WhiteDiamond

Patrick G tuned my Z after the Ragin Racin install. After he dialed it in, I decided that I needed to go to a smaller cam. Patrick took down all my thoughts and desires with the set up and sent over a cam profile for the EPS/Cam Motion grind. I had my favorite head porting expert look over the grind, Darin Morgan, and he liked the numbers, but questioned the need for the advance and if the lobe would really produce the lift quoted. Move forward to this week and I called Geoff directly. We discussed the profile, I sent it to him via e-mail, and my desires. He likes Patrick's grind and I will be moving forward with it once Geoff gets me the complete parts quote. Looking very forward to the swap.

Basically, I am saying the Patrick and Geoff have some GREAT knowledge that more should take advantage of. Brian Tooley is well known and he recommendations on valve train items are on the list going in my LS7 soon.

vertC6

Do you have the specs?

vertC6

It all depends on what cam you go with, a higher lift will require dual springs. They all agreed beehive are the best but not on high lift cams.

WhiteDiamond

Yes. Patrick sent me what would be a "complete" cam grind card when he spec'd the cam. It includes the actual valve events in degrees and the typical duration, lift and LSA numbers. I am not a cam expert by any means, so this info is beyond my level of comfort. I understand the basic idea of it and why I have been spec'd back to a non-overlap grind, but there is a lot at work in cam design and I was impressed with the knowledge provided.

vertC6

That's great, when you get the specs card will you please post them I'm very curious to see how they look. Thanks!

WhiteDiamond

224/238 at 0.050" 118 LSA with +4 advance
I think I am going with the middle of the 3 lobe profiles they discussed with me, so that will put my lift right around .665. Once Geoff gets the full package price to me, I will make that final decision. The mild lobes yield around .635" lift. I was told there is little difference in VT noise between the 2 profiles.

vertC6

I would STRONGLY recommend sticking with the 635 lift. There's just no need to go that high, the ports will only flow so much on a 224 duration, the gains are minimal but the valvetrain wear is much greater.

The Ported ls7 head maxes out around .650, and according to Brian Tooley the rocker is on the edge of the stem at .660, just my .02 cents. I am eager to see the gains with this cam I like those specs.

MyLS1Hauls

WD-What are your current cam specs, and what don't you like about it?

Bossdog

After researching cams for my C5, i came to the same conclusion that you did. I/m no expert but the CM story was a compelling one. I ordered a Titan 3. However, CM was consistent among everyone I spoke to there that the 51xx steel will perform exactly the same as the 68xx steel, no difference. Perhaps in a straight-up racing application, but they didn't even use that qualification. Its not much more money, so why not, but according to CM, you don't get anything for the extra money.

Regarding valve lift, I am having an engine development company in Michigan do my cam upgrade installation and tune. I was told that .620 and above is where valve train distress is introduced. I'm not certain I understood his explanation, but I thought he was saying above .620 the rocker arm begins to be pushed slightly off center. I could be wrong on that.

I hope this is helpful to those investigation LS Cams.

BigVette427

I believe the LS7 valve tip geometry starts to become less than ideal around .645" and even less ideal over .660" of lift. Generally, stay below .650" and you should be fine.

MTPZ06

I've seen .630" - .635" reported as becoming less than ideal (rocker wipe is outside of the center ~1/3 of the valve stem tip).

Bad_AX

You have to be cautious about the veracity of this kind of information. I would like to know how this .630" - .635" maximum lift with stock LS7 rockers was determined? Over at Speedtalk late last year there was thread relating to the LS7 valve train, and RW TECH an OEM Racing Program Manager from Detroit posted the following regarding LS7 rocker arms:

"The stock rocker has a peak valve lift (by design) of 0.6567". After that, you get into a tighter radius on the slide surface and that'll cause fits. Of course, this assumes all dimensions like valve tip height are where they need to be. "

This assertion also agrees very closely with the max lift of .660" for the Katech 501 cam, and I would dare to say that Katech has had very a very close working relationship with GM and would be privy to such technical details or would have derived them through their own testing.

http://www.speedtalk.com/forum/viewt...0e1eca4503e66f

MTPZ06

Could be we're speaking about two different view points here. Will the OE rockers work at those lifts? Yes, they most certainly will...and many do so regularly.

