My Willys 3A and 3B Community

3A, 3B, DJ Technical Knowledge Base => "Original"-- Technical Questions, Answers, Observations => Topic started by: garage gnome on January 02, 2016, 01:06:47 PM

Title: head question
Post by: garage gnome on January 02, 2016, 01:06:47 PM

What is the most that the head on an L head can be milled down? Trying to get the most compression I can.

Title: Re: head question
Post by: Jesse on January 03, 2016, 12:19:24 AM

I think the maximum is about 10:1, read it a few places including here


http://www.pirate4x4.com/forum/jeep-willys/1018587-l-head-dyno.html

But if you can take that much out of a stock head or not is a different story. Maybe 8:1 with cast iron? A shop should be able to check it out and see how much could go. You could also change the pistons to some degree.

-Jesse

Title: Re: head question
Post by: Lee on January 03, 2016, 09:20:33 AM

I cannot answer your question, but, there are several things to consider. If you take to much off the valves will hit the head. Even more so if in the past your block has been decked. Years back on the 2A page this was a topic, I remember some talk of taking to much off causes turbulence in the combustion chamber and the effects of it reduces any gain to compression ratio.  Perhaps a search on the 2A page would answer your question, but good luck with that!.

Lee ;), and Happy New Year!

Title: Re: head question
Post by: Bruce_W on January 03, 2016, 08:11:28 PM

  I don't think there's much danger of causing the valves to strike the head, the valve lift is about .312" if I remember right, and the combustion chamber in the head is around .572" deep. There is a possibility of "shrouding" the valves by reducing the space between them and the "roof" of the chamber, thereby reducing breathing ability. This was always a problem with the Flathead Ford V8's. But there again, we've got plenty of room above the valve that the Ford didn't have, plus the valves are recessed into the top of the block in the Ford, and the Go-Devil valves are above the deck. So, this may be an issue with the Go-Devil, and may not. I don't know.
  The problem that I see, is that there is a flat place on the Go-Devil head directly over the top of the piston. The iron is not real thick there, and whatever amount you plane off of the head, will reduce the thickness of that part of the chamber.  BW