Hi All -
been searching through threads and was hoping for a tad more guidance. I need to order plugs for my carbed (but otherwise stock) 2.7 that is running an MSD 6AL and coil, and a pertronix. In my reading, it looks like the NGK plugs seem to be the favorite. However, there are two listed numbers in several of the threads:

BPR5ES and BP5ES.

Is one of these better for my application than the other?

Thanks!!
Scott

I just used the BP plug. I never had stock compression and used 6 or 7 but BP5 should be good for the stock comp.

Resistor vs. no resistor?

I just slugged through 15 pages of spark plug threads on the Pelican 911 BBS. ugh.

It looks like there are three heat ranges that have several reccommendations from lots of folks:

BP5ES - hottest, better for starting but could be too hot at higher RPM's
BP6ES - middle - not as many choose this plug
BP7ES - coolest and reccommended by Pelican

Most seemed to say that the BP8Es was far to cold - but they also say to go as cold as possible where the plug stays clean to avoid detonation.

I live at 6300' above sea level, so my car will probably run a bit rich compared to most of the folks who are on the Pelican site. I am thinking that I should split the difference and go with the BP6ES.



Maybe I am just being too anal......

Yeah, maybe.
I ran BP 5s in my 2.4L low compression motor ....IIRC 7.5:1, BP6s in the 2.7L 9.7:1 motor, & BP7s in my 2.7L 10.5:1 motor (same motor, different pistons). Piickem'. The latter 2 would foul out a plug occasionally.

I think the 7's are more popular (done the research myself as well). The 5's are recommended for carbs.

2.7s used 5s. Just because 7s are "popular" doesn't make them right for this engine. Or any other 911 (well, maybe a 2.4T with MFI running on leaded premium gas) or 914 engine, for that matter. They're a pretty cold plug.

Correct, you want the hottest plug you can get with those carbs using the gasoline we get today.

You don't need the resistor plugs because the plug connectors (OE type) have built in resistance. If you have aftermarket wires other than Beru, you're on your own.

The Cap'n

You have never steered me wrong Capn - I just emailed Jonathan at GPR and changed my order to the BP5.

Thanks for the help all -
Scott S

BAM!!! Got it.

Scott I know your title says NGK , Just to show Bosch numbers are opposite for the heat range,

Basically, you have to find out for yourself which heat range works best for you.

I was bent over at the Parade AX staging lanes replacing a fouled plug (BP6). A fella came walking up & was looking over my shoulder but I didn't straighten up & turn around to see who it was. He said"Shouldn't you be using BP 7s?". Still hunkered over I sez. "Maybe, but the 6s foul less". I pushed on the plug wire & straighted up....."Oh, hi Steve"(Weiner...a real live guru). He says "Whatever works best for your application. No detonation?" "Nope." says I. He gave me a nod, a good luck, off he went.

Pretty sure I used BP8ES in my previous 2.2S-spec carbed engine; track use running in 5000-7000RPM range in warm conditions virtually all the time.