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Posted By : Neil Nasralla, 13-Oct-2005, 10:40am
Hi all, just a quick and hopefully straightforward question about which spark plugs I should get for my Spitfire 1500. I seem to remember James C stating a
particular type of Spark plug but I cannot remember which type they are and where I can get them from. I can order the standard ones from Canley (etc) but
James C mentioned the same brand (NGK?) but with slightly different temperature rating. I don't know whether they will be better for my purposes. There
probably won't be any noticeable difference but I just thought I would ask.
My 1500 has a Stage II engine and head with fast road camshaft runs on SUs with appropriate needles and springs, sports manifold and exhaust system and
K&Ns. I presume these facts are relevant. I'm probably fine with the normal spark plugs but thought I would ask.
Anybody got any pearls of wisdom on this.
Thanks in advance and regards, Neil N
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Posted By : Nigel Gibbins, 13-Oct-2005,
12:04pm
I just had my 1500 engine tuned on a rolling road and he was surprised I was using BP6's (standard for the engine), we swapped them out for a set of
BP7's (cooler) and got an improvement.
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Posted By : Mark Stradling, 13-Oct-2005,
01:02pm
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Posted By : Neil Nasralla, 13-Oct-2005,
01:48pm
Thanks Mark and Nig. I will get 6s or 7s. I'll toss a coin. Interesting that the 7s gave you extra performance Nig. I wonder whether the
'performance' alternatives (listed on that website) give any advantage. I suppose its all about whether you have a bigger spark and cleaner and
more complete combustion of that mixture. I'm going to steer away from buying something that has a 'performance' label as those marketing people
always see me coming!
Thanks for the pointers.
ps. That coin said 7s so there you go!
Cheers
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Posted By : Nigel Gibbins,
13-Oct-2005, 04:47pm
I feel I should clarify my (extra power) statement - it was only 2 Bhp more and that may have been due to the plugs being new.
The spark kernal (yes I've been reading up on the subject) doesn't really have any effect on the power output, a spark plug does two
things...
1) provide ignition
2) dissipate heat from the combustion chamber
The 7s will dissipate heat better and so the engine will run cooler, as the engine can run cooler you may get a power benefit. However, if the
engine runs too cool then you'll lose it all again as the plug will become contaminated. The plug needs to run at an optimum temperature and
when it does it will self-clean, ie removes the carbon deposits itself. If it doesn't operate in this range then it will eventually foul-up and
again lose you power.
Honestly speaking only time will tell, but when my 6s came out they were a bit 'mucky' which is part of the reason we decide to go cooler.