Ken move this if its not appropriate but i did a search and couldn't find much info on this.

I was just given a 6 liter core with 4,800 miles on it, out of a 2003 ambulance that has aluminum heads and a toast cam shaft but no other damage. I was wondering if any of you guys can tell me a few things.

a. how much can this block be safely bored.
b. what is the largest stroke crankshaft I can put in it.
c. Are the heads as good as everyone says.
d. what are the largest valves that can be put in these heads.
e. What are the best hyd roller valve springs for it.
f. Is there a bell housing that will mate my 6 speed out of my 95z and what else will i have to change to make it work.
g. What can I expect to pay for a computer and wiring harness to use this motor. Or are there any stand alone ecms for this engine.

Thanks In advance Guys

 

a. I've heard .090 but no need to take it over .030 the first time.
b. 4.125" stroke crank is a 421!
c. yes those heads are nice! They have great mid lift numbers
d. 2.08 valves can be put in with new seats
e. depends upon the cam lobes you are using
f. Don't know about that, but it will bolt up to a T56 in a 98-up F-body so I would expect so, it's the same dimensions as a LS1 aluminum block.
g. ? got me

Hope that helps

Bret

 

6.0 vs LS1 vs LS6 heads.

anyone care to compare?

 

Thanks Bret its a good start

Custom Cam specs are

Duration 292 294
@ 50 242 244
Lift 612 618

I know this is pretty radical for a stock ls1 but should be a good fit for a 421 hehehe

And yes Trey I would like to see a comparison on the heads.

421 I like the sound of that I used to have a 421 super duty in an old pontiac that was awesome maybe this will be too.

Bret any idea if Scat makes that crank and what rod length and pistons would i need. And does some one make rods and pistons for this combo currently or are they special man.

 

Try Howell Engine Development

http://www.howell-efi.com/wk_mpi_tpi_index.html

Look at LS-1 Chevrolet Corvette, Camaro, ASA Racing Harness

Discussing it with them might help a lot. These folks know their scat.

 

So you are using a XE-R LS1 lobe at about as big as you can go. Anything in that lobe set over 230 deg of duration @ .050 should use the Comp R lifters and a 977spring. That with aftermarket rockers is a good idea. Depending upon your heads I don't know if I would run a cam that big, I would have to run some numbers to see what would work. I know that TEA has a set of Judson Masingil 6.0L ports that might work really well.

As for the cranks.

Scat's is a nice piece but it's billet and costs a TON!

Cola as a nice piece, but their money problems might not help you out to well.

Lunati was the first to market. I didn't like their process, but it's still stronger than you need.

Callies has a new set of stroker cranks too that look REALLY nice.

As for the rest of it.

I would go with a Diamond Custom piston and a 6.125" rod. That with the +.015 out of the hole piston will be about as much as you can do. You could even run a 6.00" rod too. There are more rod choices there then.

Bret

 

It's okey dokey with me.

 

I looked at this a little more and you might not need that much camshaft at all. You'll find with the way this engine works that less cam will give you more TQ and a better driving car with close to the same HP, without a doubt.

Done right that motor would be a monster!

Bret

 

Bret

What kind of specs would you suggest. If you have some good specs That will give me better drivebility with the same hp and more low end torque I am all ears send it down. Cam Motion is right here in town an they have a few custom grinds for the ls1 crowd here but nothing for the stroker versions.

I am going to send the heads to Larry Meaux and have them worked.

Lunati's price on that crank seems to be around 2200. I will check with Dean at Callies today he's been real good to me in the past and I especially like their process and quality. Also I'll send and email over to HTC and see where he will come in at price wise I Like his stuff to.

Bret thanks for all the help. This means putting 2 motors together in the next month my 535BB and this one.

 

From Chevy LS1/LS6 Performance by Chris Endres - a good investment for anyone with in interest in Gen III engines:

LS1:

PN 12559853 (97/98)
PN 12559853 (99/00)
PN 12564241 (01-03)

CC Vol. 66.67cc
CR: 10.1:1
Intake port: 200cc
Exhaust port: 70cc
Intake: 2.00"
Exhaust: 1.55"

I: 137@.200, 187@.300; 207@.350, 223@.400, 228@.450, 237@.500, 242@.550, 243@.600

LS6:

PN 12564243
CC Vol: 64.45cc
CR: 10.5:1
Intake port: 210cc
Exhaust port: 75cc
Intake: 2.00"
Exhaust: 1.55"

I: 156@.200, 204@.300, 225@.350, 243@.400, 257@.450, 268@.500, 275@.550, 278@.600

6.0L:

1999-2000:

Cast Iron
PN 12561873
CC Vol: 71.06cc
CR: 9.5:1
Intake port: 210cc
Exhaust port: 75cc
Intake: 2.00"
Exhaust: 1.55"
-------------

2001+ (LQ4):

Aliminum
PN 12562317
CC Vol: 71.06cc
CR: 9.4:1
The rest is same as above.
-------------

2002+ (LQ9) "This is the Escalade head, virtually identical to the LS6"

Aluminum
CC Vol: 71.06cc
CR: 10:1
The rest is same as above

No flows quoted, but they note the port work is identical to the LS6.

GMPP "Gen-III Racing"

An LS6 head with a CNC-port.

GMPP "Showroom Stock Racing"

LS1 head with 63mm CC.

GMPP C5-R:

11-degree head
30 - 38cc CC
raised runner
Requires Kinsler intake manifold

 

I spoke with our local head specialist last night he told me that the 6 liter heads measured identical to the ls6 heads except for the combustion chambers were slightly larger. They too can be worked and will flow as good as the ported ls6 heads.

he stated that he could do several things but his build suggestion would be to take the block and get a 4.000 stroke crank and a 4.030 bore making a 405. He told me with the larger combustion chambers in the heads and the right piston give it 8.75 to compression and put a ATI blower on it for about 750 rhp. What do you guys think.

I tend to like N/A engines myself they ususlly last longer. Are there any problems with going to a 4.125 stroke crank for a 421 that can't be overcome. Do I need to go with a shorter rod or do they make pistons using the 6.125 rod that have a wristpin that doesn't get into the bottom oil ring.

 

I'm a NA guy myself because to do a blown car right it just costs more.

As for the heads, there are slight differences in the ports. I've yet to see a 6.0L head flow what awellworked LS6 head does. There are small differences but they do count. Figures though because the LS6 was designed to flow at .550 lift where the 6.0L was designed to flow below .500, the mid lift numbers of those heads stock will show you that. GM really does custom talyor intake ports for each engine combo they do now.

On the 421, it can be done. People are building 396 Aluminum block motors now. Look at this math on the wristpin and oil ring situation.

Deck Height 9.240"
Stroke/2 2.0625" for a 4.125" stroke
Rod length 6" or 6.126"

9.240-2.0625-6.125=1.0525 Compression Height.
9.240-2.0625-6.000=1.1775 Compression Height

On a LS1 you only need oil support rails (meaning the wristpin is in the oil ring area) on a piston with less than 1.125" Compression Height. The 4.000" stroke, 6.125" rod combos that have this compression height don't have oil support rails. So to answer your queston, No you can't get a piston with a 4.125" stroke and a 6.125" Rod that doesn't have oil rail supports.

Bret