Sadly, I think I found the answer, it looks like I need special tools 4B8267 "Nut" and 4B8268 "Stud", plus the jumbo sized wrench V456, looks like that gear isn't going on today!

Could you use a “coupling” nut to attach a piece of threaded rod to the male thread on the end of the camshaft. Then you could use a nut, a plate with a hole in it and a section of pipe to pull the gear onto the camshaft. I don’t know what pitch and diameter the thread on the end of the camshaft is but if it happened to be a common size, an outfit like McMaster Carr might have it. Failing that you could have one made to fit.

Or remove the pushrods, valve lifters and camshaft to allow you to press the gear on. I would not press from one end to the other for fear of bending the camshaft slightly. I suppose there will be a flange or other feature next to the end where the gear goes that would allow you to support it right next to where you’re putting pressure on it.

All in all, more work to remove the cam but aside from making some gaskets or using RTV silicone the process should go quicker and cheaper than having the coupling nut ordered and shipped or made special for the task.

Hello Jim, thanks for your input, the thread on the camshaft looks like 1-1/8", 12 TPI, the bore hole of the gear is 1.5", so I'm thinking if I get some 1.5" allthread, and 2 nuts and a washer to suit that size, then get a internal 1-1/8" thread cut in one end of the all thread to screw on to the camshaft, and weld a nut on the other end, I might get close to having what I need.

The Cat workshop guide says definitely do not try and drive the gear on with a hammer, it will punch the plug out the back end of the block allowing oil to enter the bellhousing.
Thanks
Mike

I think I have a easier solution worked out, I've bought a grade 8 nut in 1-1/8" size, and am machining it down to 1.48" to fit inside the bore of the camshaft gear, I'll weld that nut to a piece of all thread I have here, and use that to push the gear on, hopefully this time tomorrow I'll have it all buttoned up, provided the forecast rain holds off.

I'll put up some photo's of the bodgy tool when I get it done, , the weak link will be my lousy welding, I doubt it's a tool anyone else will need, and if they do, hopefully they can duplicate my solution.
regards
Mike

Sounds like you are well on your way to resolving your "fuel issue" Mike. Well done! Sounds like you are doing a proper job of it.

OK, so I got busy, bought a Grade 8 nut the right size to screw onto the camshaft, machined it down to fit inside the bore of the camshaft gears, for those who don't have a lathe, you can grind it down with a bench grinder, I did a mixture of both, bench grinder and lathe, only because I'm just learning how to use a metal lathe, and a Grade 8 nut is hard.

Once I had the nut ground down to the right size to slip easily inside the gear, I slipped a second nut, a old bearing and a large flat washer onto a piece of allthread I had here, then welded the threaded sleeve onto the end of the allthread, making sure it was centered properly, just tack weld it first and try it on the camshaft to make sure you can turn it easily inside the camshaft gear.

I then added a spacer that would fit over my new sleeve, but was a good size to fit inside the camshaft gear, I found a flogged out bearing hub from a D4 bottom roller was perfect, with this basic rig the gear went back on without any drama's, though they are very snug on the shaft, I needed some gentle heat on the gear for the last 1/4", to pull it up tight.

I found when I pulled the old gear off I needed to gently heat it, and I was interested to hear my buddy Steve 3,000 miles away, who kindly gave me the replacement gear, told me he needed to heat the gear to get it off the shaft.

Next time I'd use a fine thread allthread to create the puller for this job, but the coarse thread worked OK, and I had it sitting under the bench, so the total cost was $10 for the nut, you will see there is a second nut welded onto the end also, this is essential to hold the allthread stationary as you tighten the second nut. I've used this allthread in a home made H beam puller previously, to pull things like steering clutch packs off cross shafts, so you don't always need fancy tools to get the job done, just time and imagination to create something that will do the job, you might only use it once.

One interesting thing about this old D4, it's obviously done a million hours and been rebuilt several times, someone got creative years ago and made a new crankshaft oil seal housing, I'm not sure if it was because they couldn't find the right size seal, or that they wanted to move the seal lip away from a rust damaged or worn section of the crankshaft, you can see the seal they used way back when has worn through the leather and has been running on the spring, so it was time it was replaced, that old piece of paper is the remains of a spacer they used in behind the seal, to move it slightly.

Sadly I can't find those old steel case seals here, it would have been nice for this application, so a modern seal was used, with the lip facing forwards, or outwards, I believe it's role is simply to prevent dirt entering the crankshaft bore.
Mike

Here is a photo with the D4 bottom roller bearing housing I used as a extra spacer.