"Growing a Piston"

[Jerry Wyss]

A while back I think it was Kevin B Or Preston H that was telling me about "growing" a piston in an oven. I have a situation with the Thunder Tigers

P/S fit is not the best, I have been using a .003 "sleeve shim" from Grim that has

been giving good results. If I could "tighten' this area up some it would save me from "weeding" thru a bunch new P/S sets to find one that is a little better.

I heard of "pinching" the sleeve with a devise and I've also heard some "horror" stories of doing that very thing. What does "anyone" think about either of these two methods??

 

[dave roach]

This is what I do. Take you piston and use a small tubing cutter and go around the top of the piston . You do'nt what to cut it but it will make the piston grow. Do this about .040 to .050 from the top of the piston and in two places.

 

[Jerry Wyss]

This is what I do. Take you piston and use a small tubing cutter and go around the top of the piston . You do'nt what to cut it but it will make  the piston grow. Do this about .040 to .050 from the top of the piston and in two places.

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Hey Dave, You say "You don't want to cut it", but you are talking about putting small "grooves" with "flared" sides of the groove?? I'm a Plumber of 27yrs so I know what this does in "copper" pipe,, just wanted to understand correctly.

 

[Jack Garcia]

A while back I think it was Kevin B Or Preston H that was telling me about "growing" a piston in an oven. I have a situation with the Thunder TigersP/S fit is not the best, I have been using a .003 "sleeve shim" from Grim that has

been giving good results. If I could "tighten' this area up some it would save me from "weeding" thru a bunch new P/S sets to find one that is a little better.

I heard of "pinching" the sleeve with a devise and I've also heard some "horror" stories of doing that very thing. What does "anyone" think about either of these two methods??

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Jerry,

This what I have done with great success. We have one of those counter top electric ovens, what I do is lay the piston skirt down on the alum. tray that comes with the oven. Bake the piston at the highest heat setting (500o) for a couple of hours. Turn off heat and let the piston cool naturally. You'll need to break in the piston again. Good luck.

 

[Jerry Wyss]

A while back I think it was Kevin B Or Preston H that was telling me about "growing" a piston in an oven. I have a situation with the Thunder TigersP/S fit is not the best, I have been using a .003 "sleeve shim" from Grim that has

been giving good results. If I could "tighten' this area up some it would save me from "weeding" thru a bunch new P/S sets to find one that is a little better.

I heard of "pinching" the sleeve with a devise and I've also heard some "horror" stories of doing that very thing. What does "anyone" think about either of these two methods??

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Jerry,

This what I have done with great success. We have one of those counter top electric ovens, what I do is lay the piston skirt down on the alum. tray that comes with the oven. Bake the piston at the highest heat setting (500o) for a couple of hours. Turn off heat and let the piston cool naturally. You'll need to break in the piston again. Good luck.

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Thanks Jack!! I Would Just Love To "Break" The Piston Again :lol: I just need it a "little" tighter, The sleeve only has one race on it, using the same MC-9 all day so I know it's not "hurt".

 

[VansRacing]

Jerry,

Believe it or not, the pipe cutter will restore the piston but you can over do it so easy.My cutter has been modified, it has been sharpened to remove the small flat that is on most wheels. This allows for a much lighter groove.

If you elect to do this, do it very carefully and lightly. You will have to break the piston back in slowly but you actually can run the piston a couple of more weekends.

However, you will find that this trick is only good for a short time and will

have to be done again. After the second groove job, I typically scrap the piston.

REMEMBER I SAID: You can really screw up quick if you are not careful!

Carl,

 

[Jerry Wyss]

Jerry,
Believe it or not, the pipe cutter will restore the piston but you can over do it so easy.My cutter has been modified, it has been sharpened to remove the small flat that is on most wheels. This allows for a much lighter groove.

If you elect to do this, do it very carefully and lightly. You will have to break the piston back in slowly but you actually can run the piston a couple of more weekends.

However, you will find that this trick is only good for a short time and will

have to be done again. After the second groove job, I typically scrap the piston.

REMEMBER I SAID: You can really screw up quick if you are not careful!

