Main Plug (instead of change over valve)

[Chris]

There is a thread on the other site, which I have never been able to get signed onto, that has a discussion on how to get a change over valve out of the head. Here is my experience with trying to get the "Main Plug" out of a Lister VA head.

The Lister VA that I have now was rescued from a small Cay that our familly used to own. We used to visit on vacation when I was younger. On one of my vacations I was informed by the caretaker that the Lister had been acting up and the Lister guy came and fixed it, but it was now hard to start. I went and took a look and I could see that parts had been replaced, including the head. I tried to find out what work had been done on on the engine and why. Why-- it would not start. What-- did not know other than when the Lister guy let the unit was running, ie fixed. The engine was a bitch to start. The caretaker said he had to use starting fluid to get it going. I cringed, starting fluid! The valves were sticking and when running, lots of smoke.
I pull the head off and yep all carboned up. Decarbonised the unit and reassembled. The starting was still hard. Checked the spill timing. That seemed OK. Slept on it for a while. (We had a second VA that was working OK, so that was used while trying to figure out what was wrong). I spent weeks that went into months, several vacations, trying to figure out what was wrong. Changed injectors, had injectors re calibrated, check head clearance again. Got the Lister guy back to take a look. He could not figure out what was going on. The unit would carbon up real fast. Say a week with minor use. The engine acted like it had low compression, but why?

On the back of the head, where I guess a change over valve would be, (I have never seen a change over valve. All I had ever worked on were VA and sometimes a 8/1 with no change over valve), is a big square headed plug. I had never taken this plug out before. Never had a need to do so. I thought may be I would be able to see what the injector was doing. Took the plug out. no luck could not see the injector. More sleeping on it!

The next day or so something clicked in my head. Took a look at the parts list and the blow up of the head. Saw the plug I removed and something else, item 1 THE MAIN PLUG was missing! I did not a spare. I checked one of our worn out heads, (Valve seats ground down way below recommend levels), took off the square headed plug and there it was, a MAIN PLUG. Now how to get it out? It was so far in there and no space to get anything in there to try and pry it out. More sleep on it, or as Rom would say, another rum and coke.

OK enough of the back ground story.

This is what I did. Sprayed a bunch of WD40 in the smiley mouth of the head. WD40 between the MAIN PLUG and the screw in plug. More rum and coke and sleep. The next day I bolted
the old head on the engine. Took out the screw in plug. Poured oil into the injector hole, installed the injector. No valve rockers. Slowly rocked the flywheels back and forth and POW, the main plug shoot out of the head and put a big dent in the concrete block wall of the generator shed. If someone had been in the way, bye bye. It scared the sh-t out of me, but I now had a MAIN PLUG. Installed it in the good head. Problem sovled.The VA is running, woomp, woomp, as I type, same head same MAIN PLUG.

Regards,

Chris

[dubbleUJay]

Chris, I read in one of the manuals somewhere that they do something similar. I cannot find it right now, but it's recommended to clean out the plug once in a while. We don't hear about that anymore as most of the 'roids haven't got them in.
I've taken great care to do my ListerCS according to spec, ie bumping clearance exec. and although it does start with the plug turned out (lower compression) it starts much easier with it in when cold (Higher compression)
The other nice thing about the plug is that when its out, one can put the engine at "TDC" with the exhaust valve open and blow compressed air into the chamber trough the compression plug to get rid of carbon before it gets to hard, which might prolong de-coking intervals.
The way to get the plug loose is to give the outer plug a quarter or half turn out/loose and run the engine, which usually pushes the inner plug out a bit or loosen it from its carbon seat. You got to this regularly though before it get stuck to much.
It beats taking the head off so often when running WVO.
I've also got a blanking off plug that I've never used so far (I wanted the changeover Valve in mine), which I made a puller for in the picture, it has a threaded hole on the outside, the PLUG that is. I presume the 'roids have something similar.

dubbleUJay