How To: Restoration of Ford M8 armoured car US Ordnance number 7373

[Big D]

Hi all,

I don’t have a lot to report this week as I’m still waiting on gearbox parts, so progress on that has ground to a halt. I’ve attached a few more pictures of the components now that I have everything stripped. You can see the damage on third gear and to the synchro hub for 1st and 2nd gears.

As Willy pointed out to me, cleaning out the oil galleries in the front of the gearbox housing are very important. This is the feed for the front bearings from the oil pump. My housing had a broken plug in the front and at first glance it looked like a Welch plug to me, but it is a NT 1/8” brass plug which I had to remove with an extractor. New bearings and the replacement third gear and synchro rings should hopefully not be far away.

I managed to get hold of a set of the elusive engine bay panels. Many thanks to R for coming up with them. I'm told these are quite important for the cooling on these engines. I’ve cleaned a couple of the panels up already and painted them. The metalwork on the two bigger panels is quite thin in places so I didn’t blast them and instead have been removing the paint using paint stripping discs and a wire wheel. I’ll do some patching of the holes and then get them painted. These panels are a great score.

That's it for this week.

[Big D]

More photos.

[Big D]

Hi all,

Not a lot to report this week as I’ve been busy getting the rebuilt Hercules engine back into the scout car, which has taken up a bit of my time. It is looking good though.

As far as the M8 goes, here are a few photos of the lower engine panels temporarily fitted into place so you can see how they are arranged. I think I will leave the small panel under the fuel tank in there prior to the fitting of the engine. It is not the easiest of things to fit into place. The other panels can go in once the engine is fitted and everything is looking good.

With the help of a friend, we’ve started assembling the engine for the M8. The machining has been done on the head and bores have been taken out to 0.060” oversize. Don’t you just love cleaning all the cosmoline off those NOS parts! I’ve fitted the plumbing to the new oil pump so that it is ready to fit.

I was going to remove the crankshaft pulley wheel from one of the old crankshafts I had and reuse that, but it is a little rough and the locking nut is quite badly rusted. I figure it will take some time to remove that so I will search out a NOS pulley wheel instead. If anyone has a spare one, I’d be interested.

For the information of the Scout Car engine rebuilders, I’ve attached a photo showing the difference in diameters of the M8/M20 pulley wheel and the Scout Car pulley wheel; 6 ½” on the M8/M20 versus 7” for the Scout Car.

The new ring gear for the flywheel has arrived, as has the third gear and synchro hub for the gearbox. I’m just waiting on the synchro rings now to be able to reassemble the gearbox.

The other protectoscope box I was looking for has also arrived.

Does anyone have any of these adjuster screws for the timing covers for the JXD engines?

That is all for this week.

[Big D]

More photos.

[Big D]

Hi all

Not a lot to report this time around as I am still fitting all the bits and pieces to the Scout Car engine, which is chewing up a lot of my time and money.

I have managed to paint and fit the new fuel tank into the M8. It has the correct fuel sender (thanks Kenet) and gas gauge so they should work correctly. I’ve made up all the fuel lines now and it is now plumbed and bolted in and ready to fill with gas. I bolted it to the cross member in the hull.

I also finished tidying up the second protectoscope box that I got and that is now fitted.

The new pulley wheel arrived as did the starter motor adaptor(thanks Brent and Rod). I am on the lookout though for the cast outlet for the water pump and the upper pipe to the thermostat housing, as per the attached photo. The water pump outlet is different to the one on the Scout Car.

Has anyone got any of these parts spare?

I have started rebuilding the starter motor. The stamp on the armature shows 2006 which is interesting. The armature and fields appear fine but one of the brushes is broken. From what I can see in the parts manual, these brushes are used on the M29C Weasel. Does anyone have a source for these brushes?

That’s it for this week.

[Big D]

More photos.

[Big D]

Hi all,

Progress on the M8 the past couple of weeks is still a little slow with most of my time going into working on the Scout Car, so I’ve just been tinkering away on the M8 when I can.

We got the M8 crankshaft assembled into the block last week. The journals on this crank were at 0.060” so near its limits for wear but it looked to be in nice shape. All appeared good until we measured the end-float which was over 0.011”.

After some searching for the problem we identified the problem as being the crankshaft itself. The gap between the rear main bearing shell thrust washer face and the crankshaft journal was too great. It looks like that journal where it meets the thrust washer has been ground at some point, possibly in the process of its last refurbishment?

Why that would be is a mystery but we were wondering why the rear main bearing shell had punch marks around the circumference of the thrust washer face of the shell and this would explain why. Whoever did the last work on it was trying to take up the excessive clearance by putting the punch marks in the shell and dimpling the thrust washer surface.

After some discussion with the engine reconditioners I decided to go with the option of resurfacing the thrust washer face of the bearing shells. This has the effect of building up the surface and taking up the excessive clearance. Apart from the end-float the crankshaft is in very good condition and I felt that it was a shame not to use it especially when we had gone so far with it. Now that the crankshaft is back in the block with the resurfaced shell, the end float measures at an acceptable 0.003-0.004”.

I do have a spare crankshaft which is at standard size along with some 0.020” shells but I will save that combination for a future rebuild on either the scout car or the M8.

I have a number of other parts on the way including the water pump parts I needed (thanks Brian). I am in the process now of gathering up all the loose parts and taking them to the workshop where I will assemble all the bits and pieces onto the engine prior to lifting it into the hull. The gearbox synchro rings are due here anytime so I’ll be able to reassemble the gearbox and get that fitted to the engine block before the assembly goes into the hull.

I had the generator that I rebuilt tested at the local auto electricians and it tested fine. I can’t say the same for the voltage regulator. I bought that believing it would work but it is a no-go. Fortunately I have another which looks like it has never been used so I will test that one out. Despite it appearing to be NOS, I had to solder a wire back in place. It had broken away as one of the coil mounts was loose. I still need to find another pulley wheel for the generator, or else repair the one I have.

I am making up an ignition lead harness. I had the tubing but it came without cabling in it. Complete NOS ignition lead sets are available but I figured I might as well use what I had and the leads don’t take long to make up.

I have the later thermostat housing and pipe outlet. I tested the NOS thermostat I had in the thermostat housing and I see the fit isn’t right. This thermostat is a French one – part number G136 73 47630. The length of the thermostat means that it seems to be pushed hard against the inner surface of the housing so I don’t see how it could work. The 3” diameter at its widest point also makes it a little big for the water pipe outlet to fit against the thermostat housing so that the two pieces close.

I am aware that there are different types of thermostats and housings but does anyone have any photos of the variations of these so I can confirm things?

That’s it for this week. Merry Xmas.