I'm not stating that the OE rocker has a "max lift" of .xxx"...I'm saying, does an OE rocker arm exhibit an "ideal wipe pattern" at those lifts (above ~.635")? Ideal meaning that the rocker arm pad never scrubs outside of the center 1/3 of the tip of the valve stem. I have seen evidence to suggest that isn't the case. That's also why we're starting to see cases of "fixed" heads and "high lift" (~.650"+) cams showing up with worn out guides again (in a hour-glass wear pattern) from side-loading.

That's what I'm trying to convey.

Bad_AX

I believe I understand your position. Keeping in mind that the stock max lift is .593", I would opine that anything much over this is going to result in a greater contract area, and perhaps more "scrubbing". One thing we don't know as owner/enthusiast is the designed geometry of the system and how much roll vs. scrub is designed into the system at .593" lift. The stock design does not allow any adjustment in the position of the rocker arm, and any increase in lift is achieved by pushing the rocker arm pallet a greater distance from the same starting position vs the stock cam. If the rocker arm geometry could be accurately modeled, it may be possible to optimize the contact area by slightly adjusting valve stem height with custom lash caps and stem adjustments. This is the stuff of race engine builders, and you would have a tough time finding anyone willing to do it and at a cost any of us would accept. The Toyota NASCAR Cup engines are designed to use lash caps to maintain correct lash and do not use adjustable rocker arms. Of course, the position of the arm in the TRD Cup engine can be changed via the shaft support system. For the LS7, the 9-pound hammer fix is to just ditch the OEM system altogether and go with high-end shaft rollers, but this comes with a whole new set of challenges. With rollers, we always see the seat and open pressures go through the roof, and few of these systems have been tested for stability throughout the rpm range. Anyone who thinks that these big spring pressure and roller systems are going to be low maintenance is kidding themselves.

There is also the reality that the OEM rocker arms, due to manufacturing variation, rarely have ideal contact between the rocker pallet and the valve tip regardless of valve lift. Looking at wear patterns on rocker pallets often shows very uneven contact which results in increased friction and uneven valve stem loading. Many of the rebuilt heads have combined the OEM CrN coated intake valves with bronze guides which a recipe for rapid wear of the guide due to the incompatibility of materials and coatings. Bronze guides play nice with stainless steel and Moly coated Ti valves, not CrN.

If a guy wants to drop a big lift cam in any LS engine, increased maintenance and rebuild cycles come with the territory. For some reason, the LS7 guys want to have big cam power and 100,000 mile durability. If the owner wants high mileage reliability, better to say under .620ish lift with endurance type lobes. Everything is a compromise.

-Scott

vertC6

From my un-scientific observations over the last 10 years it seems the high lift cams are going to wear out the guides regardless of the wipe pattern of the stock rocker. Michael D did some testing that showed anything past .660 began to slide to the edge of the stem, but even before that point you are still to the bottom 1/3 of the tip which in my opinion is causing a lot of the guide wear issues.

For me, I wasn't going to go past .610 because the risk wasn't worth the extra few ponies. I went with the YT rockers, and so far so good at 3k miles. I plan to check the wear at 20k miles just to see how they are doing.

vertC6

Great post and oh so true that there is compromise with everything! I played around for days with my Yella Terras just to make sure I had the right contact point on the stem. I had YT send me an extra set of shims just to get it perfect.

MTPZ06

Agreed. I do feel a roller setup would be more ideal if there were enough testing data available. Part of the reasons I stayed with a stock cam and OE rockers.

Precisely why I chose the MS90 guide material...and I hope over time we will see more and more conclusive data on its durability, even if utilized in "less than ideal" setups.


Exactly...awareness is key. Again, its certainly fine to run a .660" lift cam with OE rockers, but expect to perform periodic maintenance. That's the trade off that many don't seem to be aware of. They think "fixed" means fixed once the heads are done; but it really does depend upon their own individual application. I think even Katech recommends a spring refresh every 20K miles with their cams.

lamboworld

I just bought a cam motion cam for my new build and I went with a .650 intake lift and a .652 exhaust lift.

I have been running a .650 lift in my AI rebuilt heads with CHE guides over the past 5,000 miles and my guides had no wear. I had Phil at AI check them while I had my engine apart and the guides measured the same as when he put my heads together.

cv67

Surpised GM even offers warranty with any .600 lift cam!


driving style & expectations has to change...most complain of a low rpm suge after they put thier too big YUtube cam in still have a stock gear too. They blame the cam....

If you need crazy lift and duration go straight to a solid youl be changing springs anyways

corvettenutz

What about truing up the factory rockers?