At the Pomona NMCA event two weeks ago I had two easy qualifiying passes at 9.94 and 9.91. Then we did the 30 mile drive and parked in staging for two hours wiating for our three consecutive shots in the True Street class. On the first pass the car got soft at mid track but I drove through the lights and at the turn out it died, not normal. I restarted it and it sonded like seven cylinders, I picked up 10.25 time slip and just made it to my pit space.
A quick valve cover inspection showed a broken #7 valve spring and an a stuck stuck stump of a valve stem underneath the rocker. The keeprs and retainer were intact on top of the remants of the valve spring. The lash cap was down in the oil channel in the head.
I finally got it fully out of the car and pulled apart today and found #7 with the valve head shoved up in the pocket, and evidence of shrapnel bits in all the other seven cylinders, mostly imbedded in the quench area of the head and the piston. Other bits had been dragged up and down the walls of the other cylinders and #7 had some nice dings from the valve head before it landed in its final resting place.
I found another lash cap and the tip of the hollow stem Ti Valve from #2 in the oil return channel of the other head. So I'm not certain if the spring on #7 failed first or if the valve tips separated creating valve to piston interference. While the springs had tested good on the head three weeks ago before my last pre-Pomona event, it could beI waited too long to change springs with the new faster lobe cam. Or there could be a valve stem issue.
Either way the block may well be shot as it was at its last over bore at 4.560" and it would appear to need at least six sleeves which doesn't make sense to me. There are at least five killed pistons and I'll see next week if the rods and mains are good. The cam and lifters look great amazingly but either way this is a major rebuild so as I'm #91 on the waiting list I'm going to pull my name and focus on 2014 with the new car and return the convertible to more street and road course/auto-x/fun mode.
Best luck to everybody at DW 2013!
A quick valve cover inspection showed a broken #7 valve spring and an a stuck stuck stump of a valve stem underneath the rocker. The keeprs and retainer were intact on top of the remants of the valve spring. The lash cap was down in the oil channel in the head.
I finally got it fully out of the car and pulled apart today and found #7 with the valve head shoved up in the pocket, and evidence of shrapnel bits in all the other seven cylinders, mostly imbedded in the quench area of the head and the piston. Other bits had been dragged up and down the walls of the other cylinders and #7 had some nice dings from the valve head before it landed in its final resting place.
I found another lash cap and the tip of the hollow stem Ti Valve from #2 in the oil return channel of the other head. So I'm not certain if the spring on #7 failed first or if the valve tips separated creating valve to piston interference. While the springs had tested good on the head three weeks ago before my last pre-Pomona event, it could beI waited too long to change springs with the new faster lobe cam. Or there could be a valve stem issue.
Either way the block may well be shot as it was at its last over bore at 4.560" and it would appear to need at least six sleeves which doesn't make sense to me. There are at least five killed pistons and I'll see next week if the rods and mains are good. The cam and lifters look great amazingly but either way this is a major rebuild so as I'm #91 on the waiting list I'm going to pull my name and focus on 2014 with the new car and return the convertible to more street and road course/auto-x/fun mode.
Best luck to everybody at DW 2013!
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