Dirty Howie

So unfortunately the Katech thread was closed at Jason's request. I didn't see the posts any more cantankerous than normal. I should probably be happy it was closed as I was starting to get bashed pretty good

Anyways, regardless of what some may think I actually want more information. My focus is on stock cam setups only. Thats what I have and will keep. It provides more power than necessary for my track addiction.

I have a lot at stake here. I put 500 daily driver miles on every week (now have 132,500K miles) and track the car at least once a month. I have blown up a motor going over 120MPH and really don't want to do that again.

But my motor and several others I have seen blow on the track all had stock setups. And the forum is full of plenty of other completely stock motors that have and continue to fail on and off the track.

So my question is simple: How many if any of these failures is do to valve bounce. Is it possible that valve bounce is irrelevant up to and maybe beyond the Comp Cam safety limit of 0.02"

Is it reasonable to assume that SS valves are going to be much more resistant to bounce that hollow ones. It seems likely.

I will not switch out my SS valves. I saw a broken hollow valve in person as well as many pictures on the forum so SS is staying. Now I would be open to changing springs to PSI or anything else if they are more likely to prevent a blown motor than the duals.


DH (DDS)

MasterDave

I...cannot..read..any..more..valve..issu e...threads..........!!!

wolf8218

You'll do it and you'll enjoy it.

Bill Dearborn

DH,
Are you talking about floating the valves?

Bill

1Sikstik

You'll do it and you'll enjoy it.


^^^

Dirty Howie

Well I'm not concerned with what anyone says or asks so I will not be asking for this thread to be closed.


DH

Dirty Howie

Bill

I'm talking about the VALVE BOUNCE that was analysed by the Katech Spintron testing.

Katech is stating that all of us guys with stock cams, ss ex valves and dual springs are 0.001" over their 0.015 safety limit. Our motors are therefore at risk. I am trying too see if there is any real world correlation.

Maybe bounce is part of the reason stock valves are failing. And maybe even though SS valves have more bounce they are so much stronger that they will not fail from this issue.

I know between you and me we have seen a lot of stock motors blow up. Ever hear of one failing from valve bounce??


DH

Achilles97

Could someone please explain what the danger is with valve bounce? (Honest question). Are the valves exposed to increased forces during bounce which may lead to breakage? And/or are there other issues such as the exhaust gas traveling backwards through the intake valve into the intake manifold?

Thanks

ZIE06Bernie

Unfortunately the few childish chest thumping "look at me bogans" hell bent on personal vitriol ruin it for everyone. Not mentioning names and cannot be bothered with it either as it helps nobody.

When someone is prepared to supply highly technical and relevant valuable information to a forum in an attempt to help people with such highly technical and relevant issues, I would suggest a bit of decency be shown to the supplier of the information regardless of irrelevant personal issues.

Anyhow the bickering has now removed one of the only sources of such useful information so that is truly a shame. All the repeated dredging of "he said she said" stuff is sickening when what is really needed is co operation and respect. Not that difficult surely?

z0sicktanner

Howie valve bounce is not an issue with your setup or anyone else for that matter using the spring Richard uses or any good duel springs, ss valve have been used for a long time.in hotrods for over 50 years. you ask any vendor that besides k an you will get the same answer. the issue with valves dropping is heat related as richard has told you I'm sure

Coach62

That's not even remotely what Jason said. You need to re-read his posts. After the way some of you treated him I'm not in the mood to explain it, especially if you didn't read it that close to begin with.

Dirty Howie

Thanks Chad

As I have said before......

Since there is a difference in opinion between the experts, it is up to the individual to pick the expert(s) he wants to trust.


DH

Mark2009

I assume that since everything is in intimate contact, not only is such stress on the valve, but it is also on the rest of the valvetrain... shims, retainers, locks, rockers, pushrods, lifters, and cam lobe. It should be obvious that zero bounce is the goal, but based on testing it is also obvious that zero cannot be obtained. Therefore minimizing bounce should be the goal. And no, a .001 difference surely can't matter much. However, the RPM should be factored into the equation, not just the gross difference in bounce (in this case, .001).

Problem is, on the Spintron tests w/the stock cam the Rev valve hit .011 bounce at 7000 RPM while the OEM valve was at .007 at that particular RPM, which happens to be peak shifting RPM unless one was short shifting. Depending on how the stresses mentioned in the Manley article break down with regards to measured bounce (data unavailable), that difference between .007 and .011 bounce could be 7,000 lbs of force. Or 11,000 lbs. Maybe the valvetrain can handle that extra 7K lbs or 11K lbs. Or maybe not. I'm sure that some safety factor is build into the design, but the question is how much.

