Topic: To weld or not to weld... (Read 7692 times)

AbaZ · « **on:** October 26, 2009, 07:58:29 PM »

That is the question,

I have a cast aluminum piston that has a indentation in it about 3mm deep and about as round as the small end of a valve. So heres the question, Should it be welded? can it be.. and how long will it last?

The first thing you are going to say is.. fuck just buy a piston, but when dealing with buying/selling cars an extra 45 bucks for a piston and the 30 mins to press it out when your overbudget isnt going to work.

So how about just whizzing the top with a rolac and calling it good? Well that is what I normally do, however a couple cars ago that I sold came back with a dead cyl #1. I looked down the hole and that small 3mm indentation had burnt all the way through. So what I do now is pull every piston and check the bottom sides of the pistons to see if there is any cracks/marking.

this is the piston, bad pic. I buy lots of 03-05 Kia Rio's with blown up tbelts and try to scrap them back together.

Any input would be appricated.

malichite · « **Reply #1 on:** October 26, 2009, 08:33:48 PM »

JB Weld

patsmx5 · « **Reply #2 on:** October 26, 2009, 08:41:28 PM »

I'm no expert, but if you do weld it, I would get it clean clean clean where it's going to be welded, and bake it in an oven to get it preheated well before welding it.

1991civicsi · « **Reply #3 on:** October 26, 2009, 08:41:47 PM »

Welding it would be true to the nature of this website

dvst8r · « **Reply #4 on:** October 26, 2009, 08:51:54 PM »

I would weld it.

Urban Indian · « **Reply #5 on:** October 26, 2009, 08:59:43 PM »

i want to see it welded

any tips Passenger?

bluerex · « **Reply #6 on:** October 26, 2009, 09:15:18 PM »

Quote from: AbaZ on October 26, 2009, 07:58:29 PM

So how about just whizzing the top with a rolac and calling it good?

Ive done this a couple times on dsm failures with no issues.

Sold AS IS

Conceptz-X · « **Reply #7 on:** October 26, 2009, 09:17:26 PM »

deburr and run the bitch!

weirtech · « **Reply #8 on:** October 26, 2009, 09:42:35 PM »

my question is: how long does it have to last? that should determine your answer jeff. if it is going in a car you intend to keep for a while, i'd replace it with a new one. if it is going in a motor you intend to beat the piss out of until it grenades, then weld it.

AbaZ · « **Reply #9 on:** October 26, 2009, 09:50:37 PM »

ok Beau just welded it, and complete failure. it distorted all to shit, the wrist pin is jacked.

ok next time I'm tapping it out. I like that idea.

Conceptz-X · « **Reply #10 on:** October 26, 2009, 09:53:06 PM »

it was what, 1cc? it would have hurt nothing to run it

Joseph Davis · « **Reply #11 on:** October 26, 2009, 09:58:53 PM »

Quote from: AbaZ on October 26, 2009, 09:50:37 PM

ok next time I'm tapping it out. I like that idea.

+1

Sometimes c0mpl3x says something really good.

AbaZ · « **Reply #12 on:** October 26, 2009, 10:59:33 PM »

Quote from: Conceptz-X on October 26, 2009, 09:53:06 PM

it was what, 1cc? it would have hurt nothing to run it

Well no shit, its not the big burr that I'm worried about, its the underside of the piston when this happens. small chunks come off and make it thin. Then if you run it, just from combustion inside the cylinder it burns right through that hole.

I'm down for trying the tap/trick, what should I seal the threads with? JB weld

88dx · « **Reply #13 on:** October 26, 2009, 11:07:16 PM »

How many of these cars do you buy/sell

patsmx5 · « **Reply #14 on:** October 26, 2009, 11:12:40 PM »

I'd use a 1/4" pipe tap probably, 1/4" pipe plug, seal it with some JB, and grind it down flush. In for pics.

AbaZ · « **Reply #15 on:** October 26, 2009, 11:13:47 PM »

Quote from: 88dx on October 26, 2009, 11:07:16 PM

How many of these cars do you buy/sell

5 this year..

like I said my piston is fucked I gotta buy one. I tried fitting some a6 pistons in, little sloppy.

snm95ls · « **Reply #16 on:** October 26, 2009, 11:15:20 PM »

Quote from: AbaZ on October 26, 2009, 11:13:47 PM

Quote from: 88dx on October 26, 2009, 11:07:16 PM
How many of these cars do you buy/sell

5 this year..

like I said my piston is fucked I gotta buy one. I tried fitting some a6 pistons in, little sloppy.

Awesome!

Teg2boo · « **Reply #17 on:** October 26, 2009, 11:34:39 PM »

JB weld is only good with temp < 500F tho $:-\$

HiProfile · « **Reply #18 on:** October 27, 2009, 12:04:18 AM »

And aluminum melts at the 1200F. Doesn't mean that the piston actually gets to those EGT temps. You've got 250F crankcase temps on the other side, as well as windage oil cooling it down, and the heat soaked up by the skirt/sleeve. If nothing else, it would be for plugging the gaps in the threads. If 2/3 of it melts, it still holds. You'll obviously want to use an aluminum plug. Just be careful with the sharp edges, since the threads alone are enough of a stress riser for cracks to form at.

