Cylinder wall honing surface finish & ring gap

[jpowel29]

What is the preferred surface finish for seating rings on Mahle's race cast pistons/rings? I have 240 and 320 grit hones available. Also what ring gaps are preferred (compression and second ring)? Running small twins and maybe a small nitrous jet to clean up as needed.

 

[jkholder09]

Google search
Federal mogul plateau finish
Then find a 600 grit ultra flex to micro polish.
Or a sunnen with diamond cutter will provide a simalar ra and finish.

 

[Fingers]

0.012"-0.018" on the top ring. Open up another 0.005" at most for severe hot rodding, but no more. IMO

0.020"-0.025" for the second ring. I prefer to keep this one tight, but philosophies vary here. Keystones seal better with less inter-ring pressure. Or so I am told.

 

[jkholder09]

0.012"-0.018" on the top ring. Open up another 0.005" at most for severe hot rodding, but no more. IMO

0.020"-0.025" for the second ring. I prefer to keep this one tight, but philosophies vary here. Keystones seal better with less inter-ring pressure. Or so I am told.

Could you see any benefit to gapless rings file fit or 3 piece in a diesel?

I am asking because the 6.7 psd fords have some decent crankcase pressure.
I have never used this type ring in a diesel application.

 

[jpowel29]

Appreciate the feedback!

 

[S Phinney]

Guy usually recommends a 320 area hone finish. It would be best to ask the ring manufacturer their recommended finish John. They should tell you that and ring end gap tolerances for the application.

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[jkholder09]

Guy usually recommends a 320 area hone finish. It would be best to ask the ring manufacturer their recommended finish John. They should tell you that and ring end gap tolerances for the application.

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320 would most likely be the spec for the grit of stone.
The wall finish will be indexed by an RA number.

 

[S Phinney]

I understand that as well. That is why I recommended asking the ring manufacturer. I was given specs to use as follows. RPK of 12-18, RK of 35-40 and RVK of 50-60 with a 45 degree included angle. There are only a few shops in the country that has the right equipment to even measure the roughness of the surface as well.

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[LtEng5]

Fingers - why do you have the top rings so tight?? using the 0.004"- 0.006" per inch of piston diameter recommended by Mahle, FM and a couple other ring manufactures... 0.012" - 0.018" in a boosted application just seems small...

 

[jkholder09]

Fingers - why do you have the top rings so tight?? using the 0.004"- 0.006" per inch of piston diameter recommended by Mahle, FM and a couple other ring manufactures... 0.012" - 0.018" in a boosted application just seems small...

That's why I asked about a sealed ring or file fit.
Fingers has done a bunch of homework on these at our gain and his expense.
Thanks for that fingers by the way.

 

[Fingers]

That is GM production spec. The gap grows quickly during break-in. At least with Stock rings.

So 0.004"-0.006" x 4.06" = .016" - .0024"

That is only .004" - .006" more than GM spec.

As I said, I would go up to .005" over spec for a hot motor.

 

[LtEng5]

Which area so you think is wearing away enough during break in to allow the gap to grow.??.. The rings themselves being soft or thw cylinder walls wearing that quickly....

 

[jpowel29]

My ring gaps are coming out to:

Top Ring = .023-.024"
2nd Ring = .027-.028"

Mahle Race Cast pistons and Mahle steel rings. This motor will see some heat and likely some nitrous at some point. Are these ring gaps enough?

 

[Hot COCOAL]

Is this info rendered to the customer in a balanced and blueprinted build: ie ring gaps, tolerance, and surface friction/smoothness of the cylinder bore, or is that optimistic thinking?

 

[Andrew]

Subd

 

[JoshH]

Is this info rendered to the customer in a balanced and blueprinted build: ie ring gaps, tolerance, and surface friction/smoothness of the cylinder bore, or is that optimistic thinking?

If a build is truly blueprinted, you should get some sort of documentation with all the measurements and clearances on everything. That's what blueprinting is.

