I'm planning on makeing changes this winter and need to begin acquiring parts.

What will it take engine-wise? I'll be using my Radix on whatever I build.

I'm wondering whether to build a 427 or a 408. I like the bigger cubes but I'm concerned that going 427 may require some really expensive heads in order to feed that big a hole. (By the way... what bore/stroke makes a 427 and 408?)

Is there much difference between the older and newer 6 liter blocks?

Is there a GM Vortech head that would be usable (easy to find and relatively inexpensive) that could be ported to give sufficient flow or will I have to go with expensive aftermarket heads?

I'll be going with long headers (maybe custom made stepped headers if I can get the local genius interested) and Flowmaster 40's...3" all the way.

I'll be backing it up with either an 80 or 85 trans, 410 Strange (or some other really strong rearend) and big axels.

What block, displacement and heads do you recommend? I'll get cam recommendations from the manufactures.

I'm planning on makeing changes this winter and need to begin acquiring parts.

What will it take engine-wise? I'll be using my Radix on whatever I build.

I'm wondering whether to build a 427 or a 408. I like the bigger cubes but I'm concerned that going 427 may require some really expensive heads in order to feed that big a hole. (By the way... what bore/stroke makes a 427 and 408?)

Is there much difference between the older and newer 6 liter blocks?

Is there a GM Vortech head that would be usable (easy to find and relatively inexpensive) that could be ported to give sufficient flow or will I have to go with expensive aftermarket heads?

I'll be going with long headers (maybe custom made stepped headers if I can get the local genius interested) and Flowmaster 40's...3" all the way.

I'll be backing it up with either an 80 or 85 trans, 410 Strange (or some other really strong rearend) and big axels.

What block, displacement and heads do you recommend? I'll get cam recommendations from the manufactures.


whitt1 would be an excellent source of info for you, he has a Radix 402 pumping out 600rwhp.

there was also a guy on SS Silverado board that had a Radix stroker as well.

Hope that gets you started in the right direction. btw, you can do 500/500 with a Radix and a 6.0.

You can also do about 500rwhp with just a 408 n/a.

You can also do about 500rwhp with just a 408 n/a.
:eyes:

If I am not mistaken, the 427 is typically achieved with a 4.125" bore and 4" stroke. The 408 is typically achieved with a 4.030" bore and 4" stroke.

You can also do about 500rwhp with just a 408 n/a.

thats what I was thinking

check out these NEW HEADS FROM DART they are cheap the 225 should work well and I believe (could be wrong) they flow 320 at .600 without being cnc'd
http://ls1tech.com/forums/showthread.php?t=377960&page=1&pp=20

thats what I was thinking

check out these NEW HEADS FROM DART they are cheap the 225 should work well and I believe (could be wrong) they flow 320 at .600 without being cnc'd
http://ls1tech.com/forums/showthread.php?t=377960&page=1&pp=20

he said whatever he built was going to have his Radix on it, so maybe some advice in that direction would be appropriate.


On the DART heads, what great news that is!, hopefully the cost to build these motors will start dropping a bit now :)

If I am not mistaken, the 427 is typically achieved with a 4.125" bore and 4" stroke. The 408 is typically achieved with a 4.030" bore and 4" stroke.

So a 427 is .125 over! That's taking a lot of metal out of the block. Cooliing problems? I'd heard that a 454 bored .100 over is considered to be quite a bit and in danger of having heating problems. Perhaps the 6 litre has a lot more metal to spare.

I believe you would have to have it sleeved regardless of which block you start with, Im no expert though Im sure your machinist could sonic test it.

About the radix you should kill that 500 rw number, especialy with a blower on there, I wouldnt expect to see more that 5-8 psi though even with the high boost pulley on that big of an engine.

Its gonna cost alot more for those 19 extra cubes going from 408 to 427. To meet your goal I would save money on machining go with the 408 and put some good heads on it I know patriot and dart have some killer deals now and also LPE has designed some heads that should be in the same price range and flow very well all are capable of 300 cfm at .550 lift :eek:!!! Let the price wars begin, its about time.

my .02

I believe you would have to have it sleeved regardless of which block you start with, Im no expert though Im sure your machinist could sonic test it.

About the radix you should kill that 500 rw number, especialy with a blower on there, I wouldnt expect to see more that 5-8 psi though even with the high boost pulley on that big of an engine.

Its gonna cost alot more for those 19 extra cubes going from 408 to 427. To meet your goal I would save money on machining go with the 408 and put some good heads on it I know patriot and dart have some killer deals now and also LPE has designed some heads that should be in the same price range and flow very well all are capable of 300 cfm at .550 lift :eek:!!! Let the price wars begin, its about time.

my .02

I like the 402-408 deals, best bang for the buck in this scenario.

