Piston ring gap?

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Model T Ford Forum: Forum 2012: Piston ring gap?
Top of pagePrevious messageNext messageBottom of page Link to this message  By ken bechtel on Thursday, October 25, 2012 - 09:32 pm:

My pistons measure 3.780,my cylinders are bored to 3.784. I bought a set of .030 over Hastings rings and squared a ring in the bore and my ring gap is .018. seems a little loose. anyone else have this problem? maybe i should get the next size up and file to fit. my pistons are aluminum, what ring gap should i looking for? thanks. Ken


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Thursday, October 25, 2012 - 09:54 pm:

You need .018" on the top ring, at least .015 on the second and a little less on the oil ring.
If they all measure .018 you are good to go.
I set my customer's engines at .020 on the top ring just to be safe.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Thursday, October 25, 2012 - 09:58 pm:

That's about where you should be on the compression ring. It's only nat's eyelash too wide. When the engine comes up to OT, the gap will close to about .003-.004. and still allow for some overheating.

Also, to be real nit-picky, you should consider the ambient temperature too. If it's 30 degrees when you're setting the gap, you'll want it wider by .003-.004.

You have over 11" of cast iron that expands (elongates) about .000006" per inch/degree. That's why you need a gap. Better to be slightly wide than too tight.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jack Putnam, Bluffton, Ohio on Thursday, October 25, 2012 - 10:00 pm:

You need .003 per inch of piston diameter or .003 x 3.780 = .01134 or .012. Check each ring in the bore with a feeler gauge.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Thursday, October 25, 2012 - 10:28 pm:

I respectfully disagree.
With today's gasoline and higher engine temps you need .005 thousandths of an inch per inch of piston diameter.


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