Ya know, I asked you what the spring pressures were set at - not if you could tell me AGAIN that they were "correct". Obviously something was not "correct" or you would not have a problem.

Have fun figuring it out...

 

120 on the seat and don't recall open pressure, I feel its spring related and was a miscalculation onthe cylinder head assembly, its a time consuming fix but could of been worse

 

spring pressure: installed 1.780
110 on seat
300 open
.080 before coil bind

 

Ding Ding Ding, we have a winner!!

Have you done a compression check yet? Or you guessing that there is a compression problem? Maybe the opti ate its self and is firing late out the headers, seen that happen before.

 

brand new MSD opti, its definitely a compression problem, you can tell by the unevenness when rolling the car over with coil wire removed

 

How many cylinders? Exhaust or Intake valves?

 

yeah its important to find that out....I would not pull the engine back out yet, could be very simple thing here

 

its on the ex. side , #7 and # 8, I'm sure the others have touched aswell

 

Man that sucks, I would make the engine builder pay for the R&R as that is definatley his F-up. Who did the motor?

 

what springs did you use?? And those springs are definatly too weak for the 847, you probablky got valve float on them. What is their coilbind height?

 

+1

I have a little bit bigger cam than yours and my springs pressures are around 170-180lbs closed seat. (yes it is too much than normal, but I have Morel lifters) It should be at least 140-150 area, if they are not beehives! 110lbs is a ridicilous pressure for that cam.

 

They are a little weak, but bad enough to start bending valves??

I run the 987s and they are 120ih on the seat and 340 open, but alot of people run the 918's and they are only around 300 open.

I think PTV clearance killed it.

 

1.105 is coil bind, I'm not going to disclose the builder, hes going to take care of the problem, its a PITA, but it could of been worse. Its tractor pulling season now for me and the car is just a filler for the down times inbetween events. my son will definitely be getting some experience r& r the F body, they should of named it the "MF BODY" , its a mf to work on, but looking forward to the ride, the 200 shot on top of everything should put it in the 10's

 

I'm with 12SCNDZ on this one. My bet is that you did indeed run into valve float at 6400 RPM, and with the tight clearance with the high lift of the 847, as the valves were bouncing around you got some good contact with between them and the piston.

 

110 on the seat, that's where a lot of flat tappet cams would run. I'd say the sound of valve float you heard was correct which lead to more serious problems. Bigger valves are heavier and would require more spring pressure. 140#'s of seat pressure is where I'd like to see em but that's also with 918's and 794 retainers. You said you had zero deck height if that valve hung open too long then the piston prolly nailed it.