You can get the LS2 low compression 402 from SLP and run with a small pulley to get high boost with the Radix. I am sure with a stock set of heads you can get 500 RWHP and be able to run high boost. The package is all forged too.

http://www.slponline.com/view_product.asp?P=12413

Crate-Engine-Assembly, "ZL402" LS2 Aluminum Short Block (Low Compression)

--------------------------------------------------------------------------------
The ZL402 LS2-based aluminum short block builds on the success of our original ZL402 iron short block. This new package uses the same race- proven internals as its iron block predecessor but features the all- new LS2 block for weight savings of over 100 pounds compared to an LQ4/LQ9-based engine.

Although designed primarily for use in late-model F-Bodies and Corvettes, the aluminum ZL402 also makes a great choice for most late-model GTOs, street rods, muscle cars, and trucks. Best of all, it’s sold outright, without core charges.

You won’t find a higher quality, better value LS2 stroker short block anywhere!

Includes:
Built entirely from brand-new parts.
Sold outright, no cores required!
402 CID displacement
GM LS2 aluminum 6.0-liter block (includes block plugs)
4.000" Eagle 4340 forged steel crankshaft, balanced to rotating assembly
4.000" Ross 2618 forged alloy pistons with -28.50cc dish (includes new rings and full-float pins)
9:1 compression ratio (nominal; ultimate compression ratio will depend upon heads and gaskets used)
6.125" Eagle H-beam rods
Includes new, factory-installed cam, rod and main bearings.
Comes with everything required to retrofit into an LS1-equipped car or truck
Designed for naturally aspirated use.
Assembled to OEM tolerances and specifications.
Capable of supporting over 700 hp.
Oil pump, camshaft, pans, and plates not included.
ZL402 badges (pair).

If you go with an LS1/LS6 block, you will need to have it re-sleeved (as already mentioned). There are many vendors that sell the blocks, and yes some have had their issues (cooling, leaking, etc). I would check with SDPC (http://www.sdpc2000.com) for a 402. This is utilizing an LS2 block with a 4" stroke. I know they will build to suit, and they post a lot on ls1tech. IMO, I don't believe there are really very many NA 500rwhp cars out there. However, with 400+ cubes, a radix, and an intercooler, you should be able to get there. Also consider the drivetrain, and it's impact on your dyno #'s. After working with a really kick-ass load dyno, I have come really care less about DynoJet #'s. Just go hold a heat gun next to the dyno's thermometer and see what happens. :)

Thinking in terms of $$$$ I'm wondering what I can get out of a 408 with maybe Dart heads and a compatable strong street cam with the Radix and about 8 pds boost. Any guess-timates?

8psi from a 112 on a 408 will equall lots of hot air.

You can alky mist before the supercharger or even nitrous to drop IAT.

Thinking in terms of $$$$ I'm wondering what I can get out of a 408 with maybe Dart heads and a compatable strong street cam with the Radix and about 8 pds boost. Any guess-timates?

have you talked with whitt1? he has just about this exact setup, I think he is making 6lbs of boost, don't quote me though. I think 500-550rwhp would be a realistic number not knowing your backround.
You will enjoy gobs of power under the curve! :eek2:

I have a radix on my LQ9 (SS Silverado). With various bolt-ons I did 473RWHP and 491RWTQ. I feel that with meth, more timing, more freeflowing exhaust and a more blower friendly cam...500 is attainable. The current internal mod is only a mild cam.

If you want a sure bet, go with the 408. If my engine ever takes a dump, you can bet I will do the same

I have a radix on my LQ9 (SS Silverado). With various bolt-ons I did 473RWHP and 491RWTQ. I feel that with meth, more timing, more freeflowing exhaust and a more blower friendly cam...500 is attainable. The current internal mod is only a mild cam.

If you want a sure bet, go with the 408. If my engine ever takes a dump, you can bet I will do the same

have a link to your dyno charts? what are your mods?

I have a radix on my LQ9 (SS Silverado). With various bolt-ons I did 473RWHP and 491RWTQ. I feel that with meth, more timing, more freeflowing exhaust and a more blower friendly cam...500 is attainable. The current internal mod is only a mild cam.

If you want a sure bet, go with the 408. If my engine ever takes a dump, you can bet I will do the same


Do you have aftermarket cam and heads, or stock heads w/some work? What other bolt on's?

I sent a request out over the salvage yard network yesterday and got a hit.

Guy with a long rep in business has a 6.0 w/trans, 2004 with 24k and wants $2750 shipped, guaranteed for 90 days (or maybe it was 30 days... forgot).

Sounds like this may be a good deal but needs to be checked out.

