Venny Piston Pinch

We are running a 526 TFX Billet bolck with Venny 2.40Intake billet head. We run a kobelc superman @29% over which makes 42 psi max boost.Out the back door the fuel is running,12.46 GPM. The timming is set @ 32 with 3 pulled out at 2 gear.We are running mag 44
Last year we went thru 29 pistons that were pinching the ring right above the wrist pin. We changed to the M 88 wrist pins (wich was very expensive, considering that it did not help.)The fuel flow at 2000 rpm idle is right at 1 GPM.
Any help welcome.Timming, fuel,or what ever.

 

I can't help with specifics on your combo, sorry... but I have had this happen once or twice on a couple of pistons. Is it pinching the 2nd ring ?
You can be pretty sure there is some detonation happening at some point to cause this. It doesn't happen when everything's happy.
I aslo saw a bit of scuffing on the skirt when it happened.

Have you tried a bit less timing ?
Do you have any bolts coming loose ?

 

Yes 2 nd ring just above pin.Yes piston skirts cracked or hard scuff.We added barrel 90% and put 20 smaller on pump loop . timming set at 30 with 3 out in 2nd gear. car sluggish.

 

That's a lot of changes at once.... not that surprising that it was sluggish.

These are just suggestions:-
It might just need a degree or 2 of timing out with no other changes. (I have no idea how much timing those particular heads need).
It might be lean just on the hit.
Do you have any idea when it happens ?

 

Mike is right, Jimmy is the guy. Do I understand that 12.46 @ say 9400 is the gpm. Seems low to me. You will need to know what it is at 8000 and 9000 rpm, then peak. That is assuming you have a computer. How much static and cranking compression do you have? You shouldn't need more timing unless you are running above 3000 ft corrected. Has to be detonating. What do the bearings look like?

 

we crushed the rings on a few pistons when we had to kill the motor after we fired, before a burnout. apparently, we didn't back it down enough before we fired again, and it hydraulic'd. you seem to be to lean, but i fugured i'd throw that out there anyway.

bryan brown

 

thanks

thank everyone for your input,it has been a big help

 

are you getting the same cylinders every time?You may need to decrease compression in those cylinders-shorter connecting rod or a lower ratio intake rocker arm