piston fit

[Terry Keeley]

Thanks for passing on all your years of experience and expertise here Jim, much appreciated, I'm gonna get back to chroming and making pistons shortly and your experience is valuable information.

When you fit a piston you mention "crunch" numbers, in other words where the piston stops in the bore. I've always found this very subjective depending on how hard you push and the taper in the sleeve. Is there a more precise way to fit a piston? Possibly making the O/D match a certain size at some point in the liner? Ideas?

Looked at this sequence in your gallery but still wondering?

Piston OD is the same as the liner ID Notice in this photo the piston goes to the very top of the liner. Its OD is the same as the ID of the liner at the top. A motor fitted like this will run, but will not make any serious HP. Either one of the two pistons in the middle will be good to use in this liner. To determine the correct size of a piston for any tapered liner; first, measure the liner top & bottom carefully; second, check for roundness at these points; third, check at different points above the exhaust for roundness & taper to the top of the stroke. Out of roundness at the bottom has no effect. Liners with insufficient taper CANNOT be fitted properly with the correct crunch point! Four, add .0005 to the liners dimension at the top & cut this dimension on the piston's OD. Last, cut the top taper to achieve the correct crunch point. The total length of the top taper should be about .100 to .110 in long, measured from the piston crown. If the piston's top taper becomes to long, very small amounts (.000025) should be taken from the piston's OD. Engine manufacturers machine large numbers of pistons & liners, then select parts that will give the correct fit.

 

[Jeff Lutz]

Here is how us cave men do it.

and a little 600 to 2000 grit and lot of Patience. It's not down to the .0001 but it will do.

David

This is not a good method to use to hold the piston for final machining. A snug fitting 3.000" long pin placed in the wrist pin hole while it is being held with a Hardinge expanding collet, can be easily zeroed. This insures that all the final cuts made on the OD & the piston crown are square to the axis of the wrist pin hole. The wrist pin hole itself should be in the middle, unless offset is desired. Using the expanding collet will give the piston a semi barrel shape. Since the piston is rocking in the bore, this helps reduce side wall friction. It has no effect on what will happen if the wear band taper is correct & the liners taper is correct. Piston top taper amounts are tied to liner taper amounts. Liner taper amounts are tied to the stroke of the engine. Short strokes allow steeper liner tapers & vice versa.

Only poylcrystaline coated tool bits that have been lapped can cut the very small amounts, .00005"/side, that are necessary for fitting pistons to liners. The final machined finish should be very smooth, between 25 & 50 micro inch.

Jim Allen

Note: Both the final side cuts & the taper side cuts should be made at the same time. This can be easily done in manual lathe. The compound will have to be set to the desired top taper amount. A .00005" indicator can set the compound using a taper master. Accuracy of the finished taper cut will be .00005"/2.000". Anybody think this type of precision can be done with a piece of 2,000 grit paper held in your hand????

Jim, As I pointed out to David, he knows it really can't be done. But to you Jim, for you to tell these guys that can be done on a manual lathe easily is a stretch. Plus, in the end you do not get as good of a result as cnc. Your finish cuts are to slight in my experience to achieve the best finish also.Plus, a piston going up into a tapered liner working with .0001-.0003 is fine for achieving a good fit.I know you will get on here and disagree, but that piston is not going up into space.

 

[Jack ODonnell]

I have never had much luck machining pistons on a manual lathe.All the the pistons i make now are done on a cnc machine.

 

[Jim Allen]

Thanks for passing on all your years of experience and expertise here Jim, much appreciated, I'm gonna get back to chroming and making pistons shortly and your experience is valuable information.

When you fit a piston you mention "crunch" numbers, in other words where the piston stops in the bore. I've always found this very subjective depending on how hard you push and the taper in the sleeve. Is there a more precise way to fit a piston? Possibly making the O/D match a certain size at some point in the liner? Ideas?

Looked at this sequence in your gallery but still wondering?

