Mild 6.0L Build Suggestions?

[Matthew Jeschke]

Do you know what LS builds used the 90mm throttle body? Guy at machine shop made it sound like factory 90mm throttle bodies were falling out of trees.

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[Tonyrodz]

Do you know what LS builds used the 90mm throttle body? Guy at machine shop made it sound like factory 90mm throttle bodies were falling out of trees.

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I heard the stockers are good til 500 horsies.

 

[Matthew Jeschke]

I am bot sure why guy at machine shop recommended bigger intake and throttle body... other than he builds more racecars than trucks?

I love idea more torque with smaller heads... but I really cannot afford to increase compression.. I go to places where there is no fuel at higher octain for that level of compression. I am already bit worried about the flat top pistons.

I don't understand all the factors though... Depending on when events takeplace with cam, will effect compression (i think). Also I would assume the smaller intake ports flow / scavenge better at low rpm than the bigger ones on 317 heads.

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[Tonyrodz]

I am bot sure why guy at machine shop recommended bigger intake and throttle body... other than he builds more racecars than trucks?

I love idea more torque with smaller heads... but I really cannot afford to increase compression.. I go to places where there is no fuel at higher octain for that level of compression. I am already bit worried about the flat top pistons.

I don't understand all the factors though... Depending on when events takeplace with cam, will effect compression (i think). Also I would assume the smaller intake ports flow / scavenge better at low rpm than the bigger ones on 317 heads.

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I know it would be a pain, but for special cases you could always carry a few cans of octane booster--to add to low octane gas.

 

[Matthew Jeschke]

Yeah was thinking of that haha

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[iamdub]

So you think the 706 heads with larger valves would generate better power / down low than the 317?

Any idea what compression ratio the 706 heads would be with the flat top 6.0 pistons?

I am super concerned about compression as I go to places where they sell as low as 84 octaine and you cannot find any higher than 87.

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Better low end, but they still won't choke it in the upper end, either. I can't say for the compression ratio because I don't know what your actual chamber volume is. The only way to know is to measure them. They're pretty much always larger than what GM specs. If you're not the original owner, you probably don't know for sure if they've ever been milled, either. Once you know the volume, then you can do the calcs to determine your SCR. If it's too high, run a thicker head gasket to drop it to where you want it. The chamber volume will change with the new valves.

 

[Matthew Jeschke]

So the connecting rod mystery continues. I ordered another set of rods w/o the oil relief. They are refuebished and look like new. However, there is no casting number anywhere on any of the rods... It is super weird.


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[Dantheman1540]

Do you know what LS builds used the 90mm throttle body? Guy at machine shop made it sound like factory 90mm throttle bodies were falling out of trees.

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The 90mm TB came from ls2s and ls3s. The gold blade 90mm is from the ls3s and is great for NA engines or low boost they tend to snap shut under high boost. The silver blade 90tb is from the LS2s and is the holy grail of OEM TBs, I think they go for $200-$300 last I checked. Anyway, they love boost and most big boost guys are running them. I've had one on my Silverado at 18psi and it never had any issues.

 

[Mudsport96]

So you think the 706 heads with larger valves would generate better power / down low than the 317?

Any idea what compression ratio the 706 heads would be with the flat top 6.0 pistons?

I am super concerned about compression as I go to places where they sell as low as 84 octaine and you cannot find any higher than 87.

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The trick is not larger valves, but unshrouding the existing ones in a 706 head. Get some 6.0 head gaskets and lay them on the 706s, then use a marker to trace the bore of the gasket. After that you slowly make a relief in the wall of the chamber next to the intake valve and that will help increase flow. Putting a larger valve in a 706 head will move it closer to the chamber wall and increase shrouding and not increase flow as much as you would think. You can unshroud yourself vs paying someone to cut the head and buy valves.
I'll look around and see if i can find the info, then post it back here.

 

[Mudsport96]

-6.7 CC Dish Pistons...

They flow nearly the same....

Flow data (317 Heads)
Lift In. Ex.
0.050 33.3 24.5
0.100 63.4 54.2
0.200 144.1 103.8
0.300 200.2 142.5
0.400 234.6 167.9
0.500 241.7 183.1
0.600 243.3 193.7
0.650 244.8 195.1

Flow Data (243/799 Heads)
Lift In. Ex.
0.050 31.1 24.7
0.100 65.4 52.6
0.200 142.2 98.1
0.300 193.5 133.5
0.400 230.2 160.1
0.500 243.4 175.5
0.600 248.1 185.8
0.650 249.3 188.2

http://www.superchevy.com/how-to/en...numbers-from-our-stock-ls-cylinder-head-test/

I couldn't find the page i thought i had saved, but here is some information from this site. The 317 is basically the same as the 799/243 heads everyone loves. But Richard Holdener did a comparison of 706 vs 799s on a cammed 6.0 and the results were interesting. Below 5500 the 706 heads made more hp and tq. Above that the 799s made more power. How often are you going to be over 5500 revs? And these heads hadnt had the valves unshrouded.