Pontiac Grand Prix Forums : Grandprix
 

Grand Prix Forums is the premier Pontiac Forum on the internet. Registered Users do not see the above ads. Please Register - It's Free!

Pontiac Grand Prix Forum - Welcome Register today! Contact us!

Results 1 to 10 of 10
  1. #1
    SE Level Member
    Join Date
    Jun 2017
    Location
    Florida
    Posts
    14
    Chats
    0

    Default Tear down report for a very high mileage, stock engine

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

    I thought Iíd 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. Hereís 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 itís 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 canít trace, thatís 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. Itís 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.

  2. #2
    GTX Level Member QUICKSILVER462's Avatar
    Join Date
    Jun 2009
    Location
    HUDSON
    Posts
    1,029
    Chats
    0

    Default Re: Tear down report for a very high mileage, stock engine

    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.

  3. #3
    SE Level Member
    Join Date
    Jun 2017
    Location
    Florida
    Posts
    14
    Chats
    0

    Default Re: Tear down report for a very high mileage, stock engine

    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.

  4. #4
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
    Join Date
    Sep 2009
    Location
    Rogers, MN
    Posts
    20,405
    Chats
    80634

    Default Re: Tear down report for a very high mileage, stock engine

    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.

    SMGPFC Member #1

  5. #5
    SE Level Member
    Join Date
    Mar 2017
    Location
    Internet
    Posts
    127
    Chats
    1279

    Default Re: Tear down report for a very high mileage, stock engine

    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.

  6. #6
    GrandPrix Junkie
    Join Date
    Oct 2009
    Location
    St. Louis
    Posts
    3,722
    Chats
    0

    Default Re: Tear down report for a very high mileage, stock engine

    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..

  7. #7
    GTX Level Member
    Join Date
    Dec 2012
    Location
    troll land
    Posts
    1,033
    Chats
    63

    Default Re: Tear down report for a very high mileage, stock engine

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

  8. #8
    SE Level Member
    Join Date
    Jun 2017
    Location
    Florida
    Posts
    14
    Chats
    0

    Default Re: Tear down report for a very high mileage, stock engine

    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.

    2005 GTP

  9. #9
    SE Level Member
    Join Date
    Jun 2017
    Location
    Florida
    Posts
    14
    Chats
    0

    Default Re: Tear down report for a very high mileage, stock engine

    [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.

    2005 GTP

  10. #10
    GrandPrix Junkie
    Join Date
    Oct 2009
    Location
    St. Louis
    Posts
    3,722
    Chats
    0

    Default Re: Tear down report for a very high mileage, stock engine

    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.

Similar Threads

  1. Engine tear down pics
    By TwiztdWun in forum 3.8L V6 Supercharged (L67)(L32)
    Replies: 14
    Last Post: 03-24-2014, 09:58 PM
  2. ENGINE TEAR-DOWN - pics and need advice
    By aimhigh86 in forum 3.8L V6 Supercharged (L67)(L32)
    Replies: 13
    Last Post: 06-30-2013, 12:40 AM
  3. High Mileage
    By jetscrazy44 in forum The Rant Forum
    Replies: 47
    Last Post: 08-02-2010, 06:19 AM
  4. Pics of my engine tear down dial up user beware
    By TorqueAutoMotiv in forum Off Topic Discussion
    Replies: 135
    Last Post: 12-13-2009, 10:09 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •