Yikes, my "fixed" OEM heads only lasted 5 years as well, but at least my 5 years included 20k miles, which is a lot more than the 7k miles in OP's experience. Now the same heads have been completely rebuilt by Greg Good and he believes they should be fine for the next 50 k miles. I am still using the OEM rocker arms with bushings instead of the needle bearings and my max camshaft lift is 0.648". I am NOT a believer in pedestal flex problems, but do believe that roller-tipped rockers will result in improved valve guide/valve stem life. At the time of my last rebuild, I would have considered TSP's roller tipped rockers if I could find more satisfactory experience with them. Now I have to wonder why they are not in the TSP catalog and are only sold on special request. Any long term experience on the TSP uniits?

The other reason I did not push harder to find a roller-tipped rocker arm assembly is that the added mass of the roller tip will resulted in the need for larger valve spring stiffnesses for control at high RPM. My concern was that this will require dual valve springs. After looking at the Katech valve train dynamics data, I really preferred to stay with single beehive valve springs.

 

Oops, forgot to ask how many LS7 engine cars with aftermarket head castings have surpassed 20,000 miles without needing a rebuild, including new valve guides? Please state whether these LS7 engines are using OEM or aftermarket rockers and camshafts (including camshaft lift if over 0.591". My theory is that the aftermarket casting heads do not have a longer service life than the OEM casting heads, even when fixed. Please prove me wrong.

 

My Fixed heads, with Katech parts and WCCH machining/ assembly were well within spec when cheked at 10K miles and showed no problems after 26K mile and new springs /retainers. 8-10 track days, 0.5-mile, 1-mile and 1.5-mile trap speed events and ~ 500 miles at or above 150 MPH.

 

For some reason a few days ago when I was looking for the CHE twin shaft roller rockers they were not loading in their website. I just checked tonight and 20+ rocker options came up for the LS7. So who knows what happened, all I know is when I called the sales rep knew exactly what I was wanting and had no problem locating them I ordered them Monday afternoon and just got them today.

 

Its just physics....a factory rocker is an arc'ed pad and it scrubs (not rolls) from one side of the valve tip almost clear across to the other.

While providing the necessary vertical up and down forces to open and close the valve it also imparts unwanted side loading on the valve stem and the valve guide at the same time as it moves thru its travel.

The more the lift the more sideloading forces that are created and the wider that wipe pattern becomes. This is why BTR and some other shops typically recommend only running .600 lift cams with OEM rockers. I put practically all my customers in roller rockers to extend the longevity / service life of the valve guides and reduce friction / wear to the valve tips.

This is the same cam with an OEM rocker that's brand new and not even broken in yet (that wipe would get wider and even longer when it wears a bit) compared to a roller rocker which leaves a cleaner much more narrow contact patch on the valve tip imparting forces mainly on the center of the valve reducing sideloading a great deal

See pics below





There is alot more to the whole "head fix" situation (trust me I say "head fix" in huge air quotes), but this is clearly one part that's often misunderstood and overlooked by enthusiasts as well as alot of shops all across the country

Modded engines (meaning engines with aftermarket high lift cams and aftermarket springs with twice the OEM spring pressures) will wear out the guides much faster as the side loading forces are much greater than stock with OEM rockers

Optimizing valve train geometry is a real thing and getting it right can extend the life of the parts in additional to making a little more power

Hope my pictures say 1000 words and some of you find this educational

Regards,
Tony

PS.....To Z.06 who I quoted above.....your on the right track regarding roller rockers increasing life and you can still run beehives with the Yella Terra Ultralight brand as long as you pay attention to valve weight. I normally run PAC 1276 springs and Titanium retainers for my guys on board with the lighter mass of the beehives and who are comfortable with single springs

Stock rocker weight with bearing assembly below compared to the YT Ultralite with its bearing included as well

 

This is why I went with @Tony @ Mamo Motorsports for brand new heads instead of "fixed heads" from Rich at the Corvette Connection in Denver or Lingenfelter.

 

Which brand new heads?

 

I’ve heard a lot of theories over the last 15 or so years regarding the LS7 head issue. One of the theories I remember was that the heads were cast/prepped through different suppliers or locations, with some claiming one batch was machined correctly and another was not. I’ve heard Mexico, Canada, different machining processes, certain years, certain casting marks, and about every other version of the story.

To Tony’s point, I do believe the factory friction-tip rockers can contribute to valve/guide wear, especially when you start adding more spring pressure, camshaft changes, higher rpm use, etc. But at the same time, there are countless modified LS1, LS6, LS2, and LS3 engines where owners chose to keep the factory rockers and it never became this widespread, engine-defining issue.