Bore it .030 over, do a cam, work the heads or do the Dart heads and I should have a pretty strong piece. Then have the trans "built". Sounds like I'd be able to have a pretty strong combination for somewhere around $6k.

if you're going to do a 408 with a radix, try and keep the compression around 10.0:1. you're only going to be able to get around 8psi or so which means there is absolutly no point at all in going low compression. i'd also recomend sticking with stock heads and keeping the cam small. keep the duration below 225@.050.

My mods are:

SLP cam 214 / 222 .559 / .566 on a 115LSA
Radix with 2.9 pulley (8psi max)
Full exhaust (ASM headders, HF cats, Magnaflo)
FAL fans
160 thermo
Yank 3000 TT
tr6's, Taylor wires, some little stuff
Custom CAI

Moregrip: Send me your E-mail and I will send you a dyno sheet. Do you want to see highest HP or highest TQ. I recently dyno'd and only pulled 455HP and 480TQ with the converter UNLOCKED. The truck was very hot and the ambient temp was 90*. IAT's were 130 to start and topped out in the 190's by 6200rpm's :eek2: I also saw a few degrees of KR. My E-mail: krambo74@hotmail.com

FWIW, my set-up is very similar to Richard's (BigTex).

The truck was very hot and the ambient temp was 90*. IAT's were 130 to start and topped out in the 190's by 6200rpm's :eek2: I also saw a few degrees of KR. My E-mail: krambo74@hotmail.com
A STS kit with a FMIC will take care of that problem. And you will get your 500rwhp easy.

A STS kit with a FMIC will take care of that problem. And you will get your 500rwhp easy.
:zzz: Butt turbo :jest:

:zzz: Butt turbo :jest:

booty blower.

booty blower.
:jest: :jest: :jest:

A STS kit with a FMIC will take care of that problem. And you will get your 500rwhp easy.


it will get him the numbers he wants on the dyno. they just don't show up at the track. STS trucks seem to be dyno queens. Rarely does one put down the track numbers reflecting their dyno numbers.

it will get him the numbers he wants on the dyno. they just don't show up at the track. STS trucks seem to be dyno queens. Rarely does one put down the track numbers reflecting their dyno numbers.

funny how that average horsepower can reach out and slap a ho :twak:

it sounds like i'm being a dick by saying that, but all i ever read or hear about the STS trucks is how impressive they were on the dyno. i've only ever seen two of them impress me in track numbers. one was F8LZ71 who worked his kit to death to get good numbers including 3 engines and 2 transmissions if i recall. the other was allen nelson which i called B.S. on his claims. he claimed his times were on 5psi of boost with outstanding dyno numbers yet blew the engine up shortly after. 5psi of boost doesn't blow up a 6.0L...

My mods are:

SLP cam 214 / 222 .559 / .566 on a 115LSA
Radix with 2.9 pulley (8psi max)
Full exhaust (ASM headders, HF cats, Magnaflo)
FAL fans
160 thermo
Yank 3000 TT
tr6's, Taylor wires, some little stuff
Custom CAI

Moregrip: Send me your E-mail and I will send you a dyno sheet. Do you want to see highest HP or highest TQ. I recently dyno'd and only pulled 455HP and 480TQ with the converter UNLOCKED. The truck was very hot and the ambient temp was 90*. IAT's were 130 to start and topped out in the 190's by 6200rpm's :eek2: I also saw a few degrees of KR. My E-mail: krambo74@hotmail.com

FWIW, my set-up is very similar to Richard's (BigTex).

Are you running w/6.0 displacement or some overbore/stroke? What heads? Are they stock and worked? .... or stock? or aftermarket? Sounds like a good setup for me.

Stock displacement. Stock heads (317 casting #'s I believe). Just the LQ9 with a cam. Granted the cam came with new retainers, springs etc. SLP doesn't make the cam anymore however if you know anything about SLP, most of their cams are from COMP Cams...just with their name on it. They just own the grind specs. I am sure you can find a very similar one as it isn't anything special, in fact is a bit mild for some people.

it sounds like i'm being a dick by saying that, but all i ever read or hear about the STS trucks is how impressive they were on the dyno. i've only ever seen two of them impress me in track numbers. one was F8LZ71 who worked his kit to death to get good numbers including 3 engines and 2 transmissions if i recall. the other was allen nelson which i called B.S. on his claims. he claimed his times were on 5psi of boost with outstanding dyno numbers yet blew the engine up shortly after. 5psi of boost doesn't blow up a 6.0L...

5psi and going lean will kill a 6.0L. But then again why would nelson, who tunes vehicles himself let it go lean?

I'd think that a fairly good compression ratio would get the 500 you are looking for. Something like BigTex is doing. Whitt1 might also be onto something, going with a 90mm throttle body to prevent the supercharger pulling a vacuum on the inlet side of the blower.

Just some food for thought.