04’ Yukon SLT 5.3 L59, Engine replacement?

[Police428]

Got my test result from my Oil change a week or so ago. It’s a “yikes”. Possible engine rebuild in the works?. Will update regularly

Test Result by BlackStone Labs in IN

If it comes to the engine being out, should I rebuild and upgrade, or just put in a OEM replacement long Block?

 

[rockola1971]

Got my test result from my Oil change a week or so ago. It’s a “yikes”. Possible engine rebuild in the works?. Will update regularly

Test Result by BlackStone Labs in IN

If it comes to the engine being out, should I rebuild and upgrade, or just put in a OEM replacement long Block?

If you plan on keeping the Tahoe for 6-10yrs+ more then I would throw a long block in it and be done with it. As far as "upgrades" it just depends on what you intend to achieve.

 

[Erickk120]

yup, if you want to keep it for 5+ years I would def slap a new one with some mods while at it.

 

[rockola1971]

yup, if you want to keep it for 5+ years I would def slap a new one with some mods while at it.

Ls6 Cam and 799 heads.

 

[tRidiot]

Do a rebuilt 6.0 and call it good.

 

[Mudsport96]

6.0 btr stage 1 ( or other truck designed cam) and 706 heads. These things are heavy and need the torque. 799 heads are worth 9hp over 706s all the way up top with the comp 459 cam and its way more rowdy than an ls6 cam. So with a cam more suited for a Tahoe, 799 heads arent worth the torque loss you'll see in normal driving conditions.
Big problem is injectors if you go 6.0. The flex injectors will be fine as long as you stay on gas, but you'll run out of supply if you go to fill up with e85.
Head comparison 706 vs 799

 

[Erickk120]

6.0 btr stage 1 ( or other truck designed cam) and 706 heads. These things are heavy and need the torque. 799 heads are worth 9hp over 706s all the way up top with the comp 459 cam and its way more rowdy than an ls6 cam. So with a cam more suited for a Tahoe, 799 heads arent worth the torque loss you'll see in normal driving conditions.
Big problem is injectors if you go 6.0. The flex injectors will be fine as long as you stay on gas, but you'll run out of supply if you go to fill up with e85.
Head comparison 706 vs 799View attachment 364967

You are giving future ideas

 

[rockola1971]

6.0 btr stage 1 ( or other truck designed cam) and 706 heads. These things are heavy and need the torque. 799 heads are worth 9hp over 706s all the way up top with the comp 459 cam and its way more rowdy than an ls6 cam. So with a cam more suited for a Tahoe, 799 heads arent worth the torque loss you'll see in normal driving conditions.
Big problem is injectors if you go 6.0. The flex injectors will be fine as long as you stay on gas, but you'll run out of supply if you go to fill up with e85.
Head comparison 706 vs 799View attachment 364967

Isnt that a chart comparison for a 6.0L? Where's the comparison for the 5.3L? Or how about a chart with 799 heads/LS6 Cam on a 5.3L bored to a 5.7L(LS1)?

 

[Mudsport96]

Isnt that a chart comparison for a 6.0L? Where's the comparison for the 5.3L? Or how about a chart with 799 heads/LS6 Cam on a 5.3L bored to a 5.7L(LS1)?

Well, a 5.3 bored to 5.7 with a ls6 cam would be an ls6. And the 799s are supposed to be the same as the ls6 heads without the hollow valves so you may get float at elevated rpms.
But heads are going to do what they do. 799s drop compression compared to 706s so you will lose average power everywhere. And how often will the normal guy run his Tahoe above 5000 anyway? Richard Holdener has videos of stock cam and head comparisons and the fbody and vette cams always lose to even the stock 5.3 cams tq below 4600.
The LS6 cam lost 30ish lbft at 2500 rpm and probably more at 2000. Now my Tahoe only runs 2200ish at 70mph. So mileage would suffer because now the engine is lugging way out of its power band. in each pic the stock 5.3 is blue and the ls1 and ls6 is red. Sure the ls1 is worth 30 and the ls6 is worth 50 hp each. But tq suffers.
If and it is a big if. If i was to use a factory cam for an upgrade it would be the L33 cam. Minimum loss down low but only 16hp up top. An aftermarket cam is the way to go to prevent tq loss as much as possible. As for heads. The 5.3 is small. Compression is its friend. Use 706s unless you are geared and have a stall to get passed the tq dip you will have.

 

[rockola1971]

Compression is not my friend unless I am on a racetrack. Jacking compression up in an engine that is a daily driver raises fuel costs everytime you goto the pump. There is likely already a cam grind available for the 5.3L bored with 799 heads that yields better torque and more suitable for a K chassis. The 799 heads outflow the 706 heads all day long and always will unless someone drops a rag into a port while the intake is off and forgets about it.