double06

Hey great news, keep on going.

heavychevy357

Finally got the car back running. This morning actually. Went with PAC 1206X spring kit as PAC suggested. They told me with the OE lifters that the 1207 & 1208 kits would have too much spring pressure. So he said to go with the 1206 and by the time I shim up it'll have enough pressure to keep the valves controlled while not eating the lifters.

All the intake installed heights were between 1.7400" and 1.745" and all the exhaust heights ended up being 1.750" which is what PAC said to install at. Took a .060 and .015 combo for all of them. Between .080-.090" coil bind clearance. Letting her cool down now from her first start up and bring her to full operating temp.. then I'll start her up for the second heat cycle, let her cool off then I'm taking her for a drive.

All seems to be hopefully it it stays that way. 2 weeks from now I'll take it to be retuned

heavychevy357

Another update. Got the Z retuned after replacing the valvesprings. Final numbers were 575rwhp/506rwtq. I'm satisfied with those numbers. I was really just ecstatic that it held together after I did the valvespring swap.. half way expected it then to fly apart haha!! But apparently I did it right(pat myself on the back).

Did 4 pulls on the dyno all very similar:
1st pull- 568/501
2nd pull- 571/50
3rd pull- 572/506
4th pull- 575/506

we waited about 30 mins between the 3rd and 4th pulls to let her cool down. It was 94* F with 35% humidity down here in south Louisiana so she got pretty warm during the pulls.

anywho I'm happy and she flat out hauls *** now. Dyno vid and sheet underneath

heavychevy357

Here is a comparing of the HP values when we did pulls with the broken valve springs compared to the new setup. You can clearly see the loss in valvetrain stability which resulted in loss of power.

Michael_D

Well done sir. The 1206x is a great spring.

When you took the old springs out, did you happen to note what height they were installed at? Distance to CB? And can you verify whether or not they are BTR springs?

Mordeth

Great job Brenton! Looks and sounds real good. Glad you tackled this on your own. Now you can hopefully enjoy her for a bit. Be safe and keep an eye out for any C7Zs moping around.

heavychevy357

Thank you Michael!

To answer your questions. Yes they were installed ranging from 1.760-1.765. So calculating using their coil bind specs of 1.060" it had .040-.045" CB clearance. And no they were NOT BTR springs! They were junk PRC .675 springs. Previous owner had them when he sent the heads to TSP.

The PAC 1206 kit looks beefier when next to the old spring(which I have thrown in the trash!). I think it was a mix of tight CB safety margin and poor quality springs/spring material.

No valve float with the PAC springs. Everything held together . Hopefully this is the last hiccup for awhile.

And thanks Anthony, I am ready to run one now no matter the outcome just want to run one for the fun of it and to compare.

Michael_D

Anything under 50 thou CB distance will have the results you had. That is not the spring's fault. My min is 60.

heavychevy357

Fair enough. I still think PAC is a better spring than the PRC's