Super Chevy article says bronze valve guides can prevent LS7's from dropping valves - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Lightsaber · 02-01-2015, 02:40 AM

So I did some research on the LS7's valvetrain, and found an interesting article in the May, 2014 issue of Super Chevy magazine. It is about Katech engineers testing different valvetrain configurations of the LS7 with a laser measuring the valve lift while revving the dummy engine all the way to 12,000 RPM. They tested OEM sodium-filled valves, solid stainless steel valves, solid titanium valves, OEM beehive springs, PSI beehive springs, and dual-coil springs with different camshafts.

Short answers:
1) To prevent the LS7 from dropping a valve, simply fit the cylinder head with bronze valve guides;

2) Solid stainless steel valves: Bad idea, because they are too heavy.

3) Dual-coil springs: Mediocre idea, because they are unstable at high RPM.

Long answers:
Read the original article, it's enlightening.

At last, please be aware that these are just Super Chevy and Katech's opinion based on the short term test, and are not meant to be taken as the words of God. If you have other source of knowledge about the LS7's valvetrain stability, please share with us!

Sapper12b · 02-01-2015, 02:44 AM

Very interesting , something to consider and think about

Lightsaber · 02-01-2015, 03:02 AM

Quote:

Originally Posted by Sapper12b

Very interesting , something to consider and think about

I also found an article on Engine Builder magazine: Valve Guide Reconditioning, which says that bronze valve guides retain the oil better than steel ones and thus offer better lubrication; they can do even better if there are oil retention grooves inside.

forklord · 02-01-2015, 10:42 AM

I thought this was common knowledge?

Mikebrinda · 02-01-2015, 11:01 AM

Why doesn't the factory use bronze valve guides?

blessedhellride · 02-01-2015, 11:33 AM

I believe over time issues are larger than the guides. I've seen slack develop in the bronze valve guides too.

Unreal · 02-01-2015, 11:43 AM

Valve train stablity is a lot more than what valves/springs. Plus valve "bounce" is arguable on the effect and what it means.

Dual springs range all over the place, so the set they used with that cam and that valve showed some bounce, while if they used a different one it may have been better, so all you can use is that exact setup has some mild bounce. Can't say dual springs are bad, or SS valves or bad, or anything like that based off that.

And bronze guides isn't the fix, the "fix" is a properly machined set of heads with correct geometry. Bronze works great, but so does PM. You also select the valves/springs based on your application, so depending what you are building the motor for will determine what valves/springs you want to use.

Drag race, promod, 2000+hp cars use dual or triple springs and 150g+ valves revving to 8500rpm, so saying a SS valve or dual spring won't work is not just wrong, it is misleading.

Lightsaber · 02-01-2015, 05:47 PM

Quote:

Originally Posted by Katech_Jason

It seems like all I do lately is answer PMs and emails about cylinder heads, valves and valve guides. Rather than type the same thing over and over I'm going to put some information down here. This isn't a debate, it's what we (Katech) know. Take the information if you wish.

1. Exhaust valves
THERE IS NOTHING WRONG WITH STOCK EXHAUST VALVES. Do not replace your lightweight hollow-stem sodium-filled exhaust valves unless the shop suggesting otherwise can provide valvetrain dynamics testing showing their combination is stable with the heavier valves. You may be doing more harm than good.

2. Rocker arms
THERE IS NOTHING WRONG WITH STOCK ROCKER ARMS. We have never failed one EVER. PERIOD. There was a small batch problem in 2007. If you have a 2007, buy new GM rocker arms. If you have any other year, forget about it. Do not buy "upgraded" trunnions. We have seen those fail.

3. Valve guides
We have seen high valve guide wear on both intake and exhaust valves on LS7 and LS9, but never once have seen valve failure from worn guides. If this concerns you, replace the stock guides with bronze. When doing so, you need to change the intake valves to Katech titanium/molybdenum valves because the molybdenum coating has better material compatibility with the bronze. These valves also have steel tip that eliminates the lash caps. We have been collecting data on valve guides and I've said before that we are going to publish a report, but at this point we don't know when. Our engineering department has been so busy with crunch time for the upcoming racing season and our increased business, this report has been on the back burner. What you read above in this paragraph is what we know and what you need to know. We don't know what the root cause of the wear is, but the fix is noted above.

