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Old 03-08-2020, 09:23 AM
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Originally Posted by Jays_SSZ28
There was not enough PTV clearance.
Now you have a bigger cam and it works, well you can add .250 lift and change the valve opening and closing times and it can provide a ton of clearance. That cam card you have pictured says a lot. the exhaust closes 23.5 degrees after tdc, the intake opens 19.5 before tdc.
It didn't break right away because with dome top pistons the valve hit flat, if it was a flat top piston it would have hit the valve on the edge and been a problem first time.

Most reputable shops won't throw other shops under the bus. The most important thing to say, read this carefully. If the first builder didn't do anything wrong why did he put inadequate valve springs in it? The second shop didn't say anything about the first shops mistake of installing weak springs? Hmm. What did he do just trust the specs off the box? Didn't check the actual spring rate? Someone fucked up. You can't say it was Lunati's fault, someone put the wrong springs in it if thats what you're claiming the problem was. It looks like lack of piston to valve clearance. So someone fucked up right? Who do you think it was?
I disagree. If it were a PTV issue, all pistons would have witness marks. Incorrect spring setup here is my guess. Valve float will beat up rollers and a camshaft. This explains why cam and lifters were hurt. Looks like 823 heads from the chambers. They are known to break intake valves with float. Valve bounces on the seat repeatedly each time it’s supposed to be closed, much like a basketball dropped from 1’ off the floor. Seen it happen a lot. Exhaust valves will usually hit first, in a valve float situation, because the exhaust valve is open as piston is moving upward.
When valve float is present, all valve closing timing events go out the window. It gets messy quick.
Now...could PTV have been a little on the tighter side? Sure. For a race application, you’ll always lean toward the tighter side, for power sake...pushing things to the limits. That’s what race engine builders do. But here, I’d point to incorrect springs, or springs not set up correctly as the culprit.
Old 03-08-2020, 09:51 AM
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Originally Posted by Che70velle
I disagree. If it were a PTV issue, all pistons would have witness marks. Incorrect spring setup here is my guess. Valve float will beat up rollers and a camshaft. This explains why cam and lifters were hurt. Looks like 823 heads from the chambers. They are known to break intake valves with float. Valve bounces on the seat repeatedly each time it’s supposed to be closed, much like a basketball dropped from 1’ off the floor. Seen it happen a lot. Exhaust valves will usually hit first, in a valve float situation, because the exhaust valve is open as piston is moving upward.
When valve float is present, all valve closing timing events go out the window. It gets messy quick.
Now...could PTV have been a little on the tighter side? Sure. For a race application, you’ll always lean toward the tighter side, for power sake...pushing things to the limits. That’s what race engine builders do. But here, I’d point to incorrect springs, or springs not set up correctly as the culprit.
Ok, it's no so much what caused the problem than the problem existed. Not even the OP so it makes this confusing but whoever posted this said the engine was set up by a professional, then after the failure checked by another professional. The concern is whose at fault.

