Must_Have_Z

I don't get the hate on Katech by some folks here. Katech is not GM. They are an extremely valuable partner, though. That doesn't mean they blow smoke up everyone's hole. I find Katech's posts here and elsewhere to be up front, honest, and detailed.

Also, no one should use any single source or company as the definitive defacto end-all-be-all answer to a technical issue either. Research should be done with multiple companies and sources regarding issues like rocker arm and valve guide failures. However, Katech should be near the top of those sources when doing your research based on what I've mentioned above.

Just my 2 cents.

Bad_AX

I spent some time looking at rocker arms at the PRI show back in December. While this isn't quite the whole universe these arms comprise most of the options available for LS7 heads. I didn't concentrate on the aluminum shaft mounts other than Y-T as they hold no interest for me.

I didn't get any pics of the Yella Terra rockers, so I'll steal one from Tony Mamo. Like ALL aftermarket rocker arms, there is no data from the manufacturer on mass MOI, so it is incumbent on the builder or customer to come up with a compatible group of valve train components. These are available with or without adjustors and the non-adjustor model will have lower mass MOI and require less spring pressure to control. These rockers have a common shaft for each cylinder pair which may improve rigidity, and they are not terribly expensive for roller tip rockers. Dan_the_C5_man has posted a lot of information on this rocker, and it has been Spintron tested with the OE LS7 cam with good results.



Bolt-on solutions get really expensive from here.

This is the Jesel LS roller tip rocker for unmodified heads. They cost about the same as the full race shaft mount Jesels and according to the Jesel staff at PRI they are not as ridged as the shaft mount models. These are being made to comply with some class racing rules that restrict modifications.


Another bolt on, no-mod solution is the T&D rocker. These cost about the same as the Jesels.


Now on to the real valve train ****:

This is the Jesel Mohawk adjustable. These are also available without adjusters. If money is not an object and you don't mind big, heavy, high force duel springs, this is what you want. NASCAR CUP quality with the price to match. They offer a complete LS7 setup if you have the financial tolerance.


T&D also has an outstanding CNC masterpiece in this class and price range. Drool!


For less than half the money of Jesel and T&D, these Crowers are without fault. Honestly, if I needed a LOT of lift, this is what I would buy. Just know that unless you pay a company like Katech to validate your valve train components you are in the dark about the stability and durability of the system. You gotta pay to play at this level. It just comes with the territory.


This is the Texas Speed roller tip rocker that is a bolt on solution for the LS7. I paired one of the rockers with a CHE modded OEM rocker for comparison. Predictably, there is no mass MOI data for this arm. Ya just gotta have the faith of a true believer. NOT!






Of course, you can always try improving the OEM rocker. I was most impressed with the quality of the CHE DIY bushing kit. I also enjoyed meeting Charlie, the owner. In fact, I would say any CHE product is going to meet or exceed your expectations. The bushing kit certainly looks better in person than in any of the internet blurbs I had seen.


There are even services for truing up and polishing the tips of the OEM rockers. Improving the surface finish and contact patch could potentially alleviate a lot of valve stem deflection, especially when paired with DLC lash caps. This in conjunction with the CHE bushing kit would be hard to beat up to ~.650" lift.


A promising design is the Comp Cams SPR rocker arm. Currently these are only made for the LS3 and have a 1.77 ratio. These rockers looked very good in person and the engineering behind the tip radius is solid. In fact the TRD Cup engines use similar tip design on a non-adjustable rocker arm to drastically cut mass. The lash is adjusted via lash caps. Must be nice to have a budget which allows that! The SPR rockers look like they will mount on an LS7 type rocker stand although the geometry is probably wrong. I asked if these may become available for the LS7, and the answer was, "maybe".