Piston OD is the same as the liner ID Notice in this photo the piston goes to the very top of the liner. Its OD is the same as the ID of the liner at the top. A motor fitted like this will run, but will not make any serious HP. Either one of the two pistons in the middle will be good to use in this liner. To determine the correct size of a piston for any tapered liner; first, measure the liner top & bottom carefully; second, check for roundness at these points; third, check at different points above the exhaust for roundness & taper to the top of the stroke. Out of roundness at the bottom has no effect. Liners with insufficient taper CANNOT be fitted properly with the correct crunch point! Four, add .0005 to the liners dimension at the top & cut this dimension on the piston's OD. Last, cut the top taper to achieve the correct crunch point. The total length of the top taper should be about .100 to .110 in long, measured from the piston crown. If the piston's top taper becomes to long, very small amounts (.000025) should be taken from the piston's OD. Engine manufacturers machine large numbers of pistons & liners, then select parts that will give the correct fit.

Terry,

The photos shown in the gallery are of pistons made for the same K-67 liner. This liner has a very low taper amount, but it is still possible to arrive at a good crunch number. The liner needs to be finished ground with an 8 to 12 micro inch finish. (look at a good quality dowel pin) Everyting needs to be dry, clean, & free of oil. If you look in my gallery in the machinery section, you will see the indicators used on the carriage, cross feed & compound that must be used to easily accomplish what I have said about the accuracy. IT IS ABSOLUTE NECESSARY TO KNOW EXACTLY WHERE THE CARRIAGE, CROSS FEED & COMPOUND ARE AT ALL TIMES!

Mitutoyo two inch diameter, jeweled, water proof indicators that read .0001", with a resolution of .000010", properly mounted are more precise than a .00005" digital readout that has a .00005" resolution. Ask any person that is a tool maker, he or she will tell you that indicators never lie!

If you have more questions, fell free to ask. If I do not know the answer, I will say so. I will never give IMHO information!

Jim allen

 

[Jim Allen]

These photos show two complete piston, rod & liner assemblies. They are pre-run on the dyno for breaking in purposes & to check the roundness of the piston liner combination. Notice the very obvious "wear band" .100" down from the top of the piston crown. Notice the 8 to 12 micro inch finish on the liners chrome. No lapping of any kind is necessary to produce this finish. A 240 grit wheel turning at 20,000 RPM makes this possible. Notice the 25 micro inch finish on the piston's OD. Polycrystaline coated diamond tool bits will easily produce this finish at spindle speeds above 2000 RPM & in feed amounts of .00005". Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

All of these parts were made on a manual lathe, a manual milling machine & a manual grinder!

Jim Allen

Note: Did anyone notice how high up in the piston the wrist pin is? The connecting rods center distance is 1.741" with a .902" stroke & there is no bushing used in the upper end.

 

[hugh hargett]

 

[Terry Keeley]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

 

[dwilfong]

These photos show two complete piston, rod & liner assemblies. They are pre-run on the dyno for breaking in purposes & to check the roundness of the piston liner combination. Notice the very obvious "wear band" .100" down from the top of the piston crown. Notice the 8 to 12 micro inch finish on the liners chrome. No lapping of any kind is necessary to produce this finish. A 240 grit wheel turning at 20,000 RPM makes this possible. Notice the 25 micro inch finish on the piston's OD. Polycrystaline coated diamond tool bits will easily produce this finish at spindle speeds above 2000 RPM & in feed amounts of .00005". Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

All of these parts were made on a manual lathe, a manual milling machine & a manual grinder!

Jim Allen

Note: Did anyone notice how high up in the piston the wrist pin is? The connecting rods center distance is 1.741" with a .902" stroke & there is no bushing used in the upper end.

Jim what is the advantage of a short compression distance from the pin to the piston top?

Is this just to get the long rod to work in the case hight?

Also can the pressure that it takes to set the piston hight be measured?

I made a valve spring pressure tester when I was working on V8 engs. just a simple plunger cylinder with a gage on it.

Just thinking this might work to get the same pressure all the time to check the fit.

If so what pressure would be a good standard to use?

