Haans249

iTrader: (24)

The guy i talked to said they have a 253 and a 255 as well on the XER, but he said they would only run to 6500 rpms "or it'll destroy the valvetrain"...phhhffff...whatever...haha. The guy I talked to was a real jackass when I asked if there was anything larger, so much so, that I just hung up on him lol.
I think I'll stray away from the solid lobes, i don't want to "destroy the valvetrain".

crb99ws6

iTrader: (7)

Mine is hydraulic, pulled to 7000 no probs with stock rockers and crane 99893s.

SLED28

iTrader: (7)

Too much lift for 1.8 rockers and stock LS7 heads.... They only flow up to 620 lift then die... ALthough with the intake on, its not as drastic at .620 lift and higher

Haans249

iTrader: (24)

Dave has a valid point, just dig up that flow graph that Katech posted. As far as your cam, you'll have to post dur's at .006/.05/.2 so I can compare/contrast lobe styles.

I'm looking at something at 242/255 now..."its going to rip"

DAPSUPRSLO

iTrader: (14)

http://www.speedtalk.com/forum/viewt...161&highlight=

Have a look here. I don't think reducing lift on the ls7 head will do anything but cost you power considering your valve train isn't going to see .620 lift or whatever gross lift because of deflection anyway.

"its like the old NHRA SuperStock Rules/ Cylinder Heads
back then, a typical unported Legal SBC Heads usually stopped
gaining Flow CFM on a FlowBench, at and above .450-.500" Lift,
yet,
everyone found much more HP using Solid Roller Cams
with .660 to .740" Lift" A quote from Larry Meaux on that subject.

I don't think the ls7 head does anything that drastic past .600 that would cause you NOT to lift the valve past .600.

http://www.compcams.com/Technical/Ca...obeCatalog.pdf

Have a look in the comp master. They can put just about any of the roller lobes on the ls1 core cause it's so damn big compared to everything else. Just cause it doesn't say "designed for ls1" doesn't mean it can't be used on an ls1.

For instance, the extreme marine roller hydraulic lobes go all the way up to 278 at .050 and being their designed for the heavy big block valve train and you want to use a 1.8 rocker they may work very well for you. Not 100% posative but I bet they can be put on the ls1 55mm core.

Lots of morons that work at comp, and some geniouses as well. You kind of have to get lucky if you're not an engine builder to get through to the right guy, ha.

SLED28

iTrader: (7)

How much deflection do you think it loses with Morel lifters?

I have many times put BBC lobes on LS1 cams, and other small blocks....And Haas and I looked at every lobe in the catalog the past 2 weeks trying to get this 101% right!

Dave

Haans249

iTrader: (24)

I remember you mentioning this before, and the fact that you're running some damn high lift despite the fact that your heads "stopped" flowing a while ago.
I have been thinking that the reason why people find so much more power with the higher lift is the amount of time spent at that particular lift point, because if you stop lift at say .62, when your heads reach "max" flow, then you only hit that lift point once....BUT, if you run your lift to say .67, you're going to hit that point of maximum flow twice, and for more degrees of dur then just touching it on the nose. Thats my theory behind it, but thats just based on what I THINK is happening, and not substantiated by fact....lol.

SLED28

iTrader: (7)

Also we are trying to keep the valvetrain light so the beehives we picked are good for just under 700 lift and with the 1.8rockers, there's not much to pick from... We do want other specs, but couldn't fit it into the overall setup...
Dave

crb99ws6

iTrader: (7)

Here's the rest of the cam info.

Intake Lobe
Duration @ .006" - 306
Duration @ .200" - 164

Exhaust Lobe
Duration @ .006" - 316
Duration @ .020" - 295
Duration @ .200" - 166

LSA: 113.5 CAM DEG
valve overlap: 35.8 CRANK DEG

Haans249

iTrader: (24)

That would be a horrible choice for cam lobes. The intake lobe is WAY too big, and to top it off, the dur at .2 is pretty low for being a .657 lift lobe and a 257 dur at .050. Wtih the XER, you can have 165 at .200 at a 242 dur and have a MUCH lower .006 dur to BUMP WAY UP your DCR. These lobes look to be poor performers, they just seem to be pretty slow.

Beast96Z

iTrader: (21)

The lobe he chose is still close to the same ramp speed of an XE-R, but it must come on later. Were the XE-R may jump off the seat fast, his may jump from .2 to .4 faster than the XE-R. It's just one of those things about cam profiles. Maybe saying there slow off the seat may be a little better than just "slow", because it isn't. I agree that it's a bit big for a 402, but it may be helping a bit seeings how the ET 245's he has are intake crutched.

SLED28

iTrader: (7)

Now this is some good LS1Tech boys! Keep it up!

Abdullah

iTrader: (2)

how to calculate DCR? any one can tell me?

also what is a good cam choice for a NA LS7 427 with ported LS7 heads and intake? i mean i want to know the specs?

thanks.

DAPSUPRSLO

iTrader: (14)

Haans, remember that your 1.8 rockers will make the lobe faster everywhere in comparison to something with 1.8 rockers. I would certainly think you'll have to pick a slower lobe for your valve train to work with any kind of higher rpms. My lobes are not meant for a huge ratio rocker that I have by any means, but because I run a solid cam I can throw lots more spring pressure (250/700ish) at the setup to control things. also, I have titanium valves and in the big picture 7500rpm isn't a whole lot.

As far as deflection probably not a whole lot. Hydraulics don't have as much according to what i've been reading and discussing with others. Maybe .010-.015 or so. That is also assuming the morel lifters don't give any thing away in translating the true shape of the lobe to the valve (that is they don't allow the pushrod to travel farther in the lifter then their correct function when oil body is locked out would dictate or pump up when traveling over the nose of the lobe).

As far as the lift thing I tend to agree and THINK the same thing. Many others that i'd consider "in the know" believe the same thing and it does make good sense. More duration at higher lift points being the point with higher lift cams generally.

SLED28

iTrader: (7)

SLO, but Andy's just make 600rwhp (440ci/GM LS7head) with a small cam and small lift not hitting those big lift's. Probably .625 lift.....

DAPSUPRSLO

iTrader: (14)

But how much would he make if he had .670 or so lift with a valve train that can control it? That is the only way to compare anything i'd think. Don't get me wrong, you don't need super crazy lift to make power, but I think you'll gain power by increasing the lift in 80% of circumstances granted your valvetrain doesn't loose the ability to control the vavles.

SLED28

iTrader: (7)

I just feel its easier on the valvetrain if you run .625 vs .675 lift, especially with a hydraulic setup... WHats the most lift you have run in a Hyd roller LS1 succesfully?

DAPSUPRSLO

iTrader: (14)

.651 via a 239 at .050 lsk lobe. Had comp 921 springs shimmed to .050 from coil bind.

Yeah, if you're going to keep everything hydraulic less lift will probably work better when considering the valve trains ability to control things. Good luck with that setup, look forward to hearing about it in the futuer!

SLED28

iTrader: (7)

Me Too! I think haas will go solid roller next year as its quite a bit more expensive... What companies have adj rockers for the LS7?

DAPSUPRSLO

iTrader: (14)

I'd contact ET performance on that one. they can probably point you in the right direction in regards to rockers. i'm sure jesel is working on something if they don't already have something that will work.