There is some good technical info here:
http://www.powerperformancenews.com/...w/#prettyPhoto

MTPZ06

^ Nice overview! My only comment pertains to the cost differential between the new bolt on pedestal mount Jesel's and the T&D pedestal mounts. You mentioned they were similar in cost, but the pricing I received from Jesel was $220/ea...so ~$3500/set. The T&D's were ~$80/ea...or roughly $1300/set. If those Jesel's were $2000/set, I'd already own them.

ssbowtie1

All these roller options look so enticing, but on the other hand, Katech has validated the stock rockers up to .660 lift (K501 cam)...it would be nice if we could get more spintron testing done, but I know that's a dream.

AzDave47

O darn, I have OEM rockers and the K501

Bad_AX

And one of the rare, few validated combinations on the market.

AzDave47

My WCCH heads also have new OEM exhaust valves, Katech Ti/Mo intake valves PSI 1511 springs and Ti retainers. I run a modest 7300 RPM FSO on my build as the torque peak is around 5000 RPM and the power peak is just under 6700 RPM.

I'll be running the Mojave Magnum in April and expect to shift at ~ 7000 RPM into 2nd, 3rd and 4th, but carry 4th to close to 7300 before the shift to 5th to take advantage of the 1:1 gearing vs 5th. The torque curve is almost flat from 4900-5500 rpm.

I'll be reporting in late March on the before/after dyno runs when I swap from my flashing cleaned MSD to a MAMO ported MSD, with no other changes other than retune (91 octane tune) for the ported intake.

RichieRichZ06

I'm in the same boat and with a similar setup, but with Katech Ti/Mo intake and exhaust valves, K501 cam, PSI springs and stock rockers with 13:1 CR and Sunoco GT260+ 104 octane fuel.

If needed, I also take the car between 7k and 7,500 frequently and do not have any issues. Currently my car makes 642/571 and peak HP is 6,600 RPM. It makes over 500 rwtq from 3,850 - 6,600 RPM and peaks also at 5k RPM.

I don't have any plans to go with a more expensive rocker arm set as of now and certainly not something as big and heavy as the YT kit.

Michael_D

It is misleading to say "no problems with my set up that includes OEM rockers and ~ .650" lift", without actually measuring clearance after a few thousand miles. I hope the individuals reading those comments have enough IQ points to realize this.

RichieRichZ06

Do you think the K501 (or other Katech cam) profile could have anything to do with there not being excessive guide wear using stock rockers? I would imagine their spinton testing and verifying valve train stability would attribute to less wear than a shop that pulls cam numbers from a hat.

I ask in all seriousness because I, along with many others, respect your opinions when it comes to stuff like this. You know a helluva lot more than I do regarding head, cam and valve train dynamics.

ssbowtie1

I've always wondered the same thing because on paper the katech combos don't make sense. .660 lift with stock rockers, or XE-R lobes @.650 lift with stock rockers.

I think the cam/spring setup has a lot to do with it. There was a recent post from a member that seemed to have the incorrect springs and setup on his torquer cam which lead to float and worn out guides on the intake side, which only run .615 lift.

One takeaway for me based on what I've read is to run the 1511 springs on a mild to moderate cam, because they seem to have the best high rpm stability on the LS7... The rest is just a crapshoot with tons of conflicting info

MTPZ06

I would be interested to see the wipe pattern with that setup. Don't see how side-loading isn't a factor that needs to be considered over the long-term.

Bad_AX

If you want my opinion, we don't know f__kall about valve side loading in the LS7. It is assumed based on the intake & exhaust oriented wear on valve guides that it's all due to side loading, but this doesn't take into account the stem finish on the valves, guide finish, clearance, concentricity, etc, etc. It's easy to see the wear, but not so easy to identify the root cause. Adding springs with considerably higher rates than stock presents another variable. Outside of GM, Katech has the most and the best data on LS valvetrain dynamics, and you have to ask yourself why after all these years and hundreds of these cam kits in service, with many getting the hell beat out them at the race track, is CF not hysterical every day with Katech cam kit and valvetrain failures?

