250 GTE Spark Plug Question

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Dave Payne
Posts: 58
Joined: Mon Dec 26, 2005 11:00 pm

250 GTE Spark Plug Question

Postby Dave Payne » Sun Jan 18, 2009 9:25 pm

Have always used Champion N-3, but recently tried NGK BP5ES. The NGK plugs go in about 8 threads, and it appears the electrode hits something in the cylinder head before reaching the gasket.(?) Obviously the electrode is a little different on the NGK. What other plug is suitable for the outside plug GTE?

Jim Wickstead
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Joined: Mon Jan 13, 2003 12:41 am
Location: new jersey
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Re: 250 GTE Spark Plug Question

Postby Jim Wickstead » Mon Jan 19, 2009 12:58 am

Dave,

I suspect you are hitting the top of the piston. To confirm this, with plugs remove slightly rotate the engine and try to put the plug in again.

Not all engines can handle BP (as in projected electrode) sparkplugs. If that’s your situation you would need to use B5ES plugs. Sometimes during rebuilding the heads are milled for flatness and that brings the spark plugs even closer to the pistons. Not uncommon to have them tap the plug gap closed, or worst.

This has been a subject on this forum before. Check the archives for more information.

When I rebuilt my 250 I had the same problem, but I’d be darned if I’d give up those new BP5’s. I used indexing rings on the plugs as an experiment and the engine is pretty happy and the plugs are a perfect color. But, that also means some plug threads are not engaged. This spring it’s tune up time (once every 3 years) so I will experiment with B5's and see how well they work.

Jim

kare
Posts: 547
Joined: Sun Sep 22, 2002 11:34 am
Location: Helsinki, Finland, Europe

Re: 250 GTE Spark Plug Question

Postby kare » Wed Jan 21, 2009 1:40 am

I have a set of BP6ES (for my Lancia Beta) and B6ES (for the Ferrari) at hand and the former is about 5 millimeters longer than the latter (measuring from the seal to the ground electrode). I've been told that is too much.

B6ES is maybe 1 mm longer than the Marchal Corindons that were recommended by Ferrari in 1960's.
250 GT 2+2 3197/GT

Dave Payne
Posts: 58
Joined: Mon Dec 26, 2005 11:00 pm

Re: 250 GTE Spark Plug Question

Postby Dave Payne » Thu Jan 22, 2009 11:31 pm

Jim - You're right. I rotated the engine a small amount, and the BP5ES plug went in without hitting. I guess I lucked out or I may have smashed all 12 plugs/pistons. Will stick with the N-3's for now.

kare
Posts: 547
Joined: Sun Sep 22, 2002 11:34 am
Location: Helsinki, Finland, Europe

Re: 250 GTE Spark Plug Question

Postby kare » Fri Jan 23, 2009 7:10 am

Minor correction; measured the plugs today:

- B6ES is exactly the same size as the old Marchal Corindon HF34.
- In BP6ES the plug is exactly the same, except that the ground electrode is about 2.5 mm longer (P=protruding).

Together with varied stories of BP6ES getting hit by the pistons this pretty much confirm This confirms that B6ES should be the correct replacement for HF34. I far from sure but would think that B5ES may be a bit on the hot side for a Ferrari. I've been told that B6ES is a good all around plug and B7ES can be used for hard driving but does not tolerate driving in the city. If it works OK, then why not.

And yes, on NGK lower number means hotter plug.

Best wishes, Kare
250 GT 2+2 3197/GT

Jim Wickstead
Posts: 68
Joined: Mon Jan 13, 2003 12:41 am
Location: new jersey
Contact:

Re: 250 GTE Spark Plug Question

Postby Jim Wickstead » Fri Jan 23, 2009 10:13 pm

Gents,

The issue of spark plug heat range is interesting. NGK B(P)6ES and its cross references seem to be the recommended heat. But consider this: I’m driving a fully blueprinted 250 engine, with max overbore, slight cutting of the heads, and factory carb settings. All of which adds up to higher compression ratio, heat, etc. My plugs are BP5ES with indexing rings (used to move them away from the pistons). The car is used every opportunity for local and longer (4+hr) runs. I check the plugs carefully since they and my ears are my best tuning tools. The car runs strong and the plug color is spot on.

So, I wouldn’t discount NGK 5’s assuming you check them for color periodically.

N3’s??? Where can you get N3’s?? My Abarth loves to eat anything hotter than N3’s and I would dearly love to get my hands on some.

Regards,

Jim W.

Dave Payne
Posts: 58
Joined: Mon Dec 26, 2005 11:00 pm

Re: 250 GTE Spark Plug Question

Postby Dave Payne » Sat Jan 24, 2009 2:08 pm

Hi Jim - The Champion N3's are all over the internet, and are easy to find. A lot of motorcycle stores sell them, too. Google search for them. They make a N3-C (copper?) plug too. After reading more info on this forum on plugs, I think maybe the N-3's aren't the best choice in my 250. In fact they always look pretty black when I check them.

kare
Posts: 547
Joined: Sun Sep 22, 2002 11:34 am
Location: Helsinki, Finland, Europe

Re: 250 GTE Spark Plug Question

Postby kare » Sat Jan 24, 2009 2:57 pm

If I get it right N3 equals to NGK B8, which means you should be driving at full throttle all the time to keep em clean!!! Champion N5 equals to B6, which should be about right. After reading Jim's experience with B5, Iwould say B5..6 is a good all around plug and B6..7 for harder driving. Best wishes, Kare
250 GT 2+2 3197/GT


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