<VV> Cracked Pistons

[Mike McCrae]

I never had any problems with the old TRW long skirt pistons, which are now 
hard to find as hen's teeth. One can always tell a forged piston by looking 
inside and actually seeing forging marks. The new "Sealed Power" pistons
have inside walls that appear to be born of sand casting...go figure....yet 
they still insist they are forged...? Where does Clark's  get these new 
forged pistons? Everything seems to be from overseas (China) so I'm 
skeptical. I've also been told, but not confirmed that the Sealed Power 
come from India and that quality control measures have been poor at 
best....can anyone confirm this?
If you're looking for performance than you may have to consult with US 
manufacturers such as Arias or Ross...I've had excellent results with both, 
but they're not cheap....remember, Horse power ='s $...how fast do you want 
to go...?

Mike McCrae


-----Original Message----- 
From: James Cuneo
Sent: Wednesday, January 22, 2014 8:49 AM
To: virtualvairs at corvair.org
Subject:  Cracked Pistons

Guys,I need some help from you engine gurus out there.I have cracked 3 
pistons in the #5 cylinder in the past four years. 2nd time I thought it was 
a coincidence that it was the same cylinder, third time, now I wonder what 
is happening in #5 that sets it apart from the others.What I have:2G 
rochester carb modified.F/B turbo on 140 heads. Clarks Hi Tech pistons D cut 
to 8.25 crCrank, flywheel, Pressure plate, rods, pistons balanced.TB20 otto 
cam329 turbo dist.Wide band o2 sensor, cruise afr 14.5, boost afr 
12.0SafegardWater injectionSecond time this happened was just last august so 
I recently installed water injection. Was doing a tuning run last Sunday 
when after a 5 second run at 10psi I felt the piston give way. Safegard 
indicated no knock. I had done a lot of homework on water injection and was 
sure this would be the cure to this problem, it was not. Spark plugs all 
appear dark brown, #5 a little lighter brown in color. Piston failure mode 
is a crack forms in land between
#2 ring and #3 oil control ring, then travels to oil return slot in #3 
groove.Questions: 1. what is unique to #5 cylinder running hot, lean? I can 
imagine the hot air off the turbo being distributed there. 2. Is there a 
better, more appropriate piston to be using?I have decided to replace all 6 
pistons with new. It appears there are only 2 choices of forged pistons 
easily available, Clarks brand and Sealed Power, which one?I appreciate all 
and any advice.Thanks, Jim Cuneo39 year corvair owner, Journeyman auto 
mechanic, FAA Airframe and Powerplant mechanic, Farm/ Industrial equipment 
mechanic.








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