valve size ?
 

okay I am buildin my LS head I read awhile back in ht magazine that on the gsr head you only need to over size the intake valves. My question is would this theory also apply to the ls? What it be okay to run stock ex valve with the larger intake? thanks for the help.

Re: valve size ?
 

Why even bother oversizing the valves on an LS head? A cam in a b18a1/b1 head would produce better results. Besides, if you want to rock it all-motor, you wouldn't really bother with an LS head anyways.

Re: valve size ?
 

not all motor, big boost I am tryin go as big with the ls as I can. ---- All-Motor

Re: valve size ?
 

bigger valves arent really needed, good springs and retainers with fat cams and an aftermarket intake mani. is all you need for head parts on a big power ls motor, if you want to make real big dog power save the money you would spend on a bigger valve job towards sleeving the block and a big ass turbo, or if your a baller then ---- it go +1mm on intake and exhaust sides, and get a gt40R ......

Re: valve size ?
 

I am sleeving the block. I gotta figure out what rod and piston combo to go with next. So stock valves will hold up under the pressure of the new spring I have heard of the crower springs braking stock valves I just figure if I need to replace them why not up size

Re: valve size ?
 

I'm not saying to run your stock valves, I'm saying just to stick to your stock valve size. A big lift cam is going to make up that 1mm difference in the valve size at high boost. But all in all, hope you don't plan on revving over 7500 rpm on that head, unless you have a plan for keeping the rocker arms from flying off.

Re: valve size ?
 

Bump the LS intake valves up 2mm to B16/GSR spec if you really want to, or just buy a P8R casting that comes with 33mm intakes, but the big hold up is the cam situation. You can make good power with stock LS cams, but the stockers really do suck. Cheap Delta regrinds will give you more midrange and top end, better spool, etc.

Don't go over 33mm intake valves unless 84mm bore, and even then I don't see any difference. You pick up a cosmetic bump in VE, but VE is both bullshit and expensive. Follow closely. Say in this example you have 31mm stock LS intakes vs 33.5mm OMG JDM oversized intake valves as per HT (Honduh-Tech?) magazine's build:

- Your turbo's compressor flows 500 whp worth of air. You can hit 500 whp on 31mm intake valves, and 33.5mm intake valves don't allow you to make more than 500 whp. Why upgrade?
- You make XXX whp at 2 psi less boost with the 33.5mm intake valves, and your pump gas knock limit is 380 whp instead of 368 whp. Congrats on the higher hp-per-psi thing and the 12 whp higher ability with pump gas. It cost you a couple hundred for valves, oversized seats, machinist's labor, and port work to meld it altogether smoothly. You daily drive at 10 psi/235 whp level, have zero traction past 330 whp, and are scared to beat on it too much at the 350whp level because, well, it's pretty close to knock limit, so you just dump in racegas when you crank the boost controller. Awesome spend of a big chunk of money, right?

One thing I'll disagree with, you can spin LS head to 8K unless there is funny wear on the rocker arm ball seats. It's past 8K, with a good head, that they start flying off. TurbodEG has revved his to 8500+ and not had any problems, but that dude was seriously lucky. :l

Re: valve size ?
 

Ehh, I've seen a few LS heads take 8k once and while, and sometimes by accident, but I honestly don't trust the design for anything much higher than 7500 reliability-wise. Especially when alot of people don't check their valve lash as often as they should. :l

Re: valve size ?
 

I've known people to have problems, but those are the rides that like to pop the rockers out of the ball socket when you're tightening down the nut during valve adjustments. I agree, it's not a great design, but if spring and cam profile are of good quality then the harmonics that have a part in rockers flying out are muted or shifted to a different (higher)frequency.

liveforphysics Luke sent me a link to a site that has all sorts of slo-mo video of valve train in action. It's pretty crazy how the springs cycle/flex a couple times per valve event from the harmonics.

Re: valve size ?
 

okay now I understand a little better thanx for the explanation. I'm just gonna stay stock valves this is what I'm gonna do then Skunk2: Im,dual springs,reatainers,delta cam regrind, a full race p&p on the head I'm tryin to figure out the cheapest way to go about a bigger tb also. I think I might just through the head on a stock bottom end and see how much I get be fore she blows