the year. It is a 22-24 lb. cap. I also had to put ceramic seal in at the beginning of the year because of crack in the valve seats. Could heat be caused by this leak starting to open up again? I'm wondering if I should add another bottle of the sealer.

Should I purchase a 22-24lb cap, or a 29-31lb cap to replace the one that Iím currently running?

My timing is set at 34 right now, I've heard you should increase by 2 or so degrees once it starts to really heat up outside to help prevent detonation since the air temperature is so high.

I also have not dropped down my jets much at all from when it was still pretty cool out. Can a rich fuel mixture of Alcohol make the engine run hot?

Iím running a 180* thermostat with 2 3/16Ē holes drilled in it. I canít get it warm enough, fast enough with a 160*.

I realize 230 is not that HOT HOT, but when your engine never gets over 215 or so, it starts making you wonder what is going on.

Dirt Forum Champ
Total posts: 505
posted July 20, 2005 12:51 PM  
I'd switch to the 29/31lb cap if you're sure the water is coming out the overflow.

Rich mixture on alcohol won't make it run hot, it'll just increase your cylinder wear.

Advancing the timing will make detonation worse.

Make sure your fill point is at the highest point of the system to get all the air out.

Dirt Forum Champ
Total posts: 2007
posted July 20, 2005 08:02 PM  
I dont know if Id worry about it too much other than losing water. 190-200 is about ideal on the track, and if it only gets to 215 pulling into the pits thats pretty nromal.

I would make sure you are losing water out the cap and not losing it in the head if you had a crack earlier in the year. You could be burngin the water in the cylinder and not know it...yet. Pull the plug on that cylinder and if it looks clean likes it new then you are prob gettting water in that cylinder.

If thats not the problem then sounds like your cap might be weak. A new cap would be an easy way to fix that. 22-24 is prob enough but 29-31 is a little extra insurance.

Try running an overflow bottleto catch the water, then it will pull it back in when it needs it. We just have a plastic pop bottle tied to the frame beside the rad with the overflow hose in it. At the end of the feature the bottle is sometimes almost full but by the time it cools down it pulls most of it back in. Just like the overflow on a street car.

Like the previous poster mentioned do not put more timing in it. That will only make it more likely to detonate and burn something up.

When was the last time you had your radiator out and cleaned it. WE take our out every 3 or 4 weeks and soak it in a baby pool of water and you'd be amazed at how much dirt comes out. At the very least just take it out and hold it flat aand tap it gently on concrete floor and tap the dirt out of it.

You might want to change the t stat in case it si sticking or take it our altogether. It could be enough restriction to make it run hot this time of year. to warm it up cut some cardboard to block airflow when waiting in staging lanes.

Last thing check belts and make sure they are not slipping.

I would look in to the losing water to start with then start working through the other stuff but again I dont think you have that much of a problem. The last few weeks our car has been 220+ coming off the track and hits 245 by the time he gets to the pits, but thats on gas.

[This message has been edited by dirtbuster (edited July 20, 2005).]

Dirt Forum Champ
Total posts: 5390
posted July 20, 2005 10:19 PM  
i'd do a compression test and leak down on the cooling system . mine was doing the same thing this year wouldn't run hot at all but would puke water out the over flow to a certain point and stop . haven't had a chance to try to fix it yet cam gear got chewed up and haven't fixed it yet but this did not happen untill i put a different set of heads on so it could very well be pressure from a cracked seat.i do agree tho yuor temps are very normal. we have a old fire water bottle that we spraythe rad down and rev it up after the race brings her right back down to 180 or so then when you shut it off will go up to about 210-220 start it up and drops right back down as soon as the water flows again

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