SprChrgdGT

I have a 99 ss m6.... I would like to do H/C/I.... as far as a head setup, if the following info is true, what are some opinions on getting a set of 243 heads and having them milled .030 to raise the compression? I plan on a h/c/i combo with a 150 shot. Thanks for any opinions fella's...

If I remember correctly the LS6 (243) stronger spings than the LS1 (241) -

Hands down the LS6 head flows better than the LS1 due to the runner volumes and the smaller combustion chambers!

LS6 heads are refined and improved LS1 heads, basically:

- Intake runner volume increased to 210cc vs. 200
- Exhaust runner volume increased to 75cc. vs 70
- Combustion chamber is smaller at 64.45 cc vs 66.67
- Compression ratio is higher at 10.5:1 vs. 10.1:1
- "D" shaped exhaust ports vs round

If you mill the deck on the LS6 head 0.030" you will get 11.1:1 compression.

Flow #'s (Stock heads @ 28") Head vs Lift

Head/.200/.300/.350/.400/.450/.500/.550/.600

LS1 / 137/ 187/ 207/ 223/ 228/ 237/ 242/ 243

LS6 / 156/ 204/ 225/ 243/ 257/ 268/ 275/ 278

In short smaller and more efficient combustion chamber allows quicker burn times, requires less ignition timing resulting in higher torque.

kinglt-1

iTrader: (26)

if you send the 243's out to a reputable company such as Advanced Inductions, they can make killer power. 450+ whp on the right combination of parts. In stock form, milled, and cleaned up 430whp should be about par with a decent cam in the 226-228 duration range.

SprChrgdGT

nice... I believe the nitrous would love the extra compression too. That may be the route I take then.

Is the fast intake worth much more than the ls6 intake?

SSCamaro99_3

iTrader: (1)

The 243's had marginally better valve springs. However, just about any aftermarket cam upgrade will require new valve springs.

SprChrgdGT

really liking this sound. Wish there was more info on this guys setup.

Grr

iTrader: (2)

you can mill the heads ALOT in an NA application and have good success, case in point my stock bottom end with 243 heads is right at 13:1. You would have no problems milling .030

PREDATOR-Z

The problem lies in the size cam he will be able to run.

SprChrgdGT

Yeah I was thinking that with the heads milled, you cant run as large of a cam. Is that right?

Grr

iTrader: (2)

not without doing the appropriate cutting of the pistons. If you do not wish to do so you are much more limited in cam selection when milling

PREDATOR-Z

Correct. Another option is to send your stock heads to AI and get their 241 219cc CNC program. Then can keep stock valves, no milling and weld the chambers to reduce size and therefore you get close to stock clearance but with higher compression.

95ONE

iTrader: (1)

I'm curious how you got to 13:1 with your application!?

Stock bottom end 346?

What size chambers do you have? - cc's?
headgasket thickness?

How much did you mill your head?
If more than .060, did you run into any intake manifold fitment issues?

bww3588

iTrader: (49)

The most common reason for intake fitnemt issues is people not milling the intake face of the head like they are supposed to. Any amount milled off the deck surface should not cause intake fitnemt issues if the machine shop did the milling correctly.

PREDATOR-Z

That is because Grr is not telling you the whole story.

Grr

iTrader: (2)

Sure guy, not telling the whole story. Whatever man

Stock 346, .05 stock mls gasket
Pistons are out .008
Heads are 46.x cc
best guess is they are milled around .135-.140, do not remember what was taken off the first time. Calculated at 12.96:1
Dynamic compression is 9.65:1

PREDATOR-Z

Still not the full story....

Grr

iTrader: (2)

So tell me what the full story is since I obviously don't know what I did. 0
P to v bullshit?
Run a smaller cam then, this cam is a little overkill for most anyway

Drokkers

iTrader: (2)

dr_whigham

iTrader: (49)

You're 900ft above sea level..... but I still don't get how you can safely run 9.65:1 dynamic on 93

Sales@Tick

iTrader: (3)

He runs E85....

PREDATOR-Z

bingo