That is all.

(Source: KATECH PSA: LS7/LS9 cylinder heads, valve guides, valves and rocker arms)

If I read this right, the valve guide wear is not the issue. The issue is that some valve guides are machined wrong. So if the replacement bronze valve guides are machined right and precisely, with the new valves coated in molybdenum, I should be able to sleep like a baby, yes?

Zslash28 · 02-02-2015, 12:37 AM

Not until I pay off the car can I modify it, says my wifey. Decisions, decisions. I'll be watching everything there is as this issue develops in our Z/28 community.

Lightsaber · 02-02-2015, 06:20 PM

Quote:

Originally Posted by Mikebrinda

Why doesn't the factory use bronze valve guides?

If I get it right, the material is not the problem. Although GM is maybe going for cheap here using stainless steel valve guides, it is really the machining error of the guides that blow up the engines.

I believe you can perfectly get stainless steel valve guides, have them inspected to be free of machining errors before installation, and have a reliable LS7. However, since we are paying money to have the job redone anyway, why not just get bronze valve guides.

I think that is the logic here.

Quote:

Originally Posted by Zslash28

Not until I pay off the car can I modify it, says my wifey. Decisions, decisions. I'll be watching everything there is as this issue develops in our Z/28 community.

Your wife is right. I'm a finance professional, and I agree with your wife.

Saving and investing for all future needs (medical, children's education, entrepreneurial endeavour) should be the priority. Modifying a car to go fast is when you have money to burn.

Preventive measures are different though. I wouldn't mind spending $2K on a Z/28 to have some precisely machined bronze valve guides installed and the factory valves surface-treated in molybdenum, so the engine won't sit like a grenade, waiting to blow up someday.

b4z · 02-05-2015, 10:38 AM

1) lack of Bronze valve guides has been the small block Chevy's Achilles Heel since 1955.

2)the 80 yr old guy who lives across the street from me was spinning 265 CID Chevys to almost 9000 rpms using late '50s early '60s technology.

3)my understanding that most of issues with the LS7 was due to one machine at the factory that did the heads being out of spec. Causing valvetrain geometry issues.

Unreal · 02-05-2015, 10:43 AM

Heads are machined or made at GM. They had a supplier maching them, and doing a piss poor job at it. They show up bagged and assembled ready to install.

Yep, people have been spinning v8s up to 8k+ for a long long time.

Firefighter · 02-05-2015, 10:54 AM

Quote:

Originally Posted by b4z

1) lack of Bronze valve guides has been the small block Chevy's Achilles Heel since 1955.

2)the 80 yr old guy who lives across the street from me was spinning 265 CID Chevys to almost 9000 rpms using late '50s early '60s technology.

3)my understanding that most of issues with the LS7 was due to one machine at the factory that did the heads being out of spec. Causing valvetrain geometry issues.

1) Sure has...

2) Seen that crazy stuff back in the 80's it's not a big deal as long as it gets done right.

3) I've see one out of spec machine shut down an international mfg. company for almost 10 days and cost near a million dollars.

Valve train geometry is critical to so much with the way a car runs and it's durability.

I found this article the other day and still haven't had time to sit down and go over it but it seems like it's pretty good.

http://www.enginelabs.com/engine-tec...ting-it-right/

Sent from my SM-G900V using Tapatalk

JeffInDFW · 02-20-2015, 03:44 AM

I've been part of the LS7 valve issue for 4-5 years now. I'm a Viper owner that is badly in love with the Z06 (and now Z/28), so I've followed this issue closely. There is a library of information available to you guys in the C6 Z06 section of the forum for Corvettes. You know, Forum for Corvettes. The latest info is, a few months ago a set of heads were purchased at the parts counter. Upon measurement, one head was perfect but the other one was wildly out of spec. This was at the end of 2014 on brand new never installed heads. Out of members who have had their heads inspected and reported back, over 200 of them, over 80% were out of spec.