MTPZ06

Not my assumption at all...at least not on OE valvetrain.

Michael_D

Premature guide wear and valve train instability are mutually exclusive failure nodes. Both have different root cause failure mechanisms.

Whenever stock valve lift is exceeded, risk of accelerated guide wear is exasperated. The end user should be mindful of this and should practice due diligence with respect to periodic guide clearance checks. My personal experience and observations through my own testing methods, indicate that the OEM rocker wipe pattern starts to move past the center third of the valve tip at roughly .625" valve lift. The wipe pattern movement is exponential as well. It looks quite horrid at .680" lift.

It is for these reasons that I recommend keeping total lifts under .650, and also recommend users check clearance periodically. .660 may be perfectly fine, as these heads are not all identical, but it would behoove users to not make that assumption. I am a huge "wiggle test" advocate. It's worked for decades.

And for what it's worth, I have the utmost respect for Katech and their testing /opinion. However, I also trust my own judgement on these matters.

MikeOC

Michael_D's thread on valve guide wear should be required reading for anyone who still has questions on this issue

https://www.corvetteforum.com/forums...uide-wear.html

NVA2010

"There are even services for truing up and polishing the tips of the OEM rockers."

^ Saw this line in that rocker arm overview.

Who offers this service? Does anyone know anything more about it? I found a thread titled "Z06 Micro polishing factory rocker arms" but it didn't really reveal all that much and is pretty much the only thing that pops up regarding this topic in my google search.

AzDave47

I have 10K miles on my K501/ PSI 1511 springs, Katech TiMo intake valves and new OEM exhaust valves and OEM rocker arms (~ about 30K miles on those?), WCCH head work with CHE bronze guides. CPR checked my valvetrain a couple months ago (not more than wiggle test) and all looked good. I will have a more extensive check done at 20K miles.

Since the HCI work (~600 rwhp) the engine had 4 road course days, three half mile days and 3 Silver State runs for 90 miles each running at 4800-5300 RPM steady. My street driving is relatively easy.

Dan_the_C5_Man

Bad_AX, nice write up.

I think I might have posted a link to the YouTube video of the shop milling the end of the rocker tip face to square them up.

MD and I diverge slightly on the "if it isn't broke, don't fix it" philosophy when it comes to the stock rockers. We do know the guide wear pattern is always front to back, the same direction as the rocker sweep. We know that a roller-tipped rocker also has a sweep (half the time the roller isn't "rolling", but sliding instead), but pretty much everyone agrees they offer a smaller scrub rsdius than the stock rocker.

i went with a roller-tipped rocker on the idea that I wanted to spend more time driving and kess time pulling heads. Now, I certainly could be "solving a problem that doesn't exist"; the issue is, I am not running a development and engineering house, I am not going to "try it and see" and then, "oh darn, my guides are out again". I was focused on a "one shot - one kill" strategy, and did everything possible to avoid a re-work for as long as I own this car (which will likely be for tens and tens of thousands of miles). I also ran YTs on my LS1/6 for a decade w/o issue, so I had experience and confidence in the product.

I have about 15K on my setup at this point, I have a set of gold-plated Katech covers to mount, I will report what I find when I pulll them. And of course if everything checks out, I will be told "yeah, and you'd see the same result with stock rockers", and that is certainly a possibility.

long_tall_texan

I'm in the same boat as Dan_the_C5_Man. I was looking to have the "one-shot, one-kill" strategy as well. I did research until my eyes were crossed, talked with Dan_the_C5_Man, Talked with others, talked with VP of R&D at Yella Terra at length, and feel like I have a very solid and as close to bullet-proof setup you can get with stock heads on my LS7.

All new bronze guides
New CONCENTRIC seats cut
New Ferrea F2042P hollow stem exhaust valves
PSI 1511 Springs with titanium retainers
Stock Cam
Yella Terra Rockers
New pushrods due to milling heads 0.030" and adding Yella Terras

Better than new!