new heads/ valve spring broke.
Thread Starter
Staging Lane
Joined: Feb 2006
Posts: 86
Likes: 0
From: Boise, Id
new heads/ valve spring broke. ok, so about a month ago my friend and i did a h/c package on his 99 vette.... prc stage 2.5 ls6 heads with 228r cam. springs good to .675. we installed the cam straight up, double-checked everything and it ran great untill last night. we were doing a few pulls last night and all of a sudden it started sounding like it was missing a cylinder. we tore into it today and found a blown head gasket and a broken spring on the exhaust of the no. 8. with a bent valve and a small dent in the piston. my question is; is it ok to run the piston still or do we need a new one? also has anyone had a problem with a spring breaking like that with such a small cam. any ideas how it could happen or could it just be a faulty spring.
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He said above that he got it all from TSP. So I would assume these are there dual gold kit, since he said good to .675 lift. This is a pretty mild setup to be shelling springs. Kind of scary really.
Thread Starter
Staging Lane
Joined: Feb 2006
Posts: 86
Likes: 0
From: Boise, Id
TECH Apprentice
Joined: May 2005
Posts: 300
Likes: 0
From: Boise Idaho
That sucks, but it doesn't look as bad as I expected from the texts. I was worried at first that it may of cracked it through and if you reused it that it would burn through but that doesn't look bad enough to really worry about. I'd have no problem reusing it. But like I told Jon I'd have the head checked out well, as well as replacing the valve and springs. Let me know if you need a hand.
How high were you pulling this setup? Is there any indications in the dyno curve that indicate instability? Why did the head gasket fail?
Just because a spring is good to a certain lift doesn't preclude other issues such as surge. I think you need to examine all the parts and how the motor was used and assembled to ensure a valve spring swap to a different one will solve the issue.
Just because a spring is good to a certain lift doesn't preclude other issues such as surge. I think you need to examine all the parts and how the motor was used and assembled to ensure a valve spring swap to a different one will solve the issue.
Thread Starter
Staging Lane
Joined: Feb 2006
Posts: 86
Likes: 0
From: Boise, Id
on the last run, (on the street) the motor went to 6400. we havent dynoed it yet.
we were using stock gm head bolts with mls gaskets. and tightened them down to spec. as per ls1howto.com 1-10 22 ft lbs, 1-10 90 degrees, 1-8 90 degrees, 9-10 50 degrees, then 11-15 22 ft lbs. prep work was good. i have no idea what could have done it. it ran like a champ for a month. maybe the spring letting go caused the blown head gasket????
we were using stock gm head bolts with mls gaskets. and tightened them down to spec. as per ls1howto.com 1-10 22 ft lbs, 1-10 90 degrees, 1-8 90 degrees, 9-10 50 degrees, then 11-15 22 ft lbs. prep work was good. i have no idea what could have done it. it ran like a champ for a month. maybe the spring letting go caused the blown head gasket????
That's what I am struggling with, not sure how that could happen. Were any of the piston exceptionally clean? Where was the leak, to the outside of the head or into a cylinder?
If you can't sort this out, you may want to put a machinest's straight edge across the block and the heads and check for flatness. How is the surface finish?
If you can't sort this out, you may want to put a machinest's straight edge across the block and the heads and check for flatness. How is the surface finish?