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Discussion Starter · #1 ·
I am assembling a 6.0 iron block LS and I'm a bit confused about which head gasket to use to obtain the proper squish. I currently have stock .051 thick stock GM head gasket . The pistons are flat tops .004 out of the hole. Do i need to get .045 gaskets? Cometic ($$$) seems to be the only alternative for my 4.002 bore but I'll bite the bullet if necessary.
Another question: For daily driving should i go with 243 heads which will around 11:1 CR or 317 heads which will around 10.4:1? I'm not trying to set the world on fire. Just an old guy who refuses to grow up.
The cam is a Comp XR265
212/218 @.050
.558/.563 lift
115 LSA
 

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Discussion Starter · #3 ·
Thanks, that was my plan but I wasn't sure about the squish number. The rest of the equation is: 1950 Chevy pickup, 9" posi 3.70, TCI 4 bar rear suspension, 3200 stall converter and a C4 front suspension with coilovers mounted on a cross member from Flat Out Engineering. Also I think I can squeeze in some 1.75 long tubes.
Should be a fun ride for a 71 year old kid.
617402
 

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In regard to squish/quench clearance for head’s aluminum is more tolerant than cast iron and fuel injection either port or direct is more tolerant than a carburetor or throttle body injection. Going in that direction of things that are more tolerant on high compression through design selections the GenIII and up engines use a straighter valive angle than the Gen I and II,s 23 degrees which is more tolerant of high compression with a wider squish/quench.

None of the above is to say that optimization isn’t gooder if you can get it but anything beyond adaquate is just something hiding in the back ground. One of those things that’s good to have for emergencies like all you could get was 87 octane and you have to run the engine at 270 degrees of coolant temp while lugging a 15,000 pound trailer up Pikes Peak, in overdrive.

Chevy ran a cumulative squish/quench of .078 inch on the aluminum headed Gen I, L98 and and the Gen II, LT1 and LT4 with port injection and a detonation sensor. Ford several decades earlier ran a squish/quench of .080 with iron head’s and a carburetor on the 400M engine quite unsuccessfully. The engine basically is a damn good design and the few hot rodder‘s that dare play with it found that modifications that bring the squish/quench back in the range of .040 that by itself wakes this pinger up a lot. That with the addition of aluminum head’s and you’ve got a screaming monster on your hands. But it’s a hard engine to buildup as the needed parts are not widely available off the shelf.

So n your case the build is on safe ground.

Bogie
 

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Discussion Starter · #10 ·
In regard to squish/quench clearance for head’s aluminum is more tolerant than cast iron and fuel injection either port or direct is more tolerant than a carburetor or throttle body injection. Going in that direction of things that are more tolerant on high compression through design selections the GenIII and up engines use a straighter valive angle than the Gen I and II,s 23 degrees which is more tolerant of high compression with a wider squish/quench.

None of the above is to say that optimization isn’t gooder if you can get it but anything beyond adaquate is just something hiding in the back ground. One of those things that’s good to have for emergencies like all you could get was 87 octane and you have to run the engine at 270 degrees of coolant temp while lugging a 15,000 pound trailer up Pikes Peak, in overdrive.

Chevy ran a cumulative squish/quench of .078 inch on the aluminum headed Gen I, L98 and and the Gen II, LT1 and LT4 with port injection and a detonation sensor. Ford several decades earlier ran a squish/quench of .080 with iron head’s and a carburetor on the 400M engine quite unsuccessfully. The engine basically is a damn good design and the few hot rodder‘s that dare play with it found that modifications that bring the squish/quench back in the range of .040 that by itself wakes this pinger up a lot. That with the addition of aluminum head’s and you’ve got a screaming monster on your hands. But it’s a hard engine to buildup as the needed parts are not widely available off the shelf.

So n your case the build is on safe ground.

Bogie
Thanks, I'll leave well enough alone. It looks like I"ll pretty much just have an iron block LS2 with a bit more cam, Except for the truck intake.
Ernie








































ls2
 

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I have an LQ9 6.0L with ported LS6 heads and with an .041 gasket I'm at .035" quench and 11.35:1 compression. That's a pretty tight quench, but the cam will run out of steam at 6300 so I think it will be more than adequate.

Next you'll ask me if it works. I don't know. I haven't fired it up yet. Here's hoping that 93 octane doesn't rely on the knock sensors too much.

I actually built it with the intention of more E85 becoming available in my area which is happening slowly. I figure I can run 93 until more E85 comes around.
 

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As far as heads, the 317 heads are functionally the same as 243 LS6 heads, but with a larger chamber. You can treat them as a way to alter compression without changing flow potential. Your cam suggests using the 317s. You'll give up 10 hp, but you'll save money at the pump by being able to use the cheap gas. Your choice depending on how much money you want to spend on gas. For me (a drive it every day kinda person) I would give up the 10 hp so I could fill up with cheaper gas.
 

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Discussion Starter · #15 ·
More food for thought. I don't really mind giving up 10 hp or I wouldn't be using the stock intake. I could gain that back and a bit more by swapping to an NNBS intake but there has to be a point where enough is enough.
The 317's are sounding more practical.
Thanks for the input,
Ernie
 

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Squish is really important, especially in an engine running 10.4/11.0 compression. I would not rely on published specs as to what your compression will be. Get a burette and check to see what you actually have. Personally I would look for lowering your compression some if possible. It doesn't cost you as much HP as you might think and makes your engine a whole lot gas friendlier. If you measure it, then you know for sure what you have. If you are mistaken about what you have, it could get expensive later on. I'm building a somewhat nostalgic 500 Cad, and I'm going to keep the compression at 9:1 (or 9.5) so I can run regular gas. Lose maybe 10 hp. That said, I have a factory crate LS3 480 I'm installing in an S10..........no regular gas there. Nice truck.....I have one partially done thats waiting for me to get back to it.
 

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Discussion Starter · #17 ·
Thanks for the input. I'm open to head choice because when i bought this engine it was an LQ4 with 706 heads which actually works pretty well if what I've read is correct but they are in need of help. This was a "ready to run" deal. Right! He had washed it down with high pressure and stored it for two or three years. Rust in two cylinders. Bore job, bearings, piston, etc. We've all been there. Might as well buy flat tops which i did.The seller did pay for the parts and machine work. Now I need heads. Simple solution is to just get some 317's I'm thinking. I'll have an LQ9 with a baby Comp cam and probably all the hp/tq that old truck will ever need.

Ernie
 
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