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Discussion Starter · #1 ·
ive been looking at the moroso radiator caps from jegs, they have 3 different ones 19-21, 23-25, 27-29lb. which one would be best for a street engine? i know the more lb. the higher the boiling point but would a higher rate hurt anything on a street engine?
 

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I think the main thing depends on what type and what kind of shape your radiator is in. If its new I would contact the builder and get thier recommendation. If its used then I would take it to a GOOD rad. shop and see what they think it could handle. I have a PRC alum rad. and 16# cap, thats what they recommened.
 

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Save a horse, Ride a Cowboy.
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runn141 said:
it will be a factory full size chevy truck radiator so i figure ill use a 16lb. cap then.
Buy a brand name cap and make the store test it with their tester while you watch. Most 16# caps hold only 11-12#. They tested 5 to find one that tested 15#... one tested 3#...... and the store man was not happy with ME.

Murray Brand from O'Reilly's Auto Parts is junk,,,, j.....u....n....k.
 

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Race it, Don't rice it!
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If your engine overheats three things are gonna blow under the pressure of the water, either the water hoses or the tubes in the radiator will swell or the cap will blow off.

If the cap blows off, or the hoses break, you'll lose the water and have no hope of getting the thing cooled down to get water in it. You'll have to wait it out. Takes hours.

In racing, I use a 30 pound cap because I know the steel braided hoses won't break and the cap won't blow off. I don't mind throwing out a rad. $250 is cheaper than my engine. $250 is cheaper than my entry fee's.

If the tubes swell it's still gonna give me time to get the thing cooled down with a water hose. On the street, I would run a 20 pound cap because I know the hoses won't break at that pressure and the rad tubes won't swell. It give you an extra margin for losing the water. if you blow a head gasket and the pressure goes sky high, you'll at least get a small amount of time to get the engine colled down before the cap blow off.

When you lose the water, the metal temps spike outa control and the hot spot will expand the metal too fast and cause your cracks.

I'd rather have an engine run 300' with a full radiator then a engine at 230 without water.
 
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