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philipl

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    engine rebuild? l6

    in Nissan L6 Forum

    Posted

    hey just curious im rebuilding an l6 gonna get all new crank bearings and piston rings.old bearings look real good no real bad wear or anything cylinder walls still have cross hatching.all cylinder walls are within spec measurerd in several locations as well as all crank journals.everything looks real good can i just get STANDARD SIZE bearings and rings what do you guys think ....do i need to plastigage the bearings or anything?thanks phil

    bead blasting piston domes and combustion chamber

    in Nissan L6 Forum

    Posted

    This is way off subject but i do know i used to use crushed WALNUT shells to run through natural gas turbines to do what the company called carbo blasting this would run through the turbine and clean the high pressure and low pressure turbine wheels therefore making the turbine run more efficently this was done will the turbines were running.These were older turbines from the 50's known as ge frame three turbines...

    bead blasting piston domes and combustion chamber

    in Nissan L6 Forum

    Posted

    thanks for everyones input heres a snibit of info ive found from people who have tried this process.What's wrong with beadblasting pistons?

    > this is data from a motorcycle forum...

    > Steve

    > '72 Commando (with freshly beadblasted pistons)

     

    Glass beading will imbed into the aluminum pistons and will score your cylinders like crazy! Regardless of how much you clean them afterwards. The best alternative is walnut shell blasting or nothing at all but solvent baths!

    Good Luck

    Mike A in NJ

    Date: Wed, 24 Jan 96 18:50:41 EST

    From: Mel Smith

    L. Reiter enquired about cleaning(scraping) pistons a hardwood wedge makes an ideal scraper when de-coking crowns in-situ. Won't damage the bore, easily sharpened with a rasp and material is cheap (screwdrivers and chisels are phillistine-gouges and scratches).

    Years ago, Continental Motors(aircraft) found that polished pistons had a higher failure rate than ones with a dull finish. The reason was of the boundary layer that insulated the piston crown from the combustion heat. A polished crown would absorb heat and melt/burn thru. I've wrapped pistons with duct tape over the ring lands & skirt surfaces and bead blasted(cleaned) the crown surface with no failures and minimum carbon build-up.

    Another old process that may be of interest to the trident/goldie crowd with sleeved liners is Koethurizing-a shot peen process for pistons. The piston is expanded in a jig about 3-5 thou. A nozzle sprays steel shot inside the piston in a circular pattern up inside the skirt. The piston is allowed to 'grow' a few thou against the confines if the jig (looks like a little circular clamp, adjusted for desired clearance) Saves having to rebore when a little slop or clatter is the problem. Knurling is just a cheap shortcut and warps the piston. The shot peening also stress relieves and stabilizes. -FWIW

    Regards, Mel Smith

    From: Latte' Jed

    Date: Wed, 24 Jan 1996 19:52:47 -0500

    > Glass beading will imbed into the aluminum pistons and will score your

    > cylinders like crazy! Regardless of how much you clean them afterwards.

    > The best alternative is walnut shell blasting or nothing at all but

    > solvent baths!

    I would hope nobody would try to clean anything but the top of a piston anyway, bead blasting the skirt would be dumb. A wire wheel will clean the crown about as quick as bead blasting will with less risk. Bead blasting generally shouldn't be done to the anything on the inside of an engine. I always polish the piston crown to help avoid carbon buildup, but even I admit it's a bit over the top.

    From: Pete Serrino

    Date: Thu, 25 Jan 1996 08:04:29 -0500

    Regarding glass beading pistons, Mel Smith brings up an interesting point on boundry layer effects. Former list memeber Dr. Rob Tuluie has written an excellent article on the subject which can be seen @ http://www.motorcycle.com/mo/mcrob/rt-fuel2.html.

    Glass beading when properly done will not remove metal but has an effect similar to shot peening. It has little effect on the overall dimension. If you glass bead the skirts it will serve the same purpose as honing the cylinder, that is it will improve oil retention. I've rebuilt about a dozen motors in the past 5 years and have never had a problem with scored cylinders due to glass. Cleaning them in hot soapy water is all that is needed.

    Sandblasting on the other hand will change the dimension of the piston. A short application of sand, ground glass, or silicon carbide normal to the surface will *raise* it by about .0005" or .001" across the diameter which could help to compensate for a slightly worn cylinder bore. Cheers,

    Pete Serrino

    bead blasting piston domes and combustion chamber

    in Nissan L6 Forum

    Posted

    I GUESS IM TALKIN ABOUT GLASS BEAD. IM SEEING THERE ARE A FEW PEOPLE DOING THIS ON THE INTERNET IT APPEARS THAT THE PROCESS SOMEWHAT PEINS THE TOP OF PISTON AND MAKES ITS MOLECULES MORE COMPRESSED MAKING THE ALUMINUM DENSER/STRONGER....ANYBODY OUT THERE DONE THIS :eek: SEEMS LIKE A GOOD IDEA FOR TURBOS OR HIGH COMPRESSION MOTORS ANYTHING BORDERLINE DETONATION!!:wink:

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