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Hemi Cylinder Wall Pitted

Discussion in 'The Hokey Ass Message Board' started by Dirty30Dodge, Sep 13, 2009.

  1. What kind of hone are you using? The old three-stone, spring-loaded glaze breaker won't do anything but make a worn cylinder bigger.

    It don't take but a minute to hog out .002" with one of those P.O.S.
     
  2. ne57
    Joined: Jul 17, 2009
    Posts: 7

    ne57
    Member
    from usa

    And yes, ductile rings (as opposed to cast) are somewhat forgiving, however, at 0.009 can you find a 4.010 ring set or do you go to 4.020 and squeeze the shit out of them?


    .[/QUOTE]

    Well....009 was the suggested clearance, not a bore oversize. Since I'm at .007 clearance now with a 4.040 bore, if I kept hoing til I had .009 clearance then my bore theoretically would be 4.042. In which case if my only concern was the rings I'd use file to fit rings that come in a 4.045 size(speedpro I think they were).

    But the concern really is cylinder clearance, or rather the consequences of big clearance. Which of course really depends upon the accuracy of the claim that old Jahns could handle .009" .

    For the sake of arguement, let's just suppose that the Jahns spec is actually .007". If the motor is built with higher clearance, like the mentioned .009", what are the mechanical implications? Is it just going to sound rattly when cold or will there be some sort of cylinder/piston malfunction or accelarated wear? I think if I'm pushing the limit I really should know exactly what's on the other side.

    I'm thinking I should pop some pistons in the oven and measure the expansion, just to get a feel for how much the jahns will grow. What temp do you suppose a piston skirt runs at? 225? 250? More?

    As far as hogging out .002 in a minute...not these bores with these stones, They show VERY little change in diameter for alot of honing. I don't quite get it, but the numbers show that.

    BTW, I ordered a bore gauge, I hope Fowler is a good brand, seemed to be in the middle of the price range.
     
  3. That was an exaggeration but you can take out more than you realize in a short amount of time.
    Do you have a 4"-5" micrometer? Mike the piston, "zero" the d/b gauge on the mike, then measure your bores. That will give you your actual clearance.
    Repeat on the rod/main bearings.

    I consider .006-.008" cylinder taper enough wear for a rebore.
     
  4. 73RR
    Joined: Jan 29, 2007
    Posts: 7,175

    73RR
    Member

    I think what you will find is that the ring lands/grooves in the pistons will wear quickly with an ever increasing clearance. The more they wear the bigger the risk of a broken ring and...disaster.

    .
     
  5. lippy
    Joined: Sep 27, 2006
    Posts: 6,825

    lippy
    Member
    from Ks

    I can understand a budget build, but Sheesh!! Save up your money, build it right. If your going to go to the trouble to ring it, bearings, ect... spend the extra money and get it bored if needed and pistons. A cheap quick re-build may run a long time without smoking, losing oil pressure and rattling, but then again, it may be smoking and running bad in a few hours. JMO. An engine is an engine, same for all engines. Hemi, studebaker, allison, spend the time and do it right. again...JMO. What happened to pride in a good job? :D Lippy
     
  6. ne57
    Joined: Jul 17, 2009
    Posts: 7

    ne57
    Member
    from usa

    >That was an exaggeration but you can take out more than you realize in a short amount of time.

    I've been going real slow, take a few passes with the hone, measure, more passes, measure.

    >Do you have a 4"-5" micrometer?

    Yeah I bought a set of mics 0"-6". I've been using a snap gauge but have gotten some variance in the readings (driver error no doubt). But consistent enough to see the bores have very little taper, barrel or out of round. Its partially because these bores seemed shaped and sized so well that I'm looking into reusing the pistons.

    >I think what you will find is that the ring lands/grooves in the pistons will wear quickly with an ever increasing clearance. The more they wear the bigger the risk of a broken ring and...disaster.


    Aha! That's what I'm looking for.

    > What happened to pride in a good job?

    Yeah, yeah, OK shame me into it.

