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Old 10-13-2012, 01:10 AM   #21
Shaolin CraneShaolin Crane is offline
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Not arguing, just stating my experiences. Probe extensively tests their pistons, something like 100k hours at red line. In some of the high winding motorcycle engine ive built I'd break a timing chain and the valve would leave its full impression on the piston. That bike is still going strong with the same owner who bought it from me 6 years ago. This was a 15:1 compression 36whp single cylinder thumper. Small impressions like that are nothing and have personally ran much worse for a similar amount of time. Gashed or grosh material removal anything where you can see that metal has been "moved" is the kind of stuff to look out for. Those are really no big deal. Its no difference then when a piston skirt has been shaved or valve reliefs have been cut or the dish has been opened up. I wouldnt worry about them even slightly. Hell the diesel guys take the 6.4 pistons and cut the dish open nearly 5cc then polish the edge and run 70-80psi on a hypereutectic.
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Old 10-13-2012, 02:17 AM   #22
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Plenty of light and not any heat in this thread. The metallurgic stuff is fascinating. Continue on. No one's taking a piss.
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Old 10-13-2012, 07:59 AM   #23
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Quote:
Originally Posted by Shaolin Crane View Post
Not arguing, just stating my experiences. Probe extensively tests their pistons, something like 100k hours at red line. In some of the high winding motorcycle engine ive built I'd break a timing chain and the valve would leave its full impression on the piston. That bike is still going strong with the same owner who bought it from me 6 years ago. This was a 15:1 compression 36whp single cylinder thumper. Small impressions like that are nothing and have personally ran much worse for a similar amount of time. Gashed or grosh material removal anything where you can see that metal has been "moved" is the kind of stuff to look out for. Those are really no big deal. Its no difference then when a piston skirt has been shaved or valve reliefs have been cut or the dish has been opened up. I wouldnt worry about them even slightly. Hell the diesel guys take the 6.4 pistons and cut the dish open nearly 5cc then polish the edge and run 70-80psi on a hypereutectic.
Piston manufacturers typically have one as forged piston that can be machined into many different configurations. An area that has quite a bit of variability is the valve reliefs and so there is typically extra material in that area to accommodate all the different combinations. Having the valve hit in that area is one of the better ways to make contact with a piston. Unless you had huge reliefs because you had valves that barley fit in the head and a really high lift cam, you probably had some extra material. Also, that area is going to be predominantly in compression so that works in you favor too.

The OEMs are pretty well known to throw metal at pistons; it is cheap insurance. It doesn't surprise me the diesel guys are able to use their stock pistons in heavily boosted applications.

Machining aluminum is different than upsetting aluminum. Machining metal cuts and removes the material like when you opened up the valve reliefs or shaved a piston skirt. As long as a dull tool that generates a bunch of heat isn't used, everything is fine. Upsetting the material imparts strain into the part. That is when things get fuzzy. Different process conditions can produce vastly different results. For example, certain alloys will crack if they are upset at low temperatures versus high temperatures. Also, putting stain into a parts acts like an aging process. Aging is how you get the different -T8 or -T6 tempers after the same quench operation for the same alloy. The main reason that I get worried when I see damage is because I know of affects it MIGHT have but I don't have enough technical experience to be able to quantify if it happened or to what magnitude.

After all that hot air, the pistons are probably fine.
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Old 10-26-2012, 09:46 PM   #24
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I picked up my kit today. Next up is to clearance the bottom of the cylinders for the new stroke and then drop the block off at Pacific Engine for the machining.
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Old 10-29-2012, 04:39 PM   #25
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I clearanced the cylinders and dropped the block off at Pacific Engine. Of course I forgot the pistons so I'll be making another trip out there so they can machine the block for .004 piston to wall clearance.



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Old 10-29-2012, 04:56 PM   #26
Shaolin CraneShaolin Crane is offline
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Checked my log book. Mine came in at .005 I got it confused with the spare forged internal motor that was already bored but wiped out the bearings. Came right under. 007
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Forget about winning and losing; forget about pride and pain. Let your opponent graze your skin and you smash into his flesh; let him smash into your flesh and you fracture his bones; let him fracture your bones and you take his life. Do not be concerned with escaping safely lay your life before him

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Old 10-29-2012, 05:15 PM   #27
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When we did Eric's 331 I had it set to .0045. I'll run it by Dick when I drop off the pistons to see if he thinks .004 will be enough. I think it will be but I'll see what he says.
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Old 10-29-2012, 07:00 PM   #28
Shaolin CraneShaolin Crane is offline
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Should be fine. He wanted to run a bit more because of the amount of boost. The other motor had some rust on the cylinder walls and he cleaned it up without boring it so thats why it has so much
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Originally Posted by Bruce Lee
Forget about winning and losing; forget about pride and pain. Let your opponent graze your skin and you smash into his flesh; let him smash into your flesh and you fracture his bones; let him fracture your bones and you take his life. Do not be concerned with escaping safely lay your life before him

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Old 10-31-2012, 01:34 PM   #29
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I dropped the new pistons off with Dick today and he had already bored half the block. We measured the bore on the other side as well as the old pistons and the clearance was .005 which worked well. I didn't have piston slap with the old combo and there weren't scuff marks on the skirts besides where the rivet hit. So we are clearancing this build at the same. Hopefully I'll be able to start assembling it this weekend.
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Old 10-31-2012, 02:47 PM   #30
Shaolin CraneShaolin Crane is offline
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I'm going to call Joey today to see about the cam
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Originally Posted by Bruce Lee
Forget about winning and losing; forget about pride and pain. Let your opponent graze your skin and you smash into his flesh; let him smash into your flesh and you fracture his bones; let him fracture your bones and you take his life. Do not be concerned with escaping safely lay your life before him

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