Tear down report for a very high mileage, stock engine

[jmiska]

I’m new on this forum, but have read here a bit and it seems like a good group.

I thought I’d share what I found with a tear-down of a very high mileage older engine, for those of you who are getting to that point, as well. All these cars are old now, but mine has an above average number of miles, so it might be a good predictor of things to look for on your engines in the future.

The car is a basically stock 2005 GTP, and has 245,000 on it now. It had developed the usual lower-end oil leaks, as well as a valve lifter noise. All this meant the engine was coming out. Here’s what I found:

The lower end is stout and well made, and probably will last forever with good oil pressure and no leaks. If you have an old engine, plan on re-sealing the entire bottom end. It was leaking from everywhere. It had seeped from the rear main for about 30,000 miles, but suddenly got bad and I knew it needed to be dealt with right away. The bores were flawless, even at this mileage, and still had nice clear cross hatching. They were left alone. The cam was shot. This was a surprise, as it’s a roller cam, but two lobes were badly pitted, and the corresponding rollers were as well. This was the source of my valvetrain noise. If you have a loud lifter click combined with a strange squeak/chirp that you can’t trace, that’s a place to look. Another surprise was the intake manifold. What I thought was the intake manifold gasket seeping turned out to be a water passage block off that was corroded right through. The manifold needed to be replaced. The exhaust cross over pipe had a crack opening up along a seam. With the heat shield off, I had it welded, then wrapped the pipe with thick header wrap. It’s better insulation than factory and keeps the throttle body much cooler.

Otherwise, everything was holding up very well. I put in a new oil pump, timing set, did a valve job with new springs and otherwise just cleaned it all up and put it back in.

[QUICKSILVER462]

Thats is great info, thanks! I am not surprised to hear the cylinder walls still in good shape, modern fuel injection helps keep proper fuel mixture and atomization, this prevents raw fuel from removing the oil film on the top part of the cylinder walls where it is needed most. Every high millage carbureted engine I have seen always has a ridge on the top. Of course proper oil and changes, along with a clean air filter also helps.

[jmiska]

Good points. The intake valves were the cleanest I've seen on such an old engine, but it's also the first modern FI engine I've been into. The first engine I ever took apart was a 1975 Triumph Spitfire. At about 60,000 miles it blew the top of a piston off when I had pushed it too hard. Upon tear down I discovered ridges at the cylinder tops that were a good 1/32" thick! The top ring hit the ridge on high RPM and that was the end of that piston. That was at only 60K. It's impressive how long modern engines do last with high quality materials, precision machining and good mixture control. My truck has the original Chevy L31 Vortec 350 that has 425,000 miles and has never even had the heads off. It uses a quart of oil in 2000 miles, which isn't bad, by my standards.

[Fivefingerdeathpunch]

GM roller cams of this era are pretty common to pit like that or completely wipe the top of a lobe off.

The LS motors see this problem very often. I have a stock 5.3 cam from a rod failure motor in my tool box with like 200k on it or something with a lobe wiped pretty good. The metal on the lifter roller is harder than the metal on the cam itself in some motors.

[BillBooost37]

When I pulled mine apart at 186K it also showed cross hatches. And the rings were not worn much at all. The motors were built well in some aspects.

[FordMan77]

Interesting, I wonder what the inside of the motor in my 00GT looks like at now that it's sitting at right around 302K. I did recently have the LIM out to regasket everything and the inside that I could see at that point looked nice and clean. Just a nice golden brown color. Now with the rest of the car at 402K not sure what else may be waiting to happen, lol..

[l67ss]

You didn't take the main caps off did you?

[jmiska]

No, I left those and the rod caps on. There seemed no need to remove them. The crankcase was very clean, the engine has had all its oil changes, and spent most of the time on long highway trips, and the oil pump looked good. I just re-sealed everything and changed to a new Melling oil pump as a matter of good practice. My feelings are, unless something had gone wrong with the bottom end, it's probably still in better spec than anything I or a local machine shop could do, so why mess with it? Also, had it given symptoms of a lower end bearing problem before coming apart, I would have made the choice to either find a new engine or a new car rather than put the time and money into this one.

[jmiska]

[QUOTE=FordMan77; Now with the rest of the car at 402K not sure what else may be waiting to happen, lol..[/QUOTE]

The good news is, if you have access to a lift, you can effectively do a complete mechanical restoration on this car by dropping the whole cradle out the bottom with the engine attached. With that out, you can get to your steering, suspension, transmission, AC and engine all in one shot. My good friend has a professional shop, and that's how we did my car. While it was out we did struts, sway bar bushings/end links, half shaft assemblies and motor mounts, along with the engine work. This is the second time that's all been out. At 200,000 it had come out for a transmission rebuild and steering rack/tie rod replacement, however, that time the engine remained hanging in the bay from above. I would not have attempted to drop the entire cradle/running gear out without the lift, but I guess some guys do it at home. I'm too old, and too busy for that, nor do I have the garage space to devote to such a big job. Actually, it's not dropping the cradle. It's supporting the cradle and then lifting the car off it, but you get the idea.

If the body and interior is in good shape, and you want to keep the car, start thinking about that approach. I would not have bothered with the car without the help of my friend and his shop, but being a Florida car, the body is spotless, so it was worth the mechanical rebuild, and it was a fun thing to do.

[FordMan77]

Oh trust me, it's had all of the mechanical things replaced at least once already. Rack, all new struts, Eibach springs, rear control arms, multiple front wheel bearings, entire a/c system minus the evap coil, trans, couple axles, LIM/UIM, front control arms. Pretty much rebuilt the car over time. Really the only things left I need to do are replace all the subframe mounts, engine and trans. mount (again), and fix the fuel sending unit so I really know how much I have in the tank vs. the trip odo.

Interior is dying since this car saw a lot of abuse in the 120Kmi. that my brother owned it. Kids pretty much took care of the back seats and carpet. I have a complete set of GXP seats waiting to go in. Just need to find some carpet. I'll probably strip and redo the headliner while the int. is out. As long as I can keep up with the mechanical side of things the int. is just a side note, but it sure would be nice to ditch the drivers seat with all those miles on it. A true PITA, lol.