 

[Jeff Lutz]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

Terry, You will be better off getting started with a "push of the thumb",---- then---- alter the sizes of your pistons. Then you will have something, going off your measurements. After all, hitting your size is most important. Get a size established that gives you a certain pitch, then alter the size to find what works best for you. When I say pitch, let me give you an example. PICCO 45 BLACKHEAD PISTON AND LINERS WERE COMING IN AT WHAT MOST WOULD CALL A GOOD PITCH. IF TDC WAS .100" (TOP OF PISTON TO TOP OF SLEEVE), THE PISTON WHEN PUSHED IN SLIGHTLY WITH THE THUMB,WAS AROUND .200". You have already run many pistons and liners that were capable of running way over 100 mph, so you probably should put your attention more on what makes engines run, then making custom pistons.( Just a suggestion). No pun intended. If you want to play with millionths on the o.d. of your piston go ahead,but working with anymore than 50 millionths is starting to get a little, well, (insane).Jeff Lutz

 

[dwilfong]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

Terry, You will be better off getting started with a "push of the thumb",---- then---- alter the sizes of your pistons. Then you will have something, going off your measurements. After all, hitting your size is most important. Get a size established that gives you a certain pitch, then alter the size to find what works best for you. When I say pitch, let me give you an example. PICCO 45 BLACKHEAD PISTON AND LINERS WERE COMING IN AT WHAT MOST WOULD CALL A 50% PITCH. IF TDC WAS .100" (TOP OF PISTON TO TOP OF SLEEVE), THE PISTON WHEN PUSHED IN SLIGHTLY WITH THE THUMB,WAS AROUND .200". You have already run many pistons and liners that were capable of running way over 100 mph, so you probably should put your attention more on what makes engines run, then making custom pistons.( Just a suggestion). No pun intended. If you want to play with millionths on the o.d. of your piston go ahead,but working with anymore than 50 millionths is starting to get a little, well, (insane).Jeff Lutz

Well put Jeff. I have found more power with the pipe, port timing, intake timing and last but not least head design. the fit to the enth degree seam to be just the icing on the cake.

Do not want to diminish the value of the fit at all just don't need to do mental masturbation with it.

Their is a lot of very good info going around here.

As far as the pitch what have you found works good on the 1,01RS stock sleeve if you don't mind me asking?

 

[Jim Allen]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

The correct quanity will be different for different strokes, different liner tapers, different piston top tapers, different engine operating temperatures, different piston liner finishes & different bore sizes.

For my engines with the short .902" stroke & a 1.125" bore, the liner's total taper from top to bottom is .007" (.0035"/ side/ 1.635" long) The amount of taper from the top of the exhaust to the top of the stroke is .00107"/ side/ .502" long. This would be considered a large amount of liner taper. Sometimes engines were so tight I had to unscrew the head bolts to wind the starter cord.

The piston's top taper is .002"/.100" long/ side. With these numbers the crunch amount is set at .150", measured from the top of the stroke & .250" measured from the top of the liner. I cannot tell you the amount of force used when pushing the liner onto the mounted piston, but many times it is necessary to twist the liner to get it off.

Hope this answers your question. Total liner taper amounts from .002" to .008" were tested in .0005" steps. Piston top tapers from .001" to .003"/ side in .0005" steps were tested. Piston alloys tested included Mahle-138, Dispal-250. & RSP-444. Liner materials included 360 brass, 444 Phosphor bronze & 4032 aluminum.

Jim Allen

 

[Jim Allen]

These photos show two complete piston, rod & liner assemblies. They are pre-run on the dyno for breaking in purposes & to check the roundness of the piston liner combination. Notice the very obvious "wear band" .100" down from the top of the piston crown. Notice the 8 to 12 micro inch finish on the liners chrome. No lapping of any kind is necessary to produce this finish. A 240 grit wheel turning at 20,000 RPM makes this possible. Notice the 25 micro inch finish on the piston's OD. Polycrystaline coated diamond tool bits will easily produce this finish at spindle speeds above 2000 RPM & in feed amounts of .00005". Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

All of these parts were made on a manual lathe, a manual milling machine & a manual grinder!

Jim Allen

Note: Did anyone notice how high up in the piston the wrist pin is? The connecting rods center distance is 1.741" with a .902" stroke & there is no bushing used in the upper end.

Jim what is the advantage of a short compression distance from the pin to the piston top?

Is this just to get the long rod to work in the case hight?

Also can the pressure that it takes to set the piston hight be measured?

I made a valve spring pressure tester when I was working on V8 engs. just a simple plunger cylinder with a gage on it.