    Its funny, in my business people pay me to be meticulous and do the very best job possible, yet I also know that sometimes, a less costly approach might do the same task asked of the materials and processes. That's what I'm trying to do here, ascertain that balance, that point of no return, make that informed judgement. If I was intent on an abortion the short block would have been buttoned up by now, but instead you all have to listen to me whine, [​IMG]
     
  7. ne57
    Joined: Jul 17, 2009
    Posts: 7

    ne57
    Member
    from usa


    Well the bore gauge arrived, looks like a quality piece just judging from fit and finish.
    I tried zeroing the gauge with a micrometer. My fumble fingers had trouble with holding the mic on the anvils while trying to adjust the indicator, two hands don't seem to be enough. Is there some secure way of holding all the pieces together while making the adjustment?
    And what exactly am I supposed to do with the two sliding pointers on the outside of the dial? I gather they're min/max but how do I know how to adjust those?
    Sorry to be asking such a Machinist 101 question.
    Thanks
     
  8. Dyce
    Joined: Sep 12, 2006
    Posts: 1,973

    Dyce
    Member

    If you are dead set against boring you need to find someone with a knurling machine. When I had the machine shop we had a Perfect Circle piston knurling machine. We had a good old boy that did a number of rering jobs. He would hone the block with a ridgid hone untill it quit jumping around, that could be .008 over the piston bore but that ment it was round. Round is good. He told me if you didn't have them round the rings would work around and line up, which is not good. Then he would bring me the pistons to knurl. I would put a heavy knurl on the pistons, and he would take them home and fit each piston to each cylinder. He would file the skirts until they slid in the cylinders with a slight drag.

    As far as file fitting rings, be carefull. If you don't have a straight cylinder your ring gap will change from the top to the bottom. If the ring gap closes up you will have a mess. If you are better off with to much ring gap.
    Jeff
     
  9. Dyce
    Joined: Sep 12, 2006
    Posts: 1,973

    Dyce
    Member

    With light preasure preasure put the mic in a bench vice. Set it to the "standard" bore. I'm sure the bore gauge came with extensions and shims to get it in the "range" you need to check. Then put your thumb under the anvil of the mic to stabilize the one end of the bore gauge, then you just float it around, and move the dial indicator around to zero at the lowest reading you can get off of the mic.

    Jeff
     
  10. the SCROUNGER
    Joined: Nov 17, 2005
    Posts: 518

    the SCROUNGER
    Member
    from USA



    a 331 hemi has pretty thick cylinder walls, you should just have it bored out and get rid of the pit- of course that means you now have to get new pistons

    you could sandblast/glass bead the rust out of the pits, then hone the cylinder, and put rings in, but that cylinder will almost definitely have blowby from lack of constant ring seal, and you'll be pushing a lot of blowby/oil out of the breathers, pcv valve, front/rear oil seals leaking, valve covers leaking- from crankcase pressure

    as me how I know, I budget built a 455 Pontiac one time, and there was only "tiny" rust pits on a few bores, so small you'd think they were nothing- honed it, put brand new rings in, took it for a ride on the interstate for about 100 miles- holy cripes it was throwing oil all over the place from blowby, it was literally dripping off the valve cover breathers and smoking on the exhaust

    if it's an early 50's hemi with 7.5 CR the problem may not be as bad, because the pathetically low compression doesn't build as much cylinder pressure. If you were building one of these engines for street use with new parts, you'd want 9.25 CR with pump gas for some decent power.

    I would NOT put a sleeve in it, unless it was worn right through to the point it had less than .080" cylinder wall left- because if you put a sleeve in a block to repair it, it almost always throws out the main bearing journals and cam journals- I have put sleeves in 2 motors before, and both times the cam then would not go in the block with brand new cam bearings, because the cam register holes were tweaked out of line. If you put sleeves in a motor, you may end up align honing the cam journal holes and crank journals to re-straighten it.

    again, ask me how I know, I had sleeves knock the alignment out twice on me before, and it was a real PITA to get it straight again.
     
    Last edited: Nov 5, 2009
  11. ne57
    Joined: Jul 17, 2009
    Posts: 7

    ne57
    Member
    from usa


    Well, I'm not completely dead set against boring, I just would like to make a well informed decision... cost/benefit and all that, and be abe to actually pay for whatever it is that I wind up doing. I had heard about the PC machine, but find way too little info to feel comfortable with it yet. I'm concerned with longevity on a knurled piston, although in concept it seems like something to explore.

