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McDonald Imperial Super-Diesel Engine

Darryl

Registered
Essentially, the tubes only hold the o rings in position until the head is on so don’t worry too much .
About the “ atmospheric valve “ , it’s just a farmer fix to hold the cap on.
The engine does breath at the cap though .
 

isandian

Registered
McDonalds would not have used UNC threads, only Whitworth, but the difference probably does not matter in this case. The only real problem arises with 1/2", the only size where UNC and Whitworth threads differ in pitch. Otherwise it's just the difference in thread form - 60 degrees in one and 55 degrees in the other. There is usually enough clearance in threads to mix nut and bolt fit, but I would not mix them when high torque is necessary. The biggest issue in mixing UNC and Whitworth is the different AF sizes of nuts requiring more spanners in the toolbox.
 

cobbadog

Registered
With those 3/4" head studs the UNC ran down most of the way by hand then I used the screw drivers to get the last 1" or so. Same with the nuts the tap went almost all the way through before dirt and crap stopped it. Today I found the 1/2" ones on the head itself where the exhaust flange bolts to. I used my thread gauge to establish whether it was 12 tpi or 13 tpi which is the difference between BSW and UNC these were Whitworth and the threads cleaned up nicely and now the head is arse up soaking with some caustic solution inside the coolant section to clean out a bit of dirt.
Something I am enjoying is identifying the nuts and bolts that go into this engine, Most of the nuts are squared off flat on one side and have a slight chamfer on the top. The heads of the bolts are squared off flat.
 

isandian

Registered
Good to see you trying to keep the authenticity of the nuts and bolts. I try to do this, especially on pre-war built engines with the larger size hex. The problem with this is nuts especially are often rusted beyond recognition, and replacements hard to come by. For some reason I am forever searching for old-style 3/8" Whitworth nuts. McDonalds also often used half nuts and there is no choice but to make them yourself.
 

cobbadog

Registered
Sometimes it is all the small jobs that take most of the time. Today I borrowed the Rolls Royce of flaring tools to make the new oil pressure line to the bush on the crank shaft. I bought a new nut to replace the split one so I dug out a short length of 5/16" copper tube, cut it to length flared one end put on the two new nuts then flared the other end. Then dug out my small tube bender and made the basic shape required and bolted it in place. Lastly the thread for the sum plug was a bit how ya going so again I borrowed the tap to clean that up. 20200429_134818.jpg20200429_134829.jpg20200429_140032.jpg20200429_140549.jpg
 

isandian

Registered
With some heat, even that much will often unscrew using vice grips leaving a clean thread. It's typical of many of the engine I have tackled. I have a McDonald VBR with every nut and even some studs removed and replaced - one of the reasons it's on the back burner.
 

Darryl

Registered
The diaphragm in the oil indicator usually leaks and needs replacement . Sometimes the set screw holding on the vaporising cup onto the injector needs to be left a bit loose so everything sandwiches up tight with the hold down nuts. Always leave the engine stop lever in place when the engine is stopped or the engine can fill with fuel. Make sure you initially use clear hose to the ” injector” so you can see if the fuel needle is sealing when cranking engine.
 
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cobbadog

Registered
Now thats news I really did not want to hear about the diaphram in the oil indicator. I did try to remove it for cleaning and could only loosen 2 of the 4 screws, mainly due to lack of space to put my hand around the stubbie screw driver and since I did not want to chisel them off I left it. But something that I did do there was to face the elbow up and filled it with Lanox and it held that in there for 4 days so I thought I was in the clear.
Clear fuel line is a great idea to watch for bubbles but I just know I will have to be reminded about that. Not heard of the info about the injector vaporizing cup is something I will look at when it is time. IS there a gasket where the injector fits into the head?
Today I picked up 2 new crank shaft seals and the speedi-sleeves will be here soon as there are some grooves on the crank shaft.
 

cobbadog

Registered
Spent part of today cleaning up threads of the studs on the head and did a trial fit of the head to the engine to check that it would go over the new copper tube and it did. Then dug out part of the linkage system just to see what it would look like. I now need to clean up the linkages that I have to see if it is all there and I think it is. Also had a look at the coffee pot part of the hopper and cleaned up the 2 small 3/16" studs that hold the fuel tank in place.
Yesterday I bought home a pair of Speedi-Sleeves to fit to the crank shaft as the grooves in it for the new seals were a bit bad. 20200502_091236.jpg20200502_134616.jpg20200502_143503.jpg
 

Scotty 2

Registered
Hello John
Do those engines have a de-compressor? Is it the little governor weight/bob looking thing just in front of the spring on the push rod?
Cheers.
 

asw20

Registered
Yes, that is the decompressor. It drops into the gap when one opens up. Crank like mad and then flip it up. Hope for knocking noises...

