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Technical Reusing used pistons

Discussion in 'The Hokey Ass Message Board' started by ekimneirbo, Jul 2, 2020.

  1. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,110

    from Brooks Ky

    I'm quite sure many older folks have reused pistons when money was tight....just a simple rering job. I was thinking though:eek::eek::eek:.......what about some of the more expensive forged pistons and maybe even custom made ones. They ain't cheap. Anyway I was thinking that one of the problems with reusing pistons is cylinder wear. So if someone has a predilection toward a certain engine and could get them cheaply.........
    He could buy new pistons for the worn engine and have one of the spare engines bored and honed to fit the used pistons. That way he plans ahead and and still has high dollar pistons for the next engine. I know the pistons are gonna wear some in the first engine, but if you hone the second engine to fit the old pistons and file fit the rings............:D
    Any flaws in that plan ?
    loudbang and Desoto291Hemi like this.
  2. If the old pistons measure and spec out fine, go ahead and reuse them. Keep in mind though, aluminum does not have an infinite fatigue life like steel. At some point, aluminum will fail due to fatigue, no matters what. Used pistons are just that much closer to an end of life fatigue failure.
    CNC-Dude, loudbang and ekimneirbo like this.
  3. KenC
    Joined: Sep 14, 2006
    Posts: 406


    I've reused, used OS piston many time. Bore a block to fit the pistons on hand and run it. Just be sure to check ring grooves closely. That is the most often worn area, especially the top groove, IME. Sloppy grooves will break rings.
  4. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,156

    Rusty O'Toole

    It used to be common practice to knurl the pistons to take up wear, if it was not too severe. There were shims for worn ring grooves. If the pistons and cylinders are that worn you might as well rebore and put in new pistons, they are not that expensive for most common engines.
    Another thing, since the mid 80s cylinders and pistons don't wear the way they used to but piston rings do. I put this down to low tension rings and synthetic oil. So it is a lot easier to rering an engine without boring or changing pistons.
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  5. RmK57
    Joined: Dec 31, 2008
    Posts: 1,461


    I bought 3 used pistons to replace the ones that were messed up from detonation. Sometimes finding standard bore pistons for a rare engine can be a tough part to source, so you take what you can get.
    Last edited: Jul 3, 2020
  6. lake_harley
    Joined: Jun 4, 2017
    Posts: 944


    As soon as you fire up a fresh engine you're running used pistons. If you have pistons that are not all galled and scored I say why not bore and hone as appropriate and use them. In years past a lot more "mechanicing" was done. Now it's remove and replace, and sometime entire assemblies, not just individual parts.

  7. squirrel
    Joined: Sep 23, 2004
    Posts: 46,115


    Pistons wear out....the pin bore wears, the skirts wear, the ring lands wear. And the metal fatigues, as mentioned.

    I will run used pistons, if I don't expect the engine to have to last more than 50k miles (or less, if the pistons are really worn). Without knowing the intended use, it's tough to say what to do.

    I just put the used cast iron standard size (original, most likely) pistons back in a Model T engine. It has a wild amount of taper, as well as out of round. And it runs fine....for a while. The old rings had the Ford script on them, if I can get a few years out of the new ones, I'll be happy. I expect they would last the rest of the car's life, because as time goes by, it gets driven less and less each year.
  8. RJP
    Joined: Oct 5, 2005
    Posts: 1,532

    from PNW

    Built many claimer motors with used pistons. Also used cams, mix and match lifters, push rods, rockers, springs, if it was within reach on the bench it got used. Close was good enough. Real close was golden.
    37hotrod, ottoman, bobss396 and 9 others like this.
  9. There is a wrecking yard that I used to go to that had a sign in the main office. It said/says. "all cars run on used parts"

    If a piston is not worn too bad or damaged in some fashion there is no reason to throw it away. ;)
  10. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,086

    Atwater Mike

    I've used 'previously installed' pistons for eons. (dependent on wear) When I was an apprentice, my boss would send used pistons out to our machine shop to be knurled at the skirts and "G.I.'d", meaning the aforementioned 'shims' in regrooved ring lands!
    Recent re-use of pistons was in my 59L flathead block, bored it .040" over for some very slightly used pistons.
    Best thing for used pistons I can think of, as nobody smokes around here anymore...o_O
  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 26,917


