Ring gap for alum pistons

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Model T Ford Forum: Forum 2018: Ring gap for alum pistons
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Wyatt on Monday, December 17, 2018 - 05:24 pm:

Several sources state that ring gap is .003, .005 and .008, top to bottom on std pistons. My '15 has alum .060 pistons. I just measured .040 on the top ring. I only ran it twice and no smoke, but compression was 32, 32, 28, 32.
Is there a different ring gap for alum pistons?
jerry


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Monday, December 17, 2018 - 05:52 pm:

Yes, Even those you have posted are wrong, should be around the other way, top ring runs the hottest so .008 cast iron pistons.
As for aluminium the standard rule is .003" for every inch of bore, so .012" for all those rings.
Your .040" is far to much and will contribute to your compression problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Wyatt on Monday, December 17, 2018 - 06:05 pm:

Thanks for update.
..
I did read it in several places copied from engine specs section:
Ring gaps (original rings)
Top .003"
Center .005"
Bottom .008"

So alum pistons should have the same gaps as original pistons?
jerry


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Monday, December 17, 2018 - 06:12 pm:

If you use the cast iron ring gap on aluminium pistons you will score the bore and lock up the engine.
Set at the .012" all rings.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Monday, December 17, 2018 - 06:29 pm:

Unfortunately there is a lot of mis-information posted over the years and people get caught out costing them another engine re-build.

The Ford service book is the best for specs.

Cast iron piston ring clearance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark A Strange on Monday, December 17, 2018 - 06:39 pm:

https://www.youtube.com/watch?v=xC789a7CW28&index=31&list=PLYG_lIhIwKyLG8WQm4tGm KK1nA0Yctp6G


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Monday, December 17, 2018 - 08:06 pm:

Could be someone installed rings for like .040 over sized pistons instead of .060 rings. There would be enough spring in the ring to spread it out but would leave a larger gap. I think you are going to need new rings with a gap like that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan McEachern on Monday, December 17, 2018 - 08:11 pm:

With modern gas, I feel that .012 is too tight and .016-.018 is safer for the top ring. Gas today burns much hotter than in the past. .012 on the oil and 2nd ring seems to work well IMO.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John E Cox on Monday, December 17, 2018 - 08:49 pm:

really not related to ring gap; but I have been trying to start my new to me 1915 Runabout.
Pulling it over with no plugs installed I could hear sounds from the front two spark plug holes similar to the breathing problems that I had a couple of years ago, thankfully now gone. Nothing from the rear two. The car had sat for two or more decades so I was hopeful for maybe stuck rings. I sprayed some rust magic in the cylinders and worked on other interesting things for a couple of days. I then went trough three carbs and finally took the working card off of my 25 pickup. Still no noise from my new love. I had my wife pull on the choke wire while I built up my left arm muscles no no avail. She is a definite keeper! Remembering the online advice of Steve Jelf and Ron Paterson I advanced the spark lever away from the normal all the way up positions and it started. I did it in stages because at almost 80 the bones are brittle.
As it turned out I think that the timing is very much retarded in the full up position.
And back to the start of my dissertation I think that the rings freed up.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Tuesday, December 18, 2018 - 02:09 am:

Hastings Rings
3.5" to 4.3" bore, .012" to .022" ring gap, so anything form min to max and in-between, go for it!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Tuesday, December 18, 2018 - 02:15 am:

And stagger the ends 120 degrees apart when you fit them.

Allan from down under.


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