Carl,

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Thanx Carl, I'm gonna try the other method first, cause the sleeve is pretty new without any lean probs,,Its' just a Thunder Tiger Thing

 

[VansRacing]

Jerry,

I have tried the heat treat process and you have to wonder if you are actually growing the piston in diameter or is the piston distorting and causing the fit to become tighter??? I am not sure but I do know that I have heated the house up trying to make a piston diameter change by .0002".

I am not knocking anybodies method here because I have done it myself. I am just not sure what is actually happening when you heat one up like that but it does seem to change the feel of the piston fit. I like the pipe tool because I can take it to the pond with me and if needed.... I am ready to use it!

The heating method is a much safer way of doing it.

Carl,

 

[izitbrokeyet?]

Jerry,

If it's a 19.5mm sleeve I can send you the tool to resize it or you can send the p/s set up to me for resizing. I've done a bunch of these things now with good results. It will cost you return shipping.

I've also baked pistons before....Baking only seems to work with the older cast pistons. It doesn’t do squat for the Novarossi Microcast or CNC pistons. Their material is just too stable. Baking would probably work on the TT piston since it’s a cast piston.

 

[james irwin]

Jerry,If it's a 19.5mm sleeve I can send you the tool to resize it or you can send the p/s set up to me for resizing.  I've done a bunch of these things now with good results.    It will cost you return shipping.

  I've also baked pistons before....Baking only seems to work with the older cast pistons.  It doesn’t do squat for the Novarossi Microcast or CNC pistons. Their material is just too stable.  Baking would probably work on the TT piston since it’s a cast piston.

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YES GIVE ME THE OL TUBING CUTTER ANY TIME . THEY HAVE SO MUCH SILLICONE IN THE ALUM PISTONS NOW THAT YOU MUST ALMOST BURN THE HOUSE DOWN , AND I AINT SO SHURE IT WOULD MOVE THEN . PAY ATTETION TO WHAT CARL IS SAYING ABOUT BE CAREFULL . IF YOU THINK YOU MAY HAVE GONE TOO FAR ??? THEN YOU HAVE , LOL CARL WE WONE THE NABA NATS IN WICHITA. KA 1995 30 CC HYDRO 1.22.00 WTH AN EGINE WE HAD DONE THE TUBING CUTTER BIT ON ,( MADE THE HALL OF FAME )

 

[Jerry Wyss]

HEY GUY'S!! IT WORKED GREAT! That is REALLY COOL!! It worked So Good that I was able to put in a .005in shim under the sleeve instead of the .003,,Thats closer to where I wanted be anyway, and Still have great "pinch"! I couldn't be Happier at This Moment( well ,,yeah i probably could) :lol:

My "jeweler" friend has 3 diff "ceramic" ovens and we used the smaller one and heated it to 675degF was the "high" point for the low setting,,it bounced back and forth between that and 645degF for an 1 1/2 hrs and turned it off and it took 2 1/2 hrs to get down to 160deg. Man, so far it's great! Two things are Great,,my headbuttons that I've been designing for a while came in the mail today from SPD Props, Steve did the machining and I have a .17cc,, .18cc and a .19 too. The engine has shown steady improvement with every mod I've done with the help of several here including Massive help from TimD. The boat is already running Very well right now and this is going to be "Icing" on the cake, BIG TIME! Thanks Y'all for your help, The Knowlege On this Site is STUNNING!!

 

[GRoth265]

Hey Jerry you going to come up and play with us? I'm planning to come down on the holiday and see how those tigers run. Greg Roth

 

[Jerry Wyss]

Hey Jerry you going to come up and play with us? I'm planning to come down on the holiday and see how those tigers run.   Greg Roth

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OK Big Daddy, I'll Be Ready,,I Hope,, :lol: :lol:

 

[lohring]

They run very well. I've had to warm up the MAC to try to keep up. The Thunder Tiger also has the advantage that the pivot pin can be angled independently from the propeller. This and Jerry's other mods have made his Leecraft into a new boat. I want to see it run against the Van Hootens.

