Patrick G

iTrader: (14)

Anybody know anything about them? From what I understand, these have the higher flow ports like the LS6/6.0L aluminum heads, not the older style 5.3L heads. GM is supposed to go to the higher flow LS6 ports on all 5.3L heads in 2005. I'm wondering if the SSR heads were the first to use them? I'm able to pick up a set, but I'm not sure if these will flow more than the older style 5.3L heads.

family sedan

iTrader: (3)

When someone finds out the part number please post it...

Sport Side

iTrader: (6)

I'd guess the '04 heads are the same. That model yr SS-r came with the standard 315hp. Or it could have been 325.

I believe the '05 head will be the LS6 style 5.3 head.

thefast1

where can i find out more about those heads

Closer_2001

iTrader: (6)

05 SSR gets the LS2.

Patrick G

iTrader: (14)

Yes, I know the '05 SSR gets the LS2. That's good news, but even bigger news is that ALL GM V-8s get the high-flow LS6 ports for 2005. The 4.8/5.3Ls get new heads with the higher flow ports. This new head should be a kick-*** bolt-on with a little bit of work. It will already have the 61cc combustion chambers like the old 4.8/5.3L heads, but the port runners will mimick the LS6/6.0L heads...much better flow. Interestingly, GM will still keep hp ratings at 295 (same as it was with the lower flowing heads). My big question of this thread is, what is the casting number of these new 4.8/5.3L heads with the kick-*** ports? Is it 706? I doubt it because that's the number used on many current 4.8/5.3L heads, but I wondered if GM had tried out the high-flow heads on the 300hp SSR in 2004? Don't know. If anyone can get the casting numbers on the new high flow heads, it will be a big help for us hot rodders on a budget.

VINCE

iTrader: (1)

This is interesting... It seems I can bump my compression up even more minus milling and put an EVEN BIGGER CAM IN Just kidding, but this is interesting.

Sport Side

iTrader: (6)

Also, remember that the heads will be made to fit the 5.3 bore, being as they are 5.3 heads. Truck/SUV guys will benefit. eh hum

That is interesting GM will keep factory hp ratings the same, seeing as the increased efficiency of the head should stack up a few more ponies.

sry, no part number.....

Closer_2001

iTrader: (6)

WOW!! Thanks for the clarification!

That sounds like an awesome bolt-on for my 04 GTO.

thefast1

i wonder if the cores will be cheaper than the ls6,if so that would be a killer set of heads.ls6 flow with small chambers

Patrick G

iTrader: (14)

Keep in mind, the new 4.8/5.3L heads will most likely continue with the smaller 1.89/1.55 valves like the older heads (since the truck motors have 3.78 bores). This may require upgrading to some lager valves on a 3.90 bore motors or larger.

Sport Side

iTrader: (6)

What size port's do they get? Same 200cc, or will they step up to 210 like the LS6 heads?

NO-OPTION-2002

iTrader: (2)

Hello!

The part # for the 4.8/5.3L heads is 12578925. It is the same part # from 1999-2005 on all 4.8's and MOST 5.3's. It has 1.89/1.55 valves.

Part # 12564825 is the LS6/LS2 head. But as of 2005 it will come on the DOD trailblazer 5.3's, the L33 aluminum block 5.3's in 1/2 ton silverados, and the DOD 5.3's soon th be out in the Grand Prixs. They use the 2.00/1.55 valve setup. These motors all have larger camshafts to match these better heads.

Looks like lots of LS6 heads in salvage yards in the years to come!

BA in KC

I can tell you this much for absolute certain about those 706 castings from 2004.......IF they are Castech castings.......throw them in a firepit and melt them into blobs of scrap aluminum. That's about all they're worth. They have porosity problems and are the most susceptible to cracking around the oil returns and the number 1 head bolts. I know from experience. I took a pair off of my truck and turned them into fish attractors.

KCS

iTrader: (20)

In the future, please check the dates before you post and revive another 11 year old thread...

wph351

iTrader: (3)

Nice work on the exhaust. It's pretty tight along the boss. While I was practicing, I had trouble with my burr bit jumping in that area.

squalor

iTrader: (3)

Since this thread is back from the dead it seems like a good place for me to return from the dead.
Not all 706 heads are Castech. The heads have 200cc intake ports shaped like the 241 head but have small 61cc chambers. These heads are die cast and have smooth surfaces. 862 heads are identical to 706 except they are sand cast and have rough surfaces.
How ya been KCS ? Still putting big valves where they don't belong ?

KCS

iTrader: (20)

Haha, you know it. I have a new hobby now; I'm putting big cranks where they don't belong lol.

squalor

iTrader: (3)

Interesting, that can be a expensive hobby, got a link ?
I'm getting ready to sell my '93 RX7 LSx swap. I'd like to do a LM4 Fox swap but my wife want's me to act my age and get a vette.






Edit to stay on topic. 706 heads ported by Mikey97Z . .600" lift 289 intake-cfm 235 exhaust-cfm

The second pic is your own work. Didn't you tell me once that the closer to the valve, the more important the work ?

KCS

iTrader: (20)

https://ls1tech.com/forums/generatio...ld-thread.html

Pretty much, especially on a street car with relatively low lift. For most of the time, the curtain area is less than the cross sectional area in the port so the valve is most of the restriction from air getting into the cylinder. The valve is only open far enough to make the port the restriction for a very small amount of time. Focusing on the greatest restriction will net the greatest gains.

You can see the difference in where each of us concentrated our work between those two heads. The ports in the 5.3L heads have been reshaped and smoothed, but they look like they still have the stock valvejob, and minimal blending into the chamber. The venturi is probably still pretty close to stock size.

I took the opposite approach. All I did to those 241 heads in that second pic was cut a 4 angle valvejob, open up the venturi, and blend it all in to the port and chamber. You can see that the guide boss and the rest of the port are untouched.