LS7 Guides how bad can it get?
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- Опубліковано 7 вер 2024
- Customer brought us a pair of re-worked LS7 heads, and he has put 70k miles on them so far. Unsure of who did the original work but he wanted to make sure they were good to go another 70k. At this time, I do not recall ever seeing a head this bad, on an engine that was still running. The worst one we see so far is about 0.020 clearance, not 0.002....but 20 thousandths clearance!!!
I know that's the craziest wear I have ever seen personally on a running LS7! I'm very impressed nothing let go before customer realized this was this bad!
What running, definitely misfiring like there's no tomorrow
Erik, I've seen a set worse than that. They were so bad that Katech called me to ask who was in there before them. The oval wear is so bad that it can be viewed from 10' away by eye.
One set had deteriorated to the point that there were witness marks on the intake valve from impacts with the exhaust valve.
My guess is that there were no obvious signs or noises indicating the guides were worn that badly! 😳 Frightening!
From what the customer told us, he was reading online about it and thought he would have them checked out. You are correct, there was no indication it was this bad.
the only two things my inexperienced ass can think of is too much friction due to improper lubrication or improper guide material. i just wanna know what else led to 20 entire thousandths of extra wiggle room. a destroked LS7 will make it into one of my cars eventually, thats why i wanna know.
That's a smoker there
There is probably zero chance that it's valve wear and it is probably only guide wear? Wear from any oil starvation?
Correct
thats why i only put in hard cast iron guilds ,brozons wears to quick
Looks like bronze guides installed. If it's not the right kind they wear out fast. The only ones I find that work the best was Speed Pro manganese bronze but I don't think you can get them anymore.
CHE bronze guides with proper stem to guide clearance & valve stem surface finish. HPR for the win!
Some of these OEM LS7 valves are like files
I just don't get how that could happen in any running engine. This must be builder error. Would love to see the guide profile with a split ball gauge. if it is not flared (i doubt) it is builder error. The oil consumption must have been huge
Hard to say, a split ball won't check the intakes, they are that bad. Our Sunnen gage will show up to 0.008 but nothing past that. You can see the taper in the exhaust in the video, top number is the top of the guide and the lower is the bottom part of the guide. When we put a caliper, yes it's that bad, a caliper on the top of the intake guide they are over 0.023" clearance (measured 0.338ish if I recall right). Our thought might have been the valve being to rough itself but so far the profilometer doesn't show anything that abnormal on the stem.
So many people think bronze guides are great. Not me they are too soft
They must be having geometry issues.
Hard to do on a OE LS with stock rocker arms and valves as all of that is locked in place. Doesn't sound like it was crazy lift but we also only have the heads to go off.