McDonald Imperial Super-Diesel

Yes the carby cleaner gets to so far then fails to get any more out but I will continue with my efforts.
This is becomming those flywheel removal revisited as far as being stubburn. The up side is that if I manage to dmage the needle theother one is in good order and ready to go only requiring a new spring but this spring is knackered too so that part wont worry me. So far my patience is ongoing.

The McDonald valve guides are an odd shape to say the least. With that step in the top to hold the valve spring in place, the wide shoulder to stop it going down the hole in the head then they differ in length as to how far they protrude into the port area.
The widest point they are around 28mm on that shoulder. So today I found a supplier of the cast iron and it will be on its way soon. Spoke to the engine bloke today and he removed both guides so they can be copied and also spoke to Bills Motor works about the supply of some new valves. Bill was out doing a walk-about and he will get back to me soon, I hope along with some good news about the rings for the engine too. So maybe some progress is about to happen again.
Back to that needle soaking in kero. This seems to do nothing and a very generous hit with carby cleaner also has not shifted anything so far. So the plastic jar of petrol and into the ultrasonic tank looks to be the next step.

Most guides can be lined with bronze wire ,any cylinder head service would do it............I would have reamed the guides until the bores were about 90% round ,then modded some s/h valves to suit............I doubt the original valves were anything special ,likely a stainless steel would be suitable for both............No need for KE 965 or Nimonic 90,like GM valves.

A problem pointed out with the old guides was that they were badly worn and out of round. If the bore is not straight the head of the valve would ne=ot seat properly so I made the decision to search out and buy the cast iron today and make new ones. This then gives me a couple of options with the valves. These are suppose to be 7/16" stems and both pair of valves I have, do have their own issues. One pair the stems are stuffed with wear and the other ones are badly pitted on the surface that requires facing and I do mean badly pitted. I am still waiting for an answer about new steel valves which I was told are available but supplier is off the grid today so will try again tomorrow. Other choice is to get made to measure stainless ones made.

Cobba ,put up the valve dimensions and Ill see if I have any old valves that might suit.......At one time I could have done all this but all my machines are sitting out in a paddock ,and useless.

This is the new fuel tank that should be bombproof against any blow back from the injector. Just adds more weight to the transporter but should work well.
Also this is the condition of the new piece of 30mm wide flat bar iron acting as the anode in the bath tub. This is just 1 days worth of crud and the amount of pitting under all that stuff is amazing.

Thank you John
Stem is 7/16" OD
Stem length is 7" in overall length
Head is 1 1/2" across
Thanks again for looking.

A possibility, if you're as tight as I am is to turn the heads off the rusty ones and cut the shafts off the not rusty ones. Drill and tap the good heads and thread the good stems. I am building (ever so slowly) some 3 hp International M type valves reusing the heads and making new oversize stems. After screwing them together, I plan to peen over and braze them.

You could also bore your new guides undersize, after turning the worn valve stems true. Lots of possibilities.


Jarrod.

Thanks for the suggestions Jarrod. I did not know that could be done, machine the stems undersized and or do a cut and shut with the valve heads. The intial almost good heads have such a badly worn groove on the valve where it seats that by the time you grind them away they too would be undersized. I will phone again tomorrow to see if the new ones are available in steel. If so they are $25 each but if they are not available I dont have a price on the stainless ones. Finding stems that are 7" long aparently is a challenge.
The new guides wont be machined until I have a definite size of the stems.
I sent back the cam gear the other day to have a small part of it built up a little higher than he did it originally and I will get it back tomorrow then continue on the linishing process ready to install after the piston and crank are back in place.

Back home again and it looks like you've been busy? Twenty five posts I missed and had to catch up on!

Would it be a good idea to do a quick diagram showing what you need, as there may be other valves that could fill your needs elsewhere, sitting in surplus parts collections amongst forum readers???