Ill_Born_ss

Yeah **** breaks all the time! You mentioned a mark on the bore wall from the valve....carefully check the other bores in the area of the intake valve open position for any damage even discoloration in that area can indicate it is too close. If I remember correctly with the recommended max lift by GM it is .525 and at that it is only like est.maybe.020 from the wall...so as you increase lift it goes even closer and then there is heat

DavidGXP

iTrader: (14)

Cylinder walls looked great still had cross hatch marks in the walls.

Ill_Born_ss

David , do you know the new springs installed height and the max lift #`s

DavidGXP

iTrader: (14)

Lunati springs.

O.D. 1.306 inch; I.D. 0.676 inch; Max lift: 0.660 inch; Seat load:
153 lb/in @ 1.810 inch; Open load: 400 @ 1.150 inch;Rate: 379 lb/in; Coil bind: 1.100 inch

PAC-1518

1.290 VALVE SPRINGS -OVATE BEEHIVE (16) Premium Nitrided Beehive LS1 Spring OD: 1.290" 130 lbs @ 1.800" 337 lbs @ 1.150" Lift: 0.650"

Ill_Born_ss

Thanks, and your cams max lift is? Also these are the stock valves, yes

DavidGXP

iTrader: (14)

.596"/601" stock valves

Ill_Born_ss

been searching and reading some... when did you change the pushrods, why

DavidGXP

iTrader: (14)

I bought the pac springs new from another person last Febuary, for a screaming deal. Pac produced a bad batch and I think I might have fell victim.
Also, it is wise to change the springs once a year if abused. I have taken this blown engine to 7000 rpm a few times.
The pushrods where swapped out when I did the Cam install.

Pac springs with 7¤ locks and titanium retainers are a kick *** combo if one was willing to pull a spring every so often and check the pressure.

Ill_Born_ss

your cam was a complete MATCHED kit (lifters, cam, pushrods), bear with me I see something that does not make sense.

DavidGXP

iTrader: (14)

Yes.. The Cam was a spec'd by Pat G. I purchased everything that he recommended and had my heads setup by my machinist.
Keep in mind that my setup had been running perfect for 10 months or so up until the spring broke into 3 pieces.

Ill_Born_ss

Hey David, I will try to explain what I think is happening

The stock spring installl has specs like installed height of 1.8 same with your new ones.
The stock open spring height is around 1.3, which falls within the approx .500 lift of the stock system. The new lift is .600. The springs themselves actually touch/bind at 1.225 and the retainers are possibly hitting the oil seals on the stems too. So this info leaves you 1.8 - 1.225 = .625 which is .025 from total spring compression.... Ok it still can work but... add a little for heat expansion and a little for system pump-up, lets say .010 now that leaves you with .015 before the coils on the springs start to hit each other. OK here too, close but possible!
Now here is where I think your pushing it.
The factory pushrods are 7.325 and I see in your sig you have 7.450 which is .125 longer/more lift... plus you have shaved/milled your heads to add even more to this number. On a stock motor this small difference can be tolerated somewhat but in your case repeating the exact build will again shorten your fun and wallet. If you were to use a stock length or a little shorter length pushrod you may see longer and better performance from your build.

DavidGXP

iTrader: (14)

I agree with what you have posted above. However, only one spring failed and all other valve seals and and related valve train items look great.
I will have to check the pac spring pressure. Also, none of the other pistons had kiss marks from the valve, none of the walls had scuff marks.