Setting the piston groove clearance

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Model T Ford Forum: Forum 2016: Setting the piston groove clearance
Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Bourgeois on Monday, October 10, 2016 - 10:08 pm:

I can set the ring gap in at the end of the rings.
The rings seem to be tight in the piston grooves. The manual states between .001 and .002. I would assume this would be for the cast iron pistons. What should the clearance piston grooves for aluminum pistons?
Here is the picture of the new piston and how tight the rings are.
Thank you.

Rings





Rings in grooves.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Chaffin......Corona, CA on Monday, October 10, 2016 - 11:12 pm:

Are you sure those rings are not for use with cast iron Pistons.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Tuesday, October 11, 2016 - 05:29 am:

Min on a aluminium piston (modern gas engine) would be .0008" to .0012" Diesels up to .004"
T's are happy with .001" to .003".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Bourgeois on Tuesday, October 11, 2016 - 07:17 am:

The description for the rings is:
"Hastings brand rings for Aluminum Pistons"
How can I tell if they are for cast iron or aluminum pistons?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, October 11, 2016 - 08:35 am:

Looks like 1/8" thick rings, so they're for aluminum pistons for sure. Old original cast iron pistons has 1/4" thick rings.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Tuesday, October 11, 2016 - 11:10 am:

Mark, Can't you see from the picture they are for aluminum pistons??


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Chaffin......Corona, CA on Tuesday, October 11, 2016 - 11:12 am:

Never used that brand before. The large Oil ring is very different than the one I'm used to using.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Sullivan on Tuesday, October 11, 2016 - 01:53 pm:

Used lots of Hastings rings, way old US company, in Hastings Mich. Always good product. Dave in Bellingham, WA


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Bourgeois on Tuesday, October 11, 2016 - 09:50 pm:

The smallest feeler gauge that I have is .0016.
How do I verify that the piston gap clearance is .001 or just above it?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Tuesday, October 11, 2016 - 10:55 pm:

Before you put the rings on the piston you need to set the gap. Place each ring in the cylinder about where they would be when the piston is at the bottom of the stroke. Make sure they are square with the bore. Measure the distance between the ends with a feeler gage. File off what you need to meet the spec in the Ford manual.

You should borrow a hone from the auto supply or a local auto enthusiast and hone the cylinder. This will allow the rings to seat and should give you a little extra clearance as it is likely the piston was fitted with too little clearance and that is why it galled in the first place.

The machine shop that bored the block may have left a burr on the bottom of the cylinder so be careful and if one is there remove it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Wednesday, October 12, 2016 - 10:12 am:

As I recall from way back, the end gap clearance for piston rings is .001" per inch of the cylinder bore, so that would be .003-.004".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Bourgeois on Wednesday, October 12, 2016 - 10:28 am:

I have set the ring gap before. The last time I did a rebuild the piston ring groove was not as tight as it seems with these rings. I need to get the ring groove clearance good then I am going to set the end gap. The last thing I would want is that the piston expands and does not allow the rings to do their work or worse. I guess I am being a little over paranoid.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Thursday, October 13, 2016 - 12:06 am:

Don't over think the gaps........just make sure there is enough.
If the oiled rings spin freely in the grooves you're fine.
No matter what aluminum alloy it will still have a much greater coefficient of expansion than cast iron.
By the way, any corner chamfers on the rings face UP.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Thursday, October 13, 2016 - 01:03 am:

I'm sure the ring set would have fitting directions but it does make a difference for right or wrong fitting of rings with chamfers/bevels.
From Hastings, correct ring installation.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Bourgeois on Thursday, October 13, 2016 - 10:15 pm:

I took Craig's advice.
The rings do have enough groove clearance.
I was able to start checking the end gaps.
Just one needed just a tad bit of filing.

I moved the rod over from the old piston to the new one. I set the new piston in the hole with the arrow pointing forward.
It seems that the rod is backwards.

Could the old piston being put in backwards have caused the issue?

I am going to swap the rod around.
and tests it again.
Now I am thinking I need to swap the other three pistons.


Here is the picture of the wire through the bold and around the rod. Does this look ok?



Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Friday, October 14, 2016 - 12:28 am:

Sorry, No that doesn't look OK, wire has a bad habit of breaking and ending up in the magneto, a cotter pin is all that is required, as for rod, the wrist pin bolt always face the cam shaft.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, October 14, 2016 - 04:35 am:

Steve, did you remove one of the other pistons and weigh it to compare with your new one? If they are within a few grams, you shouldn't have to change the others - unless they have any cracks..

If they do differ significantly in weight you may be able to remove weight on the heavy one(s) to match the lightest? Bad luck if the three old ones are significantly heavier than your new piston - that would be a cause for buying four new ones for me. It's hard to remove a large amount of weight without risk for the integrity of the piston - grinding along the bottom of the skirt only takes a few grammes.

The orientation of the rod wouldn't be able to cause any issue - not cracking a piston anyway.

I agree with Frank that a cotter pin is enough for the clamp bolt. (Hard to place it with the hole in that direction, though..)


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