Patrick G

iTrader: (14)

The Gen IV rectangular port GM heads really respond to lift. This has been proven time and time again. But instead of a cam swap, I wanted to see how much power I would pick up just by swapping some higher ratio rocker arms to increase the lift at the valve.

The test engine was a 2009.5 G8 GT with a 6.0L L76 engine with active fuel management (DOD). All AFM motors are saddled with a very small 200/208 .472/.474" 116LSA camshaft. The 1.85 rockers would effectively increase the lift at the valve from .472 to .514". This small but noticeable increase in lift will get the large intake valve further away from the cylinder wall plus into a position where it flows more air. Effectively my engine now has a 200/208 .514/.516" cam.

For those who can't read the dyno chart, peak power increased from 342rwhp to 355rwhp (a gain of 13rwhp) and torque peak increased from 355rwtq to 362rwtq. Interestingly, both the power and torque peaks with the high ratio rockers occurred at lower rpm, but carried the power better at higher rpm. This helps pump up the overall power under the curve.



While this is a very easy mod to install, it does require a couple of other items. The heavy solid stemmed intake valves of the L92 heads did not like running the high ratio rockers with a stock valve spring. We ran into valve control issues at 5400 rpm with the stock springs. We swapped some Comp 26918 beehive springs and the curve was beautiful. The Yella Terra rockers also require a longer 7.450" pushrod to keep the valvetrain as quiet as stock.

So if you're looking to gain 13rwhp without swapping cams, the Yella Terra 1.85 ratio rockers are an excellent way to boost the power of your L92/L76/L99/LS3 engine without opening up the motor.

Damian

iTrader: (89)

Good info Patrick.

I just put a "New Era/FTI" D.O.D. cam in a G8 a little while back, but deleted the D.O.D. anyway so there's no restriction on lift with those lifters. Maybe I'll suggest these rockers and see what we can squeeze out of it. The DOD cam is only .575 lift.

Jason 98 TA

iTrader: (4)

Interesting results Patrick, I didn't see anywhere near that kind of gains with 1.85 rockers on the engine dyno.

94 guy

iTrader: (125)

that's odd

gtodoug

iTrader: (1)

I like the writeup patrick. Can you say how much the rockers are and the part number?

I was thinking about something like this for my 09 G8 GXP. I wanted to keep stock manners 100% and not lose one ounce of driveability and no real noticeable noise increase. I have heard that the Livernois Stage 1C cam gets close to stock driveability with it's 219/228 .60X/.59X 118.5lsa. I just don't want to sacrifice anything with this car.

I am hoping the rockers make a strong improvement. I was hoping to see more power from idle to 4000rpms, but like you stated it is good to see it pulling strong to redline.

Any cam suggestions would be great if you think the dollar/hp isn't worth it for those on the fence about a cam.

Patrick G

iTrader: (14)

Were you starting with a low lift .472" L76 cam or a .550" LS3 cam? If you started with a low lift cam and didn't gain much, that would surprise me more than if you started with a high lift cam and didn't gain much. There will be a point of diminishing returns at some point.

ChucksZ06

iTrader: (9)

Patrick. Do you think the heavier nose wt of the roller rockers conributed to the valve float at all?

Patrick G

iTrader: (14)

The YT rockers are not heavier over the nose than stock. It's asking the heavy valves to accelerate faster than what the stock springs can handle that leads you premature valve float.

BLOWNBLUEZ06

iTrader: (17)

I think it's more significant that you gained power almost across the board rather than giving up some at lower RPM's in exchange for more in the higher RPM range. That impresses me more than just a peak#.

Pwebbz28

iTrader: (31)

Wouldn't the rockers also change the duration since you are effectively make the lobe bigger from .006 all the way to max lift?

PREDATOR-Z

Interesting results, same day back to back?

Yes, by a very small amount.

kinglt-1

iTrader: (26)

Nice results. Im suprised no naysayers, since everybody use to say the slp 1.85 rockers was a waste on the stock ls1 for the cost. "Might as well go with a cam swap".
However I have been extremely satisfied with the 1.85's on my car, especially since they cost me nothing!!

Patrick G

iTrader: (14)

1.85 rockers on an LS1 will not give as much of gains for several reasons.

1. The LS1 is smaller than the 6.0L
2. The L92/LS3 heads gain more flow going from .450" to .500" lift compared to the LS1.
3. The L76 runs and even smaller cam than the LS1. Any help you give it will show some nice gains.

litle88

iTrader: (20)

Hello patrick, I'd hate to bring this up from the dead a little bit but I have a question for you. I have been asking around and no BIG players in the game have made up their minds about these L99 motors (for my 2010 camaro) and how to cam them. Some say I have to delete the DOD and VVT in order to do it, while others say SURE here is my stage one just get the cam phaser (set to stun) and slap it on and tune it!

But anyways Ive decided to wait until I see what is really working and what isint.

I want to do the YT RR swap and I would like to kmow if I would need different springs?

And would I need new Pr's if so what size would I need?

I would also like to know where you got the 1.85's because I have looked and most only carry 1.8's.
thanks

Patrick G

iTrader: (14)

Most of your questions were answered in post number one (underneath the dyno sheet). Yes, you'll want to replace the stock springs with a quality beehive like a PAC 1518 or Comp 26918. You'll need to run a longer pushrod to keep the pre-load within factory specs (otherwise you'll get lots of clatter).

VVT cams in an L99 are outstanding with these rockers as you'll be able to run a cam that is compliant with both VVT and AFM/DOD while getting your lift into the mid .500s. The best part is, you can do all this in phases. Do the rockers, springs, and pushrods now, then add the cam, cam phaser limiter kit, and tuning later as your budget allows.

litle88

iTrader: (20)

Thankyou

where did you get them? I have been looking all morning and havent found any 1.85 YT's

kinglt-1

iTrader: (26)

Really? Thats weird because I have seen dyno sheets showing gains of 10whp and 17wtq by swapping to the 1.85's on the ls1... There was a thread last summer in here of a guy posting these same results?? Either way I did not pay for them, they were on the car with upgraded springs when I bought it.

94 guy

iTrader: (125)

patg, have you used the ls9 cam in anything? results?

Patrick G

iTrader: (14)

Swapping 1.85 rockers on an L76/L92/LS3 is way different than swapping them on an LS1. The L92 heads really like the lift.

No. It's a weird cam.

94 guy

iTrader: (125)

i saw adm performance made made 20rwhp.