(non-Buick) Anyone changed a head gasket on a GMC 4.3 Jimmy?

Discussion in 'The Bench' started by bobc455, Jan 23, 2003.

  1. bobc455

    bobc455 Well-Known Member

    I know this isn't Buick related, but since there are a lot of good mechanics here, I figured I would ask.

    A friend of mine has a 94 Jimmy, and I think it has the 4.3 liter V6. The head gasket is blown.

    I could change the head gasket on my 455 with a blindfold and one hand behind my back (except for re-torquing), but I never trust the "newer" cars that they won't put some tricks in there.

    Does anyone know if there is something that would prohibit a regular guy from doing a headgasket on this motor? Or is this a fairly straightforward job?

    -Bob Cunningham
    bobc@gnttype.org
     
  2. jimmy

    jimmy Low-Tech Dinosaur

    peace of cake?

    I have never had to change the head gasket of any of my Jimmy's.
    I had 175K miles on my 88 when I sold it, my 99 Jimmy has 75K miles and my 92 Jimmy has 189K on it. The 4.3 engine is a small block 350 with 2 cylinders missing. They are very good engines as far as I know and easy to work on. I wouldn't be afraid to change a head gasket in a minute. If you can do your Buick then it should be a piece of cake. What year model is it? I have had my 92 for 7 years and only had to replace the valve springs due to one breaking. It was the intake spring and when it did not shut all the way the piston pushed air back into the intake and sent the MAP sensor crazy and it was smoking black and the only fault code set in the ECM was the O2 sensor out of range. It took a while to figure out but then I applied the KISS (keep it simple stupid) theory and checked the mechanical basics and found low compression on one cyl. pulled the valve cover and checked the springs. All the wiring connectors for all the sensors, etc. and different and almost impossible to hook up wrong.

    Good luck.

    Jimmy
    Dinosaur Race Team
     
  3. dave64

    dave64 Well-Known Member

    I agree with Jimmy. The 4.3 is a pretty good engine. Bought an Astrovan a couple of years ago with a weak engine. Had about 175k (miles) on it. Previous owner had not looked after it and rumour has it if you overheat them you can crack heads or blow head gaskets. Not sure about that but..... Its just a simple small block chevy with 2 cylinders lopped off.
    My Haynes manual says-
    Remove intake and exhaust manifolds, valve cover, any external brackets etc.
    Remove pushrods- store in sequence.
    Loosen head bolts in 1/4 turn sequence until they can be removed by hand.
    Lift the head off the engine.
    Install in reverse sequence.

    Some things to be careful of!
    -engine must be completely cool when the head comes off or the head could warp
    -Head bolts must be reused in the same hole they came out of.
    -IMPORTANT- there is a row of bolts along the edge of the head below the spark plug holes- 13 bolts per head total!
    - head bolts must be coated with a non-hardening sealant ( Permatex No 2 ?) when reinstalling or coolant will leak past the bolts

    Just basic mechanical work - pick up a shop manual at your local library for all the specs and details. If you can build a Buick the 4.3 won't be a problem. Good Luck.
     
  4. mygrain

    mygrain quivering member

    Last edited: Sep 17, 2011
  5. GSXMEN

    GSXMEN Got Jesus?

    Another heads up...make sure you clean out (more like chisel out) the EGR passageways in the intake while it's off!! They always seem to clog up and cause all sorts of driveability issues!! Check the heads too while you're in there.

    Don't know about the rest of you guys...but I'm not a big fan of the 'end seals' for the intake on 4.3's or 350's!! Once everything is all cleaned up, lay a nice bead of RTV across the end rails - starting about 1/2" to 3/4" up on the head and going over to the same place on the other head.
     
  6. bobc455

    bobc455 Well-Known Member

    Thanks, I'm gonna give it a shot then.

    I appreciate all the pointers!

    It seems like although computers have complicated the cars overall ni the past 20-odd years, the engines are easier to work on than some of those late 70's V8s that had a hundred miles of vacuum line all over the place...

    Thanks again.

    -Bob Cunningham
    bobc@gnttype.org
     
  7. gstewart

    gstewart Well-Known Member

    head gasket

    a good piece of advice- do NOT re-use the head bolts !! u will not get the proper torque on them ..
     
  8. bobc455

    bobc455 Well-Known Member

    Gerry,

    Alright, here is a stupid question. Where do I get new head bolts? Will that be a dealer item? Or can parts stores order them?

    Thanks,

    -Bob C.
     
  9. gstewart

    gstewart Well-Known Member

    head bolts

    head bolts can be purchased from the dealer or aftermarket autoparts stores . u will need a shop manual to for the engine to learn the torquing sequence & torque values . buy a haynes or chilton manual for the specs .
    as one of the other fellows , there is a lot of work here .
    more that likely, the head may have to be planed .
    good luck .
     
  10. bobc455

    bobc455 Well-Known Member

    Thanks, Gerry.

    I am aware that the head will have to be inspected for warping and cracks etc., I have a good machine shop nearby that can take care of fixing it if needed.

    Thanks!

    -Bob C.
     
  11. Jim Weise

    Jim Weise 1000+HP

    Bob,

    Just make sure you have the head resurfaced, and check the block deck to make sure it is flat.

    Head gaskets generally fail for a reason, and finding it will insure your not doing this again.

    JW
     
  12. VKohanski

    VKohanski Well-Known Member

    I had a '90 Blazer with the 4.3. Great engine... lots of torque off the line. When I went to look at new Hondas, the salesman was trying to impress me with the Honda's horsepower, until I had to introduce him to torque. 40 less horsepower and it would cream the Honda off the line. I drove it for the last 50k I had it with a blown head gasket... I always did my own work on it and it was always easier than I thought. My wife finally gave up on hoping that engine would die so I'd get rid of it. A friend of mine had one with 220k in it and not a sign of slowing down.

    On the head bolts... it's good advice... NEVER reuse engine hardware... parts are really cheap... I always overreplace parts when I take apart something complicated. You can get them at a "good and reliable" parts store, but check the Haynes manual or something like it for the proper grade.
     

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