mahle piston failure

General engine tech -- Drag Racing to Circle Track

Moderator: Team

sccagt1racer
New Member
New Member
Posts: 32
Joined: Wed Jul 13, 2016 9:22 pm
Location:

mahle piston failure

Post by sccagt1racer »

what is your assessment of this piston. Looks to me they got to close to the ring land with the valve relief. There is 2 others that broke the top of the piston off in the same spot. this one was on the verge of breaking.
You do not have the required permissions to view the files attached to this post.
gruntguru
Guru
Guru
Posts: 1560
Joined: Fri Apr 10, 2015 7:56 pm
Location:

Re: mahle piston failure

Post by gruntguru »

Gas ported top ring! That hole looks like it was there out of the box. If that's what it is, there won't be any questions about warranty.
User avatar
af2
Guru
Guru
Posts: 7014
Joined: Sun Jan 28, 2007 4:42 pm
Location: Grass Valley, CA :Northern Foothills

Re: mahle piston failure

Post by af2 »

I am on my phone and didn't see anything that resemble a hole?
GURU is only a name.
Adam
sccagt1racer
New Member
New Member
Posts: 32
Joined: Wed Jul 13, 2016 9:22 pm
Location:

Re: mahle piston failure

Post by sccagt1racer »

I zoomed and rotated the picture
You do not have the required permissions to view the files attached to this post.
engineguyBill
Guru
Guru
Posts: 1264
Joined: Fri Feb 26, 2010 11:15 am
Location: Gold Canyon, AZ

Re: mahle piston failure

Post by engineguyBill »

Looks like the piston has been subjected to way too much heat, which has actually melted the top of the piston adjacent to the valve relief. Look for detonation and preignition.
Bill

Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
digger
Guru
Guru
Posts: 2722
Joined: Sun Jan 27, 2008 6:39 am
Location:

Re: mahle piston failure

Post by digger »

I've seen valve relief pockets in a much more precarious position live perfectly fine with a good tune
gruntguru
Guru
Guru
Posts: 1560
Joined: Fri Apr 10, 2015 7:56 pm
Location:

Re: mahle piston failure

Post by gruntguru »

I suggest some careful measurements to determine the proximity of the valve relief to the ring groove. Looks too close to me.
Mark O'Neal
Guru
Guru
Posts: 1649
Joined: Tue Mar 06, 2007 7:23 pm
Location: San Tan Valley, AZ
Contact:

Re: mahle piston failure

Post by Mark O'Neal »

Tune up.
superpursuit
Pro
Pro
Posts: 214
Joined: Sun Apr 20, 2014 11:07 pm
Location:

Re: mahle piston failure

Post by superpursuit »

I would also look for symptoms of the top ring butting.(shiny ends, etc.) If the rings are butting then the weakest part of the piston will break first.

Allan.
Tuner
Guru
Guru
Posts: 3184
Joined: Sun Apr 01, 2007 5:26 am
Location:

Re: mahle piston failure

Post by Tuner »

Mark O'Neal wrote: Mon Nov 04, 2019 11:51 pm Tune up.
Yup. Looks to me like some preignition was going on, followed by some detonation. Too hot a plug or some funky fuel.
ProPower engines
Guru
Guru
Posts: 8686
Joined: Sun Jan 21, 2007 1:16 pm
Location: Victoria BC Canada

Re: mahle piston failure

Post by ProPower engines »

Mark O'Neal wrote: Mon Nov 04, 2019 11:51 pm Tune up.
X2
They do not stand up well when the tune is off. Yes they are close but when running correctly with a really good tune
they will live a long and happy life. Step over that edge and poof burnt piston.

While all pistons are not created equal those look like a common power pack piston. I have seen import guys have
the same issue and moving the top ring down will give a bit more area to dissipate heat but again if the tune is off
Poof
Real Race Cars Don't Have Doors
Geoff2
Guru
Guru
Posts: 1980
Joined: Mon Nov 09, 2015 4:36 pm
Location: Australia

Re: mahle piston failure

Post by Geoff2 »

Where the crack is. To me, it looks like the pressure from the burning A/F has pushed against the wall of the valve relief, where the metal is thin, & this has caused the crack.
Tuner
Guru
Guru
Posts: 3184
Joined: Sun Apr 01, 2007 5:26 am
Location:

Re: mahle piston failure

Post by Tuner »

Until 0'Neal gets around to making investment cast steel pistons you can simply consider aluminum pistons are just a reciprocating fuse.
Truckedup
Guru
Guru
Posts: 2728
Joined: Mon Jan 21, 2013 2:41 pm
Location: Finger Lakes

Re: mahle piston failure

Post by Truckedup »

engineguyBill wrote: Mon Nov 04, 2019 9:30 pm Looks like the piston has been subjected to way too much heat, which has actually melted the top of the piston adjacent to the valve relief. Look for detonation and preignition.
I'm familar with pre ignition damage on air cooled bike engines...it usual occurs in the center of the piston, very suddenly,like just a few cycles...But on that piston, the off center area that is damaged may be the weak point....
This is typical pre ignition damage...
Image
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Protech Racing
Member
Member
Posts: 81
Joined: Tue Nov 28, 2017 2:51 pm
Location:

Re: mahle piston failure

Post by Protech Racing »

Long term detonation . If the ring gaps are all lined up, it has run for a while with light detonation.
Post Reply