GIGAPUNK

iTrader: (2)

I'm building an engine with a set of Ls7 heads with some custom 1.450" double valve springs that are about 10 percent stiffer than patriot extremes.

The valves are REV stainless steel valves, part numbers X1131 for the intakes and X1137 for the exhaust. They have the following weights. Intake = 117gms, Exhaust = 98gms.

Richard at WHCCH (my head builder) advised me to stay below valve lifts of 0.630", and away from aggresive lobes/ramp rates if I wanted to spin the engine reliably up to 7500 rpm (which I do!). He also sent me a flow sheet for the heads with and withou the intake. I'm using the stock LS7 intake and there is a large, intersting dip in flow above .630" lift when te intake is bolted on anyway. I'm looking at a cam around 293/300.

Does anyone have any experience with stainless valves on LS7s? The valve sizes (and weights) are very comparable to the BBC (but of course the LS has much better valvetrain geometry).

Which lobe profiles/ramp rates are considered too aggressive? I plan on using the stock 1.8 rockers and cadilac hydraulic lifters.

I posted this over on corvette forum, but all I got were knuckleheads saing don't use xer lobes... duh!

Thanks a million for any input LS1tech-ers!

edcmat-l1

iTrader: (10)

Regardless of cam profile, I would be very surprised if it made power to 7500 with a hydraulic roller, and a factory LS7 intake.

GIGAPUNK

iTrader: (2)

I'm likely going to be running a LS6 crank. The decreased CFM of the de-stroked set up should allow the stock manifold to not be a bottle neck until at least 7500.

Robin L

I like your thinking! Your going to see a bunch of guys making more power with less cubic inches. Too many people are selling longevity for the sake of having a big cube combination.

Richard is a smart guy, I would think that he has allready expressed his opinion of the 7500 RPM deal. In my opinion your going to need either lighter components or a lot more spring pressure to run the hydralic rollers and steel valves.

The LS7 heads are designed for tumble. We have seen issues about .700 lift. They will work well in your deal. I also have an LS7 setup and al looking at building a 3.7 stroke and short rod combination.

Robin

blu00rdstr

Not an LS7, but am using Manley stainless intakes on my LS3. I also kept it stock stroke, Callies crank & rods, smaller journals (2"), 376ci. It's using an L76 manifold so I'm interested to see what rpm the power falls off. It'll be tuned and dyno'd tomorrow by Rick @ Synergy. The cam is a custom grind by Synergy also, it's a 224 duration with .610" lift.

Robin L

THe LS7 Manifold should be a bit better than the LS3/L76.

I like the sound o that cam, post up the results when you get them.

Robin

GIGAPUNK

iTrader: (2)

Did you ever explore an upper rpm limit of valve float, on the dyno, with Rick? What are the weight of the ss LS3 intake valves?

blu00rdstr

The LS3 hollow intake valves were 89grams, solid L92 intake valves are 109grams, the Manleys are 119grams.

Higher rpm tuning is postponed until we install a bigger crank pulley. I had belt slip on the dyno at 5200rpm and 14psi.

GIGAPUNK

iTrader: (2)

I was re-reading this article in GMHTP, about Katechs spintron testing:

http://www.gmhightechperformance.com...nce/index.html

Basically they used a PSI spring with a 1.29" OD, 120/360 lbs/in @ 1.8/1.175" compressed height, respectively. They didn't loose control of their solid 98g inconel ex valve (which is the exact weight of my manley ss LS7 ex valve) in an LS7 unitil 6900 rpm.

Same spring with the 71g hollow exhaust valve lasted till 7600.

The article doesn't really mention any specifics about the lobes that were used but the PSI springs that they list are only good for 630" of lift.

Somebody needs to beg the Katech guys to share this same kinda info about Inconel or SS 2.2" intake valves in an LS7. They probably don't deal with a bunch of cheap bastards who can't afford ti intake valves too often, though, so I wonder if they've ever even bothered to test such a set up.