Just thinking this might work to get the same pressure all the time to check the fit.

If so what pressure would be a good standard to use?

The best stroke to connecting rod length ratio would be 1:2. My stroke is .902 & the connecting rod's length is 1.741, 1:1.93. I don't know if the force could be reliably measured & I have no idea what amount of pressure should be read.

There is a way to make a good piston holding fixture. Send me an e-mail & I'll send you a sketch.

Jim Allen

 

[Terry Keeley]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

The correct quanity will be different for different strokes, different liner tapers, different piston top tapers, different engine operating temperatures, different piston liner finishes & different bore sizes.

For my engines with the short .902" stroke & a 1.125" bore, the liner's total taper from top to bottom is .007" (.0035"/ side/ 1.635" long) The amount of taper from the top of the exhaust to the top of the stroke is .00107"/ side/ .502" long. This would be considered a large amount of liner taper. Sometimes engines were so tight I had to unscrew the head bolts to wind the starter cord.

The piston's top taper is .002"/.100" long/ side. With these numbers the crunch amount is set at .150", measured from the top of the stroke & .250" measured from the top of the liner. I cannot tell you the amount of force used when pushing the liner onto the mounted piston, but many times it is necessary to twist the liner to get it off.

Hope this answers your question. Total liner taper amounts from .002" to .008" were tested in .0005" steps. Piston top tapers from .001" to .003"/ side in .0005" steps were tested. Piston alloys tested included Mahle-138, Dispal-250. & RSP-444. Liner materials included 360 brass, 444 Phosphor bronze & 4032 aluminum.

Jim Allen

Thanks Jim, I guess with high taper the piston tends to just stop in a certain spot when you push it into the sleeve, I'll remember that 0.150" number.

Which piston material (if any) did you find to be the best overall? I see some of the Dispal alloys have up to 35% Si, does more Si mean more stability?

 

[Jeff Lutz]

These photos show two complete piston, rod & liner assemblies. They are pre-run on the dyno for breaking in purposes & to check the roundness of the piston liner combination. Notice the very obvious "wear band" .100" down from the top of the piston crown. Notice the 8 to 12 micro inch finish on the liners chrome. No lapping of any kind is necessary to produce this finish. A 240 grit wheel turning at 20,000 RPM makes this possible. Notice the 25 micro inch finish on the piston's OD. Polycrystaline coated diamond tool bits will easily produce this finish at spindle speeds above 2000 RPM & in feed amounts of .00005". Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

All of these parts were made on a manual lathe, a manual milling machine & a manual grinder!

Jim Allen

Note: Did anyone notice how high up in the piston the wrist pin is? The connecting rods center distance is 1.741" with a .902" stroke & there is no bushing used in the upper end.

Jim what is the advantage of a short compression distance from the pin to the piston top?

Is this just to get the long rod to work in the case hight?

Also can the pressure that it takes to set the piston hight be measured?

I made a valve spring pressure tester when I was working on V8 engs. just a simple plunger cylinder with a gage on it.

Just thinking this might work to get the same pressure all the time to check the fit.

If so what pressure would be a good standard to use?

The best stroke to connecting rod length ratio would be 1:2. My stroke is .902 & the connecting rod's length is 1.741, 1:1.93. I don't know if the force could be reliably measured & I have no idea what amount of pressure should be read.

There is a way to make a good piston holding fixture. Send me an e-mail & I'll send you a sketch.

Jim Allen

Jim, His question had nothing to do with rod ratio.??????? On top of that a 2:1 (rod ratio), would be far too high for a heat racing engine.

 

[Jeff Lutz]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work! What I was asking in my post was if you could quantify "a heavy push fit"? Is there a certain distance below TDC you want the piston to stop?

