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4.8/5.3 heads to Ls1 heads

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Old Jul 30, 2008 | 02:43 PM
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Default 4.8/5.3 heads to Ls1 heads

will Ls1 fbody heads #241 fit on a 04 yukon 4.8 that has head #706

was told the 4.8 heads are the same as the 5.3
and ppl change the fbody to 5.3

so was just wondering if the heads would bolt up to the truck

pls help, any info appreciated

nu-B here
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Old Jul 30, 2008 | 03:32 PM
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yes but you will lose compression and the flow #s are close to the same
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Old Jul 30, 2008 | 09:04 PM
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I put L33 heads on my 4.8, and they woke it up quite a bit. They have the same size valves (2.00/1.55) as your LS1 heads versus the LR4's 1.90/1.50s. I don't know what the difference in your chamber is, but I actually gained compression with this swap, coupled with a home port job, I got a noticeable seat of the pants difference. I am running the 799 casting (that's the chamber in my sigline).
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Old Jul 31, 2008 | 11:59 AM
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with the 241s having a larger 2.0intake valve
as opposed to the 706s 1.89intake valve
affect anything?
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Old Jul 31, 2008 | 12:14 PM
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Like I said, I'm running them on my 4.8. The only thing that does is help flow. Our smaller bore can't make quite the use of it that an LS1 or 6.0L engine can, but if you're asking if valve clearance will be an issue, the answer is no (assuming your camshaft is still a stocker).
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Old Jul 31, 2008 | 12:22 PM
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Originally Posted by deadhorse66
I put L33 heads on my 4.8, and they woke it up quite a bit. They have the same size valves (2.00/1.55) as your LS1 heads versus the LR4's 1.90/1.50s. I don't know what the difference in your chamber is, but I actually gained compression with this swap, coupled with a home port job, I got a noticeable seat of the pants difference. I am running the 799 casting (that's the chamber in my sigline).
the 799 is supposed to a truck version of the 243, i dont rmember if they have d shaped exhaust ports, tho.
the chamber should be around 65-66cc's
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Old Jul 31, 2008 | 12:28 PM
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Okay, that's what I had heard too, and you are right on the chamber. Mine checked at 64 before I polished them (didn't check afterward). What is a stock LS1? Never CC'd one before. Surely they aren't 72 like the LQ4 are they?
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Old Jul 31, 2008 | 01:42 PM
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Originally Posted by deadhorse66
Okay, that's what I had heard too, and you are right on the chamber. Mine checked at 64 before I polished them (didn't check afterward). What is a stock LS1? Never CC'd one before. Surely they aren't 72 like the LQ4 are they?
ls1 is 67cc,
ls6 is 65cc
ls2 is 67cc
lq4 is 71cc
or so it goes
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