Life is like a box of chocolates....L9h engine

[ckeister]

This truck is going to be the death of me I swear. Some of you may remember a couple months back I posted about the Yukon (L92) I bought for my wife that ended up with bad cam bearings. Well I found a used L9H in a wrecking yard that I was very comfortable with. 130K on the clock, I was able to hear it fire up and run but not long because it had no air box or cooling hooked up. I ran several wrecking yards in the mid 90's so very familiar with the business. I ran a CARFAX on the vehicle it was comming out of. 3 owners. First two owners bought it from the dealer and it was serviced by the dealer. 90K service the whole deal. Last owner had it for 1 year, had a ton of work done on brakes, steering, and suspension. oil was changed 1 month before the car was wrecked. The dealer and all the prior owners are in a very wealthy area. Zero red flags on the CARFAX an everything indicated this vehicle had been very well taken care of.

The yard would only sell it to me in complete change over form so I got everything intake to pan, wiring harness, ecm, etc. They wouldn't really negotiate on the price which was the going rate everywhere I checked and not cheap but everthing told me this motor was good to go. The plan was to drop this in and go and rebuild the original motor in the truck.

Well......"Momma always said life is like a box of chocolates. You never know what your gonna get."

I get it home and on the stand. Start taking everything off the re-seal it and find this........

Well son of a *****, wasn't expecting that. So me being me im thinking, what happened? When did it happen? Who did the work? Was it done right?

 

[ckeister]

The pan is clean as a whistle, dug my finger deep into the valley before the drain plug and saw what, in my opinion is normal metal deposits on a 100K plus motor, no chunks of anything just super small metallic reflections in the sunlight. Inside of the valley pan clean as a whistle, nothing in the oil pick-up screen. From what I can see, cam lobes look good. I pulled the heads and cleaned them up so they look like this......and that is about as far as i've gotten. I'm gonna pull the camshaft and if it looks like the cam bearings have been replaced, I think I'm going to assume the work was done correctly, seal it up and run it.

 

[swathdiver]

Looks good and the plan sounds good; I'd do the same, except maybe put all new bearings in it since it's apart.

 

[j91z28d1]

what's in the rod pics that made you concerned?

 

[rdezs]

Looks like it might be a fairly recent rebuild. Just starting to show that gold hue. I'm thinking you probably got a deal. And you're right, the cam bearings will tell the whole story. Push rods and rockers just as clean?

 

[ckeister]

what's in the rod pics that made you concerned?

If you look at the rod caps, you'll see yellow dots on one side and line on the other. One the second pic, you will see yellow writing on the main cap. That is not factory. The yellow is engine marking paint. The marks on the rod caps are marks that the engine builder or mechanic used to mark the positions of the pistons and rods. I don't know why someone would have written on the main cap ad I can't read what it says. It is possibly the machine shop or the mechanic shop marking the parts to identfy the owner/vehicle it belongs to. Either way those marks mean someone has opened up the lower half of this motor.

what's in the rod pics that made you concerned?

 

[ckeister]

Looks like it might be a fairly recent rebuild. Just starting to show that gold hue. I'm thinking you probably got a deal. And you're right, the cam bearings will tell the whole story. Push rods and rockers just as clean?

Push rods yes, rockers not so much. There is some small blue marker paint marks on the heads along with what looks like heat tabs that may have been affixed to the back of the passenger side head but no signs of overheating. So some indications that the heads may have been used from a wrecking yard but nothing definitive. I can't wrap my head around a scenario in which the lower end of a motor woulnd need rebuild but put used heads on it. This is my first LS "build" or deep dive into the internals so what do I know? Maybe the rocker needle bearings blew so they put new rods/mains and used heads?

I do have an initial theory based on the CARFAX info but bottom line is I'll probably never know. The head castings are 821 if that means anything. I have not spent a tone of time but my understanding are they should be either 823 or 5346 something like that.

This one definately has me scratching my head. Just out of curiousity, I want to tear the whole thing down to try and figure out what happened but my wife and 2 month old son need a safe car to travel in so I have to balance my "while your in there" mindset and now curiousity over this engine with "What needs to be done to make this relaible for the next 3-4 years" until I do a full rebuild on the origianl motor

 

[rdezs]

I would finish checking it out, I'd get some ARP head bolts to fasten the heads down.... And call it good

 

[justchecking]

Those marks look more like an experienced rebuilder than a knucklehead.

 

[ckeister]

I would finish checking it out, I'd get some ARP head bolts to fasten the heads down.... And call it good

Agree. I ended my day on not a high note. After fully cleaning #1 piston and cylinder, the cross hatching is not that great. WTF is up with the carbon on these engines anyway. If cleaned a ton of used motors in my day but this shit is caked on and hard as a rock. Took me 3 hours just to do the one piston and cylinder? E85 is available in the area where this car lived. Maybe that's it? IDK but this carbon is hard and stuck like glue......

I'm stopping with that noise at this point and gonna pull the camshaft tomorrow.

