mgs
[Top] [All Lists]

Re: reading sparque plugz

To: Will Zehring <wzehring@cmb.biosci.wayne.edu>
Subject: Re: reading sparque plugz
From: "John M. Trindle" <jtrindle@tsquare.com>
Date: Tue, 17 Oct 1995 11:02:22 -0400 (EDT)
On Tue, 17 Oct 1995, Will Zehring wrote:

> After a weekend of highway driving and a few miles of surface streets, into 
> the garage and engine off:  
>         plugs 1 and 2 have a medium brown appearance on the electrode and a 
> dry black color on the threaded ring around the electrode (fwiw: #2 is 
> slightly darker brown than #1).
>         plugs 3 and 4 have a dirty white appearance on the electrode and a 
> dry black color on the threaded ring around the electrode.
> 
> I haven't check gaps since mid August, when they were fine.  
> 
> My interpretation: the rear carb is lean and the forward carb is perfect.  
> The dry black color suggests that my oil 'consumption' is attributable to 
> the poor seal at the rear main in this early 3-main engine, and not to 
> excessive burn.
> 

I'd agree 100% with the following addition:  If there is actually a dry 
black deposit on the outer ring (as opposted to a thin layer of soot or 
just black color) you may be looking at a different mixture at speed than 
at idle.  The outer black ring is deposited at idle but not burned off at 
speed.

I had a more extreme case where the insulator was black and the electrode 
was white, causing a bullseye effect.  Try looking at the pluges after 
idle to see what the deal is...

Excessive oil running through the combustion chamber will cause cruddy 
buildup unless you have extremely "hot" range plugs.


John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP     | '69 Spitfire E Stock | '88 RX-7 C Stock
Home Page:  http://www.widomaker.com/~trindle
"Lowery's Law:
   If it jams - force it.
   If it breaks, it needed replacing anyway."


<Prev in Thread] Current Thread [Next in Thread>