Chevy 454 Question

Discussion in 'Domestics' started by morelach, Feb 9, 2017.

  1. morelach

    morelach Newbie

    Joined:
    Feb 9, 2017
    Messages:
    4
    Likes Received:
    0
    I have a 1988 motor home with a chevy 454. It runs great - or seems to - until I get it under load, and it randomly backfires in a kind of popcorn popping like fashion. It does not always do it, and it seems very random - meaning there is no discernible pattern or symmetry to the popping. There does seem to be some power loss when it is happening. My thoughts for possible causes: water in the fuel, timing advance off or not working, worn valves, worn cam lobes. Anybody with some possible insight as to what might be the problem would be greatly appreciated. Thanks!


    Sent from my iPhone using Tapatalk
     
  2. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    I would go for this.

    On a motorhome such as this, timing is taken from underneath.

    Do you know how to time a 454 motorhome?
     
  3. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    All symptoms above indicate pinking and advance timing.
     
  4. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    On a funny note, a guy came with his family from Alberta to quebec and the 454 split a block.

    9000$ later, he was back on the road, just to call me back from manitoba. Split another block. Damn. I must say.

    That was all due to bad timing, pre ignition, and one heck of a bill.
     
  5. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    Client said he could hear the 454 knocking bottles, kept going as long as it krept up the slope to get to quebec.

    Lesson learned.
    ;)
     
  6. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    He did the same going back home, the decompression on the 454 did the same as the acceleration on the way back home.

    2 454 split.

    Wow, what else can I say.
     
  7. morelach

    morelach Newbie

    Joined:
    Feb 9, 2017
    Messages:
    4
    Likes Received:
    0

    Yep. That was going to be the next thing I did after making sure the fuel tank was completely dry. Start with the free stuff and work toward more expensive solutions.


    Sent from my iPhone using Tapatalk
     
  8. morelach

    morelach Newbie

    Joined:
    Feb 9, 2017
    Messages:
    4
    Likes Received:
    0

    Ouch! That's not funny! Heh heh!


    Sent from my iPhone using Tapatalk
     
  9. big al

    big al Hero Member

    Joined:
    Aug 27, 2007
    Messages:
    252
    Likes Received:
    0
    Is this a carb, or tbi motor? I agree with nick but also want add i hate these tbi units. They were alot better on the small blocks but still had issues when they aged. Have had to repair many of these tbi units. Check where the wires go into the unit for chaffing, regulater, injector. Not to mention they didnt help produce much power, have even changed some over to better aftermarket units
     
  10. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    @big al, I think it was split back in 1988. Most were carbs, some were TBI's
     
  11. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    But since I am soon to be 42yrs old, can't say for sure if the TBI system was a major item back then on the motor homes. I was 13yrs old at that point and my only priority then was my BMX or my dads lawnmower.:D:eek:
     
  12. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    @morelach, do you have a timing light and a dwell meter? And know how to use them?
     
    Last edited: Feb 9, 2017
  13. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    I did find this for you however. Check it out.
     

    Attached Files:

  14. big al

    big al Hero Member

    Joined:
    Aug 27, 2007
    Messages:
    252
    Likes Received:
    0
    Yep, you are correct, they were split but that was the start of tbi. I am 42 also but had to drive older stuff when i could drive. Sometimes took alot to keep that stuff going. Then got into the performance seen. Many people thought the motors were junk, but if eliminated a few problem could get decent power out them. Although not like todays pwer options. Altought i do have a 98 454na motor puts out 515hp easily, also have a built 88 old tbi motor with turbos lays down 943hp. I guess we need to know if its carb or tbi (like you said could go either way) also maybe could have the electrictronic q-jet carb back then. With a few slight mods the q-jet was a excellent carb also.
     
  15. nickb2

    nickb2 Wrench. I help when I can

    Joined:
    Nov 22, 2008
    Messages:
    7,375
    Likes Received:
    104
    Gender:
    Male
    Occupation:
    northern car tech
    Location:
    Schefferville, Québec, Canada
    The TSB says they were TBI, so big al was right. Check the egr.

    ;)
     

Share This Page