154 Ring Size Clarification

[jimybud]

I am in the process of replaceing the rings in my 154.

The piston have the following number stamped inside it: 531532r1 ( i believe this is the part number for .030 over, except that it has a r11 instead of r1 at the end).

The approximate measurement of the piston is 2.6464, whereas the specifications for .030 over is about 2.655 (std 6.2625 + .030).

I just want to be sure that I am purchasing the correct sized rings for this. At this point I am leaning toward the .030 rings which I believe is part number 539356r1.

Any information would be appreciated.

[George Willer]

30 over is what I would order. That will give you a chance to very carefully fit the rings to proper end gap (.007 with the ring square with the honed bore at the bottom of the stroke)

[jimybud]

I measured the cylinders, the details are as follows:

#1 2.65748
#2 2.65550
#3 2.65400
#4 2.65660

Should I compare this to the .03 over quote of the pistions 2.655 (std 2.625 + .030)? The difference between the measurements and 2.655 is very minor (.00248,.0005, .001, .0016).

The cylinders have very little ridge. The issue with the engine was that it had excessive "blow by" and was low on power when the mower deck was engaged.

[jimybud]

It seems that the .030 rings are only available from the dealer and I am trying to stay "low budget" and would like to buy them afermarket.

The NAPA dealer can only get .040 over. Would there be any issue with using such rings and "size" them by filling the end as needed to get the appropriate end gap. I would square them in the cylinder and sand the end until the proper gap is achieved.

I was not sure if the difference in size would abnormally wear the cylinder walls or if the .01 difference is negligble, especially considering that the walls of the cylinder have wear beyound the .030.

[RaymondDurban]

I would be concerned about putting .04 rings on .03 pistons. Even when you gap the rings, they would not be able to "seat". Results in the short term might be what you are looking for (curing the blow-by), but in the long term, you may be worse off (even less power). I have heard of people doing this when the cylinders are worn out but not willing to rebuild the motor when trying to off-load a piece of equipment. Shop around, check with a machinist to see if other suppliers can provide .03 rings. Best of luck, let us know what you find out.

[Eugene]

Of the two choices, I would purchase the .030 rings from IH. There is a posibility that a machinest can obtain the rings.

[jimybud]

What are your thoughts on this? I was thinking about using 80 grit paper.

The other thing people overdo is hone. They want to see a
pretty 350 chevy cross hatch pattern but that is not necessary in
our old engines. You are grinding away precious cylinder wall
material. The extra piston to cylinder wall clearance will allow the
piston to cock around in the cylinder and will break the seal of the
rings. If you can't resist the extra honing get a piece of emory
paper and do it by hand. When your arm is tired you know that
you are done. Leave the power honing to the professionals who
have modern marvels like oversized pistons in their bag of tricks

[George Willer]

What are your thoughts on this? I was thinking about using 80 grit paper.

The other thing people overdo is hone.

The paper won't work. You'll have to use a file and even then it will be slow going. I hold the ring in a vise with soft jaws. Use a feeler guage to check the size often.

The honing isn't intended to change the size of the cylinder. It's to create a surface that the rings can seat to. Don't omit this necessary step, but just don't overdo it.

[Gary Dotson]

George is correct on this! .040 over size rings, filed to fit will work fine, no concern about extra wall tension. High end engine builders use this procedure all the time.

Yes, you do want that "beautiful 350 Chevy crosshatch pattern". It's even more important in an older engine, with well glazed cyl. walls. Just use a flex hone (or ball hone) to prepare the surface, it won't remove enough material to measure.

I think your cyl. measurements are close enough, that .030 over rings will work ok, but the end gaps will likely be a little over spec.

[BigBill]

The "Crosshatch" used in the cylinders depends on what kind of piston rings your using. Chrome rings require a tighter cross hatch with regular rings require a more open crosshatch. Remember the crosshatch holds the oil for lubrication too.

Make sure your going to hone use a flex hone or a ball hone so your not making the cylinders larger if your just doing piston rings. I have a gear driven hone that can bore cylinders to any size but i don't use it when just doing rings for the reason a cylinder can be out of round and in the process of making it exactly round to within .0000 to .0002" in can bore it larger at the sametime. If your using a spring loaded hone i back off on the spring pressure just a little too so i just get a crosshatch nothing else. Just remember to lube the hone and cylinder often.

Make sure the ridge at the top is completely gone so the new square compression ring won't break in the radious left by the old top compression ring.

The 40 over rings will work but you need to use a "ring gap filer" so the end gap will be exactly square.

For anyone wanting a new gear driven hone for boring they cost between $125 to $185 depending on where you shop(ebay). Then you need coarse stones for boring and fine stones for finishing.(removing that last few .001" & hatching)