Piston clearance with Z Head

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Model T Ford Forum: Forum 2012: Piston clearance with Z Head
Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Thursday, May 24, 2012 - 09:09 am:

What is the min. Piston clearance with a Z Head without a gasket ? Now the piston lift the Head 0,004 without a gasket. Is that OK ?
Thanks for your answer.
Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Cassara Long Island, NY on Thursday, May 24, 2012 - 09:44 am:

Bolt it together with a small blob of play dough on the pistons and valves. Roll the motor over 2-3 times and then pull the head and measure. Do each piston and valve.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Horlick in Penn Valley, CA on Thursday, May 24, 2012 - 09:53 am:

What is the thickness of the gasket? I grind away all interferences without a gasket by marking them with die-chem. Then I install the gasket and I'm good to go.

You can put in two head bolts very loose then with your hand on the head turn the crank 360 degrees. You will be able to feel if a piston is hitting or not. You can put that piston on TDC and with a feeler gauge determine how much metal to remove from the head. With the dye you will know exactly where to grind.

I have found that without a gasket thickness worth of clearance the engine will eventually start to knock when it builds up enough carbon for the pistons to hit the build-up of carbon.

TH


Top of pagePrevious messageNext messageBottom of page Link to this message  By paul griesse--Granville,Ohio on Thursday, May 24, 2012 - 09:59 am:

there should be NO contact with your Z head when you test without a gasket.Better for MORE clearance, especially if you are running Aluminum pistons----.0004 contact needs to be milled out a bit. I`ve done 3 heads--each needed to be milled---good Luck Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Thursday, May 24, 2012 - 10:08 am:

Correct Paul

Don't run it with the pistons lifting the unbolted head up, when no gasket.

Use Prussian ink and cover the inside of the combustion chamber to mark where you need to grind away some alum from the Z head.



Once you have that done, then test again and install with gasket and bolt down, nice results :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Paddison, Portland Oregon on Thursday, May 24, 2012 - 11:34 am:

Interesting point. My "Z" head does not lift my head off the block with no gasket...and the pistons don't touch even with a decent layer of carbon in the combustion chamber (before I cleaned it).

I think I'm okay...but you have me worried now.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Thursday, May 24, 2012 - 11:48 am:

We put a Z head on a friends T. The block had about .005 taken off the deck. I bolted the head on without a gasket and had no issues. I would guess that it would depend on how much the block or head has been cut in the past as to whether there will be interference.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Paddison, Portland Oregon on Thursday, May 24, 2012 - 12:12 pm:

Mark,

Same here. I ran my "Z" head on my old motor for 5 years with no problems. Bolted it to my new block and even with a thick layer of carbon...no interference.

I think I will pull it off and check it just the same though to be safe.

...will try some play-doh :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Cassara Long Island, NY on Thursday, May 24, 2012 - 12:52 pm:

U makin fun of me ...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Paddison, Portland Oregon on Thursday, May 24, 2012 - 01:59 pm:

Heck no John, it's a great idea :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Cassara Long Island, NY on Thursday, May 24, 2012 - 02:09 pm:

:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Horlick in Penn Valley, CA on Friday, May 25, 2012 - 02:15 am:

Due to a blown head gasket I had a warped Z head. I had to have it decked and after running it for a while and getting some carbon I got a knock. That is when I found that I had strikes with the gasket off. I relieved it so I have no strikes and added the gasket... about 7 or 8 years ago, no problem since.

TH


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Friday, May 25, 2012 - 01:53 pm:

Thanks ALL , That is what I need !!

Toon


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