Vortec350ss

iTrader: (20)

Yes they do use them on the L76, but that's exactly why I pointed him to pat g's thread. He removed them in favor of AFR 230's with pretty crazy results. 500 to the wheels in a build that wasn't even 'max effort'.

I don't think they are the best choice for a 4" bore unless they are worked over really well with a 4" bore in mind. My opinion, maybe, but that's what these forums are for. We all hope that people have somewhat informed opinions, but everyone it entitled to them none the less.

If it were me, unless you are willing to put the effort that skeet did into the LS3's, I would go for a AFR230 or the like on a 4" bore.

sleeperlqx

iTrader: (3)

yea, thats the thing.. we are all entitled.

I read that Pat G thread.. but Geez its like he is working with AFR on these deals/marketing... If I went AFR route I would be out about 2Gs per head. my Entire L92 swap is been done for around 1950 total. give or take head gaskets.

When my wallet allows, Ill ship my heads out to AI have them done up for the L92s.

That said, at that point, Ill prob build a 427 or something stupid. So Ill need a way better head than cathedral, and well my L92s will move right over. For a good bit bigger bore than the 4".

So the user really has to think future goals as well, when planing.

I also read another 1 of Pat Gs threads. He himself was saying how well the L92s setup was he slept on them, and it was a super stock build, unmilled etc. and I think he put down almost 500rwhp as well, by NOT using the AFR heads. On a Ls2 build that was down compression after the swap!

rpm620

Wow it's been a while since I've been on this site.. I completely forgot I posted a thread here.

I've learned more I the 3 pages you all have been talking then I did in on ls1 tech..

So I talked to Texas speed performance and gave them info on the lq9 and what it was going to be used for and also where I wanted my power band as well as max rpm and my power goal of 450-500whp thru the t56.. The following is what they spec'ed me so I would not have to flycut the pistions.

1. PRC 225cc As-Cast Aftermarket Casting Heads, 62cc chambers
2. PRC .675" Lift Dual Valve spring kit
3. MS4 Cam 111 LSA
4. Pushrods
5. Comp Cams Retro-Fit Rocker Arm Trunion Kit
6. Katech rod bolts
7. ARP Head bolts

They told me to go that route and use the stock lq9 thickness headgasket so I would not have issues with PVC. They also said compression would be around 11:1.


With all that said people are saying no to the ms4 cam due to the lobe design and that it is to much for the valve train and that it would break stuff. I would like to at least go from April to December with doing maintenance to the valve train.

LSter

Wow 20 hp and how much did they run ya
Man I would be pissed all that and 20 horse
Datsagood1

lsxperformance

iTrader: (2)

I personally like the ls3 heads over even mild fully ported cathedrals. I do a lot of builds, so I have become more partial the the ls3 heads. What I have noticed is that you can easily overcam a ls3 head. They are prone to reversion in the intake, and port velocity is slower than say the cathedral. So it takes a cam shaft in turn with a lazyier lobe profile. IMO say something with a lot of area @.200"+ to take advantage of the mid lift air flow numbers. Even on a 4" bore the heads are flowing higher air volume than a cathedral head way sooner in lift than a cathedral. So IMO the ls3 head design is better because you can a less aggressive camshaft than you typically would on a cathedral based engine and still make the same or more power with a less aggressive combination. But like already stated the valves are large (heavy) and spinning them hard is probly not the best idea. Also if you run a more aggressive spring to try to keep the valves from floating they WILL collapse the stock lifters at around 185+@ seat at roughly 3k rpm I've found in testing so an after market lifter such as the comp short travel or morel would be better suited in high rpm engines.

Ps. M3 LS.... Your my hero!

Koots

If it was 20HP over stock, It would be sad, but it's 20HP over worked 243 heads, which was probably a 20HP increase over stock alone.

Sometimes you gotta spend big money to make further gains than skill and a budget will allow.

rpm620

Im not swapping to LS3 heads... I already picked up and brand new cathidral port LSXR 102 Intake manifold that i got for 800 shipped.

I dont really need crazy.. just something that will get me between 450-500 with a good tune.

lsxperformance

iTrader: (2)

Friend of mine is sellin a set of 243 heads off a trailblazer SS. Pm me if your interested

69Camaro427

Anybody know the drive train loss through the t56? I know our trucks are roughly 20-25% depending on the wheel size. OP I'm sure your m3 will have less drive train loss maybe 15% so mimic some builds that truck guys have done to reach 450 and you should be in the 460-470 range. It will be a challenge to make that N/A 6.0 reach 500rwhp, but it can probably be done!

Yella terra or any roller rockers would help, maybe give you another 10hp from less mechanical restriction. But $400-500 is expensive for the gains! I would slap an ASP or SLP under drive pulley on it also.

Will you have to make custom longtubes or will some corvette/camaro LTs work?

Regardless this m3 is going to be one bad b****

69Camaro427

A lot of head cam gtos are putting down 430-450 range with ported 243s and ls2 intake so with the Lsx intake I could see you getting close to 450-470 range