Mongrell

Hey guys,

I'm building a LQ4 for offroad purposes only...probably much different than what most of you guys build engines for. Most of the time the engine won't see anything over 4500 rpm. I really want a lot of torque, lower end power, and a lot of useable power under the curve....not to say I want to lose all of my top end either, though.

I'm wanting to run a set of 243 LS6 heads with the sodium valves, most likely with Patriot Dual Gold springs & chromoly pushrods, and have them milled down .035" and run a thinner head gasket. I was figuring it'd bump the compression up to around 11:1 with a better quench than stock. Which gasket would ya'll recommend?

I'm going to have Jim's performance redo the wiring harness and reprogram the pcm. I'm thinking delete the abuse mode, torque management, evap, rear o2's, egr, cats, vats, and have a performance tune for 93 octane.

Here's the cam I'm going to have custom ground to go with all of it...

218/222 .595”/.597” 114LSA +4 advance (with 1.7 ratio rockers)
Comp EPS/EPS lobes 54-000-11 3 bolt cam core
13115R/13116R HR114LSA +4 advance (110 installed intake centerline)

Cam Valve Events 0.006 0.050 0.200
Intake Duration - ID 267 218 141 13115R EPS lobe .595"
Exhaust Duration - ED 271 222 144 13116R EPS lobe .597"
Lobe Center Angle - LSA 114 114 114
Intake Centerline - ICL 110 110 110

Intake Valve opens - IVO 23.5 -1 -39.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 63.5 39 0.5 ABDC
Exhaust Valve Opens - EVO 73.5 49 10 BBDC
Exhaust Valve Closes - EVC 17.5 -7 -46 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 118 118 118
Overlap 41 -8 -85.5 degrees

Anything else I should consider or do different? I have a slightly bored cable throttle body. Do I need bigger injectors? I know I need to upgrade the timing set...is there a good one to use?

Thanks for all the help!

Jim.

Darkman

iTrader: (2)

I am not a fan of strokers, but this is one application where I would consider it.

For timing chain, I like the IWIS Lsx timing chain (Thunder Racing has these).

Any reason for not porting the LS6 heads?

Mongrell

Yeah, I wouldn't mind doing a stroker...but I don't know that I want to drop that much $$$$ and completely tear down such a low mileage engine.

As far as porting the heads, no reason really for not doing it. I just didn't think I'd really be out flowing a set of stock LS6 heads.

I'll check into that timing chain too. Is the stock LS6 timing chain an upgrade over the LQ4's...or is it the LS2 or 3's that everyone likes to use?

Thanks again,

Jim.

Darkman

iTrader: (2)

The lower cost alternative to the IWIS chain is the LS2 chain. What ever chain you choose spring for fresh sprockets.

Having the LS6 Heads ported by Total Engine Ariflow or the like will gain flow. Ported heads like increased compression, if done properly, can add power everywhere.

Mongrell

I'll definitely check into having them ported...

Do they hand port or cnc port them?

I thought about just dropping the money on a set of PRC or Patriot heads, but again...I don't know if they'd be worth it to me over just a stock set of LS6 heads. I mean obviously they're worth the money, but I'm just trying to do a cost to performance anaylsis and make sure I don't end up spending to much money on this project because I have a tendency to over do things.

Darkman

iTrader: (2)

Most of the porting work is CNC, subject to touchup by hand. I would suggest you get some info first hand. I would call Total Engine Air Flow, AFR, Texas Speed, etc. and talk to them about your specific needs. I suspect having your existing heads reworked will give you the most bang for the buck, but I could be wrong.

MikeG

iTrader: (33)

Don't forget about advanced induction, they do a mean set of 243s too.

AINT SKEERED

iTrader: (2)

if you are mostly wanting low end, just get a valve job and bowl work done to some 243 heads. dont open them up big to where you have to rev them to the moon.

Mongrell

Yeah, that's the other reason I was just going to stick with stock 243's...I'd like to keep the port velocity up.

Thanks guys!

What about the head gasket? Just use a standard GM MLS? What thickness?

Mongrell

Anybody else?

KCS

iTrader: (20)

+1 on leaving the ports alone. Peak torque on a stock LS2 (which is basically what you're building) is right around 4500RPM, so the last thing you'd want to do is open them up and move that peak torque any higher. As far as the heads go, I would cut a fresh valvejob, work the chambers a bit, and call it a day.

You probably don't want to go lower than .040" on the gasket thickness. You would have to go with a custom gasket since stock is ~ .051", so it's up to you to decide if the extra coin is worth the small bump in compression.

Sounds like a nice build though, good luck.

Mongrell

I can get a .040" stock or aftermarket gasket without going custom, right? I was going to get all of my compression bump from shaving the heads...I was just thinking if I went with a thinner gasket I could shave the heads a little less and end up with the same final result but with a better quench.

That was my thought anyway.

Would .035" off the heads with a .040" head gasket be to much of a bump. She'll be run on 93 octane all the time.

Thanks again!

KCS

iTrader: (20)

Sorry, instead of custom I should have said aftermarket. I'm pretty sure Cometic stocks .040" gaskets. I think your best bet would probably be to do the thinner gasket and then shave the heads accordingly.

Mongrell

Is there a rule of thumb or a calculator to use to figure out how much of a compression bump from the thinner gasket and shaving the heads?

Mongrell

I'm trying to get to 11:1 or 11.5:1.

I guess I'll do some searching around and see what everyone else on the forum with this combo has done.

Darkman

iTrader: (2)

I am not convinced that porting will necessarily have an adverse affect on low end torque or shift the peak torque higher.

I added a set of TFS 215s (milled to 61.5cc) to my LS6, which already had a baby EPS cam. The peak torque before adding the 215s was at 4,800 rpm and was still at 4,800 after adding the 215s. Additionally the 215s resulted in torque at least equal to the 243s everywhere up to 3,400 rpm and significantly above the 243s throughout the 3,400 rpm to 4,800 rpm range. In short the addition of 215s only helped the torque values.

KCS

iTrader: (20)

Here is a good article to figure it out for yourself. There are some online calculators, but I have noticed a lot of them are inaccurate. Many times they neglect the head gasket volume or just get it wrong.

How to Calculate Compression Ratio

AINT SKEERED

iTrader: (2)

thats because a 215 head flows more but is not a bigger runner to the point of killing air speed.

Darkman

iTrader: (2)

Okay, so the difference between stock 243s and 215s is just the chambers, is that right? (Setting aside the larger valves and valve angle change.) It is my use of the word "porting" that gets off track?

Mongrell

Awesome!

Thanks!