    With a snap gauge the bores appear to be in good shape as far as taper, out of round, etc. I got the DB gauge to verify what I measured. We'll see.

    >>With light preasure preasure put the mic in a bench vice. Set it to the "standard" bore. I'm sure the bore gauge came with extensions and shims to get it in the "range" you need to check. Then put your thumb under the anvil of the mic to stabilize the one end of the bore gauge, then you just float it around, and move the dial indicator around to zero at the lowest reading you can get off of the mic.<<

    Somewhere I have a copper jaw liners for a vise.

    It seems to me, neophyte that i am, that both the snap gauge and the bore gauge rely on the operator getting "The Feel" for the tool. I'll have to work on that.

    But hopefully this will all become mute in the near future...I'm getting the gut feeling that business is about to turn around and money won't be such a concern. In the meantime this is still good experience even if its a bit oddball.

    many thanks to all
     
  12. 73RR
    Joined: Jan 29, 2007
    Posts: 7,175

    73RR
    Member

    Knurled skirts? Way back in the dark ages it was common practice to knurl skirts in 'slap 'em together low-low budget' operations, but keep in mind that you are only changing the clearance of the skirt. It does nothing for the area above the pin, you know, where the rings are located....:cool:


    .
     
  13. I clamp a rod-piston in the vise. Mike the piston skirt at the widest place, lock the mike.
    Lightly clamp the mike in the vise (still locked on the piston diameter) and -zero- the dial-bore gauge with the mike (takes a little "finesse"). Now you can gauge the cylinder/piston clearance.
     
  14. the SCROUNGER
    Joined: Nov 17, 2005
    Posts: 518

    the SCROUNGER
    Member
    from USA

    I had pistons knurled before, pistons being somewhat soft metal aluminum, the knurling wears right off in no time, as little as 5000 miles, and the piston is slapping in the bore going "tonk-tonk-tonk" hollow sound like a bell, at idle- it also stresses and puts micro-cracks in the skirt, which may lead to the skirt breaking off the piston later
     
  15. ne57
    Joined: Jul 17, 2009
    Posts: 7

    ne57
    Member
    from usa

    Well, broken rings and broken skirts is enough to put me off! Thanks for giving me the bigger picture.
     
  16. junkjunky
    Joined: Aug 19, 2009
    Posts: 110

    junkjunky
    Member

    If the pits are'nt to bad they'll fill up with carbon, run the cast iron rings.
     
  17. krooser
    Joined: Jul 25, 2004
    Posts: 4,584

    krooser
    Member

    Knurl the piston and run cheap rings... drive the crap outta it and fix it right when you have the $$$.

    I'd sooner drive a car that ain't quite "right" than see it sitting in the garage... in the 60's we Obama-rigged everything cuz we were broke and we still raced 'em.

    As far as sleeves causing camshaft misalignment those probably weren't early Hemi engines... these things are stout! I have five sleeves in my 354 and I used to run a 427 Ford with seven sleeves... never had a problem.
     
  18. Dyce
    Joined: Sep 12, 2006
    Posts: 1,973

    Dyce
    Member

    You need a heavy knurl. Then you file to fit each piston to each bore. This gives you more surface area to wear on.

    If this was my engine there is no question I would buy pistons and bore it. Hell I have my own boring bar and have used it alot through the years. I just don't think alot of people out there realize the junk a person can put together that runs forever.... Then on the other hand I've seen people spend cubic $$$$ to run like hell for a few hundered miles, and end up with a pile of scrap.

    Have you measured each piston? You need to measure just below the ring lands, and measure again at the tip of the skirts. If it measures smaller at the tip you have a collapsed piston and it needs to be scrapped.

    I would like someone who has ballanced a hemi running a set of the cheaper cast pistons to speak up. Are they close to the stock weight? Some of the cheap cast sbc pistons were sluggs. Way heavier then stock, making it a real pain in the ass to ballance.
    Jeff
     

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