 

[Hot COCOAL]

If a build is truly blueprinted, you should get some sort of documentation with all the measurements and clearances on everything. That's what blueprinting is.

Thanks Josh, that's what I thought but wasn't totally sure, and, it's kinda what I'm expecting from Cam @Adreniline, thanks for the response and answer, I just wanna make sure I'm not being over "zealous" about what I am or am not going to get out of/from this build, after all...

it's my first time

:roflmao:

 

[LtEng5]

final diameter of the bore is deemed by the piston manufacturer... they give you the size of the piston and the size of how much clearance they want to see for a specific application. i.e. - street use, racing/high rpm, boost and/or nitrous. you may find that a manufacturer will say for a 4.030 piston - the piston will actually measure at 4.028. that particular piston for a street use enigne will have a finish bore of 4.032 to 4.034. you may also find lower down in the instructions sheet that these same pistons may be used in a boosted/nitrous engine.. with a finish bore of 4.034 to 4.036. the manufactures have already figured out how the pistons will "grow" under different conditions and have listed it so in the paper work that comes with the pistons when bought new.

as for the ring package - it is also the manufacture that gives the recommended finish and cross hatch patten to be applied to the cylinder wall. they also give recommended ring end gaps for all the ring sets in the packaged set.. based on use of the engine.. street use may call for 0.004 to 0.006 inch gap per 1 inch of cylinder bore diameter.... a boosted or nitrous application may call for 0.006 to 0.010 gap per inch... this info is in the paper wok that comes in the box with the rings from the manufacture....

every manufacturer is different and these numbers are just a basic industry standard for most applications. there are shops and engine builders that work very closely with piston and ring manufactures that will deviate from these numbers for testing purposes or even "builders secrets" to try and get just that little bit more power or length of life out of a ring set.

I cant tell you how many shops I've been into and everybody has their own little something that they feel gets them just that little bit more than the other guys... sometime it works and sometimes not... and even some of the stuff seems to go against what you would think and will hurt performance; but actually works to the builders benefit.

one of these places that EVERYBODY is fiddling with is piston to bore clearances, ring end gap clearances and bore finishes for the rings.

 

[gmduramax]

final diameter of the bore is deemed by the piston manufacturer... they give you the size of the piston and the size of how much clearance they want to see for a specific application. i.e. - street use, racing/high rpm, boost and/or nitrous. you may find that a manufacturer will say for a 4.030 piston - the piston will actually measure at 4.028. that particular piston for a street use enigne will have a finish bore of 4.032 to 4.034. you may also find lower down in the instructions sheet that these same pistons may be used in a boosted/nitrous engine.. with a finish bore of 4.034 to 4.036. the manufactures have already figured out how the pistons will "grow" under different conditions and have listed it so in the paper work that comes with the pistons when bought new.

as for the ring package - it is also the manufacture that gives the recommended finish and cross hatch patten to be applied to the cylinder wall. they also give recommended ring end gaps for all the ring sets in the packaged set.. based on use of the engine.. street use may call for 0.004 to 0.006 inch gap per 1 inch of cylinder bore diameter.... a boosted or nitrous application may call for 0.006 to 0.010 gap per inch... this info is in the paper wok that comes in the box with the rings from the manufacture....

every manufacturer is different and these numbers are just a basic industry standard for most applications. there are shops and engine builders that work very closely with piston and ring manufactures that will deviate from these numbers for testing purposes or even "builders secrets" to try and get just that little bit more power or length of life out of a ring set.

I cant tell you how many shops I've been into and everybody has their own little something that they feel gets them just that little bit more than the other guys... sometime it works and sometimes not... and even some of the stuff seems to go against what you would think and will hurt performance; but actually works to the builders benefit.

one of these places that EVERYBODY is fiddling with is piston to bore clearances, ring end gap clearances and bore finishes for the rings.

I would never follow what the manufacture says. Especially Mahle because they cannot make their pistons perfectly round. So you must adjust your piston to wall clearance accordingly.

 

[Fingers]

Tops are round, bottoms are not. Ever wonder why?