They started a feature "Ask Tadge" where the Corvette chief engineer would answer one question a week. They asked him about all of this. He took double the length of time to answer, got some big wig from powertrain to chime in, and completely infuriated everyone. All they said was that the LS7 was a performance engine and the valvetrain made more noise than a normal car because it had big valves. They went on to say that a very small number of heads in 08 and 09 were machined wrong, and GM warrantied 33 engines. That was it. We had asked them to let us know what had gone wrong so we could know what to change. We needed specifics. We told them that brand new heads were out of spec, that we had a list a mile long of Z06 from 2006 to 2013 that had dropped a valve, we told them that over 80% of members cars checked were out of spec. Didn't matter. They just ignored the actual question and gave us a smoke screen.

Fortunately, the Z06 owners have already done an insane amount of leg work that you Z/28 guys can build on. For example, the Katech article you mention above, that spin tron testing where they tested the stainless steel valves and detected bounce, etc, that test was done because members of that forum asked Jason at Katech to do that testing. He said it was expensive to do. The members then donated the money to pay for it! All kinds of combinations have been tried, all kinds of motors have been destroyed. BUT, at least you guys will not be starting from scratch.

I just wanted to share that, I hope it helps get you guys kick started. Best of luck, and congrats on owning such a bad ass car.

02-01-2015, 02:40 AM	#1
Lightsaber Drives: conscientiously Join Date: Jan 2015 Location: Canada Posts: 61 View My Garage	Super Chevy article says bronze valve guides can prevent LS7's from dropping valves So I did some research on the LS7's valvetrain, and found an interesting article in the May, 2014 issue of Super Chevy magazine. It is about Katech engineers testing different valvetrain configurations of the LS7 with a laser measuring the valve lift while revving the dummy engine all the way to 12,000 RPM. They tested OEM sodium-filled valves, solid stainless steel valves, solid titanium valves, OEM beehive springs, PSI beehive springs, and dual-coil springs with different camshafts. Short answers: 1) To prevent the LS7 from dropping a valve, simply fit the cylinder head with bronze valve guides; 2) Solid stainless steel valves: Bad idea, because they are too heavy. 3) Dual-coil springs: Mediocre idea, because they are unstable at high RPM. Long answers: Read the original article, it's enlightening. At last, please be aware that these are just Super Chevy and Katech's opinion based on the short term test, and are not meant to be taken as the words of God. If you have other source of knowledge about the LS7's valvetrain stability, please share with us! __________________

02-01-2015, 02:44 AM	#2
Sapper12b HTCC Member Drives: 2013 Camaro SS Join Date: Dec 2012 Location: Houston, Texas Posts: 1,868 View My Garage	Very interesting , something to consider and think about __________________

02-01-2015, 10:42 AM	#4
forklord Drives: 2010 2SS Join Date: Sep 2012 Location: Canada Posts: 800	I thought this was common knowledge? __________________ 2010 2SS- 562whp/634wtq 12 psi on3 turbo 78mm magnum /w aem truboost, pat g cam, Kooks 3" catback, Factory Rep 41s with 285/315 20" michelin PSS, Snow Meth, Hex Hood Vents, ZL1 FP & ADM FPCM /w JMS BAP, ID 850s, DSS lvl 4 axles & aluminum 1 piece D/S, Total Pro BMR bushings, fe4 sways, toe rods & trailing arms, Prothane engine mounts, MGW shifter, eaton true trac, mantic 9000 clutch, idealg master cylinder, JDP clutch oil reservoir, ram clutch pedal adjust, Tick clutch & bleed lines, Dewitts Rad

02-01-2015, 11:33 AM	#6
blessedhellride Drives: 2014 Z/28; 2014 Ram 2500 CTD Join Date: Jan 2014 Location: DFW-Fairview Posts: 498	I believe over time issues are larger than the guides. I've seen slack develop in the bronze valve guides too. __________________ 2015 Silverado 2500 2014 Z/28

