Has anyone reused damaged pistons that have maybe come in contact with a valve or had small nics from something breaking off and bouncing around inside the cylinders? A friend of mine recently had a retainer break in half and dropped a valve on his brand new 84mm ls block. The valve got smashed and bent bad by the third piston(putting a small groove in the piston top near the valve relief, the valve guide also broke off and smashed around in the cylinders causing nics on the piston.

I was wondering what would be the negative effects of reusing these pistons. My friend took a dremel to them and smoothed out all the nics and stuff to prevent any hotspots from forming. Should he still replace them or will he be ok with the old pistons? Thanks.

 

i know who joo are talking about

 

expletive it, throw them back in and fire it up, see what happens. if it was me, and there was no cyl wall damage id just slap it in and see what happens. the only thing u have to lose it time right??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost &raquo;</TD></TR><TR><TD CLASS="quote">i know who joo are talking about </TD></TR></TABLE>
cough*JDM S1eeper*cough

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by I Have an STD &raquo;</TD></TR><TR><TD CLASS="quote">expletive it, throw them back in and fire it up, see what happens. if it was me, and there was no cyl wall damage id just slap it in and see what happens. the only thing u have to lose it time right??</TD></TR></TABLE>
well it is all together and running fine already he sais. I haven't yet retuned it and i'm just kind of worried about possible hotspots on the pistons that can lead to detonation. This will be a 500+whp engine so a possible hotspot problem could prove to be very bad. He smoothed all of the little nics out pretty good, but i still dont trust it.

 

you could order just one new piston from the manufacturer if you think it will cause a problem.......

 

more than one piston was hurt

 

the nic's were very small, like a grain of sand small. 90-95% of the damage was removed just buy polishing over the nics.

the only viewable damage still is a small ding from the valve contact. It was smoothed out also but has a small, but smooth indent.

BTW, when the valve contacted it didnt bend the crap outta the valve. It was tapped just enough to make it not strait enough to glide back into the guide w.o friction. If you look at the face of the valve you cant even tell it tapped the piston other than the stem having a 10-15 degree bend. (thank god it droppin at idle and not at 8500 @ 25psi)


as of right now the bottomend is workin flawlessly w/ a LS topend back on it. Matt's just worried about them actualy being contacted but I think they are fine.

These are dished Arais pistons, 84mm. 8.5:1 on an LS

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost &raquo;</TD></TR><TR><TD CLASS="quote">i know who joo are talking about </TD></TR></TABLE>

 

I hit the valves when a cheapo timing belt let to in my beater gst. They hit hard, but i've seen worse. I chizzeled the pushed up portions of the piston off with a screwedriver. Hey, I was at my friends house with only a handymans tool set and determined to drive 60 miles home in a few hours with that car. I never did want to check the compression on that motor, but I did. I mean, its ******* perfect. I didn't even replace the cracked valve guieds and only slapped used 160K valves in it from my white gst and it runs like a champ.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">more than one piston was hurt</TD></TR></TABLE>

one piston got a mark from a valve that got slapped. then #1 and # 2 "had" small nics the size of a grain of sand. A lil TLC and it was all basicaly smoothed away.

I mean, whats the worst that could happen? Me havin to replace pistons? No problem, but I'm 100% sure they are ok.

I'm not trying to be cheap by not replacing them, I just know they are ok. If i knew i needed pistons, Id have a new set ordered and I would have them replaced the same day they came in.


Modified by JDMs1eeper at 8:12 PM 2/12/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danl &raquo;</TD></TR><TR><TD CLASS="quote">I hit the valves when a cheapo timing belt let to in my beater gst. They hit hard, but i've seen worse. I chizzeled the pushed up portions of the piston off with a screwedriver. Hey, I was at my friends house with only a handymans tool set and determined to drive 60 miles home in a few hours with that car. I never did want to check the compression on that motor, but I did. I mean, its ******* perfect. I didn't even replace the cracked valve guieds and only slapped used 160K valves in it from my white gst and it runs like a champ.

</TD></TR></TABLE>

exactly, and i used a polishing tool and put a mirror finish on the piston. they looked sexy and I know Matt was getting giddey when i rubbed his fingers over them. He drove off for 10 minutes and came back with a smile saying he was re tunning his car for the 1,000'th time. But i know he just liked how smooth i made those pistons

 

the pistons were very smooth, but still had little nics in them...only smooth nics.

 

haha

 

see.. it doesnt look that bad. smoothed right up

 

doesnt look to bad just fill in some of the deeper ones with jbweld

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Soccerking3000 &raquo;</TD></TR><TR><TD CLASS="quote">doesnt look to bad just fill in some of the deeper ones with jbweld </TD></TR></TABLE>

Yea and make sure to regap that spark plug.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Soccerking3000 &raquo;</TD></TR><TR><TD CLASS="quote">doesnt look to bad just fill in some of the deeper ones with jbweld </TD></TR></TABLE>

I was messing with matt. that wasnt the damage done. But thats the normal damge done when a valve is dropped.

I'm a very lucky guy.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93turbo16 &raquo;</TD></TR><TR><TD CLASS="quote">

Yea and make sure to regap that spark plug. </TD></TR></TABLE>

I run them that tight anyways - .000001

 

my cousins Z06 had some piston damage from slight contact with the valve...

he did the same, he smoothed it out a bit himself and put the motor back together with rebuilt heads.
he ended up selling that motor for other reasons (got rid of the car), but his friend that bought it put it in the car, fired it up and ran some more low 10 second passes.
car is still running fine and its been a few months.

you should be fine

 

yup, thats what i'm talkin about

 

i was talking to my machinist about the same situation because i have some dings on my pistons from when my sleeve went.

we concluded that its really the sharper/rougher edges that collect more heat. if the piston is relatively smooth, especially with no sharp scuffs, it should be good to go.

 

^^^^That'll buff right out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blackeg &raquo;</TD></TR><TR><TD CLASS="quote"> if the piston is relatively smooth, especially with no sharp scuffs, it should be good to go.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDMs1eeper &raquo;</TD></TR><TR><TD CLASS="quote">

I mean, whats the worst that could happen? Me havin to replace pistons? No problem, but I'm 100% sure they are ok.

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Well Brad, if you are gonna get rid of them for whatever reason, I'll gladly take those to the erm..trash dump, yeah, I'll get rid of them for you

 

I had a similar thing happen to me, when I miss shifted at the track. I took the head off and replaced it with a stock head. Drove it like that over a period of three/four months, and it worked fine.

Recentlly I took off the head to put my race head I built in the mean while, I took a look at the pistons and they were covered with some light carbon, cleaned the carbon, cleaned the pistons where the dents were and use some scoth brite to finish it off. They look good and im going to run it for this season.

BTW im running over 500 whp with my set up.