The correct quanity will be different for different strokes, different liner tapers, different piston top tapers, different engine operating temperatures, different piston liner finishes & different bore sizes. For my engines with the short .902" stroke & a 1.125" bore, the liner's total taper from top to bottom is .007" (.0035"/ side/ 1.635" long) The amount of taper from the top of the exhaust to the top of the stroke is .00107"/ side/ .502" long. This would be considered a large amount of liner taper. Sometimes engines were so tight I had to unscrew the head bolts to wind the starter cord. The piston's top taper is .002"/.100" long/ side. With these numbers the crunch amount is set at .150", measured from the top of the stroke & .250" measured from the top of the liner. I cannot tell you the amount of force used when pushing the liner onto the mounted piston, but many times it is necessary to twist the liner to get it off. Hope this answers your question. Total liner taper amounts from .002" to .008" were tested in .0005" steps. Piston top tapers from .001" to .003"/ side in .0005" steps were tested. Piston alloys tested included Mahle-138, Dispal-250. & RSP-444. Liner materials included 360 brass, 444 Phosphor bronze & 4032 aluminum. Jim Allen

Thanks Jim, I guess with high taper the piston tends to just stop in a certain spot when you push it into the sleeve, I'll remember that 0.150" number. Which piston material (if any) did you find to be the best overall? I see some of the Dispal alloys have up to 35% Si, does more Si mean more stability?

Yea Terry, You be sure to remember that .150" number.......... Sure Buddy, it just stops at a certain spot with a high taper sleeve.....Don't even worry about the size of your piston...... I know you depend on equipment to land an airplane, but now that Jim could not tell you how much force is used to push against a mounted piston, " You just figure it stops at a certain point". Looks like you need to do what I said a few posts back and start 'tweaking' off some sizes. Sorry to sound rude, I'm trying to get your attention- to help you.

 

[Jeff Lutz]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

The correct quanity will be different for different strokes, different liner tapers, different piston top tapers, different engine operating temperatures, different piston liner finishes & different bore sizes.

For my engines with the short .902" stroke & a 1.125" bore, the liner's total taper from top to bottom is .007" (.0035"/ side/ 1.635" long) The amount of taper from the top of the exhaust to the top of the stroke is .00107"/ side/ .502" long. This would be considered a large amount of liner taper. Sometimes engines were so tight I had to unscrew the head bolts to wind the starter cord.

The piston's top taper is .002"/.100" long/ side. With these numbers the crunch amount is set at .150", measured from the top of the stroke & .250" measured from the top of the liner. I cannot tell you the amount of force used when pushing the liner onto the mounted piston, but many times it is necessary to twist the liner to get it off.

Hope this answers your question. Total liner taper amounts from .002" to .008" were tested in .0005" steps. Piston top tapers from .001" to .003"/ side in .0005" steps were tested. Piston alloys tested included Mahle-138, Dispal-250. & RSP-444. Liner materials included 360 brass, 444 Phosphor bronze & 4032 aluminum.

Jim Allen

Jim, ".007" would be considered a large amount of liner taper". You think???? I would not admit to making a sleeve with that much taper, let alone tell the story of loosening head bolts.

 

[Jim Allen]

Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

Again Jim, beautiful work!

What I was asking in my post was if you could quantify "a heavy push fit"?

Is there a certain distance below TDC you want the piston to stop?

The correct quanity will be different for different strokes, different liner tapers, different piston top tapers, different engine operating temperatures, different piston liner finishes & different bore sizes.

For my engines with the short .902" stroke & a 1.125" bore, the liner's total taper from top to bottom is .007" (.0035"/ side/ 1.635" long) The amount of taper from the top of the exhaust to the top of the stroke is .00107"/ side/ .502" long. This would be considered a large amount of liner taper. Sometimes engines were so tight I had to unscrew the head bolts to wind the starter cord.

The piston's top taper is .002"/.100" long/ side. With these numbers the crunch amount is set at .150", measured from the top of the stroke & .250" measured from the top of the liner. I cannot tell you the amount of force used when pushing the liner onto the mounted piston, but many times it is necessary to twist the liner to get it off.

Hope this answers your question. Total liner taper amounts from .002" to .008" were tested in .0005" steps. Piston top tapers from .001" to .003"/ side in .0005" steps were tested. Piston alloys tested included Mahle-138, Dispal-250. & RSP-444. Liner materials included 360 brass, 444 Phosphor bronze & 4032 aluminum.

Jim Allen

Thanks Jim, I guess with high taper the piston tends to just stop in a certain spot when you push it into the sleeve, I'll remember that 0.150" number.

