Is piston repair possible?
 

As you may have heard I recently dropped a valve in my 2.7 race motor. So far the damage appears limited to #1 head and piston.

The pistons are Arias forged AL 10.5:1 - my mechanic ordered them years ago for a customer who no showed and I bought them last year when building a new 7R cased engine.

They have a high wedge dome with valve pockets. The damaged piston has pretty deep gouge marks from the bit of valve that fell into the comb'n chamber.

I fear it will be very difficult to replace one piston. When the teardown is compete I plan to call Arias and ask if I can send them a good piston to copy.

I know its a long shot but is there any way the piston surface could be repaired? For example, could you weld over the dents and re-machine the top face?

It would depend on the severity and amount of damage. I'm sure that this piston is forged and not cast. Either way you can't 'weld' the damaged area to the crown.

Post some pics here and lets see how bad it is. Arias may still have these lying around or they may have a dealer network that may still have them in stock. You would still have to buy a set, possibly 10 units if they are rare. If none are available they may tool up for another set, but again they usually do 10 at a time minimum

Alternate route may be different manufacturer and again replace the set.

SMOKE, RATTLE AND ROLL
 

There is no way to properly repair a damaged piston. Even with a minor impact you run the risk of unseen structural of damage. Throw the Arias pistons away and replace them with a quality part. My thought would be Mahle or JE.

Bet that engine sounded like it had six bad rod bearings when it was running.

I am not recomminding this but years ago I was at a race where I burned a hole in one piston during tuning and qualifing. There was no replacememnt immediately available so a machinist/welder buddy welded it up, I kid you not. Not only did it last the remainder of the weekend, but the remainder of the season as well. It was replaced out of guilt the following winter.

yrmv;)

Thanks guys - I didn't think it was possible, or even a good idea - but just wanted to make sure. I'll post some pics of the piston when we get it out. Here's a pic of #1 head.

http://forums.pelicanparts.com/uploa...1103665505.jpg

ps: mpdevelopment re - "Bet that engine sounded like it had six bad rod bearings when it was running."

A. what makes you think that? - the engine has been fantastic for a year.
B. how does this answer the qn - or even add to the discussion?

Sorry no harm ment I have run arias pistons in the past and they run such loose clearences that they rattle badly.

mpd - that's cool, thanks. i was a little confused.

nobody knows much about these things down here (australia) so i'm searching for any and all info (good or bad)

While some minor surface melting and filling to fix a few blemishes is acceptable, judging by the pic of the head I say replace it.

Ahh, that head? It's merely a scratch!

:)

Make sure that you clean everything out in that motor - there's got to be lots of bits of metal floating around just about everywhere...

-Wayne

I used Arias pistons in an engine I built years ago. I had an "event" that required replacement of one piston. Arias was able to supply me with a piston that matched. I sent them one of the good pistons, and they copied it for me. Never had a problem with piston slap with them either.

"Just a flesh wound" eh Wayne? ;)

Man, I'll bet that the intake side flows well now!!

It'll buff out...

-Wayne

even though it blew about 500m from the end of the stage - we still dragged it over the line

you do strange things when you're competing...

How fast was the engine turning over when this happened?

350

its all a bit of a mystery - the dropped valve has all the signs of a mis-shift overrev. I do not recall any overrev's during the event we were in. plus i know my 7200 rpm rotor button rev limiter works.

however, I have done a bunch of events over the past year with this engine (including a 5 day rally) and I think it may have happened earlier and put a little bend in the valve which then eventually failed after numerous cycles. the end of the valve also shows signs of a propagating crack then a brittle failure of maybe 20% cross section.

we were going uphill in 3rd when the engine lost a lot of power - and then the racket started about 100m later...

its being fully stripped as we speak, new valves, new springs, new etc etc $$$

Send the head to MM, they might be able to re-condition it - good as new!

It's not the overrev on the up-shift that kills a motor, it's the over-rev on a downshift that will toast it. And there isn't a rotor-button around that will protect against that.

I just did a complete engine on a '98 BMW M3. The kid just installed a new short-shifter and was speed shifting from 2nd to 3rd but rammed it up into 1st instead!! Clutch out, huge RPM, all valves smash into pistons!!

Took him 10 months to save enough to pay for it!!