Good Ol' 3800!

Discussion in 'GM' started by 99LeCouch, Feb 27, 2009.

  1. phoebeisis

    phoebeisis Well-Known Member

    The old V-pushrod motors have one really significant advantage over the V-OHC motors-they can be narrower which makes it easier to pack them into that crowded engine bay. This is probably the only true advantage they have, but it is important.


    Charlie
     
  2. 99LeCouch

    99LeCouch Well-Known Member

    Crowded engine bay? A GM H-Body? This car is one of the easiest-access cars I've worked on. Pretty much everything is where you can get at it, even the rear-bank plugs. Clamber onto the front bumper, lean over the engine, and they're right there.

    Other 3800-powered cars such as the W-bodies are slightly worse, but still not bad.

    A DOHC V6 I'd hate to replace plugs on.
     
  3. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    Generally speaking, the overhead cam engines have better airflow through the ports and so can make more power at higher rpm. Since horsepower is just "torque over time", adding 20% to the redline speed adds 20% to the net horsepower if the torque output were to be perfectly flat. Moving the torque curve higher in the rev band means a higher horsepower number, which sells cars and charms the auto mags, but without VVT, the little DOHC rev motors will feel weak and flat at lower rpm.

    The pushrod engines have less internal friction, are smaller in size, far less complicated, far more tolerant of neglect, and lighter in weight (when built from the same materials). But they are limited in the rev band because of the greater valve train inertia (pushrods and rocker arms changing direction 50 times a second at 6000rpm), and their intake and exhaust ports don't "flow" as well. For anyone whose tach never sees the high side of "3", there is simply no difference in driveability or noise. At low revs, the pushrod engine has a theoretical advantage in efficiency, due to less friction and fewer moving parts, but the difference is not great enough to demand the OHV powerplant.

    Those of us who give a darn about reducing our petroleum usage can get along quite well with our "crude" "archaic" "buzzy at the redline" "old school" "stuck in the '70s" "unrefined" OHV engines. In my own auto ownership experience, I've seen better real world FE from my OHV engines (consistently over 30mpg with 3.1L and 3.5L V6s in five different cars) than OHC engines (Saturn 3.0L DOHC that struggled to reach 30mpg, just over 30mpg with lots of easy driving with a Mitsu 3.0L SOHC).
     
  4. phoebeisis

    phoebeisis Well-Known Member

    99LECOUCH,

    Yep, that is why it has such a nice engine bay-it is missing that extra 2-3" of height on top of the head.

    MAXXMPG Yes, in general the OHC can rev a bit higher, and they can make more power per cubic inch because of this better high rpm valve control.
    However, as you say/imply- and judging from the relative EPA FE of the 5.3 GM vs the 5.7 and 5.6 Toyota and Nissan 4 valve motors- IN REAL WORLD driving the 4 valve OHC motors don't seem to have any real world advantage as people and "stuff' mover over GMs old tech pushrod 2 valve motors.

    Chevy/GM somehow has made the 5.3 perform as well-- real world- as Toyota's 4 valve 5.7 and Nissan's 4 valve 5.6.
    On the same 3000 mile trip
    Suburban 5.7 21.3 mpg 68 mph cc on 6000 lbs loaded
    Titan 5.6 V-8 19.9 mpg 66 mph cc on 5700 lbs loaded
    Tundra 4.7 V-8 15.9 MPG at 73 mph cc on 5500 lbs loaded
    Tacoma 2.4 4 cyl AT 24 MPG at 75 mph cc on 3500 lbs loaded
    Honda Pilot AWD V-6 22.3 MPG at 73 mph CC on 5200 lbs loaded
    Driven the same way the Pilot would have been 3 mpg better, and the Tacoma would have been about 5 mpg better, the Tundra would have been about 3 mpg less.

    The good mpg of the Suburban isn't because of tall gearing- it turns 1750 rpms at 60 mph, more than the Titan(1550) Pilot (1650), but less than the Tundra(2000).

    The small 235/75 15" wheels/tires are certainly a plus,I think.

    The current 5.3 is a full 3 mpg better than the old 5.7.They are 25mpg highway vehicles at 64 mph.Basjoosed-they might approach 30 mpg(granted they would be 3 or sofeet longer!)

    Charlie
     
  5. jkp1187

    jkp1187 Well-Known Member


    Hmmm.... It's a pain to reach the plugs in the back bank of the Impala's 3800. And did you ever try to check the power steering fluid? The manual says the reservoir is at the back of the engine....but do you see it there anywhere? (I found it.....but it is in one of the most ridiculous locations imaginable.)

    Not that an OHC V-6 engine would be better, of course. Far from it.
     
  6. 99LeCouch

    99LeCouch Well-Known Member

    It's not too bad on mine once the strut bar gets taken off. Which takes all of 1 minute. I've changed the power steering fluid several times, so I know all about access back there.

    W-bodies have the front dogbone mounts and generally smaller engine bays because they're meant as "sportier" cars, while H-bodies are cushy tanks meant for highway cruising. I do know that engine work on this car is pretty easy since there's space to swing a wrench.

