true ^^ x2

Ive been debating and researching as well... Ive been told by "smart/educated" folks that keep saying 243s without a doubt...

I personally may go with some AI 243s... should be close to 500hp

 

https://ls1tech.com/forums/dynamomet...k-results.html

The LS3 heads are awesome, but as mentioned they are better with the larger bore. People are making GREAT power with the 'old' cathedral port heads. I think pat G nailed what you are looking for in that build... and thats through an unlocked auto.

If I was doing heads again I'd either buy new AFR, or go with a very reputable porter like Advanced Induction or Flowtech induction.

 

not sure about the hokus pokus..

but GM puts the ls3 heads on 4" bore from out the factory... I get tired of this talk. They rate the engines at more power too. I went with the L92 heads, and going to mill them .020 with the .040 gaskets. The cam I have will be it, Im not looking to go radical with this setup, but IMO it should walk with plenty cathedral setups, if not out perform them. I actually am building my setup to be able to outrun the bigger bore motors 6.2s!

remember the old tbi vs vortec head debate, no the old heads are better.... yea they make more tq velocity. yes. but vortec was the way to go. On a 4" bore, for the bang for the buck, and the options, L92 might be a cheaper route for equal to more power with less effort.

My cam is pretty big too, its not tame I would say, but if I want to go bigger, like say if I had a M3... I would run the Ls3 heads, milled, about .030-.040... I would then have compression up to about 11.6:1 + and I would then measure and FLY cut the pistons to avoid PTV problems... Put some ARP rod bolts in it. And spin that **** to 8-9000 rpm. with the right valve train..

^^^probably the answer you looking for ^^^^

 

Shrouding or not, Skeet proved Lq9 with Ls3s works awesome. I modeled my set up after Skeets but with a few tweaks of my own more for a daily driver. I wont be going back to 243s. Have outrun 6.2 truck and some 6.2 camaros with my set up. Me happy!

 

i ran those valves ( in red ) i made the valvetrain as light as i possibly could, had it setup properly with dual gold .650 lift springs < i'd get with a engine builder and go with a better spring some with better seat pressure, i say this cause i ended up floating a valve over 7k rpms, we churned out 480+ pulling up to and pass 7k rpm on a dynojet dyno this is with a FAST 102 LSXr intake and same TB you mentioned through a 4k stall. every bolt on imaginable. track ET mentioned higher output numbers then i went with a different bump stick never dynoed it after that, but ran a tenth or two better. guess that'll speak for itself . 7.400 push rods will work i ran them, cam i ran was a 231/239/621/621/113+1 you'll be at 11:0-1 compression. Your stock rockers is the best way to go they're lighter just get a trunion upgrade.


if interested i have my FAST intake fuel rails and direct port system ready to sale just need injectors, i do have 50 # in jectors for it but wont fit with the direct port system. hit me up if interested. even have the altered alt bracket and bolts needed all you need is the water pump spacers and F body water pump

 

Skeet weren't your heads massaged pretty intensely to avoid the 'shrouding' that people are calling bs on?

 

they started off as TSP ls3 heads CNCed, i will say this from what ive seen out there TSP has if not the best they run a close race to the best CNC program for head porting...


then i met a not so well known head porter in Baytown, but knows his **** about porting, we spent weeks porting and bench testing the heads until we got what we wanted, then the heads were setup with the best of best of parts from custom PAC springs to ferrea valves

so to answer your question YES they were! look up Pat Foreman he had his hands on them also

 

comment of the day right there..

Im going to have fun too I cant wait... Me and you both have had Skeet give us the right advice. But more towards daily drivers with reliability.


Hey Skeet I got Brian Tooley Springs, I hope they keep up with my cam, as their .660 on the lift.

 

its not all about lift, seat pressure open/close plays a big roll in how valves act or how long we need them open or how we need them to slam closed


daily driver lol take it for what its worth if i wouldnt have floated one of the valves in my lq9 setup i was just about to put the AC back in it and call it done with just a roll bar inside the cab, but when i floated a valve i went straight to a 410 which then disaster struck and ended up with a 408, damn i miss the lq9 stock shortblock and most of all the 410, i feel it was more powerful than the 408

 

instensly or STOCK form. GM puts them on the 4"bore and if I remember correct the G8 bore is a tad smaller. NO shrouding by GM standards. IMO+

Also IIRC GM makes the square bore heads for smaller displacements smaller than a 4" bore now.