That’s why I tend to give more credibility to the theory that the LS7 issue is rooted more in the cylinder head machining/guide-seat concentricity problem than the rockers alone. The rockers may add to the problem or accelerate wear in some cases, but I don’t think they fully explain why the LS7 became known for this specific concern when so many other LS-based engines ran similar rocker setups without the same reputation.

It also seems like that theory has some support when you hear about heads that were “fixed” by simply pressing out the old guides and installing new ones, only to show similar wear again years later when checked. If the underlying guide bore, seat alignment, or overall machining issue was never truly corrected, then replacing the guides alone may not eliminate the root cause.

At the end of the day, I don’t think there is a reliable way to look at a factory LS7 head and say with complete confidence that it is “good” just based on year, casting mark, mileage, where someone believes it came from, or who performed the "fix". The only way to really know is to remove the heads, inspect them properly, and measure the guides/valve job OR eliminate them completely.

Personally, for peace of mind, the only way I feel completely comfortable is to remove the factory castings altogether and replace them with a properly built aftermarket set of heads from a reputable shop. In my case I went with @Tony @ Mamo Motorsports, as has been in the game a LONG time (not an age joke, Tony lol) and I trust him. I know not every LS7 is going to drop a valve, and I’m not trying to add to the statistics, but with the potential cost of failure, I’d rather eliminate the unknown instead of trying to guess whether my particular set of factory heads is one of the “good” ones or if the "fix" was the actual fix.

Albert

 

First off, Tony is one of the foremost experts of cylinder head design and real world experience, everyone else including myself are opinion. If he says the ls7 stock heads/cam or certain aftermarket cam combos can use stock like springs with yella terra 1.8 roller rockers and does, that testamony is gold..period. X2 about using an aluminum roller rocker with no issues concerning supposedly heavier weight on the roller end, maybe for a steel roller but not the yella terra aluminum 1.8s.

As for the comment about other ls engines not having valve train issues like the ls7, those engines have different valve train geometry..apple's to oranges.

Well documented that "fixed" OEM heads can and do fail. Tony told me he knows of none of his aftermarket new heads failing due to the heads...regardless of the miles..since many fixed heads can and do fail with low miles, making mileage somewhat irrelevant when looking at new heads.

If valve guide concentricity is the issue on OEM heads, using a rocker that increases side loading (OEM sliders), in theory can accelerate a valve train problem. An aluminum roller rocker my allow normal valve train function for a much longer time frame or no failure ever.

Lastly, the bigger issue on "fixed" heads is not whether to use a different rocker type but how to control a much heavier stainless steel exhaust valve at high rpm, necessitating much higher spring pressures which increases valve stem side loading. I heard personally from a few builders that a ss valve should not be revved to 7,000 rpm due to the aforementioned issues, stock or roller rocker, not withstanding.

 

He is referencing the fact I do not use ANY of the OEM parts.....my approach or SOLUTION to this whole situation is to completely replace all the problematic GM parts including the casting (I use aftermarket TFS casting to build my LS7 heads).

I use aftermarket valves to sidestep some of the noted finish issues on the GM Ti valves. Either hollow stem Ferrea stainless in my Stg 1 and Stg 2 heads (my hollow stem 2.205 intake weighs within a few grams of the much smaller 1.600 exhaust valve) or going with an aftermarket Manley Titanium and a Ferrea hollow stem exhaust in my Stg 3 heads (mostly for guys with larger budgets trying to make a big number with aggressive camshafts and higher RPM goals north of 7500).

I dont believe in the head "fix" at all.....using the same GM castings.....most of the same GM parts and setting the clearances back to OEM specs is a reset of the time bomb in most cases. Go down the rabbit hole and start to Google blown up fixed heads

Changing the guide material to any type of bronze guide is surely going to increase wear faster. Its simply a softer material I don't care where its sourced from or what the buzzword is regarding the material.....if its mostly bronze its going to be softer that an OEM GM steel guide which are quite hard (hone a bronze guide and then hone a GM guide or any powdered metal guide....it takes alot less time to open up an aftermarket bronze guide to the correct final size). The OEM guides are designed for longevity in mind as GM has no desire to service the heads of every vehicle that leaves the showroom under warranty.

Some guys have gotten away with the "fix" and alot of guys have not....when you break it down the "fix" retains most of the problematic parts including the OEM rockers while the clean sheet approach I subscribe to replaces them all.

I have posted about this topic at length in lots of older threads so Im purposely keeping it brief here as I feel its the beating of a dead horse.....but hoping I have helped some newer folks reading this possibly get a better grasp on things.

