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new engine or new truck?

Discussion in 'Chevy Trucks' started by jb1390, Sep 8, 2009.

  1. jb1390

    jb1390 Senior Member
    Messages: 710

    i have a 1998 chevy 2500 (hd with 8 lug, 8600 gvw) with air bags, reg cab and 8 foot box. I had the transmission (4l80e) rebuilt last october when it lost reverse. I had the infamous intake gasket issue, which killed the bearings before I caught it. i got a cheap craigslist motor and dropped it in, and i think there is a burned valve (can't find my compression gauge, so I ordered a new one, will post with results in a week). I have a persistent misfire on cylinder 6, and I've tried everything (replaced dizzy, cap, rotor, wires, plugs, 02 sensors, upgraded injection, which made HUGE difference in power, but still a rough idle) it is roughly running on 7 cylinders at idle, but has pep once you get moving. I have the old motor, which is a 4 bolt main 350. I am trying to decide if I want to do an engine rebuild and make it a 383, or save and buy a newer truck. The frame is in wonderful shape, the previous owner sprayed it down with oil every spring. If I had known I would've had to do the tranny and and engine swap, I would've bought I nicer truck to begin with, but such is life. So, the question is...383 with upgraded cam and injection system (and probably mail order tune), or save and buy a new truck.

    Or, do a valve job and swap out the heads from the other motor.

    Also, any risk of damage running with the misfire and dealing with the rough idle?
     
  2. mkwl

    mkwl 2000 Club Member
    Messages: 2,361

    I feel your pain- I have my truck in the shop right now for a misfire condition.

    Since you just put in a trans, I'd said re-build the engine and call it good- anything is better than a new truck payment!

    As for running with te rough idle- is your check engine light on/flashing?

    If so- running it as is will eventually fry the Cat's. That's why mine's in the shop now to get the misfire resolved (hopefully without spending too much $$$ or too much downtime).
     
  3. jb1390

    jb1390 Senior Member
    Messages: 710

    No CEL because I guess with the heavier trucks, emissions requirements weren't such that it throws a code for a misfire. Strange, but that is what I have heard. On a scanner, I can see cylinder 6 is misfiring every opportunity at idle. No difference in how it idles AT ALL with the spark plug wire unplugged, but it throws a real nice spark across it if you put an overgapped spark plug on there grounded to the exaust manifold. No noticable misfire above 1500 rpms. It's really just the rough idle that bothers me. I hate having something wrong with the truck, almost makes me lose sleep. That's a good point about the cats.
     
  4. mkwl

    mkwl 2000 Club Member
    Messages: 2,361

    IDK about that with regards to the CEL- my truck is a 9,200GVW and it's not even throwing a noticeable misfire, but the CEL is still flashing at highway speeds indicating a misfire condition :)crying:).

    I'd be the most concerned with frying the cats (very expensive), and possibly throwing a rod with the engine having 1 cylinder down.
     
  5. jb1390

    jb1390 Senior Member
    Messages: 710

    Not sure if it applies in my case, but here is where I found the (lack of) CEL info. It is misfiring like crazy, I would think it would be setting off the light if it was designed to. Your truck is newer than mine, and I don't know if chevy had different versions of pcm or what not in 98.

    http://www.ford-trucks.com/forums/518596-wondering-why-your-mil-doesnt-come-on.html

    If throwing a rod is a concern, then the question becomes- rebuild the heads with a valve job, or buy rebuilts?
     
  6. mkwl

    mkwl 2000 Club Member
    Messages: 2,361

    I think Ford is the only one like that- my Grandpa has a '99 GMC 3500 with the 350, and he has the OBDII system just like my truck- I would think your truck would have the OBDII also.
     
  7. jb1390

    jb1390 Senior Member
    Messages: 710

    The truck has an OBDII plug, but the programming could be different. Little things like setting the CEL for a misfire or unexpected post cat oxygen sensor readings. At any rate, I did a compression test on the truck last night and it went
    1-190
    2-190
    3-200
    4-180
    5-190
    6-130
    7-190
    8-190

    So there it is, I did a wet compression test with no change in readings. So I have an extra head in the garage that I pulled off that engine, and i will finish doing the swap this weekend, hopefully with the misfire gone.

    Second question still remains....upgrade to a 383 or new (to me) truck in a few years? i tow my tractor around with it (8000 lbs), so I want some more power up the hills.
     
  8. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Build the 383. That's the plan for my truck. I've only got 135K, but the extra power would be nice. You've got a good block, and get your current heads done. Just need a crank and rods.
     
  9. jb1390

    jb1390 Senior Member
    Messages: 710

    What will you be running for a cam? I know a 383 takes at least a little more cam than a 350 to account for the extra cubes. or have a just been reading too many muscle car forums, and the stock cam is best for low end torque like we want?

    Another question along those lines, is there a reliable mail order tune place that can specify a cam and other engine parts they have done before, to avoid getting a junk tune and also avoid spending money on a dyno tune (I am thinking that is probably expensive)
     
  10. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I'm no where close to those details yet. I am going to add a custom tune to the current truck/engine. Try BlackBear or Wheatley.
     
  11. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Nelson's Performance does awesome tunes too. I believe they also do custom cam grinds as well.
     
  12. jb1390

    jb1390 Senior Member
    Messages: 710

    I threw a head from my old engine on to the current engine, and compression in #6 went from 130 to 180-185. It idles much smoother now, so problem solved. Hopefully the burning oil smell is residual from adjusting the valves, and not a leaking rtv seal at the back of the intake manifold :realmad:
     
  13. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Thanks for posting the outcome. I would have that old head tested. Might be just a bent valve. Those Vortec heads are nice, and worth keeping.
     
  14. jb1390

    jb1390 Senior Member
    Messages: 710

    Yup they are nice heads. I am keeping them around for my 383 build in a year or so, I'll have them rebuilt. Can't beat those heads for performance vs cost, especially for a plow truck.