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mike mueller's Avatar
Join Date: Nov 1998
Location: antioch, ca, usa
Posts: 1,082
Type IV cooling ideas- cooled oil spray on valve guides

I plan on increasing the Comp. ratio on my 1.8 to get a little more torque and power, so to combat the extra heat I was thinking about running lines of cooled oil directly into the valve covers to spray the valve and valve gear, similar to Porsche
spraying oil directly on the valve guides of some race motors. Anyone attempt this feat? I figure it couldn't hurt.
Old 11-16-1998, 05:48 PM
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Join Date: Dec 1969
Location: Dade County, FL.
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Couldn't hurt, but I doubt it would help much either. The reason I say this is not from experience with race engines, but a limited knowledge of domestic engines. Lets look at how the heat is generated in the valve spring area, and why this area usally fails. Assuming the vavles are ajusted properly and the guides and vavle stems are within tolerence, heat from the combustion process is transfered to the vavle head. From there (once the vavle closes) it goes to the cylinder head through the seat, then up the stem to the guide and also to the head. This heat increases if compression is increased, vavles are set wrong, or the guides are worn. Spraying oil on the vavle springs and retainers probably wouldn't help because the heat should be transfered to the head already. However, I "think" the reason Porsche sprays the vavles is due to the typical failure of springs at high RPM. As the RPM's go up the springs must be stiffer to avoid vavle float (the point at which the momentum of the vavle takes over and the cam is no longer controling it). These stiffer springs generate more heat when compressed, add to this the fact that they are compressed so many times a minute (take a piece of stiff wire, bend it back and forth by hand... now think about how much heat those springs generate).

Anyway I feel like "engine mechanics, according to Lucy", I'm NOT a mech engineer, not even a machinist, just telling you the way I remember it. Anyone else care to comment?

A better idea to keep the engine cool (and nobody seems to belive me, but ALL the tinware and gaskets are important) is to 1) Clean it, get all the dirt and oil (and mouse nests) out from under the tinware and between the fins. 2) Clean the trans, it aids in cooling by acting as a heat sync. 3) make sure all the tinware gaskets are there, especially the main engine compartment gasket. 4) Make sure the exhaust system is sealed tight. 5) I soak the oil cooler in a 1 gallon can of carb cleaner (just the colling fins, I don't let the cleaner get into the oil passages). 6) make sure the timing is set right, too far advance causes heat. 7) If you still have problems then it is time to look at aux oil coolers, vertical fan shrouds, and lots-o-money.
Old 11-17-1998, 08:43 AM
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