Bad Valve?

Discussion in 'GM Powertrain' started by AZ Suburban, Jul 2, 2010.

  1. AZ Suburban

    AZ Suburban New Member

    Ok, I've got a 1999 Suburban with 181,000 miles on it. 350 Vortec. On Mon. it started pinging badly. I pulled a code that was #6 cylinder misfire. Replaced the cap, rotor and wires as they were all looking a little beat up. #6 spark plug was wet. I did a compression test on all cylinders. Got about 150 psi across the board, except for #6 and #4. They were both around 30-40 psi. I put a few squirts of oil in the cylinder and the compression stayed the same. So, I'm assuming the rings are fine(no blue smoke out of the exhaust), all I can think is that it's a carboned up valve or valves. I ran some Seafoam through it. Made lots of smoke but still had the rough idle, detonation and the same code. I may run a little more Seafoam through, but, looks like I'll be pulling the heads this weekend. What I'm thinking of doing is getting some new or rebuilt heads, an aluminum intake manifold, water pump and all the little things I come across. Am I barking up the right tree? Looking for some advice on where to go from here. Thanks
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    What are you looking to do? Are you looking for more power? and if you are looking for ease of use and design keeping the factory intake is just fine as well.. A little port matching etc might help some.. But if you arent going for a built motor I would just rebuild it fairly stock, and if you want more power i would build a new motor for it since the bottom end has so many miles on it. If you remain fairly stock 300K miles isnt uncommon for these motors.
    I guess the aluminum parts that you are looking to use really arent needed since the stock components are pretty good.
    I would go with a programmer a set of headers, and a cold air intake. and just clean everything and a good port matching otherwise id keep this motor stock..
    Last edited: Jul 2, 2010
  3. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    Identicle to what happened to my 99 it was a bad valve. for me they rebuild both heads but had I known what it was gonna really cost me to try and figure out the damn valves I would have just got a new motor and transferred the asseccories to the new motor
  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Good Point on that.. And then you have a new motor good for another 200K miles...
  5. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Good point.
    You can get a NEW GOODWRENCH from Pace Performance for $2250 delivered to your curbside.
    This is a new genuine GM motor not some BS aftermarket cheapo rebuild.
    One of the huge advantages GM trucks have is cheap ,readily available parts. It actually makes sense to keep them running for 20 years.

    It would cost 5X as much to by a Toyota or Nissan V-8 and 2x as much to get a Ford or Dodge V-8.
  6. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    X2 on the Goodwrench crate motor.
  7. AZ Suburban

    AZ Suburban New Member

    Got the heads pulled over the weekend. Found why there was little compression between Cyl 4 and 6. There was nothing left of the head gasket between the 2 cylinders. Glad I caught it before it got worse.
  8. wis bang

    wis bang Rockstar 100 Posts

    So a set of re-man heads and put it back together. Obviously the head is warped. You'll be good for another 100K...
  9. AZ Suburban

    AZ Suburban New Member

    Wanted to follow up on my Suburban. The list of replacement parts got longer the farther into it I got! I ended up replacing the heads, water pump( just because I was in the neighborhood), AC compressor (front seal was blown), Altenator (had a scratchy bearing), PS pump (leaky seals everywhere), upper manifold and plugs. I was able to clean the engine up too with everything taken apart. Cleaned up a bunch of grounding points and with the fresh altenator my headlight flickering has stopped. It runs great now has since it has full compression in all cylinders has lots more power. Brakes are my next project. Last night I pulled off the drivers side rear drum and it was coated with axle grease. Looks like an axle seal replacement is in my future. I cleaned all the grease off the pads and drum and adjusted them which got rid of my poor breaking-at least untill it all gets covered in grease again! I'm sure I'll have more questions once I dive into that project!
  10. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Indelicate question I'm asking because I expect motor problems to be in my future(214,000 miles).
    How much did just the motor parts cost-counting the water pump since you get that on a Goodwrench?
    Did you do all the work?

    My guess is a new Goodwrench installed(about $2250 delivered now) with gaskets and fluids-doing all the work myself- would probably be maybe $2600-figuring intake gaskets, exhaust gaskets and miscellaneous "stuff".

    I'm wondering how much just switching out the heads and water pump costs-not that I know how mine will fail-could be crank bearings , piston rings who knows?

    Sorry if this is too nosy a question.

Share This Page

Newest Gallery Photos