Just my opinion, a professional engine builder should be building engines that last longer than 80 miles. Is it wrong to think this?
Old 03-09-2020, 03:28 AM
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Originally Posted by Che70velle
I disagree. If it were a PTV issue, all pistons would have witness marks. Incorrect spring setup here is my guess. Valve float will beat up rollers and a camshaft. This explains why cam and lifters were hurt. Looks like 823 heads from the chambers. They are known to break intake valves with float. Valve bounces on the seat repeatedly each time it’s supposed to be closed, much like a basketball dropped from 1’ off the floor. Seen it happen a lot. Exhaust valves will usually hit first, in a valve float situation, because the exhaust valve is open as piston is moving upward.
When valve float is present, all valve closing timing events go out the window. It gets messy quick.
Now...could PTV have been a little on the tighter side? Sure. For a race application, you’ll always lean toward the tighter side, for power sake...pushing things to the limits. That’s what race engine builders do. But here, I’d point to incorrect springs, or springs not set up correctly as the culprit.
That is what was wrong. I said that in my last post that is all they found wrong. Springs were set up correctly. Just not enough spring pressure. They are AFR 245 heads. We went from a 651 lift cam and now have a 731 lift cam on the same pistons and heads. So it definitely wasn't PTV clearance. According to all involved, the springs were supposed to be enough but just were not. I questioned this because the springs were supposed to be good up to 650 lift. We had a 651 lift cam. I told them I didn't want to be on the edge. I totally agree that the reason the cam and lifters got tore up was from valve float. All they did was get a new casting put in heavier springs, a sleeve in the block, and new solid lift cam and lifters, then it was fine. Bottom line here is take it to a good reputable builder in the first place or do it yourself. Hey, live and learn right? Just sucks on how much it cost to learn even after common sense told me to ask about the springs. Even worse I was told by the cam guy I could spray 300 on that cam. Does that look like a nitrous cam to you? I'm sure there was nothing wrong with the components quality. I'm not happy with the guy that represented them. He talked a good game but bailed quick.
Old 03-09-2020, 04:21 AM
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Originally Posted by Jays_SSZ28
There was not enough PTV clearance.
Now you have a bigger cam and it works, well you can add .250 lift and change the valve opening and closing times and it can provide a ton of clearance. That cam card you have pictured says a lot. the exhaust closes 23.5 degrees after tdc, the intake opens 19.5 before tdc.
It didn't break right away because with dome top pistons the valve hit flat, if it was a flat top piston it would have hit the valve on the edge and been a problem first time.

Most reputable shops won't throw other shops under the bus. The most important thing to say, read this carefully. If the first builder didn't do anything wrong why did he put inadequate valve springs in it? The second shop didn't say anything about the first shops mistake of installing weak springs? Hmm. What did he do just trust the specs off the box? Didn't check the actual spring rate? Someone fucked up. You can't say it was Lunati's fault, someone put the wrong springs in it if thats what you're claiming the problem was. It looks like lack of piston to valve clearance. So someone fucked up right? Who do you think it was?
Take your own advise and reread my post. I clearly state that is all they found was the springs were too weak. All they did was replace them. The heads came complete. I don't know if they tore them apart to check things out or not. I have never said anyone is at fault. You are the one trying to point a finger at someone. All I did was tell a story on what happened to me. That was seven years ago. I'm over it so lets move on.
Old 03-09-2020, 05:55 AM
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Originally Posted by TTur1996
. All they did was replace them.
And the cam,
Old 03-09-2020, 10:28 AM
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Originally Posted by Jays_SSZ28
And the cam,
New head, sleeve in block, new piston, new cam and lifters. Just like I stated earlier. I see what your insinuating. We went to a 731 lift cam from a 651 lift. Don't believe you could change the valve events enough to compensate that if they were already hitting at 651 lift. It wouldn't run for ****. Plus spinning it much faster. 2 different shops were wrong about the PTV. Come on. I don't believe it. Especially since the second shop didn't know another shop put it together originally. I told them I did so there wouldn't be any he said she said. They did say whoever did the machining did a exceptionally good job on it though. The first thing I asked was about the PTV clearance. They said there was way more than enough clearance. When the motor was built originally. The engine builder called the cam supplier on speaker phone and I was standing right there. They went over what components needed to be in the heads. Then as soon as we hung up they called AFR and ordered the heads accordingly. I realize **** happens. All that I asked for from them was to let me pay cost on parts and labor to fix it and they said no. Never expected them to eat anything, and I told them that repeatedly. Couldn't have been more nice to them about everything. They even made several comments on how well I was taking everything. Ya Ya Ya we would have done this or that and still not accomplished a dam thing but get yourself upset then they win again. Like I said earlier. Live and learn. I'm out.
Old 03-09-2020, 11:12 AM
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Max lift means nothing. Piston is 2 inches down the bore when it hits max lift.

Edit -- Wanted to expand on this. When I typed I was sitting on an airplane on my phone. Here are a couple of examples.

232/240-111+3 on flat top pistons, no reliefs, .550 lift, .041 head gasket. Pistons will hit the intake valves.
226/234-111+3 on flat pistons, no reliefs, .750 lift, .041 head gasket. Pistons will clear the valves

Last edited by Darth_V8r; 03-09-2020 at 03:31 PM.
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