    If you ever read Mickey Thompson's book Challenger you will remember that in his early days he scavenged used pistons out of shop scrap bins to run in his race cars and his first wife bought him a boring bar so he could fit them to blocks.
    I've known a few low budget racers who bought another team's cast off pieces to use in their engines to be able to afford to run. Most of those were dirt track racers who didn't have any sponsors except maybe the gas station that gave them gas and oil to have their name on the side of the car.
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 46,115


    one of my back burner projects is to build my first 396 again. The pistons are plumb wore out, but I have another set of used pistons that I took out of a friends engine years ago, they're the same size, and not so many miles on them. I plan to use them, after honing the bores again. It'll have some taper and probably a bit more than specified skirt clearance, but it will probably live for a couple decades, as seldom as I drive the truck these days.
  13. bill gruendeman
    Joined: Jun 18, 2019
    Posts: 305

    bill gruendeman

    If a reringed motor with used pistons lasts for 500000 miles or so. @ 2000 miles a year for 25 years, or 10 years @ 5000 miles a year, I am good with that. It’s all about your mileage and use.
    Last edited: Jul 2, 2020
  14. Baumi
    Joined: Jan 28, 2003
    Posts: 2,423


    I have done it in the past... I had a good std bore 327 with one piston that had a busted ringland from detonation. I found a like new used OEM std size piston and now the 327 is running in my girlfriend Dani´s suburban.
    A buddy of mine recently rebuilt his 264 Nailhead and because no one seemed to make oversize pistons for a small nailhead and his std size piston were still nice they sleeve the cyls back to a little less than std bore to make up for the wear the pistons had.
    loudbang and ekimneirbo like this.
    Joined: Dec 14, 2009
    Posts: 2,373


    Does anyone knurl pistons anymore ????

    i have done it many tones on air cooled VW’s mix and match and engine back to life with success.
    And a number of times on SBC’s as well.

    albeit these where all low use / non abuse ( no racing ) type engines just Sunday and evening cruising cars and worked out well.
    tractorguy, loudbang and ekimneirbo like this.
  16. We had a 327 block with flat top piston (eyebrows) but we needed 14 to 1 to run methanol. OK, on the way back from a swap meet I as talking to our designated driver and he thought he had a set of pistons in his parts shed. Sure enough, it was a set of 12.5 to 1. Some wear...I took and bead blasted the pistons and the cylinder wall clearance was right on at .005. Everyone had told me don't blast the pistons......better than knurling....and quicker
  17. tubman
    Joined: May 16, 2007
    Posts: 4,987


    Back in the day, at Carmichael's Auto Parts (read "Junkyard") in Excelsior, MN, had a "Piston Pile" in one corner of the yard. There was always someone picking through it. I had the occasion to do it myself once. I had a flathead that had 3 broken pistons. I was able to find a set of seven almost new pistons at Long Lake Engine Rebuilders that would be just right. (I have no idea what happened to the eighth piston). Lucky for me, my dad had a complete set of micrometers, so I was able to pick through the pile and find one that was close. I actually bored the engine to match the pistons with a rented hone (I was not popular with the guy running the rental place after that), but I got everything together and the engine was still running fine when I sold it about 3 years later.
    Cosmo49, loudbang, Tman and 2 others like this.
  18. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,852


    On this site we are dealing with older engines Just did a 352 Ford that I bored .030 and used a set of pistons that I picked up at a swap meet. It is a stock engine that is in a 67 F350 If the donor was rebuilt being .030 over I figured they didn't have a bunch of miles and I have a boring bar so I was just out time.If you are doing a Valve and Ring job you will be using you old pistons. If you have over .005 taper the engine will have a short life Taper kills ring groves every time the piston goes up or down the ring moves in and out the amount of taper causing wear. They used to hone the walls straight and knurl pistons to make up for the clearence gain in honing. I have knurled pistons when I could not find replacements. A Knurled cast piston is better than a loose one. The Knurl will last a long time if it is only done on the nonthrust side.
    Last edited: Jul 3, 2020
  19. indyjps
    Joined: Feb 21, 2007
    Posts: 3,831


    Ive done it a few times, buy partial piston sets from circle track racers, at the time most guys were only running a few brands. Find another partial set or buy some singles.