This reminds me of some mag article I saw posted a year ago, and it was old itself ('99?). I think it was a Miata owner wanting mroe compression for racing, and he epoxied COINS (jb or devcon) in each piston dish. Didn't get detonation, just more power. IIRC it was a road-race class where you had to use all stock engine parts, and the rules didn't say you couldn't mod stock pistons. Supposedly they won half the races that season, before anyone found out - and let them keep the wins.

Cliffs: jb weld some big coin over the hole, get more power, call it a day.

btw found the link!! http://www.boostedmiata.com/technical/AC_05518.pdf

Conceptz-X · « **Reply #19 on:** October 27, 2009, 12:11:27 AM »

I figured you were dumping it without recourse

keelay · « **Reply #20 on:** October 27, 2009, 09:34:37 PM »

FIX'D

Quote from: 1991civicsi on October 26, 2009, 08:41:47 PM

J.B. Welding it would be true to the nature of this website

Passenger · « **Reply #21 on:** October 27, 2009, 11:18:12 PM »

Shit I am a bit late but I could told you this wouldn't have worked, not only did you distort the shit out of the piston, it would have lost all its temper, there are welding methods around this but its kind of tricky, not good for long term reliability. A 1/8" npt plug from the bottom side would have worked allright, but would add extra wear to your rod bearings, better than welding, but not quite as good as another non damaged piston.

AbaZ · « **Reply #22 on:** October 28, 2009, 12:19:56 AM »

Quote from: HiProfile on October 27, 2009, 12:04:18 AM

And aluminum melts at the 1200F. Doesn't mean that the piston actually gets to those EGT temps. You've got 250F crankcase temps on the other side, as well as windage oil cooling it down, and the heat soaked up by the skirt/sleeve. If nothing else, it would be for plugging the gaps in the threads. If 2/3 of it melts, it still holds. You'll obviously want to use an aluminum plug. Just be careful with the sharp edges, since the threads alone are enough of a stress riser for cracks to form at.

This reminds me of some mag article I saw posted a year ago, and it was old itself ('99?). I think it was a Miata owner wanting mroe compression for racing, and he epoxied COINS (jb or devcon) in each piston dish. Didn't get detonation, just more power. IIRC it was a road-race class where you had to use all stock engine parts, and the rules didn't say you couldn't mod stock pistons. Supposedly they won half the races that season, before anyone found out - and let them keep the wins.

Cliffs: jb weld some big coin over the hole, get more power, call it a day.

btw found the link!! http://www.boostedmiata.com/technical/AC_05518.pdf

Holy crap, people have actually done it. What do you guys think? Should I try this on the next one I get? I have devcon and jb weld. Which to use? How hot does the top of a piston get in a completely stock NA 1.5l NA. What is JB weld rated at? or Devcon.

This is so backyard nig. I love it.

onlyflash944 · « **Reply #23 on:** October 28, 2009, 01:27:53 AM »

i probably woudl have ground it down smooth, assuming there was enough material left. a few compression points in one cyl wouldn't keep you from flipping a beater

Joseph Davis · « **Reply #24 on:** October 28, 2009, 12:53:10 PM »

The crown of the piston is always 1050-1100 degrees, boosted or NA.

ktown powder coating · « **Reply #25 on:** October 28, 2009, 02:34:16 PM »

High temp lab-metal can withstand 1000F

HiProfile · « **Reply #26 on:** October 28, 2009, 02:49:05 PM »

I'm wondering if that epoxy held it more with suction if it indeed melted some. The Devcon FasMetal 70 I have next to me is not intended for 250F+. My oil pump is still kicking with it inside, though. I opened it up after 2k miles to check.

AbaZ · « **Reply #27 on:** October 28, 2009, 04:33:54 PM »

Quote from: Joseph Davis on October 28, 2009, 12:53:10 PM

The crown of the piston is always 1050-1100 degrees, boosted or NA.

Mr. Davis what is your thoughts on JB weld ontop of a piston. How really is it?

Teg2boo · « **Reply #28 on:** October 28, 2009, 04:40:34 PM »

I've put JBweld on my downpipe and it cracked and fail. I don't imagine how it is on a piston.

Only time I saw JBweld fail

patsmx5 · « **Reply #29 on:** October 28, 2009, 04:40:49 PM »

Quote from: HiProfile on October 27, 2009, 12:04:18 AM

And aluminum melts at the 1200F. Doesn't mean that the piston actually gets to those EGT temps. You've got 250F crankcase temps on the other side, as well as windage oil cooling it down, and the heat soaked up by the skirt/sleeve. If nothing else, it would be for plugging the gaps in the threads. If 2/3 of it melts, it still holds. You'll obviously want to use an aluminum plug. Just be careful with the sharp edges, since the threads alone are enough of a stress riser for cracks to form at.

This reminds me of some mag article I saw posted a year ago, and it was old itself ('99?). I think it was a Miata owner wanting mroe compression for racing, and he epoxied COINS (jb or devcon) in each piston dish. Didn't get detonation, just more power. IIRC it was a road-race class where you had to use all stock engine parts, and the rules didn't say you couldn't mod stock pistons. Supposedly they won half the races that season, before anyone found out - and let them keep the wins.

Cliffs: jb weld some big coin over the hole, get more power, call it a day.

btw found the link!! http://www.boostedmiata.com/technical/AC_05518.pdf

Hahahahahahaha. I'm hesitant to comment.

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Author Topic: To weld or not to weld... (Read 7692 times)