Ferrari Mailing List: Re: Spark plug reading?

[Peter Pless (ferrarilist]

Any particular reason for doing it on a dyno?

I've found better air flows and temps from doing road work....and makes the
results more meaningful. It's not like I need to do prolonged full throttle
work. 

-----Original Message-----
From: Dave Handa [mailto:dave [at] davehanda.com] 
Sent: Thursday, 16 August 2007 10:37 AM
To: 'Peter Pless'
Cc: 'The FerrariList'
Subject: RE: [Ferrari] Spark plug reading?

Yes, but use it on a rolling dynometer.

I had 140's on my 78 308, which came stock with similar jetting.  The 140
was selected based on exhaust analysis on a rolling dyno.

But from what I hear, 130 or 135 is a better fit, with a slightly richer AC
jet too (190 or 200)

Hotter plugs are often required to prevent fouling...usually an NGK 6, but
sometimes a 5.

Dave



-----Original Message-----
From: Peter Pless [mailto:ferrarilist [at] pless.com.au]
Sent: Wednesday, August 15, 2007 5:30 PM
To: dave [at] davehanda.com
Cc: 'The FerrariList'
Subject: Re: [Ferrari] Spark plug reading?

130 mains (125s drilled out) and I THINK 220 AC but I'll have to double
check that.

When I pull the plug out later, I'll confirm the type as well.

It's all interesting stuff.

One of my mechanics has a mobile gas analyzer. I guess that would make
things much easier. 

-----Original Message-----
From: Dave Handa [mailto:dave [at] davehanda.com]
Sent: Thursday, 16 August 2007 9:31 AM
To: 'Peter Pless'
Cc: 'The FerrariList'
Subject: RE: [Ferrari] Spark plug reading?

What are your main and AC jets?  What plug are you using and what heat
range?



-----Original Message-----
From: Peter Pless [mailto:ferrarilist [at] pless.com.au]
Sent: Wednesday, August 15, 2007 4:02 PM
To: dave [at] davehanda.com
Cc: 'The FerrariList'
Subject: Re: [Ferrari] Spark plug reading?

Gee...look at all the information I didn't give.

Ok..so it's originally a twin distributor car but now has 10:1 compression,
euro GTB cams, no smog equipment and programmable pointless electronic
ignition (BSM)<---which is excellent btw, starting at 12 deg btdc at idle
and max total advance of 34 deg btdc

I only pulled the one plug from the one bank. 

I will give it another go under different conditions. BUT....i'll do it
after cruising, not going flat out at this stage. I'm interested in getting
low throttle/low engine speed stuff right too. I'm running 55 idle jets.

Hopefully, I can do that later today.

-----Original Message-----
From: Jason Polzer [mailto:jason [at] internethosting.com]
Sent: Thursday, 16 August 2007 3:20 AM
To: Peter Pless
Cc: 'The FerrariList'
Subject: Re: [Ferrari] Spark plug reading?


   I agree no idle before reading plugs.  I remember in 1/4 mile racing
   cutting my engine at the same time as lifting my foot while crossing
   the finish line.  And then trying to make the turn around quickly and
   safely enough to coast back to the pits and pull a few plugs.
   Jason
   Rick Lindsay wrote:

Hey Peter,
   Everyone and his brother will have opinions on this issue but I'll add
mine.

   First of all, a plug-cut should only be done (read:
only be interpreted) from plugs that have not been subjected to recent idle.
That is, the technique
says: Go for a spirited drive and at the last second of that drive, cut the
engine WITHOUT allowing it to idle - not even rolling into the garage.  The
carbon build-up comes from idleing and that can preclude an honest read of
the plug.  This site has a good write-up on the idea:

[1]http://www.centuryperformance.com/spark.asp

   Don't forget to go to page 2 where there are more pictures.

   Your picture shows an insulator that is about the right color, perhaps a
little too cool (read: it isn't staying hot enough to burn off deposits).
The ground electrode color isn't too bad either.  Still, I would expect the
whole thing to be a dusty tan color if everything was balanced properly.
The black carbon around the base of the plug is not too much of an issue
with me.  It says that you may be running a little rich.  Still, a little
rich 11:1 to 12:1 is a more powerful charge mixture than the perfect 14.7:1
ratio.  We must also remember that a leaner mixture burns hotter.
Conversly, rich mixtures burn cooler.
Therefore, air-fuel ratio or 'mixture' must be matched to the plug heat
range.
   Then there's compression ratio.  That too changes burn rates.  Higher
pressure charge is harder to ignite therefore, a stronger ignition is
required.
Ferrari ignitions are arc welders so if you're running a stock ignition,
you're probebly strong enough (assuming it is in good health).

   Quick question: Do all of the plugs look similar or is one bank
different; or one plug different?

   Okay, that's just some stuff to ponder.  From this and someone else's
post with the 'right' answer, you'll get the engine dialed in.

regards,

rick
'79 308GTB
--- Peter Pless [2]<ferrarilist [at] pless.com.au> wrote:



Does anyone know what this means?

[3]http://www.pless.com.au/308plug.jpg

It's from my newly rebuilt 308GT4 engine. 10:1 compression running on
unleaded fuel.

Programmable ignition gives it lots of advance.

When the plug was pulled, I'd come back from quite a long drive, but the
last bit of it consisted of traffic and plenty  of idle speed stuff.

What's with the carbon on it already? Engine's only done 600 miles....and
I've been nursing it.

TIA

Peter




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References

   1. http://www.centuryperformance.com/spark.asp
   2. mailto:ferrarilist [at] pless.com.au
   3. http://www.pless.com.au/308plug.jpg
   4.
http://lists.ferrarilist.com/mailman/options/ferrari/rolindsay%40yahoo.com
   5. http://www.BidNip.com/
   6. http://www.F1Headlines.com/
   7.
http://lists.ferrarilist.com/mailman/options/ferrari/jason%40internethosting
.com
   8. http://www.BidNip.com/
   9. http://www.F1Headlines.com/
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