Lohring Miller

 

[Jerry Wyss]

Hey Kevin! It is a "19.5"mm OD sleeve :blink: See; That's What I was Sayin',"These Guy's Know Everything",,Put'em All together and It's One Big Giant

Brain :lol: I'll see Sunday(maybe) how well the "oven thing" did,,the fit right now

is right where I wanted it.The "Tiger's" P/S fit has never been good and moving the piston away from it's "critical" pinch with sleeve shims has been bothering me But the possibility of "resizing" these components has really "Lit" me Up Thanks for the offer Kev, I'll be contacting you in the near future I 'spect.

 

[Jerry Wyss]

They run very well.  I've had to warm up the MAC to try to keep up.  The Thunder Tiger also has the advantage that the pivot pin can be angled independently from the propeller.  This and Jerry's other mods have made his Leecraft into a new boat.  I want to see it run against the Van Hootens.
Lohring Miller

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Hi Lohring! It's made me "Love" the LeeCraft again, that's for sure. I think if I could "revamp" the running serface again and make the "flat section" longer it could run with the "Best" of boats.The nice thing about the LeeCraft is thats it's Hard to "Blow Over" and with the "Wedge" in there They corner like a "Bat". I plan to keep working on it while developing the WOF30 to it's completion,,,And The Winner IS,,,,,,,,

 

[steve wood]

A while back I think it was Kevin B Or Preston H that was telling me about "growing" a piston in an oven. I have a situation with the Thunder TigersP/S fit is not the best, I have been using a .003 "sleeve shim" from Grim that has

been giving good results. If I could "tighten' this area up some it would save me from "weeding" thru a bunch new P/S sets to find one that is a little better.

I heard of "pinching" the sleeve with a devise and I've also heard some "horror" stories of doing that very thing. What does "anyone" think about either of these two methods??

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use a grimracer sleeve squeezer and an inch pound torque wrench. you can get an almost new fit back again.

steve

 

[Cleatus Cooper]

Whew that tubing cutter does the job too. Had a piston that was so wore out it would fall thru the sleeve but it sure won't now.

 

[Geraghty]

Jerry,
Believe it or not, the pipe cutter will restore the piston but you can over do it so easy.My cutter has been modified, it has been sharpened to remove the small flat that is on most wheels. This allows for a much lighter groove.

If you elect to do this, do it very carefully and lightly. You will have to break the piston back in slowly but you actually can run the piston a couple of more weekends.

However, you will find that this trick is only good for a short time and will

have to be done again. After the second groove job, I typically scrap the piston.

REMEMBER I SAID: You can really screw up quick if you are not careful!

Carl,

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[Geraghty]

Jerry,
Believe it or not, the pipe cutter will restore the piston but you can over do it so easy.My cutter has been modified, it has been sharpened to remove the small flat that is on most wheels. This allows for a much lighter groove.

If you elect to do this, do it very carefully and lightly. You will have to break the piston back in slowly but you actually can run the piston a couple of more weekends.

However, you will find that this trick is only good for a short time and will

have to be done again. After the second groove job, I typically scrap the piston.

REMEMBER I SAID: You can really screw up quick if you are not careful!

Carl,

You can really get after those grooves in a piston if you have a helical lap to bring the piston back to size.[www.helicallap.com]I have a set of 3.5,7.5 and 11CC external laps and have been resizing pistons for years and then re-lapping them to fit the liner.

The re-lap job will last for one hell of a long time.Maybe not as long as a new P&S but dam close to it.

In fact I have a personal piston in a motor that I have done 5 or 6 times and the motor just gets easier to 2 stage.I don't know why,it just does.I suspect it has something to do with reduced drag but I don't really know for sure.

These laps are not cheap and they take some getting used to.Learning what lapping compounds to use is the learning curve.

When you get done wash the piston in the dishwasher with Cascade to get rid of all the laping compound in the aluminum pores.Just put a piece of wire through the wristpin hole and securely wire it on the rack in the dish washer.

The beauty of this process is the piston does't need to be perfect.I have taken siezed pistons.cleaned them up in the lathe with some 600 paper,re-cut the oil rings and then expanded the piston with the cutter and re-lapped it in to fit.The motors run great.

Carl is right,be careful and keep the cutter in the grooves when you are expanding them.

Carl,don't be to quick to go to the trash with those pistons,I'll gladly take them off your hands.