Jarrod.
 

cobbadog

Registered
Hi Jarrod, it was great to make contact today and your pics have helped out already with where and how a bracket fits. Hope the pics I sent you resolve some of your questions and we both learnt that there is a spring on the govenor arm linkage across to the injector. The more time I spend at this end and with help I am slowly working this bugga out.
I started on the injector this afternoon. It was caked in sticky stuff similar to resin as if if it sat under a tree. Then found that it continued inside. Plunger not moving and the 2 small holes in the injector cap blocked solid. I managed to get the punger out of the top and nice and free and then using the cleaners I have for cleaning out my spray gun nozzle along with some very much undersized drill bits by hand. The cleaning things I have are not like oxy accetylene tip cleaners but are various sized bits of twisted wire and only work there way through the hole with out doing any damage or boring it out oversized.
Now down inside the bottom half of the injector is another metering needle and it is stuck fast and out of reach of my long nose pliers so I have all of that soaking in paint thinners for now to hopefully disolve the resin like stuff. Open for any other ideas please to get this needle out.
 

davob

Registered
Hi Jarrod, it was great to make contact today and your pics have helped out already with where and how a bracket fits. Hope the pics I sent you resolve some of your questions and we both learnt that there is a spring on the govenor arm linkage across to the injector. The more time I spend at this end and with help I am slowly working this bugga out.
I started on the injector this afternoon. It was caked in sticky stuff similar to resin as if if it sat under a tree. Then found that it continued inside. Plunger not moving and the 2 small holes in the injector cap blocked solid. I managed to get the punger out of the top and nice and free and then using the cleaners I have for cleaning out my spray gun nozzle along with some very much undersized drill bits by hand. The cleaning things I have are not like oxy accetylene tip cleaners but are various sized bits of twisted wire and only work there way through the hole with out doing any damage or boring it out oversized.
Now down inside the bottom half of the injector is another metering needle and it is stuck fast and out of reach of my long nose pliers so I have all of that soaking in paint thinners for now to hopefully disolve the resin like stuff. Open for any other ideas please to get this needle out.

Cobba, jump onto fleabay and invest in an ultrasonic cleaner. The cheap ones like the one posted below do a good job of cleaning up small fiddly bits. Fuel injector shops use industrial versions to clean injectors during the rebuilding process.

http://rover.ebay.com/rover/1/705-5...2&toolid=10001&campid=&icep_item=323856432823
 

cobbadog

Registered
Hi Scotty,
I just re read your post about the governor weights. That little weight thing you mentioned is for the decompression and the governor is hiding away inside the engine above the piston.
Here is a close up of the governor as fitted inside the engine, sorry but the weight is full on towards the camera and there are 2 of them in situ. Then there is the main linkage that come from the cam to operate the valves. This is still in need of a clean up and there is a small T shape thing that is the decompression lock. The hole in the block is where the push rod comes from the cam to the valves. On this model there was never a seal in this place and I will see how it goes without one. If required I will make a clamp to hold some gland packing and bolt it to the engine. Sometimes oil leaks are good for weed control at Rallies and no thanks required for killing the weeds.20200503_110736.jpg20200503_111014.jpg20200503_111151.jpg
 

cobbadog

Registered
Cobba, jump onto fleabay and invest in an ultrasonic cleaner. The cheap ones like the one posted below do a good job of cleaning up small fiddly bits. Fuel injector shops use industrial versions to clean injectors during the rebuilding process.

http://rover.ebay.com/rover/1/705-5...2&toolid=10001&campid=&icep_item=323856432823
G'Day Davo,
As it happens I have a rather large version of said ultrasonic tank cleaners. It measures 2.6 metres long x 0.300 wide and is used for my business of cleaning blinds. My issue is cleaning it out after using it to do an injector as I dont want it to bugger the next cleaning job. Food for thought and thanks for bringing it it to my attention. The tanks also works best with detergents designed for certain jobs usually.
 

cobbadog

Registered
Been soaking the injector to get it apart then cleaned. I have the top section and that needle out and free but the bottom one is rock solid. It has been in some thinners for a few days and the 2 hoes in the injector cap are now clear and the cavity behind is clear so the thinners is working from both sides now.
Looks good for the oil primer from a member here, so thank you for that. I need a few dimensions for a fuel tank and although I have the cast iron casting for the air cleaner I am after the outer housing if one is king about please.
I still have not had the chance to use the ultrasonics to help clean up this injector but will give it a go soon.
 

kwfiggatt

Registered
Age
44
G'Day Davo,
As it happens I have a rather large version of said ultrasonic tank cleaners. It measures 2.6 metres long x 0.300 wide and is used for my business of cleaning blinds. My issue is cleaning it out after using it to do an injector as I dont want it to bugger the next cleaning job. Food for thought and thanks for bringing it it to my attention. The tanks also works best with detergents designed for certain jobs usually.
If you don't want to dirty up your big ultrasonic tank with an injector, put the injector, along with some solvent in a plastic bag and immerse it in the ultrasonic tank. Make sure the injector is fully immersed in the solvent inside of the bag. The ultrasonic waves will go right through the bag. Seal the bag up and Bob's yer uncle!

Kevin
 
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