Which piston material (if any) did you find to be the best overall? I see some of the Dispal alloys have up to 35% Si, does more Si mean more stability?

Henry & I extensively tested the materials listed as well as A-390 & RSA-431, running the engines at WOT for 3 to 4 minutes. Different materials required different cold fits because of the different expansion amounts developed during engine dyno tests. The higher the silicon amounts, the tighter the cold fit must be. The Dispal-250, A-390 & RSA-431 we used had to be heat treated before final machining to prevent piston growth. The best alloy tested thus far is RSA-444 (30% Si). However, when using the RSA-444, the #360 brass previously used for liners had to be changed to #544 phosphor bronze. The engines with RSA-444 pistons & #360 brass liners sometimes could not be turned over by hand, but once started they ran fine. Changing to #544 bronze made cold fitting much easier.

RSA-444 works extremely well with #4032 aluminum liners. These two alloys are used in those very tight fitting .45 Nelson long stroke engines. When the liners have the correct taper amounts & the pistons have the correct top taper amouints, the engines would last forever.

Jim allen

 

[dwilfong]

These photos show two complete piston, rod & liner assemblies. They are pre-run on the dyno for breaking in purposes & to check the roundness of the piston liner combination. Notice the very obvious "wear band" .100" down from the top of the piston crown. Notice the 8 to 12 micro inch finish on the liners chrome. No lapping of any kind is necessary to produce this finish. A 240 grit wheel turning at 20,000 RPM makes this possible. Notice the 25 micro inch finish on the piston's OD. Polycrystaline coated diamond tool bits will easily produce this finish at spindle speeds above 2000 RPM & in feed amounts of .00005". Notice the distance both pistons will go into their liners with a heavy push fit, is the same.

All of these parts were made on a manual lathe, a manual milling machine & a manual grinder!

Jim Allen

Note: Did anyone notice how high up in the piston the wrist pin is? The connecting rods center distance is 1.741" with a .902" stroke & there is no bushing used in the upper end.

Jim what is the advantage of a short compression distance from the pin to the piston top?

Is this just to get the long rod to work in the case hight?

Also can the pressure that it takes to set the piston hight be measured?

I made a valve spring pressure tester when I was working on V8 engs. just a simple plunger cylinder with a gage on it.

Just thinking this might work to get the same pressure all the time to check the fit.

If so what pressure would be a good standard to use?

The best stroke to connecting rod length ratio would be 1:2. My stroke is .902 & the connecting rod's length is 1.741, 1:1.93. I don't know if the force could be reliably measured & I have no idea what amount of pressure should be read.

There is a way to make a good piston holding fixture. Send me an e-mail & I'll send you a sketch.

Jim Allen

Jim

PM sent with my Email addy.

David

 

[dwilfong]

I had the privilege of spending a day with Mart Davis in the shop. he showed me a liner pincher that was made with a tapper cut into it.

He used it on one of my RS7 sleeve. he would turn the liner to preset marks on the jig using the centering pin notch as a reference. he used a torque wrench to tighten it at every mark.

He said this would give a .002 taper from the top of the ex to the top of the liner.

I still run this sleeve with new piston from CMB and it holds the pinch for a very long time.

The only reason I have changed pistons one time was the skirt broke at the bottom of the ex side.

For those of use that can't make are own liners we are stuck with what ever the factory gives us.

Now this specialized pincher dose give a chance to try different tappers.

But building one is probably just as involved as making the sleeve.

David

 

[steve wood]

I had the privilege of spending a day with Mart Davis in the shop. he showed me a liner pincher that was made with a tapper cut into it.

He used it on one of my RS7 sleeve. he would turn the liner to preset marks on the jig using the centering pin notch as a reference. he used a torque wrench to tighten it at every mark.

He said this would give a .002 taper from the top of the ex to the top of the liner.

I still run this sleeve with new piston from CMB and it holds the pinch for a very long time.

The only reason I have changed pistons one time was the skirt broke at the bottom of the ex side.

For those of use that can't make are own liners we are stuck with what ever the factory gives us.

Now this specialized pincher dose give a chance to try different tappers.

But building one is probably just as involved as making the sleeve.

David

harder to make than a straight one.just have to mount the block in a lathe and cut the bore with the compound