    I took a look at the engine bay of an older Toyota pickup today when jump-starting it. Eek! It was cramped.
     
  7. kvsdude

    kvsdude Member

    An amazing engine.
    I had a '99 Pontiac Grand Prix before giving it away to my 17 year old bro when I bought my new Mazda3. It's got 100k on it and feels like when it had 50. I just felt like getting a new car, nothing wrong with the ponti.

    I took a trip from NJ to VA and got 29MPG with vent shades and going around 80mph.

    The overdrive on those engines are crazy. I would try to glide in neutral to save gas and it actually felt exactly the same! That doesn't happen in my Mazda, which is only more fuel efficient due to being a 4cyl compact.

    My dad's got an '03 Bonnie. It's a crappy car in that everthing is falling apart - except for his 3800 engine and trans.
     
  8. Nevyn

    Nevyn Well-Known Member

    I have one of those. To do the rear ANYTHINGS you have to jack the whole front end off the ground, disconnect the battery, put the car in neutral, take off the motor mounts, then ROTATE THE ENGINE BLOCK to get at the backside.

    *mutters* and then if something goes wrong you have to do it all over again......:mad::cry:
     
  9. 99LeCouch

    99LeCouch Well-Known Member

    Yeah, I've heard horror stories of plugs on Grand Prix's. Great highway cars also, but darned if I would want to work on one.
     
  10. Nevyn

    Nevyn Well-Known Member

    Our GP has the 3100, but my father-in-law has a 3800. I'll have to take a gander at his engine bay sometime and see if it's as tight as mine. What transmission do you have to go with it? the 4T60 or the 4T65? I love the way they'll let the car just loaf down the highway doing 50 mph at 1500 RPM.
     
  11. kingcommute

    kingcommute Hypermiling Apprentice

    The bay on our now-traded Olds Intrigue was fine except for the rear bank of plugs - everything was done blind when we changed them. Nothing is as bad as a Mazda Mpv though.....2/3 of the motor is underneath the overhang in the engine bay. Terrible.

    I still wish we had that Olds though - twas a dang good car and much better than what we traded it for. Comfortable on long trips, well-appointed, and plenty of power if it was ever needed.
     
  12. jkp1187

    jkp1187 Well-Known Member

    Annoyingly, I just got a Blackstone oil analysis report from the latest oil change... It turns out that small amounts of coolant were found in the oil. Not a big problem yet - but could this be the lower intake manifold leak that people have reported on the 3800?
     
  13. Pryme

    Pryme Active Member

    Or possibly head gasket. :mad:
     
  14. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    The 3800s have been known to have a porous engine block that allows coolant and oil to wick through the metal. If that is the case, it never gets any better or any worse, and could potentially have existed since the car was new. If subsequent testing reveals more coolant in the oil, then the manifold gasket is the likely suspect. The new gaskets they use are supposedly the surefire fix for the problem.
     
  15. 99LeCouch

    99LeCouch Well-Known Member

    Coolant in oil is more a sign of lower IM gaskets than a failed head gasket.

    Or what Maxx said.
     
  16. jkp1187

    jkp1187 Well-Known Member

    I asked the woman from Blackstone (they called me up when the analysis was complete to talk over the results - a nice touch, I thought,) and she thought it unlikely that it was the head gasket, as she did not see certain metals present in the oil that would indicate head gasket failure.


    Interesting - I did not know that. In any event, (and per Blackstone's recommendation,) I will keep oil changes to 3,000 miles at most, and monitor the situation.

    It was good to see that, other than this small leak, there were absolutely nothing else wrong with the engine.

    How much do you think I should pay an independent shop to have the LIM replaced, if it comes to that?
     
  17. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    I don't know anyone who has had the lower intake gaskets replaced, so I don't know the exact cost, but a quick search online shows a cost averaging $350 for an independent shop and $650 at a dealer. Repair costs vary by location, so calling around should give a good idea of cost for you. The problem is in the gasket material's incompatibility with DexCool and not a flaw in the engine design, so the new gasket cures the problem.

    Check the oil every few hundred miles or so, and if it starts to look "foggy", it has coolant mixed in and an oil change is recommended. If the issue is a porous block, the next oil change analysis will reveal roughly the same coolant contamination.
     
  18. 99LeCouch

    99LeCouch Well-Known Member

    There are also a lot of "gearheads" within a few hour's drive of you who would help you do the repair a lot cheaper than a shop would.
     
  19. phoebeisis

    phoebeisis Well-Known Member

    GM V-8s 5.7 and 5.3 -also I known for the intake manifold gasket failure. I have no idea why this failure is kinda common. I've heard 'stories" that it is due to the Dexcool coolant, but I doubt that.
    Charlie
     
  20. 99LeCouch

    99LeCouch Well-Known Member

    Dex-Cool plus the type of nylon used in OEM gaskets equals failure. I'm replacing the gaskets with the aluminum ones this summer. Also doing the OEM upper intake with a re-designed unit while everything's apart.
     

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