"Lapping" the Piston and sleeve?

[Speed Jr.]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.

Larry Jr.

 

[glenng]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

Probably the sleeve Larry, But I'm curious about this myself. I bought a new CMB .80 but have noticed U.S. sellers have said "liners honed" ??? Why would this be nec. on a new motor?

Glenn

 

[glenng]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

I'm sorry Larry, I don't think I answered your original question. Lapping is a process that is used to remove a very small amount of material from the inside diameter of a cylindrical part. It involves a fine grit paste and and and an arbor which is a close fit to the inside diameter of the part.

Glenn

 

[mark voorhies]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

 

[glenng]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

 

[FloridaScaleBoater]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

How would you lap a piston & sleeve, without getting any compound on the piston?? You are lapping the 2 pieces together.

If you feel that lapping compound is too aggressive, toothpaiste works well also.

 

[glenng]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

How would you lap a piston & sleeve, without getting any compound on the piston?? You are lapping the 2 pieces together.

If you feel that lapping compound is too aggressive, toothpaiste works well also.

Either make an arbor the same size as the piston out of a harder material or-I never thought about about toothpaste Rick does it work?

 

[FloridaScaleBoater]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

How would you lap a piston & sleeve, without getting any compound on the piston?? You are lapping the 2 pieces together.

If you feel that lapping compound is too aggressive, toothpaiste works well also.

Either make an arbor the same size as the piston out of a harder material or-I never thought about about toothpaste Rick does it work?

If you use an arbor, you are not lapping, you are honing.

And yes toothpaiste works, not a gel though, old fashioned white toothpaiste

 

[TUNLBOTR]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

How would you lap a piston & sleeve, without getting any compound on the piston?? You are lapping the 2 pieces together.

If you feel that lapping compound is too aggressive, toothpaiste works well also.

You must be VERY careful here, the "pinch" is your performance, lose compression-lose horsepower....

In ABC technology (Aluminum piston, Brass sleeve-Chrome liner) you have different rates of metal expansion, vastly different, and the factorys have honed that unit to spec, and you are reading it COLD... That is where patience in the break in will be the order of the day. The Piston metal is usually a siliconized Aluminum and will set itself during break in. Run extra oil during break in, baby it through a gallon or so of fuel to set the piston and create the "pinch". My CMB's and NR's take several gallons before they come around. Trying out of the box to light the world on fire can spell early demise.....

Just my .02 (adjusted for inflation)

RP

 

[glenng]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

How would you lap a piston & sleeve, without getting any compound on the piston?? You are lapping the 2 pieces together.

If you feel that lapping compound is too aggressive, toothpaiste works well also.

Either make an arbor the same size as the piston out of a harder material or-I never thought about about toothpaste Rick does it work?

If you use an arbor, you are not lapping, you are honing.

And yes toothpaiste works, not a gel though, old fashioned white toothpaiste

Thanks Rick!!!

 

[glenng]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

Larry-just don't use the lapping compound you get from the auto supply stores as it's meant to lap steel valves to cast iron seats- Very abrasive. I would go with what Rick suggested,

Glenn

 

[El Zorro]

Years ago when flying controline model airplanes we used Ultrabrite toothpaste to hand-lap piston and cylinders in. This brand of toothpaste is very "gritty" feeling to the touch and worked well. However, I started using an aluminum oxide ( used for polishing rocks ) found in rock shops that, when mixed with Marvel Mystery oil makes a nice paste to lap the piston into the cylinder. I don't recall the exact number of the compound, but it looks like Tide laundry detergent. I did most of my lapping with the piston upside-down in the cylinder, with the connecting rod big end clamped in the soft jaws of my milling machine vice. Use the lapping mixture at a minimum only at the top of the cylinder ( above the exhaust port ) and the top part of the piston, making figure 8's with the cylinder on the piston, rotating the cylinder 90 degrees every 4 or 5 figure 8's. When this white mixture starts getting black looking, clean it off and check your fit. Your fit still needs to be slightly snug at TDC ( with the engine assymbled ). Your final lapping should be done with the piston in the cylinder the way it will be run. One other important thing I always did was to take the sharp edge off of the top of the piston with my scotch brite wheel. Don't go crazy here, but just take the sharpness off. This will help keep this sharp edge from "grabbing" at the cylinder walls when the engine is running at temperature. This final lapping should give you a thin, shiny band around the piston just slightly below the top edge of the piston. It will take a lot of hours and a lot of engines to get a feel of doing this but it will pay off in the long run!

Dick Tyndall

 

[mark voorhies]

What is meant by "Lapping" or to "lap" the piston or sleeve? Which gets "lapped" and how is it done.
Larry Jr.

It is basically to fit the piston to liner with very close tolerances. It can be done with runnin in,

or break in. Some times if piston to liner fit is too tight to, you would have to lap piston, or get

the fit to a point to start the engine and run without too many problems.I have had to take the piston

and sleeve out of an engine and rotate piston up and down in the sleeve,by hand,with lubrication or

lapping compound, until the top dead

center of the fit is close enough to run on the water. Where that point is, is hard too tell, but,

you want a very tight seal on TDC, with out having any starting or running issues.

Honing a sleeve is with a rotating, speacial type grinder, to make the sleeve fit the piston.Haven't tried

that . The tool is out of my price range, and the knowledge to do it.

I'm sure you will get many more response's on this.

Nice lookin Crapshooter, and boat holder as well.

I would not put lapping compound in a engine as it's harder than the alum. piston and will inbed itself the Piston and wear out the liner. If you feel it's nec. to lap the sleeve-remove it from the engine and do it and wash it very well before re-assembling do not put any lapping compound on the piston!!!!