    Reused stockers with new rings and a hone job, it wont be a high miler engine, but will get you back in the road. Soaking them in real carb cleaner was the way to go, not sure if you can even get it anymore. Getting the ring lands clean takes some work.
  20. oldolds
    Joined: Oct 18, 2010
    Posts: 2,970


    Not everyone has a Nascar shop. I remember guys being real happy they got a dirt floor garage to work in. They did not have to rebuild an engine outside. They used used pistons rings and bearings. What ever it took to get to the track the next weekend. The car to get to work might have gotten new rings and bearings.
    Cosmo49, bobss396, MO54Frank and 5 others like this.
  21. southcross2631
    Joined: Jan 20, 2013
    Posts: 3,757


    Have done it many times. I bought a set of .100 454 pistons that had not been run too many passes before the motor spun a main bearing so the owner pulled it and salvaged the externals and sold me the short block for a 100 bucks. I salvaged the pistons and put them in another block with aluminum rods.
    It had Crower stack injection on methanol . I put a fogger on it and sprayed 300 right off the trans brake. It was in an O/T nova.
    Finally scored a couple of them when I got a little goofy after I got some nitromethane that I got from the driver of the Smoky mountain Express.
    Ever try to spray nitrous with nitro ? You find out what kind of tuner you are when you get greedy. It can be done in moderation.
  22. primed34
    Joined: Feb 3, 2007
    Posts: 1,044


    The pistons in the 283 in my '34 are knurled. The man that rebuilt the motor for me was an old drag and dirt track racer. He told me the cylinders weren't hardly wore enough to need boring so he knurled the pistons. Said since I didn't drive the car every day it should last a few years. I guess he was right. I'm still running the motor 33 years later.
  23. big duece
    Joined: Jul 28, 2008
    Posts: 5,917

    big duece
    from kansas

    I have a couple sets of TRW forged that will be repurposed... If your new piston,pin and ring weight is different than what was there originally , rebalance is in order.
  24. Ericnova72
    Joined: May 1, 2007
    Posts: 369


    1/2 of your ring seal is the ring down against the ring land in the piston, and not just ring to bore contact.....that ring land condition is just as important as bore finish and size.

    The less silicon in the aluminum alloy, the faster the groove wear will be.
    2618 alloy forged is the worst, 4032/VMS-75 alloy forged a lot less, plain cast and hypereutectic cast the least.
    The hypereutectic has very good wear resistance, that's why most OEM stuff uses them now. Stays in emissions compliance a lot longer.
    Definition for "hypereutectic" is an alloy with more silicon than will freely dissolve in the melt, leaving little wear surface particles of silicon dispersed all through the alloy.
    The downside is it makes them more brittle than a forging. A little harder on machine tooling during manufacture also due to silicon content.
  25. big john d
    Joined: Nov 24, 2011
    Posts: 146

    big john d
    from ma

    the off topic nova my son is building is using the trw forged 11 - 1 pistons that came in my 350 hp 1969 vette so far no issues vette had only 43 k on it
    loudbang and ekimneirbo like this.
  26. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,852


    I've helped with a high school auto shop watched students beat hell out of cars and trucks with well over 200,000 miles and I have seen them fail but never because a piston came apart first.
    ekimneirbo likes this.
  27. partsdawg
    Joined: Feb 12, 2006
    Posts: 2,667

    from Minnesota

    Back in my younger days a buddy and I used to build grenade engines.Go to swaps and buy a worn out 454,a set of used 11.1 or 13-1 pistons and a used cam and lifters. Had to be racing parts not suitable for street use. And it had to be cheap as in dang near free. Sometimes the pistons would be close and sometimes we had to hone to fit.Never worried about taper or wrist pin wear Find a intake and carb and maybe a set of heads. Learned quickly that heads off a alky dragster with a lot of runs were no good due to porosity.
    Anywho, drag the cheap junk home and slap it all together. Nothing matched but we would get it running and drop it in a whatever junker was handy. Take the whole mess out on a backroad and beat on it until it blew up. Some were weak but most ran like a scalded dog. Trying to get mismatched parts to work in some form of harmony was the fun part.We ran those engines until they grenaded which in some cases spectacular. Drag it all back home and build another one.
    Point being used pistons are perfectly good to use depending on your application. If I was going to build a street engine a set of micrometers would be in my pocket when looking at a set.
    ekimneirbo likes this.
  28. railcarmover
    Joined: Apr 30, 2017
    Posts: 398



    Knock em out, a little weasel piss and scotchbrite,good to go
    MO54Frank, lake_harley and ekimneirbo like this.
  29. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,852


    I'm afraid by the time you clean up the bores they will be a little loose.
    ekimneirbo likes this.
  30. PackardV8
    Joined: Jun 7, 2007
    Posts: 888


    Yes, on the obsolete stuff, where new is not available, we re-use pistons, knurl pistons.
    No, on SBCs, new pistons are so cheap, it doesn't compute.
    Maybe, it depends on what is being built, who's doing it, what's the budget and who's warranting it.

    jack vines
    BigDogSS and ekimneirbo like this.

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