I also wonder if some of the cam lobe and lifter wheel damage we see is a result of valvetrain instability (loft, float, or bounce), even in a stock engine (recall those mangled spring seats on Z06_505's heads).
.

Dirty Howie

Sorry if you are not in the mood. Maybe you shouldn't participate in this thread if its too exasperating for you. I have legitimate questions that another member is already inquiring about too.

I am doing my best to understand what he means then. With my setup he says I must lower my redline RPM. If I don't then you tell me what he is saying will happen ???????????


DH

Mark2009

The smart thing would be for the individual to pick thru the data and make his own decision.

Otherwise you're just hoping that you chose the right guru, and you would really have no basis to claim that the other guru(s) are wrong.

Dirty Howie

Mark

The stock bounce may be incidental to the valve train components GM selected for reasons unrelated to bounce (RPM, whatever). Isn't it possible that GM would have been fine with the bounce seen with the dual springs/SS valve?

Is it possible that even the low bounce seen in the stock setup is still too much for the hollow valves but not a problem for the SS valves. And thats why we see so many hollow valve failures??

Thats why I am asking if anyone knows of a motor failure due to bounce??


DH

Mark2009

You'd have to ask GM. All I can tell you, based on the Spintron results, is that the Rev/dual setup has more bounce at 7000 RPM than the GM setup. 36% more. And I'm sure that doesn't surprise anyone that is highly knowledgeable about valvetrain design.

I am sure that less bounce is good, and more bounce is bad. How good or bad is a question for the people like Manley and GM.

I don't know of one but surely it happens. Otherwise no one would be concerned about it.

FrankTank

Howie Richard would not steer anyone wrong . Your motor is fine and will be fine . Enjoy the car track or street . His set up and work is proven .

Mark2009

I would say no. I'm sure that GM knows what the bounce profiles are from initial testing and has deemed them within design limits.

And bounce would not explain the worn valve guide issue, which is the most likely reason for the exhaust valve failures.

Edit: It's an interesting technical discussion but bottom line, on a stock cam it doesn't look to be a major issue one way or the other. I might short shift a bit, say 6800, just for a little cushion but otherwise the bounce plot doesn't look very extreme compared to the OEM plot.
.

'06 Quicksilver Z06

Apparently nothing good.

And that, I presume is why you are inquiring about that which you are inquiring about.

From all of the discussion, as well as the GM High Tech Performance article, the issue of valve bounce, causing potential failure, is apparently not something that people running the setups that have "passed" the Spintron test, should much worry about.

It is those running setups which have not "passed" the Spintron test who are at risk of bad things happening due to valve bounce.

But apparently, not many of those have been described in here as having actually failed

You know, I have read that article now several times, and several things in it stand out to me, a few of which I inquired about earlier.

But one of the other things in it, that stand out to me in the text of that article, aside from the bounce plots, was the statement:

"Conclusion and Discussion...
These rules of thumb all have an exception in some situations and configurations and are generalized to what we most often see in our valvetrain testing."

Read more: http://www.gmhightechperformance.com...#ixzz2ZeFSv2iu

About the only one that I can think of which some might be inclined to attribute to valve bounce, would be Madsen's failure.

Of course there is no actual proof that this is what happened in his car.

But his is one of two SS exhaust valve failures reported in here, the other being that of 1stZ who failed a SS valve, after first failing a stock exhaust valve, so ultimately, he lost two motors.

Now whether or not his SS valve failure was due to valve bounce, is also in question, or did he simply beat the $#** out of the car to the point to where it failed would be another question.


As far as all of the STOCK exhaust valve failures in here, in STOCK cars, the reported causes have ranged from supposed "broken valve springs", to heads of valves snapping off, possibly due to "worn valve guides", to unknown.

With regard to "cam only" setups which have failed stock exhaust valves in here, again, I cannot recall any of them being attributed to valve bounce.

Also of importance, it has been hypothesized, that some of the failures reported as valve failures, may actually have been piston failures.

You know, one would think, that after several years of these setups being around, and of course in your own environment where several of your track mates have SS valve setups just like yours, that if the worst were assured with these setups, that we would have been hearing about more failures in these SS valve configurations than we have.

But that has not been the case.

BTW, and on a side note, does anyone know, if the stock LS2 and LS3 valve trains were Spintron tested?

The reason I ask, is because they both use solid stemmed stainless steel exhaust valves.