NC98Z

iTrader: (1)

The old big block Chevy had 2 types of heads. Oval ports that were torque heads and the rectangular ports that were high RPM heads. Thats the way I figured it would be for LSX motors too. However if you have a 6.2 LSX motor that can pull a truck around with no trouble. It would be a killer motor in a Camaro just the way it is.

ExTurbo

Naturally the bigger bore has an effect on the size of the runners/valves. i'm no expert on runner sized and velocity and all that but i do know theres a difference in tuning/intake manifolds etc that help get more low end tq on these trucks. again though the 6.2 makes a big difference in the way the car/truck makes power compared to the 5.7. no the cubic inch difference isnt that great, but the size of the bore has alot to do with head selection and how streetable certain cams are going to be.

My take on it is this, a smaller runner/cumbustion chamber (for higher compression) and a decent siz comed cam (under 240/240) can make for a great all around track/street car with over 450whp without much trouble (hell ive seen cam only LS2's hit over that). In just about any car (even a 6 speed GTO) this is good for a 10 second pass. IMHO theres no reason to go with the large runners unless your over 400CI and looking for well over 500whp. Ive seen some great numbers from 5.3 heads or ported 243 castings even . cam selcetion is key as well as a good tuner. And i know its been said before in this thread but matching the cam to the heads is probably the most important mod selection, but you cant leave out headers and intakes as keyponents to making torque and HP.

66deuce

iTrader: (1)

i understand the intake design will help low end,but again it's just not the truck motors..take a look at the dyno of the LS3 in the new Vette,it's on the board here somewhere..
there is is a guy on LS1GTO.com that has the L92s on his 6.0,and only below 1500rpm did he lose any TQ compared to stock..cam is a 226/230,114lsa ground specifically for those heads..he ended up with 450+rwhp and about 415rwtq..
trust me,i'm in the smaller runner/ more velocity camp here..but what i have seen in the last month or so on here and LS2GTO.com, is that there is a lot more to this than runner size..hell,there's a guy who just swapped his 243s for L92s,retained his stock cam and lost nothing on the low end..the only other mods were headers...
anybody else have any thoughts?

JS

iTrader: (4)

Funny I made this post and have to agree,in the last 3 or 4 weeks my thoughts have changed.

It looks like the L92 is really pretty good on a 4in bore even with the 3.62 crank.

Duece is right,the guys with the 6.0 GTO's are making killer power with these heads and fairly small cams.

66deuce

iTrader: (1)

thanks JS,
right now i think it would still be more cost effective to run ported 243s on most street applications,but this will probably change in a few months..
when L92s first came out i scoffed at them for anything under 400 ci.
but the more i learn,the more i find out how much i really don't know about motors..
i do know that the right cam is needed to make these heads work,the VEs are a lot different then the typical performance LS1/2/6 cams..

badburban

I've been in the smaller runner camp for most of my hot rodding life. I still believe/preach it too, but I have learned alot in the last year or so. I worked at Ford and did a lot of intake port development for the 3.7L V6. I shrunk their ports down significantly from the sewer pipes they were and still made 315hp and 290 lbft (4k rpm with 280 on tap from 3k-7k rpm). But they were still huge by my standards. Dimensions were still huge x wide for my old school SBC brain to get a handle on but the flow numbers and power numbers were impressive. I guess what Im trying to get to is one of the most important things to focus on is area development, its not just about volume or size, but you gotta remember area development is huge. Large expansions or contractions can kill air speed and tuning effects quickly. GM seems to have nailed that. In fact I picked up a set of L92's myself for a future 408 build.

LSwonderfull

Ok im working out a set of L-92's for mi 402 build and here is mi take.
The cathederal shape of LS1 heads were a packaging design not ideal velocity shape. The rectangular runners of L92 and all the higher flowing heads is closer to the engineers blueprints. You have to realize when flow volume is higher at all lift points the larger volume of these style heads is not the problem normalli associated with big ports . To compare max flow of different heads is not the whole story, fill that larger port with higher flow at each lift point and you end up with a smooth more powerfull and efficient head. Let go of traditional SBC rules, look how much larger cams are nowadays even for street LS builds. The LS bends mani traditional rules, and all in the name of more power.