Z- Head

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Model T Ford Forum: Forum 2013: Z- Head
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Aldrich Orting Wa on Sunday, May 26, 2013 - 02:44 pm:

Anyone ever install a Z head (without high compression pistons) and get one heck of a knock?

Will be pulling the head back off as I think I have contact between a piston and the head.

Ironically, this is the 4th one I've done and never had this issue before.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Walt Berdan, Bellevue, WA on Sunday, May 26, 2013 - 02:53 pm:

Yep, I worked with a friend putting a Z head on his car. The block had been decked (not sure how many times or how much and there we needed to do some work on the inside of the head to gain the necessary clearance. Prussian blue was our friend as we trial fitted the head without the head gasket until it would fit correctly. I'm not sure if the problem was in the head or the block but all worked out fine in the end.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Gruber- Spanaway, Wash. on Sunday, May 26, 2013 - 02:53 pm:

Sometimes the top of the block gets machined off to true it up when an engine is rebuilt.
This might cause a problem.
If the pistons are hitting you can see it easily.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Gruber- Spanaway, Wash. on Sunday, May 26, 2013 - 02:54 pm:

Hi Walt...we typed at the same time!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Aldrich Orting Wa on Sunday, May 26, 2013 - 02:56 pm:

Thanks guys. Had not thought of that but Bob I know YOU aren't surprised!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, May 26, 2013 - 03:44 pm:

I had trouble with the valves hitting the Z head. Bent several valves. Bad day in the Peterson garage. Learned an expensive lesson.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Weir on Sunday, May 26, 2013 - 03:53 pm:

My TT;;; Pistons +0.080" and the head interfered with the pistons. A little trip to the fly-cutter solved it.

Sincerely

Jim Weir


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach & Big Bear on Sunday, May 26, 2013 - 04:00 pm:

The z head uses flat topped pistons because the combustion tricks are in the head not the piston as in two cycle engines. If you have flat topped pistons you can modify a high compression flat topped piston to run with a Z head. BUT, and it is a BIG BUTT, if you have domed high compression pistons you will get interference you could not imagine. They just don't work together because the Z head gets its compression through reduced combustion area by adding material where the regular high domed piston resides at the top of the stroke.


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