Spark plugs and other stuff

cobraboy

Well-Known Member
During more relaxed fiddling I happened to pull a spark plug and the colour was very black. I got a boreoscope and looked in the bore and the top of the piston was shiny and oily.
The engine has always had an appetite for oil, I have always been disappointed as it is a fresh motor. I worked on the PCV system as one day I discovered the pipe into the carb spacer had oil in it. Realising the engine was sucking in its own oil I took a baffle from over the rockers on the old 3.5 and installed it under the PCV valve and bought and fitted an oil separator and fitted this high up in the engine bay with the pipe to the carb spacer running down hill. The engine uses no oil now - result !

Yesterday I pulled all the plugs and the pic tells the result, they are perhaps a little too grey, I would have liked them to be more sandy, but they are a lot better.
Another reason for pulling plugs was to see if I could see any evidence of the motor burning coolant, I looked in all the cylinders for a steam cleaned piston crown, they were all black, phew. I have had a mystery coolant loss situation. I did have a pin hole in the rad, so changed that, but the level has still been going down. I am now hoping it may be the last of the air coming out of the system as it seems to be stabilising now.

I am contemplating some sort of fuel system cleaner additive to try to clean up the oily pistons as they don't seem to be cleaning up on their own now the oily intake has been sorted. Anyone recommend one ?

Plugs
IMG_2622.JPG
Still getting oily plug threads as you can see.
 
For engines running SU carburettors and the standard flame trap configuration, the baffle plates upon the rocker shafts are there to prevent oil in copious quantities from being drawn into the flame traps and their associated connections.

Spark plugs from my understanding are a representation of the engine running conditions at the time when the engine was switched off. The electrodes all look clean and free of oil, in fact in my opinion they look almost text book perfect, save for the oil on the threads.

Ron.
 
Hi Ron
Yes I was running the PCV valve without a baffle, installing one from the old engine helped, but still oil was getting drawn up. In desperation I made an oil seperator from a jam jar with some wire wool inside it, this cured the problem. I then bought a purpose made item from our Chinese friends, this looks better and does the job well. The proper unit ensures 100% sealing.
With no rocker cover oil leaks the oily threads are still an issue. I have read that an incomplete burn can leave fuel residue behind in the combustion chamber that gets forced by the plug sealing washer onto the threads, something I have not come across before.
 
I was often wondering myself about oily spark plug threads, when playing with A series engines, and yes, unburned fuel seems like a possibility. Regarding cleaning pistons, isn't hydrogen the fashionable thing to do these days?
Or perhaps let a steam cleaner exhale in the intake with the engine running, or wait for winter and go for a drive on a really foggy day!
 
Hi
Of course I forgot, water injection will clean up the pistons, but I do not know how long it would take, several miles probably and at the correct dosage to avoid damage.
The odd thing about the oily residue is that it is present in the well in the head that the plug sits in, you would think to get there a compression leak at the plug must be going on, there isn't though, the residue seems to creep up the threads and get by the washer somehow.
I have just called and spoke to a hydrogen cleaning agent in my area, explained to him about the oily film on the piston crown, tbh he did not seem that confident that the process would remove it.
I think I will monitor it for a while.
 
Hi, Is oily threads such a problem? It's not the first time I've taken a plug out and have the head part of the thread come with it because they've been put in without lubrication which is why I always use copperslip.

Colin
 
Hi
In the grand scheme of things no, just wondered why ?
I got into trouble once for putting copper slip on plugs ( I do so on alloy heads ) I was told it should not be done as it can cause mis fires. I was told it was a a never never !
The other reason given was that the lube meant you could over tighten and snap the plug. I said that I had been installing plugs for 45 years and had not yet snapped one.
I obtained a technical paper from NGK that indicated that is was permissible to put anti seize on the threads and gave a figure to reduce the torque setting if you did.
 
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