cwb442

Is it necessary to open up the oil drain back holes in the heads. I have restrictors in the cam. Just got a set of c heads back from being freshened up and noticed this was not done when comparing to a set of j heads that were previously on engine.

MDchanic

No, not generally.

What are you using it for? What sustained RPM are you planning on running?

- Eric

cwb442

70%street/30%strip. Max rpm 5500

MDchanic

I'll let the drag racing guys answer for the strip, but I don't think you have anything to worry about.

- Eric

D. Yaros

I guess I do not understand. What advantages are there to not opening up the drains?

MDchanic

For sustained high-RPM use, such as running at 5,000 RPM for long periods while racing, it is possible to pump all of the oil out of the pan, but have it not be able to drain back fast enough.

Not a problem generally encountered in any normal kind of use.

- Eric

steverw

It certainly couldnt hurt anything it the heads are off the car. I dont think you can open them up much, but i dont know how much is possible. There is a danger of getting into the water jacket. You can just smooth them some and the floor around them. Maybe someone else knows how much they can be opened.

cwb442

I did not request it to be done. Just wondering if it's a make or break mod with my motor. Valves/valve springs are installed ready to be put back on. Dump is scheduled for next Thursday. So all I'm asking is should I bring the heads back have them disassembled again to open up drain holes or will I be ok.

cwb442

Correction dyno time is scheduled for next Thursday. Looking at how the j heads were opened up. To me it looks like it was mounted at an angle on a drill press and opened up to about a 5/8 hole which maybe a 1/2" deep which opened up drain hole at an angle.

D. Yaros

OK, thanks! I think I understand now. So the op was talking about "enlarging" the drain holes, as opposed to unplugging them. That they would be plugged made no sense to me and is what had me confused.