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Old 09-01-2008, 06:09 PM
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Enlarging Oil Drain Holes In Hemi Heads

Is it feasible to enlarge/drill out the oil drain back holes in Hemi heads? Is there much meat there, especially the rear/front holes, or would I hit water? The holes have a really small diameter, and enlarging them might help drain-back...

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Old 09-01-2008, 07:29 PM
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Personally I'd be afraid to try.

Iíve only had experience with one early Hemi starving for oil because it didnít drain back quick enough. It was caused by the engine being fired up on a cold morning and then run all out prior to the oil warming up (happened twice, same motor same driver). A good lesson for me at someone elseís expense. I always let mine get up to full operating temp before I get frisky.

I've look at my early Chrysler Hemi heads when I assembled the 2 that I have. If I ran into starvation problems and had to I figured the safest way would be to drill into the heads where I indicated and tap and run fittings and a line straight down to the pan (I believe some of the ford FE based engines used this fix).

Just my 2 cents.
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Old 09-01-2008, 08:09 PM
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Generally speaking, I always radius the edges of drain back holes on all performance engines. Oil flows easier around a radius than a square corner.
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Old 09-01-2008, 08:55 PM
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You can de-burr them but there really is no reason to enlarge them. Early hemi rocker shafts don't require much oil and enlarging the holes is really unnecessary.
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Old 09-01-2008, 10:05 PM
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isn't there a red paint, you paint the holes with, and oil flows to them quicker?
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Old 09-01-2008, 10:50 PM
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Paitning Your Inner Engine With "GLYPTAL PAINT"
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Old 09-01-2008, 11:22 PM
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I did a small job on my 400 with the grinder and then used some air craft high temp type paint.
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Old 09-02-2008, 08:54 AM
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Early hemi doesn't need a lot of oil on the top side. You need the aluminum oil restrictor plug that goes in the block by the oil pump.

If you absolutly can not stand oil in the head rails you can drill and tap the heads for a #6 line and make a drain back to the pan. A lot of extra work for no real gain. I would not go to the effort to enlarge the drain back holes.

You can also restrict the oil going to the rocker shafts by installing a small pipe plug inthe oil passage to the heads.

We always painted the inside of the block and heads with red Rust-oleum primer. More to seal the cast iron than anything else. Some of the old cast iron stuff just continually flaked off these blocks so we just sealed it in.
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