lusting4ls1

iTrader: (15)

Is that combo a guaranteed recipe for 500rwhp? And still have a good torque curve and good street manners. It would be a lq4 408 or 414 (4.060) in a m6 ta.

Could this be possible on stock castings or would they have to be ported?

DietCoke

iTrader: (18)

You can make those numbers on a 376ci stock ls3, so yes.

the_merv

iTrader: (88)

Lot of variables here too...I've been messing with the L92 Heads for a while and been researching them and gathering information.

One thing I have gathered is these Heads like a minimum 4.06 Bore..anything smaller and it's shrouding the Chambers. They just seem to like a bigger bore.

redtan

iTrader: (5)

It's probably easier to make that kind of power on a 4.065 bore based 376ci than a 4.030 bore based 408 with LS3 heads.

Although I still think a 408 with LS3 heads and the right cam can make 500rwhp.

lusting4ls1

iTrader: (15)

So they wouldn't perform too well with a 4.030 bore?

lusting4ls1

iTrader: (15)

I'm thinking of going for a 4.060 bore anyhow as long as the block test good.

lusting4ls1

iTrader: (15)

How about rockers? Can I use stock ls1 rockers with these heads? I've read something about the intake valve being offset?

DietCoke

iTrader: (18)

Nope, youll need 8 intake rockers for the offset intakes. exhaust rockers are the same

george g

iTrader: (12)

My 408 with SDPC ported ls3 heads made 506/468 at only 5800 rpm with too weak of a valve spring, slipping clutch and a stock ls3 intake and a cam designed for a ls2 and 243 heads. So with the right parts it should definetly make over 500 in a fbody.

lusting4ls1

iTrader: (15)

Thanks George that's what I wanted to hear.lol

What rockers are you guys using with these heads? Also is PTV clearance a problem with these heads and a decent cam running 11:1???

george g

iTrader: (12)

Ls3 intake rocker ls1 exhaust with comp upgraded trunions.When you roder your kit make sure you get the pistons with the ls3 valve notches and a big cam will fit.(with in reason still need to check) My cam is a 231/242 617/615.

KingPin1094

iTrader: (12)

I know this is an oldish thread, but i just wanted to ask. What kind of MPG do you gues get with the LS3 top end making 500whp? and where does your torque start and end? im thinking about switching to rect port.

rumblebox

iTrader: (9)

dont forget the passenger valve cover too. the LS1 valve cover wont work unless you cut out the PCV baffles.

the_merv

iTrader: (88)

These Heads have a Chamber Bore of 4.060. Any Bore under that size is shrouding the Chamber. That and with the large Valves when you open up the bore and get the Valves unshrouded it helps with the cumbustion process.

A good Cam with some good Compression is key to any engine..these Heads work better with larger bores tho.

low2001gmc

iTrader: (148)

Disagree ^^^. My LQ9 with its stock 4 inch bore and Me Ported LS3s is capable of 11s n/a with 11:1cr, off the shelf cam and ported l92 intake in a truck at that. i will never go back to 243s.

rumblebox

iTrader: (9)

Granted, 823's work best with bigger bores. But an LQ4 with .040 gaskets and LS3 heads is a very inexpensive way to make an *** load of streetable power. I don't regret anything about my current setup....except the pacesetters, but those were temporary replacements after my QTP's got cut in half by a flexplate.

the_merv

iTrader: (88)

You disagree with my statement that these Heads work better with a larger bore?

And when you say "is capable"..do you have times or a reference point of sorts? How much power is it making?

Jadedbird

iTrader: (27)

I just picked up some 5364 heads.
I still nee rockers though, so will LS3 rockers be fine (offset)?
I am contemplating a 408+ ls2 aluminum block with those heads and a ls3 intake.
Im looking for 450/450 streetable and reliable.
Im picking up a shortblock and getting the rotating customized to my liking.
What compression would this work best with? 11:1? 11.5:1? Id like to remain about the 20mpg range

30th t/a

iTrader: (51)

what cam are you running? and did you have to flycut to get 11:1?

thanks

low2001gmc

iTrader: (148)

YES i disagree with your statement about shrouding and giving the impression to others that they wont work well with anything less than a 4.060 bore. Everyone is entitled to an opinion but too many stock bore 6.0s with ls3/l92 heads out there that are making lots of power.

11.90s in a heavy truck. would be much faster in a car. Not dyno tested as I dont like dynos as they vary from type to type and stalls among other things affect numbers.