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

[Big D]

Hi all,

Thanks to Willy, who is a fountain of knowledge on M8’s, Scout Cars and anything armour, I’ve worked out the differences in the engines on the M8/M20 and the Scout Car. The basic engine blocks are identical and have interchangeable crankshafts, camshafts, valves etc. The parts that are different are all the extras:

• Oil pan and oil pump
• Bell housing and timing cover
• Flywheel and clutch assembly
• Starter motor, water pipe and distributor

The reason I was keen to know this was to make best use of all the Hercules engine parts I have. I have a spare engine block from my scour car restoration which now has all the pistons out of it. The bores on this are worn, but are sound with no damage to the walls.

The three engine blocks I had for the M8 all have stuck pistons with damage to the bore walls. After comparing the spare scout car engine block with the three M8 engine blocks, I’ve decided that the scout car block is the better candidate for a rebuild for the M8, so I will use that one. I’ll remove the timing cover, bellhousing, sump etc from the M8 blocks and use those on it. I will work out what combination of pistons and sleeves etc I will use at a later time, but it was just good timing to be able to check this while the scout car engine was getting rebuilt. By the looks of things, I should have enough bits and pieces to rebuild at least two more Hercules engines on top of these two, but that will be something I will sort out later. The Hercules block and head being machined in the photos are for the scout car.

Thanks also to Willy for his recommendation on trying the rubber shock bushes for the Dodge M43. I’ve found these are a better fit than what I had. The ends still need cutting down a bit though so that they fit in the 1.75” gap in the shock absorber mounts. I used a hacksaw to do this and then smoothed the ends with a flap disc on a grinder. This gives the correct width for the rubber bushes to fit into the shock mount.

I got the turret mantle and recoil system back from the engineers yesterday. They had several attempts at removing the screws holding the recoil system in place. They couldn’t spark remove them and so they mig-welded bolts on the screws to see if they could wind them out. They kept breaking off so they arc welded them instead and that worked. As you can see, months of penetrating oil on these screws appears to have made no difference at all.

Has anyone pulled these recoil systems apart? Is the spring under load in the housing? Both recoil systems are a bit knocked about and as one is sold, I want to keep the best one for myself (sorry Lynn). It looks to me like stripping one down will be a challenge as well. There are NOS recoil systems still available so I will see how we go with this one.

I think I found out why my 37mm barrel was not straight! As per the photos, it looks like something has struck the barrel in two places, which was covered by the incorrect sleigh. I see also that the barrel has previously been cut near the breech and welded up. There is a bit of work to do there to tidy the barrel up before I put the correct sleigh that I have on there. I will also need to rebuild the mounts for the lever arm shaft and straighten the lugs that secure the recoil system coupler on the breech ring.

The intermediate and rear axles are progressing. Getting the diff housing bearing cones out was a problem but I understand a gas torch has now encouraged them to come out. I spoke to the engineering guys about the cracked differential housing and they say it won’t mig weld. We are going to look at whether it can be brazed but they tell me there is no guarantee that this will work.

Is there anyone out there with a worn M8/M20 differential who would be prepared to part with that part of the diff assembly? That would save me the trouble of trying to repair this piece which mightn’t be successful anyway. Thanks to Andrew, I might have some ready made gaskets coming to, so we are getting there.

Most of the hydraulic lines are cut and shaped now but I’ve still got to do the ½” tube.

That’s all for this week.

[Big D]

More photos.

[Big D]

Some more photos.

[Big D]

Hi all,
This week seems to be one where I start a lot of jobs and for various reasons only finish one or two of them.

I managed to source a NOS replacement housing to replace the cracked one on the differential. I talked with my engineering contacts about various ways to repair the crack in the other one and the consensus was that we could spend several hours on a repair with no guarantee it would be a permanent repair. I managed to get the NOS housing at a very reasonable price so it made sense to go that way.

As an aside, not sure if anyone has confirmed this previously but the differential in the M8 is quite a bit bigger than the one in the White Scout car. I had a spare axle for my Scout Car and I opened up the diff housing to see if I could rob the required part from there. Alas, the diff is smaller. The gaskets I got from Andrew which were made up for LP2A carriers were the right hole spacing and size for the Scout Car axle housing so I’m interested in seeing if they fit the M8 axle housing.

Thanks to Grant for his recommendation on the parts for the primer pump. I got a rebuild kit for a primer pump for an M38 jeep off EBay. The internal dimensions of this pump seem to be the same. The leather washer was a tight fit in the pump bore but it went in. I didn’t have any Neatsfoot oil for the seal so I used Olive Oil instead.

I managed to pick-up a few good parts recently like the headlight sleeves for the hull which I’d been looking for. I’ve also spent a bit of time tidying up some take-off MP48A antennas.

I had no luck finding the elusive U bolt for the rear springs, so I got one made up. It doesn’t look exactly like the original but I will shape it a little bit with the grinder and it should do the trick.

I’ve started stripping the recoil system. Despite many weeks of soaking with penetrant, I needed a big long lever on a breaker bar to remove the buffer off the end of the recoil cylinder. A bit of heat might have made it slightly easier but I didn’t have that at hand at the time. I removed the pin securing the coupler to the piston but that thing is on there real tight. I’ll get some heat onto that next and see if it will pull off.

Like Tankanic, I made up a tool to remove the follower at the end of the cylinder but I’d say I’ll need to weld a big lever onto that to get it to move, once I have the coupler off.

Meanwhile, I finally got around to arranging a truck to take the turret to the sandblasters for blasting and painting.

That is all.

[Big D]

More photos.

[Big D]

Hi all,

Here are a few photos showing what I’ve been doing over the last couple of weeks.

I managed to get the recoil system apart. Thanks to Tankanic for his assistance. I had to make up another tool to remove the follower. Version 1 just wasn’t strong enough and I needed a big lever to get the follower undone. The photos show how it all sits in the recoil cylinder. I’ll have a closer look at everything when I am back in the workshop.

The new diff housing has arrived so I’ll be able to advance the axle assembly which I’m looking forward to.

I have a brake specialist folding up the 1/2" hydraulic line for the clutch master cylinder. The tubing was pricey so I figured I'd rather get it done right first time. Hopefully this will be done shortly.

I spent a bit of a time stripping the engine blocks to see what I’ve got and what can be reused. I got the flywheel off one of the blocks and the ring has a bit of damage. However, it looks like there is enough meat on there to turn the ring over on the flywheel. Out of interest I photographed the M8 flywheel alongside a White Scout car flywheel. As you can see, the scout car flywheel is quite a bit bigger.

On a side note, for what it’s worth for those doing Hercules JXD rebuilds, next week I will photograph the differences between the oil pump for the White Scout car and the M8 and post it here. I say that as I bought what I was told was a Scout car oil pump from a reseller for my Scout car engine rebuild and it turned out to be one from an M8. There are differences in the sumps as a result of the differences in the pumps.

That is all for this week...

[Big D]

More photos.