Hi Dave,t
there are no compression figures given in Cat literature as they do not believe in it--however, I have this scan for the later D300 series engines that you can deduce from it what you like--I feel from studying the scan that anything much below 500 PSI would be getting into the hard start area.

Worn liners and rings , but also poor seating valves and definitely sunken valve heads cause compression to be low.
Cat have fairly specific ranges for valve head position in relation to the head surface--see scans below for the D4600 engine that is in your machine.
You will need to print the valve spec pages and align them to transfer the engine type over to the second page for all the data to make sense.

A leak down test will help you determine where possible leakages are as in rings by listening into the removed engine breather's tube, and valves by listening in the intake and exhaust manifolds with the cylinder being tested with its piston at Top Center on compression stroke.

Hope this helps.
Cheers,
Eddie B.

on my 9k3539, the bell housing to bolt on differential dimensions are, left side 17 1/4,, right side 20. The holes are on a diagonal. On my 8T with a 318 both sides are 16 1/2. bolts are straight across. Just memory, but the clutch seem different.

OB
On closer examination you are absolutely correct. Those bolts are set at a diagonal on the B4600 in the 9k.

It looks like the top of the final drive is pretty flat. Do you think I could just drill& tap new holes in the right place? Or is the hight different as well? Enquiring minds would like to know.

Oh
And what kind of difference do you think the clutch is. My understanding is the 318 came both wet & dry. I was guessing the dry would be the same as my dry clutch but that’s probably to easy. Any idea if the transmission input shaft is the same?

Dave

Mine has a dry clutch. The 318 clutch was beefier. I have a clutch pilot shaft for the 318 and could compare it to the 9k input shaft. There is a casting where the tapped hole is. There are shims to align perfect. I sent you a private message. Where are you located? Photo looks like so. cal countryside. Know of a nicer 8t that may be a better project in so. cal.

So you have had it a while. How much power does it have? Can you roll a full blade of moist dirt? Hard to start fixes that I did on my 318. Have you checked for timing of the individual injector pumps? Worn plungers on the pumps will cause timing to be retarded. I reset my pumps with just a wee bit of advance and it helped with power and starting. I also installed a grease cup on my intake manifold. When starting I screw the cap off and inject a little start fluid directly into the intake manifold. Fires every time. Not perfect but better than an overhaul or engine swap. PS I think the radiator inlet and outlet will be totally different , 318 to D4600. I do have a clutch pilot alignment shaft for my 8t and could compare shaft diameters of both.

It actually runs pretty good once started. After reading some of the posts here I’m thinking spending some time checking out the Fuel system including the timing you mentioned is warranted. A while back I cleaned a bunch of gunk out of the pump tower and replaced filters but I’m thinking I maybe should have done more. It seams each time I’ve started it I’ve found water in the fuel tank which I’ve drained before starting but I suspect it’s possible it’s gone further into the pump.
Dave.

Have you found the tower drain on the bottom of the tower. 3/4 inch on my 318. After sitting a while, ( weeks ) I crack each injector line till I get a squirt, before I squirt starting fluid. I am getting air into pump from somewhere. Not worth looking for. I also park grader so tank drain is low. Open the drain every time I start the machine. Have a lever brazed to the top air bleed on tower. Open that also during cranking till it dribbles fuel. hope this helps

I have the same drainage plug on my 4600. Definitely use it prior to starting after sitting a while. I typically only use it in the fall and spring Dince the roads are either to wet or dry in the summer and winter. Thanks for giving me some ideas to look into for now I need to get to the pony carb. My kit just got here from McDonald.

Have a couple of spare carbs.

Hi all
I took the Carb to bits and soaked it in cleaner. Pulled the plug under the bowl and made sure it’s clear. On further examination I’m not sure if some other ports are clogged as well. Those first time I pulled this carb apart (years ago) it was full of dirt. Got it to work sort of but I think some passages may still be plugged.

Q: can someone post a fuel flow diagram with all the passages for the zenith tu4c carb? I’ve got one cartoon flow drawing from aN old reference manual but it’s incomplete and the parts diagram doesn’t show passages. I’ll see if I can post a few pictures of the carb parts as well.

Edit: of course a pointer to a carb rebiuild article/diagram would be great.
Thank in advance.
Dave