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Spark Plugs (everything about them)

Discussion in 'Subaru Sambar' started by Andrew.r.w, May 15, 2011.

  1. Andrew.r.w

    Andrew.r.w Member

    I want to get as much information about spark plugs for Sambar engines (EN07) as possible here. As such I have some questions.

    From your experience:
    1) How long do spark plugs last?
    2) How often do you clean/file/gap them?
    3) What is the longest-life plug one can/should use?
    4) Can the newer generation of "platinum" or other fancy plugs help?

    Why I ask, is I have 4,000km on my Sambar since it was overhauled, and it has been acting up a little, hesitating a little, idling rough, etc. When I start off it's like it's running on 3 cylinders and then suddenly off it goes.

    In my investigation into the cause I checked the spark plugs and they looked pretty bad for 4,000 km. Gap was about 15 thou too wide, electrodes rounded, and they just looked old. No crud build-up, no cracking, but alarmingly deteriorated for what seems to me to be low mileage.

    I'm comparing it to a V-8 so maybe it's normal. This engine works pretty hard by comparison.
     
  2. fupabox

    fupabox Well-Known Member

    15 thou too wide will kill them early...you need a much more powerful ignition system to reliably bridge that gap every time...may have been the problem from the get go....platinum,iridium or regular copper....depends on the vehicle...I've used high end plugs on some cars that absolutely refused to appreciate them...others love them......the heat range and gap on your plugs is more important than the plug type with 1 exception....if your stock ignition is a bit weak (leaking wires,coil a bit off it's feed,worn points) then you will notice an improvement with high end plugs (again... if the vehicle likes them)............ plug gap can be inreased by about 5thou to get a bit more mileage (bit less power) and your plugs will wear out faster....decrease the gap by the same 5thou and you will get a bit more power,tiny loss in mpg and plugs will wear more slowly....on older vehicles extra grounding helps...add grounds from your neg. battery to the alternator mounts and the engine block...they're easy to do in a few minutes and can never hurt..

    I wouldn't bother filing down plugs.(cleaning them up with a bit of sandpaper is ok but reshaping a rounded plug nah.).new copper cores are super cheap...and platinums are much lower than they used to be... I would say that 50-70 thousand km on a set of platinums is pretty good...I know the manufacturers think that 120 thousand is normal (on a new car with all new components yes....no way on a 20 year old ignition system)...I also know a dude I worked with who has a 1994 Ford Tempo (bought new) 400 thousand or so km...the only things (engine wise)and I do mean only he has replaced are the air filter and the oil....I did all his maint. on his vehicles for years and he was adamant that nothing be changed unless it was broken except the oil....(of course he had some brakes and tires over the years and even a windshield but everything else is stock) I would imagine the plugs are welded into the block:):)....he retired a couple years ago but supposedly still has the tempo:p

    test the resistance of your plug wires as well...if they look iffy take them to Can. tire and match them with something on the shelf
     
    Last edited: May 15, 2011
  3. Andrew.r.w

    Andrew.r.w Member

    Thanks for all the info. This is helpful.

    Gapping the plugs seems to have sorted out the hesitation. it also idles smoothly again. I set the gap to about 38 thou, just under 1mm.
     
    Last edited: May 15, 2011
  4. Andrew.r.w

    Andrew.r.w Member

    I got some new plugs, and based on readings here I got NGK platinums, heat range 5. it seems to make a difference. I know it fixed the sluggish starts and rough idling, but it also seems to have a tiny bit more pep. Cool.

    As I was thinking about that I dropped an e-mail to Japanoid and mentioned that the plugs seemed worn and I was wondering how they could get that way so fast. I got a prompt reply saying new plugs were on the way. Cool!

    Since I had already bought the new plugs and installed them these will go in the tool box for next time. The plugs they sent me are heat range 6.

    Question: If I put the lower heat range plugs in, what difference might I notice?
     
  5. fupabox

    fupabox Well-Known Member

    one step colder will usually help if you have advanced the timing....you may notice a slightly cooler exhaust temp....if you don't bump the timing at least a little the single cooler range may end up fouling the plugs
     
  6. Andrew.r.w

    Andrew.r.w Member

    Alright, this business about heat range is getting interesting. So here's my next question:

    If the dealer, who set this up and tuned it, believes HR6 is appropriate (I haven't tried them), what adjustments should I consider making to have the rig better tuned to take advantage of HR5 plugs? Or, is it a mistake to use HR5 plugs?

    Also, I level at 2500 feet ASL, and the vehicle was tuned for air-care at sea level. From what I gather I could afford to lean out the mixture a tad and advance the timing slightly to compensate. Do you think this would make a noticeable difference? We don't have air care in our area, so I'll be tuning for performance and economy.
     
  7. fupabox

    fupabox Well-Known Member

    The best way to tune is to make small changes 1 at a time (record the changes) and then read the plugs...the plugs will never lie as to how the engine is running..not sure how elevation affects heat range...but if you lean it out and advance the timing you will run the risk of overheating your plugs...try to change only 1 thing at a time and if it's worse,you can go back to the previous setting.....timing..the old standard is advance it 1 degree at a time till it pings..then back off 2 degrees....
     

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