Fun with valve guides - WTF ????

[jens]

removed

[Stan]

Don't know about your listeroid Jens, but Penelope's inlet valve guide is driven out, and the exhaust valve guide is screwed out.  I havent' taken her's out because they are a great fit to the valve stems and don't need it.
Stan

[piperpilot3tk]

Jens, a few weeks ago when I disassembled the head on my 6/1 I alos noticed that the manual says the exhaust guide is threaded into the head.  I looked at the guide and did not any flats machined on it to unscrew it with, so I hit the net and found lots of pics of heads with press fit exhaust guides.  I used a rivet gun with an aluminum rivet set and easily drove both guides out of the head with no damage.  The exhaust guide was quite a bit longer than the intake guide, I suspect this is for heat transfer purposes but I am not sure.  Be careful when driving the guides out as the listeroid guides are made of really soft material and will easily deform. One other thing worth noting is that the guides that were installed in my head had oiling holes drilled in them to "transfer" oil to the valve stem, the replacement guides I got from CMD do not have these holes in them.  I think that the guides without the holes are the way to go, with the holes you would surely empty the valve spring oil reservoirs in a matter of minutes.   

[SHIPCHIEF]

Jens;
I don't run my 25/2 much so I haven't been there yet.
Saying that, I am a marine engineer, and know a couple of things about diesels.
What I'm about to tell you is worth what you are paying for it:
Exhaust valve guides have to transfer more heat from the valve thru the guide to the water jacketed head than the inlet.
Exhaust valve guides have to scrape down exhaust carbon that sticks to the valve stem. Various strategies are employed to do this, but the bottom line is that you would be well served to stick with the plan, or be prepared to take the head off early to cope with the problems generated by doing it your own way. Fortunately, with a Lister, it's no big deal.

[apogee_man]

As a side point, both of my heads have a substantial amount of casting porosity on the valve seat area.

Jens,

Are you sure it's porosity?

The reason that I ask, is I've read that the salt in WVO is a problem as it acts like a corrosive in the combustion chamber when ignited.  I can't remember where I read it, but I remember it clearly.

I'm wondering if that is what you're seeing.

Just something to consider.

Steve

[reno-speedster]

I went another way.  When my Ashwamegh came everything was loose as a goose.  I just took the whole head down and had them install bronze guides inside the stock ones.  Never bothered to take them out and when they did the machining everything was done square to the deck.  I also had them fit the valves while I was at it.  With only two valves the job was cheap, fast and didn't drive me nuts (like all the other stuff I had to fix!