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Discussion Starter #1
I know we all have talked about plugs till we're sick of it but my question is about heat range, i had some work done on my Alfa Romeo gtv 1982 2 litre and the mechanic who only works on Alfa Romeo and other European cars said that they put ngk b5es into all Alfa Romeo 2 litre engines, I've been running b7es as most forums say that they work well with this engine, why would a mechanic who has worked on these engines for 50 years go with that heat range ?, It's Western Australia so we don't get real cold weather in fact it's warm to bloody boiling most of the year, any thoughts, cheers.
 

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Did you actually ask your mechanic why they use the relatively hot, 5 (NGK) heat range on this engine? Maybe they saw a lot of plug-fouling issues? Also, remember that Bosch's heat range scale is opposite of NGK, so it is possible (though unlikely) that he mistakenly called out NGK #5 while he meant a Bosch #5 (which is equivalent to NGK #7).

What is the factory-recommended heat range for the '82 GTV (this was not offered in the US)? My professional experience is with Porsche engines, not Alfas. However, air-cooled Porsche 911s and Alfa Nord engines use a similar, large hemispherical combustion chamber design that generally requires a long time for the combustion process to complete (both engines need huge piston domes to effectively raise the compression ratio and thus twin-plugging becomes necessary at a certain point. I have only ever felt the need to deviate from the factory-recommended heat range in the case of a significantly higher-than-stock compression ratio, or in the case of a modified turbocharged engine.

If you do a lot of high-speed driving in hotter temperatures and plug fouling is not an issue, then a step colder than stock is good extra insurance against pre-ignition. Otherwise the factory recommendation is probably the way to go.
 

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Thanks for your reply, does the heat range affect the way the carbies would need to be adjusted, as a note ngk advises using the 7 heat range so that's what I will go with, cheers.
 

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A small step in the change of the heat range is not likely to have much of an effect on your carb settings. You certainly would not need to re-jet them, and the worst-case scenario would be a small change to the idle-mixture setting, but that is needed from time to time in any case . . . .
 

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Hi Mark,
I have been using NGK B6ES on my Alfetta GTV 2.0 but found that the plugs were fouling. Admittedly, I don't drive it very often and not for long distances either. I have since changed them to NGK B5ES and they seem to work ok but I noticed the coolant temps are slightly higher. I also have an oil leak at the back of the head and am wondering if my head gasket might be on its way out. So far no oil in the coolant. Maybe the rings are getting worn, hence the fouling of plugs. I suppose if your engine was in good nick, stick to the B7ES?
 

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Discussion Starter #7
Finger's crossed for you that the head gasket is ok, I'll stick with the 7s it seems to run ok with them and they aren't fouling up, cheers.
 
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