Should have posted this before, but there is lapping compound that is non inbedding, so you can do this

process without continued wear to piston or sleeve.

 

[steve wood]

i have lapped some nova rossi piston/liners that were toooooo tight. i know, iknow, don't need any comments. i used non imbedding lapping compound for soft metals(read aluminum). you can lap in a nova in a very,very, short time if needed. it doesn't affect the hard chrome liner at all. you have to remove the piston and liner from the case, then slop on the slurry and work away, round and round and up and down she goes. oh, yes you can lap with a mandrel. just wouldn't do it to a liner. not the type of work for the uninitiated

 

[Charles Perdue]

i have lapped some nova rossi piston/liners that were toooooo tight. i know, iknow, don't need any comments. i used non imbedding lapping compound for soft metals(read aluminum). you can lap in a nova in a very,very, short time if needed. it doesn't affect the hard chrome liner at all. you have to remove the piston and liner from the case, then slop on the slurry and work away, round and round and up and down she goes. oh, yes you can lap with a mandrel. just wouldn't do it to a liner. not the type of work for the uninitiated

The name of one of the non-imbedding lapping compounds is Timesaver. It comes in different grits, the one that we primarily use in our engines is the fine grit. It can be purchased from McMaster Carr. (Where else)?

Charles

 

[dwilfong]

I use Brownell's garnet lapping compound 1000 grit mixed with a little WD40 to make a paste.

It takes some time to do it but you can see on the piston and in the sleeve where it mates.

When used with the liner squeezer you can make a very good seal.

You must reassemble the eng to check seal because it will change when you tighten down the head.

 

[Marty Davis]

LOTS OF SOLUTIONS.........

There are a few ways of lapping a piston. I will put them in the order of best to worst.

Best: Use a Helical Lap on the piston with the compound that they sell. You use the External Holders and the insert correct for the sized piston that you are lapping. Depending on the amount that this piston is too big, you will use a compound that will either take off a lot or only a small amount. Advantage: Piston becomes PERFECTLY ROUND. http://helicallap.com

Second Best: Start with a piece of cast iron and bore a hole that is slightly smaller than the piston. Then bore with a taper matching the liner (usually about .001" for a .21 from the top of the exhaust to TDC). That way the piston can be put into the cast iron sleeve and it will not come out the top. Put a little non-imbedding lapping compound in the cast iron lap and lap only a little bit. You want the top .050"-.060" of the piston ONLY to be lapped. This is a great way to get a perfect seal, but takes some work to make the lap initially. This was the preferred method that Mike Wizniewski and his Father used during the K&B Era and it worked VERY WELL.

Third Best: Not a really good solution unless you are lazy and don't want to do one of the above. Place the piston in the liner with a very small amount of non-imbedding compound and lap only slight amount with piston near TDC to put lapped ring on the top 1/16" of the piston.

All of these methods are highly dependent on the quality of the piston material. Some of the current offerings have an alloy that is very soft and don't last a long time.

Be sure to "Clean like Crazy" with toothbrush and dish washing soap.

 

[Marty Davis]

I use Brownell's garnet lapping compound 1000 grit mixed with a little WD40 to make a paste.It takes some time to do it but you can see on the piston and in the sleeve where it mates.

When used with the liner squeezer you can make a very good seal.

You must reassemble the eng to check seal because it will change when you tighten down the head.

David:

The fit shouldn't change when you tighten the head if the button/liner fit is correct and the liner/case fit is correct. I spend a little time lapping the top flange of the liner to the case to help with this.

The compound that you use is the same that I have used for 20 years and is the best that I have found also.

 

[dwilfong]

I use Brownell's garnet lapping compound 1000 grit mixed with a little WD40 to make a paste.It takes some time to do it but you can see on the piston and in the sleeve where it mates.

When used with the liner squeezer you can make a very good seal.

You must reassemble the eng to check seal because it will change when you tighten down the head.

David:

The fit shouldn't change when you tighten the head if the button/liner fit is correct and the liner/case fit is correct. I spend a little time lapping the top flange of the liner to the case to help with this.

The compound that you use is the same that I have used for 20 years and is the best that I have found also.

Marty

I have noticed that when using the liner squeezer that the fit changes when you tighten the head.

The fit sames to loosen up so I always reassemble the eng and check the fit before I lap.

I think this is due to the way the liner pinches the sleeve. I have also noticed that if I true up the top of the sleeve before I assemble it is not as bad.

I never thought about lapping the liner to the case and button to liner.

Yes the button dose get tight after pinching sleeve.

Thanks for the tip.

David

 

[Norm Doerr]

I use Brownell's garnet lapping compound 1000 grit mixed with a little WD40 to make a paste.It takes some time to do it but you can see on the piston and in the sleeve where it mates.

When used with the liner squeezer you can make a very good seal.

You must reassemble the eng to check seal because it will change when you tighten down the head.

David:

The fit shouldn't change when you tighten the head if the button/liner fit is correct and the liner/case fit is correct. I spend a little time lapping the top flange of the liner to the case to help with this.

The compound that you use is the same that I have used for 20 years and is the best that I have found also.

Marty

I have noticed that when using the liner squeezer that the fit changes when you tighten the head.

The fit sames to loosen up so I always reassemble the eng and check the fit before I lap.

I think this is due to the way the liner pinches the sleeve. I have also noticed that if I true up the top of the sleeve before I assemble it is not as bad.

I never thought about lapping the liner to the case and button to liner.

Yes the button dose get tight after pinching sleeve.

Thanks for the tip.

David

Not to BUTT in here but...... Think about what pinching does..is the liner really round after that?