MTPZ06

Solid or hollow stem?

~STOLEN~

Sorry bout that

Hollow

LPE did a port job , decked heads .010 , guides and valves all at same time for me last year
Cam is 660/670. 236/256. 111lsa

MTPZ06

Wow, and you were getting float as low as 5800 rpm?

~STOLEN~

Yup
Here is the last run when they were floating (blue)and the 1st run after springs were changed (red)

I don't have a pic on the final graph but this is a pretty good representation

handyandy1496

Your right about having more in it because you took too much off the push rod length. You forgot there is a 1.8 ratio rocker in between. Your pushrods only needed to come down .033 to allow for the extra .060 on top of the valve. You now have .050 less lift than your cam card says it is and a little less duration as well. lol. No wonder your low end is better. It all makes cense now. You should get your old launch back with a lot more on top. probably a high 9 sec pass is in your future. GL

rsigue

LSxhotrod

I build one LS7 with GT21 and Ported stock heads, car made 597whp.

irok

you don't need to change push rod length when you add lash caps.check with an engine builder

jayyyw

Did you measure or are you just guessing?

rsigue

Definetly measured, by a ls tech, didnt want to take a chance since LPE wanted to cut the valve stems, to put lash caps on... We just adjust the push rods to the right length...Damn sure no guessing here too much too loose with this motor,,,, Was not gonna take any chances,

rsigue

Change push rod lengths and made a 2nd dyno secession solved a few issues, with push rod lengths and minor stuff.... Horsepower picked up 12 more ponys and torque picked up 30 more lbs...

jayyyw

Nice jump. Should feel much different

BigVette427

I know the OP hasn't been back since he last posted just under a year ago, but I wanted to make a couple of observations for the benefit of the forum as I apparently missed this thread when it was fresh.

This is something similar that the tech rep at Johnson lifters was telling me about their SLR, Slow Leakdown Rate, lifters. He said something like how the slow bleed-down lifter described the ability to maintain lift without collapsing, or the repeatability in the common rotation of the cam. When GM was selecting lifters for their COPO Camaros, they tested Johnson's SLR lifters alongside of GM's LS7 lifter, and as well as those with other lifter manufacturers. He said that the Johnson lifters maintained their lift 95% of the time compared to the LS7's only maintaining their lift 50% of the time. He described what this essentially meant like this, that if you had a .630" lift camshaft but if your lifters bled down .030" as the lobe of the cam rotated, you were essentially only be getting .600" lift out of your cam. The right lifter and proper pushrod length are often overlooked but are crucial to making big power.

Good luck with a GT21 camshaft and their LSK lobes lasting 36k miles; those lobes are overly aggressive and wreak havoc on your valvetrain, especially when used in the upper RPM bands. You just don't need big lifts on your camshaft in an LS7 to make good power; (.635" to .650 is fine,) unless you are really building an all-out max effort build. You went from EPS valvetrain friendly lobes to overly aggressive LSK lobes for less power on a dyno and a .10 of a second in the quarter? The takeaway here for others is do your homework and educate yourself about your cam on more than just the common specs, ask your camshaft manufacturer about the lobe profiles and what they were designed to do. There are lots of different lobe profiles out there that have different goals.

I've been wondering about this specifically, on average (because there are tons of variables) what RWHP numbers equate to what sort of times in the quarter mile in these C6 Z06 (and (n this case, other C6 Corvettes.) I would wager that low tens on street tires would usually require rwhp numbers closer to 600 and beyond for that to happen.