02-01-2015, 11:43 AM	#7
Unreal Drives: 2006 Z06 Join Date: Oct 2010 Location: Gilbert, AZ Posts: 5,712	Valve train stablity is a lot more than what valves/springs. Plus valve "bounce" is arguable on the effect and what it means. Dual springs range all over the place, so the set they used with that cam and that valve showed some bounce, while if they used a different one it may have been better, so all you can use is that exact setup has some mild bounce. Can't say dual springs are bad, or SS valves or bad, or anything like that based off that. And bronze guides isn't the fix, the "fix" is a properly machined set of heads with correct geometry. Bronze works great, but so does PM. You also select the valves/springs based on your application, so depending what you are building the motor for will determine what valves/springs you want to use. Drag race, promod, 2000+hp cars use dual or triple springs and 150g+ valves revving to 8500rpm, so saying a SS valve or dual spring won't work is not just wrong, it is misleading. __________________ Nick Corvette Z06 -1200ish rwhp

02-01-2015, 11:01 AM	#5
Mikebrinda Drives: Ferrari F430 Spider F1 Azzurro Arge Join Date: Sep 2013 Location: Irvine Posts: 858 View My Garage	Why doesn't the factory use bronze valve guides?

02-02-2015, 12:37 AM	#9
Zslash28 Jumanji Drives: '14 Z/28 - AGM - No A/C Join Date: Mar 2014 Location: Alaska Posts: 1,693	Not until I pay off the car can I modify it, says my wifey. Decisions, decisions. I'll be watching everything there is as this issue develops in our Z/28 community.

02-05-2015, 10:38 AM	#11
b4z Drives: '06 Pontiac GTO M6, '19 F150 2.7TT Join Date: Nov 2008 Location: Charleston, SC Posts: 1,424	1) lack of Bronze valve guides has been the small block Chevy's Achilles Heel since 1955. 2)the 80 yr old guy who lives across the street from me was spinning 265 CID Chevys to almost 9000 rpms using late '50s early '60s technology. 3)my understanding that most of issues with the LS7 was due to one machine at the factory that did the heads being out of spec. Causing valvetrain geometry issues.

02-05-2015, 10:43 AM	#12
Unreal Drives: 2006 Z06 Join Date: Oct 2010 Location: Gilbert, AZ Posts: 5,712	Heads are machined or made at GM. They had a supplier maching them, and doing a piss poor job at it. They show up bagged and assembled ready to install. Yep, people have been spinning v8s up to 8k+ for a long long time. __________________ Nick Corvette Z06 -1200ish rwhp

02-20-2015, 03:44 AM	#14
JeffInDFW Camaro owner for 29 years Drives: 96 Viper GTS/09 Sky Redline/95 Z28 Join Date: Jul 2008 Location: Texas Posts: 115	I've been part of the LS7 valve issue for 4-5 years now. I'm a Viper owner that is badly in love with the Z06 (and now Z/28), so I've followed this issue closely. There is a library of information available to you guys in the C6 Z06 section of the forum for Corvettes. You know, Forum for Corvettes. The latest info is, a few months ago a set of heads were purchased at the parts counter. Upon measurement, one head was perfect but the other one was wildly out of spec. This was at the end of 2014 on brand new never installed heads. Out of members who have had their heads inspected and reported back, over 200 of them, over 80% were out of spec. They started a feature "Ask Tadge" where the Corvette chief engineer would answer one question a week. They asked him about all of this. He took double the length of time to answer, got some big wig from powertrain to chime in, and completely infuriated everyone. All they said was that the LS7 was a performance engine and the valvetrain made more noise than a normal car because it had big valves. They went on to say that a very small number of heads in 08 and 09 were machined wrong, and GM warrantied 33 engines. That was it. We had asked them to let us know what had gone wrong so we could know what to change. We needed specifics. We told them that brand new heads were out of spec, that we had a list a mile long of Z06 from 2006 to 2013 that had dropped a valve, we told them that over 80% of members cars checked were out of spec. Didn't matter. They just ignored the actual question and gave us a smoke screen. Fortunately, the Z06 owners have already done an insane amount of leg work that you Z/28 guys can build on. For example, the Katech article you mention above, that spin tron testing where they tested the stainless steel valves and detected bounce, etc, that test was done because members of that forum asked Jason at Katech to do that testing. He said it was expensive to do. The members then donated the money to pay for it! All kinds of combinations have been tried, all kinds of motors have been destroyed. BUT, at least you guys will not be starting from scratch. I just wanted to share that, I hope it helps get you guys kick started. Best of luck, and congrats on owning such a bad ass car.