Piston Growing?

Stuka Stunt Main Forum · 25 of 25 known posts recovered

Stuntguy13 · May 09, 2006 10:09 PM

I'm looking for information about how George Alrich use to grow iron pistons by heating them in an oven. I know this was a method he would use if an engine was just a bit weak on compression seal. What I don't remember was what temperature or for how long and how to cool it after heating so it stays grown. Anyone remember this?

Thanks

Jim Thomerson · May 09, 2006 11:05 PM

#1 source

Someone else can tell you how. My only experience was with a ST diesel contrapiston (iron?) which had been lapped too small. Gene Hempel heated it for a couple of minutes with a propane torch and let it air cool. It is now too large and I will have to lap it down if I want to use it.

SRiese5283 · May 10, 2006 01:28 AM

#2 source

OK....put piston in oven on tin foil, Turn on oven to 450-500 degrees. Cook for one hour. Turn off oven. let cool in oven.
I have done this many time for old McCoy's.
You can do this a couple of times if need be. Using a torch will grow a piston also...BEWARE...Piston might grow to large. Most I've had one grow was a Torp 19 GH...grew .002
Hope this helps.

OBTW...I've had a few that this didn't work

Scott Riese

Bill Little · May 10, 2006 08:02 AM

#3 source

I have done as Scott describes. An hour in a 450*-500* oven and left in there to cool. I usually do this for older McCoy Red Heads which are getting weak. I don't know if it will work on an engine that is "worn out". It has returned the fit to very usable conditions.

Tom Lay has a "heat treating process" done (I guess like GMA did) so that the old Red Heads can be safely run with a muffler. He did two of my RH 40s for this purpose. So far they have been fantastic.

Big Bear <><
Character: It's what you do when no one else is watching.

ty marcucci · May 10, 2006 10:55 AM

#4 source

LAST EDITED ON May-15-06 AT 12:50 PM (CST)

x

Lane Puckett · May 10, 2006 06:49 PM

#5 source

I'd like to do this to a brand new piston and liner I got for an OS FP35. The fit on the new P/L'er is so loose that it slips all the way to the top of the liner.

I'm just fearful that it will end up being too much of a good thing and then I get to laborously hone a piston back into a decent fit.

Lane

TJDNC · May 10, 2006 08:53 PM

#6 source

Does this process work on aluminum pistons, or steel only?

Thomas

srpracing · May 10, 2006 10:08 PM

#7 source

Ron Young

This process works on any piston the problem most have is they dont use high enough temp. I used a kiln at 800 degrees for 4 hours and they would grow .003 to .006 then I would hone them to size and would work great.

OS32 · May 11, 2006 12:28 AM

#8 source

One time George had a piston -sleeve of mine that he thought was too loose. So he chromed it.

John Leidle

SRiese5283 · May 11, 2006 02:24 AM

#9 source

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Scott Riese

ghost123uk · May 11, 2006 04:58 AM

#10 source

>Does this process work on aluminum pistons, or steel only?
>
>
>Thomas

Err - what temperature does aluminium start to melt at ?

Take care

Always looking for C/L flying buddies in the N.W. - UK - mail me ! - [email protected]

OS32 · May 11, 2006 07:20 AM

#11 source

Chromed the sleeve to be exact.

John Leidle

SRiese5283 · May 11, 2006 01:37 PM

#13 source

Thanks John!

Scott Riese

gcb · May 11, 2006 08:38 AM

#12 source

Err - what temperature does aluminium start to melt at ?
Take care

If I remember correctly, about 1200 deg. F. Perhaps different for alloys.

Biggest problem is the narrow range it goes from solid to liquid. It does not go through color changes like iron.

This is from OLD memories so may not be accurate.

George

SRiese5283 · May 11, 2006 01:39 PM

#14 source

I wish I could find a web page about AL/alloy pistons? Can someone help?

Scott Riese

TJDNC · May 11, 2006 02:23 PM

#15 source

Im certainly no Metalurgist but it would seem to me that expanding the metal would also soften it to some degree. Anyone have any experience with the longevity of heat expansion?

There was a thread a while back on this or another forum that suggested it was possible to use a pipecutter to cut a grove in the piston. This expanded the metal paralell to the groove and tightened the piston in the bore.

Which method would be better?

