Conference terri::cars_uk

      I have have used BPR6ES in place of BP6ES plugs successfully before.
    They have the same reach, thread, size, and run at the same
    temperature. I was told that the 'R' is for resistive, indicating even
    better insulation(electrical) properties.

I think "resistive" plugs also give less radio interference?

Scott

There are usually two types of any rating of plug - resistive and 
non-resistive.  The former are designed to be used with copper leads and the 
latter with resistive (carbon) leads.  If you use resistive plugs with 
resistive leads then you will reduce the efficiency of the spark.  Opinion 
seems to differ on whether copper leads with resistive plugs or vice versa is 
best.

Mike.

    Hi:
    
    Thanks for all the replies so far. If my cords are carbon based, it
    should be okay to use BP6ES? I was told there are some "racing" cords
    in the market which are copper based - cost more though. Is the price
    diff due to better conductivity of copper over carbon-based cords?
    
    Mike

    
    In the same vein as the base note, I would appreciate some advice on
    plugs.
    
    In this case the problem is simple:-
    
    I wish to change the plugs on a 1987 1350cc Peugeot 205.  The plugs are
    recessed into 4-5 inch deep holes, and are completely hidden. They are
    also of a TAPER threaded type, they have no shoulder or compression washer.
    They are screwed into an aluminium cylinder head. 
    
    Up to now I have "entrusted" the service to "approved" maintainers, but
    this time I decided to do the service myself. 
    
    The plugs should only be "finger tight", as the taper thread provides
    adequate sealing. Unfortunately some a***hole mechanic has heaved on the
    plugs in the past. They are apparently now a fixture in the aluminium
    head.
    
    Please, please could I have some sensible suggestions on how to remove
    the plugs without stripping the threads in the cylinder head.
    
    thanks
    
    Pat K.

    If you get to a point where its notgoing to budge, maybe you've tried
    it, but what about gently warming the head locally to the plug. The ali
    head should expand faster than the plug and with a bit luck will come
    undo.
    
    Garry

    
    Re .7
    
    Hi Garry,  
    
    I've tried it hot, Ive tried it at normal ambient, I havnt yet tried it
    with a can of instant freezer, now here is a rat hole:-
    
    If you have a steel male plug thread screwed into an aluminium female
    cylnder head, what are the effects of heating and cooling either the
    plug or the cylinder head. 
    
    The aluminium has a bigger coefficient of expansion than the steel, so, 
    
    If the aluminium is heated, will the circumference of the plug hole
    increase?, thus freeing the plug, or will the expansion of the
    aluminium surounding the plug hole actually reduce the effective
    circumference of the hole, thus tightening the plug in the cylinder
    head? 
    
    Since the aluminium threads are in close contact with the steel, at the
    steel to aluminium interface, we can assume the temperature to be
    equal, will the extra expansion of the aluminium cause the threads to
    grip harder or easier?
    
    What do the experts say?
    
    PJK

    Isn't differential heating what is needed? Spray freezer onto the plug
    and heat the head around the plug hole. If there is any differential
    heating the plug size will drop and the hole will get bigger (if you
    heat a sheet of metal with a hole in it it all expands about the
    geometric centroid(?) and so the hole gets bigger not smaller). This
    assumes that there hasn't been any local alloying of the plug metal to
    the head. Beware, tho', nasty things happen to taper threads that are
    overtightened ........

    
    re .1
    
    >>>>Beware tho", nasty things happen to taper threads that are
    overtightened....
    
    I know, thats why I sitting here sweating over the expense I could be
    involved in!  Head of and 'Helicoils' in the worst case
    
    An interesting thought struck me, I wonder just how long these plugs have 
    been stuck?, I have visions of successive services, from new, with 
    successive mechanics struggling to remove the plugs and then saying, 
    "Stuff it, I'll not bother, he'll never know the plugs weren't changed". 
    
    And I wouldn't, cause I never asked for the old bits as proof of service,
    and I cant see the plugs in the head, they are down in a very deep
    hole!
    
    I suppose I could always polish the tin work and dump the problem to some
    over person who wants a first class ecconomical motor, 8>)).
    
    PJK

    Why don't you take your car down to some garage like Halfords, where you
    can stay with the car and watch the guys every move, and make sure that
    he removes the spark plugs, they should have the right tools to remove
    the plugs, but if they do strip the threads it's their problem to fix
    it and not yours.
    That what I did with my Fiesta that had overtightened tappered plugs in
    it, they managed to remove them O.K. and its certainly cheaper than
    doing it yourself and stripping the threads.
    
    Neil

    
    Hi,,
    
    "With a long enough lever I can move the world".... and another box
    spanner, (thanks Richard).  
    
    With some trepedation, and a box spanner capable of taking a longer tommy 
    bar, I got all four plugs out without picking up any of the aluminium 
    threads. The new plugs have gone in with correct mimimal torque! I dont want
    to have this problem next time I have to do a service!
    
    I hate "qualified" mechanics!
    
    PJK

    
    
    Unless you've tried it already put some copper ease on the threads.
    
    This will ensure that the plugs do not become seazed in the head.
    
    I've an ally head on my Lancia and the plugs are due to be changed
    soon. I'll be using copper ease. If the ally threads on the head
    are stripped then it means a cylinder head off job. Not the wisest
    of moves on a twin cam 20% slant FWD engine. You need your arm
    broken in 7 different places just to get the starter motor out.
    
    Copper ease works well.
    
    Jeff.

    My Dad has just taken over a Toyota Celica (1981).
    After lookin at the Haynes manual I noticed that it recommends
    NGK BP 6ES plugs. However the plugs that are in the engine at the
    moment ore BP 5ES.
    
    The question is do I replace them with BP 6ES as the manual states
    or as the car appears to be running fine on BP 5ES, should I replace
    them with the same ?
    
    Thanks,
    
    - Roy

    I was in Halfords the other day buying some service items for my wife's
    car and was alarmed by the price of NGK plugs. I was after a set of 4
    BP6ES and they were priced at �7.25, as were all the other NGK's.
    
    Its been a while since I've done a DIY service but was expecting to pay
    around �4. Previously NGK and Champion were about the same price, but
    the champion plugs (N9YC) were only �3.99. Guess which set I bought :-)
    
    Anyone else noticed this ? Presumably Halford's prices are the same
    around the country.
    
    Both Champion and NGK were copper core, so why are the NGK almost twice
    the price ?
    
    - Roy

    
    Once upon a time I used to use Champion plugs...
    
    After a full engine rebuild I had touble getting it started, all the
    obvious checks were performed including laying the plugs against the
    block to see if they were firing. Everything checked out ok but still
    it would not start after several hours.
    
    
    The problem was overcome by replacing all four brand new champion plugs
    with a very old set of NGK's which were lying about the bench. Now the
    car started first time, a bit of playing around proved that all four
    new champion were 'failing under pressure'. When they were returned to
    the shop there was no disbeleive from the assistant, no shock horror I
    don't beleive it could happen to this fine product, no argument
    whatsoever ... which convinced me this was not a one-off. I declined the
    offer of another set and changed to NGK which were more expensive AND I
    seem to remember have always been more expensive than champion/bosch
    etc.
    
    Having said all that 3.26 extra does seem a bit steep, is this just one
    particular source or is this average prices?
    
    
    Bill. who_prefers_something_that_works :-)