Piston /ring question

[Fordestes]

I have a set of .005 o.s. 09A 3ring aluminum pistons , will standard rings be sufficient to use ? As I remember from my childhood, we used this combination ,however what we did does not necessarily mean it was correct. I have thought about machining pistons to standard and using standard rings in a fresh bore, finding .005 rings may be impossible. What is the accepted practice ? I was always told standard rings were good up to .010 ?
fordestes

[frnkeore]

Your memory is right, the difference will be the increased end gap of almost .016.
If your putting them in a used bore (don't know where you'd find a new std bore), you will have a little taper and increased gap, to begin with so, it shouldn't be a issue.

Have it honed by a good machine shop, to minimum fit. As you say, .005 rings would be HARD to come by.

Maybe someone here can tell you where they could be found.

[flatheadmurre]

The losses due to that extra ring gap will be very little...on a stock engine i wouldn´t worry.
File fitting a set of .010 might be what looks like the correct way...but ouch what an amount of work to gain a %...
And machining pistons takes a dedicated grinder or a cnc-lathe with C-axis...not sure it will cost less then a set of pistons nowdays...

[Fordestes]

I am planning to bore some 221 engines to 3-3/16., and use up some N.O.S parts I have and install the engines in my trucks .
Many thanks , fordestes

[frnkeore]

Be aware that the maximum thickness of the cylinder wall will be .103 (@.005 over), IF there is no core shift and no cylinder wall erosion.

I have two, original Ford drawings for 21 stud blocks. One lists the outside, cylinder, core diameter as 3.38, the other 3.40.

Personally, I don't think they should be bored more than .090 over. My 37 block, is .040 now (with deep pits in #3) and I have a set of .080 over, pistons and rings for it. I found both on Ebay. I took awhile though.

[frnkeore]

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These are clips from the drawing. The 3.40, is based on the radius of 1.7 in the one drawing but, I believe the target for the outside of the cylinder is a diameter of 3.38, leaving .094 wall thickness, again, IF there is no core shift and no erosion.

[Fordestes]

These 221 engines are 41 models and have removable sleeves , with the sleeves removed there shouldn't be a whole lot more to be removed , I'm just guessing about .040 more to make a standard 239 , ford offered pistons as a replacements with the sleeves removed , they were in the .080 range if I remember right, if there are problems I will either put in a thin wall 3-3/16 sleeve or scrap the block and start over. I have plenty of the 221 blocks that do not seem to be in high demand these days, I just want to try and put them to work instead of walking around them for the next decade . Thanks everyone for your input .

[frnkeore]

OK, so it's not a 21 stud engine so, I think it should be fine with that 3.193 bore.

[Fordestes]

Sorry I didn't clarify that to begin with ,but I gained a wealth of knowledge just the same, I like the drawing ,I'll copy and add it to my files .Thanks