99 Yukon failed head gasket / Engine rebuild

[hotrdd]

Looks like my 99 5.7L SLE Yukon finally blew the head gasket with 250’000 kms on the odometer. I started to lose small amounts of coolant without any indication of where it was going. I did a compression test and found Cylinder #3 @ 130 with a wet/water on the plug and #6 at 140 the rest were around 157. So I’m pretty sure that I have a blown head gasket  Anyway the rest of the Yukon is in great shape so I want to just want to fix the engine and keep on cruising. I used the truck as a daily driver and for towing my 23 foot camper on the weekends in some really hilly countryside. So besides the head gasket I am considering a new water pump, timing chain and gears, lapping the valves and was considering doing the piston rings while I was that deep. Thoughts?

A few weeks ago I had done the MPFI upgrade, new Cats & O2 sensors and then an oil change, coolant flush and new plugs. And now this :sad72:

Is there anything else I should look at or are there other upgrades I should consider to help with performance and towing?

 

[MO Viet Vet]

If you are going to do the rings then you need to refinish the cylinders and if you have the pistons out and then new bearings then new bearings on the crank. Now you are way in to it and should just do a reman engine. IMO the best is Jasper but others will say different, I am sure.

 

[hotrdd]

I should be able to just drop the pan and then pull the pistons out and hone the cylinder walls before installing new rings. Am I missing something? I thought the pan had to come off anyway for the heads, water pump and timing chain?

 

[MO Viet Vet]

I do see what you are saying. Yes you can get the pistons out from the top, after removing the ridge at top of the cylinder, after removing the pan and releasing the piston rods. If you plan to take out from the bottom then crank has to be removed anyways so then new crank bearings and have the crank worked at machine shop. You can't reinstall the pistons with new rings from the bottom so the ridge has to come off at the top anyways. A lot of work and taes way longer than just getting a good engine with a warranty.

 

[hotrdd]

Are there any moderate upgrades that would get me a little more HP for towing?

 

[MO Viet Vet]

Rework the heads a little and match to a different cam for better torque. I still say by the time you do all this and your time you would be better off with a rebuilt Jasper engine and they can build the engine the way you want for the towing and the warranty is a big plus.

 

[lesterl]

Better towing, put on a smaller tire.....