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I’ve done a good bit of reading and research, and talked to some pretty keen ls minds. There’s an article by super Chevy. Surprising HP Numbers From Our Stock LS Cylinder Head Test They do a test of pretty much all stock heads and the 706 head outperforms the 799/243, 317s, etc etc. in different situations Where it would be thebroute to go. If I’m doin the math right, with the 706’s smaller 61.5 chamber, the lq9 flat tops, and an Ls9 gasket I should be around mid to low 11 CR.
That article was measuring the 706's performance on 5.3 engines because a lot of people would switch heads thinking they'd perform better than the smaller valved stock 706 heads. Turns out, the stock heads performed pretty well on the 5.3 and the engineers knew what they were doing. The valve sizes and port velocities matched up to the 5.3's volume is the reason behind that. The 706 heads will perform differently on a 6.0.
I have 2 sets of 706 heads and the 317s in the truck now. I originally thought this idea up because I have two sets of 706s and figured a porting job, along with the smaller chamber would bump the compression. Figured they may choke the 6L a little like u said. I could get a 2” or bigger intake valve put in there. Or buy some 243s. Million ways and can only pick one.
Just have the 317’s milled they are the same as 243 except they are 70cc I have had a few sets milled to up the compression on a lq4 which is 9.5 and milled to get around 10.5 and run a healthy cam without any problems it wouldn’t take much 30 thousandths or so will get you close to 11.1 since it is 10.1 stock anyway that will be the cheapest since you already have them I machine guy charges me $50 to clean and mill so that probably a close across the board price for most shops
Just have the 317’s milled they are the same as 243 except they are 70cc I have had a few sets milled to up the compression on a lq4 which is 9.5 and milled to get around 10.5 and run a healthy cam without any problems it wouldn’t take much 30 thousandths or so will get you close to 11.1 since it is 10.1 stock anyway that will be the cheapest since you already have them I machine guy charges me $50 to clean and mill so that probably a close across the board price for most shops
did you have to change pushrod length or anything? I’m runnin a 224 cam .575”
Bud racing is right need to check the length if you don’t have one summit racing has some that’s very inexpensive mine came from them it’s a comp cam brand and it was less than $20
I finally just got ahold of Richard holdener, and figured I’d ask him some questions about the 706 on the 6L. He said he has dyno’d the combo and with the comp259 cam and a dorman ls2 intake, the 706s outproduced the 799/243 until around 5000. Then the 799s outgain it by a slim margin. The cool thing to notice here is the torque. The 706s produce a better torque curve. That’s stock 706 too. With mine being ported may push the final number up some.
Sep 27, 2018 | 10:37 AM