Personally, I would prefer a more long term solution and like the idea of re-chroming the bore/liner. Is there anyone around that can do this?

Thomas

Lane Puckett · May 12, 2006 06:08 PM

#16 source

Folks need to get the dirtydan to post up his experince on this. He wrote a great article on the Fox Combat Special Mark VI and as I recall he had comments on doing this. If I recall right the article was in the MACA newsletter.

Lukesp · May 12, 2006 07:22 PM

#17 source

LAST EDITED ON May-12-06 AT 07:27 PM (CST)

Thought I would share my own experiences on the subject, I did blacksmithing for a few years. That does NOT make me a metallurgist BTW.

Steel and cast iron have a crystalline structure (not a grain, soft or wrought iron has that) which expands with each "critical" heat, somewhere around cherry red or higher. It differs with different alloys of steel. The longer the item is heated the larger the crystals become up to a point. The smaller the crystals the tougher the item , the larger the crystals the more brittle the item. If the "item" i.e. piston, is tempered then large crystals are a problem. I can't see any reason for a piston to be tempered, and besides, heats above black heat usually destroys any tempering.

I think the only real risk with expanding a piston using heat is the formation of scale from too much oxygen present, very common with high (i.e. glowing bright red) heats via a torch. Having said that, I have successfully expanded pistons in the past with a propane torch. I destroyed one via scaling, but that was due to impatience.

The other risk is overheating. Yellow heat and higher. Don't go there.

Sorry about being somewhat vague with the subject, I am moving house and all my books are packed away. This is all from memory.

Luke.

EDIT :

Oops, steels can permanently expand from lower heats than cherry red BTW. I think it is length of time for the heat that is important.

Lukesp · May 12, 2006 07:32 PM

#18 source

LAST EDITED ON May-12-06 AT 07:42 PM (CST)

Just a bit more info, quenching can cause distortion and cracking, I air cool my pistons when I heat them.
I made knives from basic steels (carbon steel) years ago. Kinves made from a file had great cracking potential if quenched in water, oil was the way to go. Air cooling usually normalises steels, unless they are air quenching steels. I doubt any piston would be made of that. Very slow cooling by burying the item in dry ash anneals steel, bringing it to it's softest state.

If the piston happens to be made of steel then it will be of an unknown alloy, quenching has the potential of making it extremely brittle. If the piston is iron (more likely) then I have no idea. I never had much to do with cast iron. Like I say, just my experiences when I was forging.

Luke.

50plusAirYears · May 12, 2006 10:38 PM

#19 source

I've read about the idea of using a tubing cutter to enlarge a piston. I think it appeared in an old American Modeler. I did try it once. It is very dificult to get a small piston to turn evenly in the cutter. I ruined the piston I tried it with.

Apparently, the cutting action is supposed to raise the metal around the cut a bit.

Sounded good, but just didn't work for me.

GWassenaar · May 14, 2006 05:26 AM

#22 source

Sounds like the old fashioned technique of "nurlizing". You knurl the piston surface to build ridges and prevent piston slap. I never heard that it will improve seal though.

Gerben Wassenaar

wright45 · May 16, 2006 03:34 PM

#23 source

I tried the tubing cutter trick on a McCoy 35 once. It did raise up a ridge but the piston was already so brittle that lots of small bits flaked off. After I got it back together, it seemed great. Good compression etc. But after I ran it once, it lost all its compression.

John Wright

Giffy · May 14, 2006 12:50 AM

#20 source

Anyone ever try to grow a Cox .049 piston?

Giffy

pipemakermike · May 14, 2006 02:48 AM

#21 source

start with a 020 piston and water it every day

Regards

Mike

http://www.machineconcepts.co.uk

cyclone · May 16, 2006 07:51 PM

#24 source

I know this sounds kind of crude, but it works very well on engines with domed pistons, McCoy, Forster, and others. I mic the piston, and then place it on an anvil or some hard suface, and tap it gently on the dome with a hammer. Keep checking with the mic until the piston at the top is about a .001 to .0015 larger. It is amazing, but it will be very close to round even though there is a baffle on most of these pistons. I then refit to sleeve with very fine compound. The secret is very fine compound. I use a product called buff eze from Martin Senour. Restores the fit in these engines and will run better and longer than when new.

Jim Kraft