If I accomplished that this additional time worth drafting these few posts in this newer thread was worth it

Call me if any of you guys reading have additional questions or are considering an upgrade

Regards,
Tony

PS.....And the other benefit to subscribing to my handling of this situation puts you into a head that's MUCH more efficient and offers alot more performance potential. Look at that as the big cherry on top....even for the guys just wanting to sidestep all the GM failures, the extra performance is still most definitely welcomed. An OEM head simply could never be as efficient or as effective as a clean sheet design aftermarket head that flows more air thru a smaller port. That improves everything.....throttle response....tip in throttle, torque and HP production across the entire curve and even fuel economy

 

Linimar, a Canadian company supplied all the LS7 heads, fully assembled and "ready to bolt on" to Bowling Green and to Chevy for the Camaro that ran the LS7. The valve concentricity problem, documented on brand new OEM warranty heads (by Hib Haberson) were only out of spec (but out of Chevy wear spec) by a very small amount and new guides with just minor lapping of the valve seats using the new guides as the "guide" for the valve seat lapping tool would cure that manufacturing issue. When I had my C6Z LS7 power build (added 133 rwhp, still NA) done in 2016 at 46K miles, I wanted to keep the valve train light so went with the Katech recommended parts; WCCH did the head work and they were doing all of Katech's customer head work until they took that in house around 2016. If the lightweight YT rockers were available then I would have used them rather than using LS7 OEM rockers.

As it was, I had the heads disassembled after 10K miles (when I had the bottome end fully forged and oil pan baffles installed and a Ketech modded oil pump) and the valve stem clearances were all in the .0013-.0016" range. I had no concern that they were out of spec when I sold the car in 2023 at 73K miles and many road course and other performance events on the 600 rwhp engine. I did have the valve springs and retainers replaced as PM after 21K miles on the power build, which is just good maintenance practice on a build like this.

I knew about the valve drop issue in 2010 when I bought my 8500 mile used '09Z. I would not own a C6Z that was not covered by warrant (not available now) or having the heads fixed, so followed this issue extensively until I did the power build in 2016 by Cordes Performance Racing.

 

The bottom line is if you want the greatest risk reduction probability from valve train issues, NEW aftermarket Ls7 heads are the best bet...hands down period!

"Fixed" OEM ls7 heads offer a risk reduction higher than stock ls7 heads IF, BIG IF, they are redone correctly and with the right components AND are on a cammed modified motor, more so than on stock ls7 engines. Most "fixed" heads are fine but more and more are showing up with issues, the reasons are varied.

Most stock ls7 engines and heads are fine as long as they are not raced, not modified in any way, are well maintained, use top quality synthetic oils (Not 5w-30 weight) and kept off the 7000 rpm factory redline. I replaced my ls7 rockers with yella terra aluminum 1.8 ratio rockers last summer, just for some theoretical insurance but will continue to monitor the valve train condition with more miles.

If something changes before then, NEW HEADS!

 

May have been closer to catastrophic failure than I know. The engine builder had me come by the shop last week when dropped off the new rockers and got some more bad news. All 8 intake valves have some bluing on them. So somehow they must have gotten hot. If the google search I did it correct the powder blue color is the first stage of an over heated comprised titanium valve.
I contacted my tuner to see if there were any issues in the last tune but no red flags. AFR was 12.6 non wot AFR 14.7. No knocks LTFT and STFT all in line. He asked if I used race gas, water/methanol injection? No. Also asked if I used a fuel system cleaner, which I have, I did email the maker of the cleaner they say no way their product caused the blueing. So now replacing the valves just in case. I can’t in good conscience put a possible compromised valve back in after all this work.

 

When the heads were "fixed" did you use cleaned up valves or new valves? I would never re use valves that might have been running in OOS valve guides. When I had my OEM heads redone I used Katech TiMo intake valves and brand new OEM exhaust valves. At 46K miles my stock engine had all 8 exhaust valve guides OOS and 6 of the 8 intake valves guides OOS, some by over 2x the GM wear spec..

 

When the heads were “fixed” at 11K mile they put in new Ferrea SS exhaust valves and I have the pics of the valves before the install and the intakes look like new.

February 2020

February of 2020

 

Do you know if the intake guide clearances were out of spec (.0037")? If they were, then the intake valves were seeing fatigue and are subject to increased risk of failure and likely to create more rapid wear in the new guides. 2006-early 2008 LS7s were most likely to have the exhaust valves fail as there was uneven wall thickness around the sodium cavity. Some time in mid-2008 MY, Chevy made a change (same PN but either different supplier or improved QA by the supplier) and thereafter a higher % of intake valves failed. Throughout the entire LS6 production, Linimar had manufacturing problems with valve guides being out of spec re concentricity with the valve seats.

 

The car is a 2013. As for the valve guide specs in 2020 I have no idea what the numbers were.