240sx Radiator Caps

[Tristan Smith]

Hey guys, (and you don't have to drive a 240sx to chime in) what pressure do you recommend that I get for my 240sx? Is there any benefit to go to a cap with a higher pressure, or is that just testing the "radiator hose gods"? Currently I am using a 16lbs lever cap. Thanks

[Ron Earp]

I don't think I'd go over 16lb. I remember putting a higher one on a Mustang I had, might have been from a 14 psi cap to a 18 psi cap, and blew one of my water pump to manifold hoses twice. Twice because it took me that long to realize what had happened. This was years ago and the parts guy got me one that fit, not necessarily the correct poundage I needed. YMMV.

Judson said you passed along greetings, hope to see you out at the track soon!

Ron

[erlrich]

I use the ridiculously expensive Nismo cap (18 lbs), but I'm also using a water press gauge, so I can keep an eye on what's happening (as long as I can remember to check the gauges :rolleyes:). I'm not sure the extra 2 lbs really makes any difference, but I just figured with the heat these engines make there might be times when the pressure could get up in the 15-16 lb range without there being a problem.

[Bryan88]

Water under pressure has a higher boiling point.

The normal 212 degree boiling point is at atmospheric pressure.

The higher the pressure goes the higher the boiling point is.

That is the whole reason behind the high pressure caps.

But it also goes to say that the rubber hoses can only stand so much as Ron found out on the Mustang.

[Mike Mackaman]

The more pressure the better, until something fails. When you are racing at Kershaw or Savanah in July or August and you are trying to draft by someone, you want all the protection you can get. Double clamp the hoses if necessary.

Mike

[Tristan Smith]

Thanks everyone,

I think I will stay with the 16lbs cap. It seems the risk of blowing hoses is probably greater than any benefit I would get by bumping up the pressure a few pounds.

Ron, it's funny to see Judson again. We shared shop space years and years ago when he first got into Jensen Healeys. And now he is the Jensen engine guru! I am shooting to get back on track at the July Rd. Atl. race. Need to break in a new motor (assuming it's done in time). I would prefer to be close to home for the shake down. Nothing worse than traveling for many miles only to have the car crap out on you in the first session, and especially with diesel prices as high as they are now!

Are you going to the July race? If so, hope to see you there.

[JeffYoung]

Unfortunately, no RA for us this year. Next though. Ron's car is getting painted, as is mine, and then we are saving the shekels for a haul down to Daytona in August.

There's a new race on the schedule at CMP in October....you should come out for that. You'll like the new config I think, and CMP in cooler weather is a lot more fun.

[Tristan Smith]

I just may. I need the races to keep the license, and you know CMP is one of my favorite tracks.

[DavidM]

I was doing some prep work on the car last night (planning on doing RA in July as well) and I swear the radiator cap said 24psi on it. I'll have to double check. I have not had any issues with hoses blowing off, though there's not a stock piece anywhere.

Barber is labor day weekend and I'm planning on making that one to get in a couple more races. Running a reduced schedule this year as well.

David

[Bryan88]

I was doing some prep work on the car last night (planning on doing RA in July as well) and I swear the radiator cap said 24psi on it. I'll have to double check. I have not had any issues with hoses blowing off, though there's not a stock piece anywhere.

Barber is labor day weekend and I'm planning on making that one to get in a couple more races. Running a reduced schedule this year as well.

David


Back in my dirt racing days I ran a 24 pound cap with the radiator hoses double clamped.

[betamotorsports]

I used to run a 240Z with a 3L L6 at 14 to 1 CR. I had a localized hot spot problem (#5 exhaust valve area) in the cooling system that was causing very slight detonation and making the computer dial back timing. Increasing cooling system pressure to 28 psi solved the problem. I also ran silicone cooling system hoses with T clamps.

[DavidM]

Yup. Cap has 24 lbs in big letters on it. Then it says 22 lbs in smaller letters. Not sure what that's about. My upper hoses are silicone with your basic screw clamps and the lower hose is a standard rubber hose with screw clamps.

On track, at speed I'll probably see a little over 180 at RA in July. That's with distilled water and water wetter. Bob raced in Texas so it's no surprise the cooling is good.

David

David

[ITS 300zx]

I use the ridiculously expensive Nismo cap (18 lbs), but I'm also using a water press gauge, so I can keep an eye on what's happening (as long as I can remember to check the gauges :rolleyes:). I'm not sure the extra 2 lbs really makes any difference, but I just figured with the heat these engines make there might be times when the pressure could get up in the 15-16 lb range without there being a problem.

The z32 rad cap is rated at 1.2 bar, compared to the 1.3 bar nismo.

The z32 unit is about $12 from Nissan.

[Tristan Smith]

Thanks everyone. I'll do a bit more investigating!