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LS6 heads over LS1's

Ok people want to know why use LS6 heads when LS1's are cheaper. Well i have just finished some testing and i have some answers. LS6 heads were designed with LS6 intake and it shows, flow testing 241 and 243 castings fully ported with first clay radiused entry and than with LS6 intake shows that LS1(241) casting loses between 5 to 15 cfm with a average of 10 cfm loss more than loss LS6(243)suffers with same intake.
yOUR PROLLY THINKING WHAT IS HE TRYING TO SAY?
Example: Ls1 head at .575" lift flows 305 cfm with radiused entry, bolt on lS6 intake it flows 265cfm! Loss of 40 cfm. ls6 head flows 310 cfm at same lift, add intake it flows 281cfm, only loss of 29 cfm! This is true to varying degrees across the lift range, and this adds up bigtime. Ls6 heads are much better at cylinder filling thruout lift range, especially if you keep port volume small with strong flow numbers like i did!
I hope this opens some eyes this is why i posted. <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" />

Re: LS6 heads over LS1's

What about using 6.0 heads instead of 5.7 heads? They 6.0 heads are similiar to the LS6 heads so I wonder if they would flow about the same with the intake on?

Re: LS6 heads over LS1's

Drop a set off and i'll let you know! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

[ February 22, 2003, 11:04 AM: Message edited by: LS1derfull ]

Re: LS6 heads over LS1's

I see my Heads are coming together <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Re: LS6 heads over LS1's

What I understood was LS1 heads don't have the optimum curvature on the intake ports because the designer wanted the fuel injector to have a straight shot at the bottom of the intake valve for best atomization, minimizing emissions. When they went back and looked at this for the LS6 redesign, they realized it wasn't necessary to do this to minimize emissions and instead redesigned it to maximize flow.

Re: LS6 heads over LS1's

Have you ported some 5.3 heads and tested them yet?

Re: LS6 heads over LS1's

Excellent R&D LS1derfull,
The flow numbers with the intake manifold bolted on is purely situational to how any head intake runner has been ported to begin with on either head, ie getting 281 out of an LS1 head using a Z06 intake is very simple and comes around within 2 or 3 adjustaments. Maxing out the LS6 total flow numbers with the Z06 intake assembly does come around quicker and I do agree that the Z06 heads DO respond quicker BUT they flow more to begin with. I do applaud your persistance to finding hidden power <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> .

Joe

Re: LS6 heads over LS1's

Are your examples real numbers or just examples.. I have a set of Ls-6 heads that have been professionally ported and they don't flow near 310cfm.. @ .575 I only got around 280 without a manifold.

Re: LS6 heads over LS1's

<blockquote>quote:<hr />Originally posted by LZYBIRD:
 Are your examples real numbers or just examples.. I have a set of Ls-6 heads that have been professionally ported and they don't flow near 310cfm.. @ .575 I only got around 280 without a manifold. <hr /></blockquote>LS1derful is giving real #'s.I've seen him work the bench and he double checks everything.These heads are actually going on my car.Alot of time has been put into these Heads to get the most out of them.He got around 310cfm at .575 with the stock 01 valves <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> I can't thank him enough for all the time he is spending to hook me up with some ultimate LS6 heads for my setup <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Re: LS6 heads over LS1's

<blockquote>quote:<hr />Originally posted by JPR:
 Excellent R&D LS1derfull,
The flow numbers with the intake manifold bolted on is purely situational to how any head intake runner has been ported to begin with on either head, ie getting 281 out of an LS1 head using a Z06 intake is very simple and comes around within 2 or 3 adjustaments. Maxing out the LS6 total flow numbers with the Z06 intake assembly does come around quicker and I do agree that the Z06 heads DO respond quicker BUT they flow more to begin with. I do applaud your persistance to finding hidden power <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> .

Joe <hr /></blockquote>Joe, thanks for the kind words, i agree my testing is situational. All of my time has been spent chasing and passing flow #'s with no manifold, because thats all i have reference to from, others for comparison. I will have to test further to get the higher flow with intake on LS1 castings, i do not know where to make adjustments to get flow back up to LS6 level.Thank you for releasing your findings on this type of testing because no others seem to address this.

Ragtop 99 i have yet to port 5.3 castings but because of chamber work necessary with larger valves, i feel they are best done by C.N.C. porting because of need for exact chamber sizing and shaping. I have done plenty of chamber finishing on many different types of heads, but if there is ever a task suited for CNC its this.

[ February 22, 2003, 10:20 PM: Message edited by: LS1derfull ]

Re: LS6 heads over LS1's

<blockquote>quote:<hr />Originally posted by LZYBIRD:
 Are your examples real numbers or just examples.. I have a set of Ls-6 heads that have been professionally ported and they don't flow near 310cfm.. @ .575 I only got around 280 without a manifold. <hr /></blockquote>I'm sure his #'s are accurate & real. If you only got 280 out of LS6 heads, that's pretty sub par these days. 310-320cfm at .550 to .600 lift seems to be pretty average from what I've seen recently.

Re: LS6 heads over LS1's

<blockquote>quote:<hr />Originally posted by Ragtop 99:
 Have you ported some 5.3 heads and tested them yet? <hr /></blockquote>Won't make a difference since the intake port is identical to the 5.7L casting.

The increase in flow is due to the raising of the LS6's floor to make a straighter shot out of the intake runner and into the port. Also the short-turn radius of the LS6 head is much smoother than the LS1 style castings'.