6.0 vs. 5.3 conversion questions

mattt said:

Thank you for the real world experience deerhunter1970! Are you a 3/4T with the 4.10 gear? I didn't think 4.10 gears were available in the 1/2T truck/suv? Or did you change to 4.10 to compensate for tire size larger than stock?

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deerhunter1970 said:

No, it's a stock Yukon XL 1500 SLT. It has the GT5 option gears, ordered that way by my father-in-law. I'm not running big tires and wheels - 265/75/16 BFGoodrich All Terrain T/A KO2s, so it spins pretty fast on the highway, but it rarely ever kicks down out of 4th, even with a load on it. I really think that's how the original engine and trans lasted so long (471,000) as it didn't have to work so hard pulling the beast around.

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mattt said:

Thanks. Learned something new today. When the original engine and trans gave up the ghost at 471k, was it catastrophic or just a slow dying death?

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deerhunter1970 said:

Most everything else (axles, transfer case, alternator, etc.) is original and still working fine. I drive like an old person, gotta make this thing last as long as possible

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01FormulaTA said:

The 317s are similar to the 243/799s, they have the same intake port design, the same size intake and exhaust valves, only difference is 71cc combustion chamber vs 64cc combustion chamber...you can pull the 317 heads and have them milled at a machine shop...every .006~1cc so you could have them milled ~.040 to get down to a 64cc combustion chamber instead of buying another set of heads

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mattt said:

One plus I thought of for using the 243/799 instead of having the cut 317's is the more the stock 6.0 head is cut, you could run into an issue with intake manifold fitment, as the heads become shorter, the distance between heads will grow larger.

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