Scott-EP

i just got a good deal on an LS block and it got me thinking. i know you can rev the ---- out of b18c's and b18c5's. do i have to do much to my LS to be able to rev it like those. i plan to build for 15psi daily and 20psi on occasion, but i would also like to rev it if needed or if it makes power up high. does anybody know the weak link between LS and gsr/itr?

BigBird

Rod bolts, rods, no block girdle, oil pump, and the head doesn't flow anything close to a b16 or b18c head.

Ogubudiah

rev it to 7k and enjoy the long stroke

88dx

Id say the weak part of a LS is the Cams/valve springs. I have a set of re-grind cams in my LS and it makes a huge diffrence, I now have a bent valve because the stock springs didnt like the cams and 8,000 RPMs.

Im sure JD will chime in and tell you everything on a LS is golden :P

Scott-EP

so, with balanced h beam rods, arp bolts and a gsr/itr oil pump could i rev it to 8k?

Tom-Guy

The weak link is the rocker arm design - they are not retained by a shaft and are prone to go flying off at high rpms a la SR20DE(t). The SR20 boys have an interesting widget that limits rocker motion and helps hold them in place, we don't but it doesn't look difficult to fab, but I'm pretty disinterested anyway *yawn*.

Long story short, if you have one or two or more rockers that like to pop out when adjusting valves, those are the ones that will be wanting to pop free at high rpms. Replace the seat and arm combo with a different unit and reap the goodness. Nice middle of the road NA cams and stiffer springs (turbo cars like stiff, NA does not) and rev to 8000K with power increasing all the way there and you're golden. Most decent cam setups will leave you with ability to make power at 8500+, and most LS heads will do 8500 all day long, but you've entered the territory where the rocker arms start flinging free on some people. 95% of the time you just "lose" a cylinder and have to fish the rocker back out, and reinstall, and everything is peachy. Sometimes it gets wedged in somewhere and munches some bits, usually pretty cheap to fix although you sometimes need a diff head, but there is a chance you'd drop a valve and toast the motor.

You're either completely wrong or none of those things matter anyway, I forget which. Seriously. I just don't feel like all the typing it'd take to correct you.

Scott-EP

thanks for all the info. that is pretty interesting stuff. the head isnt going to be a problem though. i plan to put a vtec head on. most likely a b16 head. i hear they are the best and i dont have the money to do my own testing on that so i will hope for the best

Tom-Guy

I hear hp/liter rules, yet big displacement RWD V8s with live axles still rule the street. Shows how much what you hear is worth. But, they have a point, if you're shooting for over 750 whp, or want a ****** NA engine that is death slow, you really should get rid of the poor flowing LS head.

B16 head flows exactly the same as GSR, people keep handing out Alaniz flowchart that shows OMG 1 CFM!!!11 difference for a very tiny portion of headflow vs lift graph like it means anything. Anyone who knows anything sees two lines drawn over top of each other. B16 doesn't have the straight drop down on the backs of the intake valves, the port bends and that causes turbulence, so the flow quality is worse than GSR, yet you "heard" B16 is better so I must be wrong. God, it sucks to not know what I'm talking about.

LS bottom end, all stock parts, isn't going to want to rev as high as the B-VTEC stuffs, but 8500 is not a problem if you remember you can fold rods compression downshifting just like B18C at 8500+, only a little easier. Big ends on the B18C are overbuilt, there are no rod bolt problems on LS they don't spin bearings they break across the beams, but you also "hear" that LS rod bolts suck. Girdles don't do anything but suck power, you never see one on a big power build at the top tier level; the block and crank likes to flex a little and isn't going to break from the flex, at the 500 whp level there's 10-15 caught up in a girdle holding engine straight which materialises to heat/friction in the bearing area. Just let it flex.

Everything is a trade off, have you heard that before? For a compressor-limited situation (turbo engine) the turbo dictates how much power you make, and until such time as your stock head restricts things (750+ whp, like, OMG) then there is no reason to run a V-Tec head. However, you can run one if you want, just be aware what the trade off is. Your trade off is money to get approval when you pop your hood, in which case you need to be posting engine bay hots to HT's Appearance forum.

88dx

Id say a LS head and GSR head are around the same price. After u buy cams and spring for the LS its about the same price and results.

Tom-Guy

Strange, I have a lot less in an low overall milage + 8K since machine shop cyl head with Crower billets and valvetrain than the run of the mill high mileage half slopped out GSR head that needs to go off to the machine shop sells for.