 

[ckeister]

Those marks look more like an experienced rebuilder than a knucklehead.

Agree however there were some red flags when I started taking things apart......

1) The oil pan gasket was factory GM with a shit ton of RTV around the entire gasket. One of the CARFAX entries list the "Oil pan gasket repaired/resealed" shortley before a"No crank, no start issue" then the vehicle was apparently traded in.

2) When I pulled the harmonic balancer, it was waaaaaay to easy to come off. Someone put three uga uga's on the bolt with the impact gun and called it good.

Part of my issue is I know waaaay to much about the automitive industry and the shady shit that goes on so all the what ifs and what happened scenarios start going through my head

 

[rdezs]

If the whole motor is as clean as it looks in the photo, except carbon deposits on the top of the piston, I would suspect whoever had it made a lot of short trips. I usually find letting it soak in some diesel overnight does wonders.

The cross hatching not looking that good does not surprise me, if the engine was gone through by a dealer. There is a TSB on the subject..... Somebody posted it here recently..... If they are tearing down the engine to do the cam bearings, it's acceptable to install new rings without honing the cylinders if any crosshatch is still visible. It takes longer for the rings to seat, but they do eventually apparently. The extra time involved in that I would guess could also be the reason for the carbon deposits.

Many people..... Like my wife, LOL..... Drive it like a grandma. Rarely reaches 2,000 RPM. After you get it all together and you're satisfied it's running right, a prolonged high-speed run up a mountain pass will do wonders for that carbon. I encourage my wife to occasionally get on the freeway and push the pedal to the floor and let the engine breathe.... LOL, but that 400 plus horsepower scarces her

 

[rdezs]

Agreed on the oil pan gasket and harmonic balancer..... Probably done after the engine was rebuilt. Shade tree mechanic couldn't figure out you need to remove the two rivets to change the oil pan gasket? And probably didn't know about the crankshaft locking tool, probably didn't replace the harmonic balancer bolt. My guess is it had a little leak at either the front crankshaft seal or oil pan and someone was trying to address it?

 

[justchecking]

Maybe someone bought a short block and then installed themselves which would explain the pan and harmonic balancer.

 

[strutaeng]

Those marks on the rods you show on the first photos I'm pretty sure are from the factory. I've torn down a few engines and I think they all had them

 

[Joseph Garcia]

Looks damn good for the mileage.

 

[ckeister]

If the whole motor is as clean as it looks in the photo, except carbon deposits on the top of the piston, I would suspect whoever had it made a lot of short trips. I usually find letting it soak in some diesel overnight does wonders.

The cross hatching not looking that good does not surprise me, if the engine was gone through by a dealer. There is a TSB on the subject..... Somebody posted it here recently..... If they are tearing down the engine to do the cam bearings, it's acceptable to install new rings without honing the cylinders if any crosshatch is still visible. It takes longer for the rings to seat, but they do eventually apparently. The extra time involved in that I would guess could also be the reason for the carbon deposits.

Many people..... Like my wife, LOL..... Drive it like a grandma. Rarely reaches 2,000 RPM. After you get it all together and you're satisfied it's running right, a prolonged high-speed run up a mountain pass will do wonders for that carbon. I encourage my wife to occasionally get on the freeway and push the pedal to the floor and let the engine breathe.... LOL, but that 400 plus horsepower scarces her

Ok that makes me feel a WHOLE lot better. I was feeling a little down last night seeing that. I don't post a whole lot but frequently lurk. I don't participate in on line forums much cuz no matter what the topic, it seems like they get over run by keyboard warriors that talk out their asses. I really like this forum because it's clear there are a number of people here that really know their stuff. Keep an eye out cuz im gonna do another thread with a bunch of questions.....

My wife is the same way....lol. Me on the other hand did my fair share of drag and circle track racing many moons ago so I drive everything like I stole it.

 

[ckeister]

Those marks on the rods you show on the first photos I'm pretty sure are from the factory. I've torn down a few engines and I think they all had them

I don't think so. When I did the oil pump/pick up tube on the original motor it didn't have it. The writing on the Main cap is 312 with four letters. I'm thinking that is the inventory tag for the vehicle and four letters of customer name to identify the vehicle/customer. I've torn down a bunch of motors in my day but this is my first LS tear down so I could be talking out my ass....lol The motor in our truck definately didn't have those markings.

 

[ckeister]

I shouldn’t have looked…..more questions than answers now for me. The cam was in there tighter than a tick unlike the one in my truck where I rocked the front of the cam and could feel the end play.

Don’t know what they are supposed to look like so…..opinions from the more experienced welcome.

 

[rdezs]

The front camshaft bearing takes a beating. LOL, most people say don't look at it and just slide the cam in. it's not difficult replacing just that front camshaft bearing.

For comparison purposes, below is a photo from my neighbors L94 that I did the AFM delete on about 6 weeks ago. Just under 200,000 miles, and he changes his oil before it hits 5000 miles....