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

[Big D]

Hi all,

Things are progressing with the engine assembly and my plan is to get this running before it goes into the hull.

I initially had the engine on some wooden blocks but now have it on a stand which we’ll run it on for a test before it goes in the hull. Yes, I know the engine mounts are upside down in the early photos…it was just easier…

I ran out of time to remove some broken manifold studs before I sent the block in for machining so I have now done that. What a pain in the butt job it was removing them. I’ve also drilled and tapped the new holes required at the ends of the block for the longer manifold used on the M8 versus the Scout Car.

I’ve fitted the water pump, oil filter, fan pulley mounts, coil, manifold and starter motor. I had to fabricate the generator mount stay and the bracket that holds the coil.

I was about to fit the fuel pump I had but realised the mount was wrong. I rebuilt this pump several years ago thinking it was for an M8 and had it stored away until now! I have since been told it is actually for a White halftrack. The correct fuel pump is now on the way to me….

The timing cover on this engine didn’t have a plug in it for blanking off what would be the oil filler hole on the scout car engine. What I did was to use a 1.5” frost plug, clean up the circumference a bit as it was fractionally too big, and tap that into place in the timing cover.

The dipsticks for the M8 and scout car are obviously different in length. Is the length of the handle the only difference? I know the sumps are slightly different but I wondered if it was just the handle being a bit longer for accessibility in the hull.

I have a NOS distributor on the way along with some water pump parts I still need. I actually wasn’t aware until now that the distributor cap for the M8/M20 uses an acorn type connection for the leads. The thread diameter is ¼” UNF. Has anyone seen these connectors commercially available?

I fabricated the small adjustable rod for the automatic choke. I modified the design a bit and included a locknut on the end of each leg to hold them onto the centre piece. I understand the original had grub screws securing the legs. I will need to go back to the forum thread where I got the dimensions and photos for this though to confirm the weight of the rod joining the two legs. I imagine that will have an effect on the operation of the auto choke….

That is all for this week…

[Big D]

More photos.

[Big D]

Hi all,

I’ve continued with the assembly of the engine as well as doing a few jobs on the hull. A few of the last parts I was waiting for also arrived (thanks Taylor and Brian).

I had to rebuild the fuel filter, so that is all done now. I’ve also plumbed the clutch slave cylinder on the side of the gearbox. This is using 5/16 tube instead of the standard ½” tube so I’ve had to get a flexible hose made up for it. I am using ‘olive’ type connections on the lines at the gearbox end, rather than flares.

My retired auto-mechanic friend and I attacked the bleeding of the hydraulic throttle. He was fairly adamant that his good old vacuum pump would do the job but we found that it just couldn’t generate enough suction to draw the fluid up over the ‘hump’ in the line at the front of the hull. After that he dug out an old pressure builder he had made several years ago and we adapted that for the M8. I couldn’t find a spare reservoir cap with the necessary 1 ¼” -18 diameter to modify for the pressure bleeder. However, I did find a cap that was 1 ¼”-16 diameter and using a bit of plumbing tape got enough of a seal in the reservoir to get sufficient pressure into the system. I have to say that this worked a treat. Perhaps it was a little too good as it was a great way to find multiple leaks in the lines! A little bit of tightening here and there on the flared connections and some water to wash the hydraulic fluid away and we were almost there. We bled at the junction point that I made up and then we disconnected the pressure bleeder then and used the vacuum pump to finish it off at the bleed point on the slave cylinder. Ten minutes later and I now have a working hydraulic throttle. It feels very smooth.

Up until a day or so ago, I hadn’t found the correct screw in connectors for the ignition leads sold separately. I thought to get around that I would use ¼” UNF cut off screws and use standard distributor ignition connectors to fit over the threaded shafts in the distributor cap. In the meantime, I got a ‘lead’ on where I could find the correct connectors and they are now on the way (thanks Brian).

I didn’t realise that there were the remnants of the old temperature sensor still in the head so I had to remove that with a ½ NPT tap. I’ve fitted a new sensor now. Hopefully this will match the temperature gauge I have.

The generator is mounted on the generator mounting bracket using two large 5/8” bolts. These bolts have a shoulder on them with the diameter of the bolt shafts a little bigger for the corresponding holes in the mounting bracket. Unfortunately I only had one of these bolts and it is not the sort of thing you can get off the shelf so I had to get a ¾” bolt turned down instead. It makes for an expensive bolt!

I have run out of time to find a replacement pulley for the generator. The one I had was broken in three pieces and had already been repaired once. I have had it brazed up by the guys in the engineering shop so hopefully it will do the job until I find the elusive replacement. Does anyone know about balancing these? If you look carefully at the photos you will see that the splined hole for the generator shaft wasn’t even centred when this was manufactured so I’m not sure I need to worry about the balance….

Is anyone still supplying rebuild kits suitable for modern gas for these fuel pumps? They seem to be harder and harder to get…

That’s all for this week.

[Big D]

More photos.

[David Dunlop]

Darryl.

Do you have a bare splined shaft available the gen pulley will fit on?

If so, you could centre the pulley on the shaft and place the assembly between two hard level surfaces (steel or glass is best) and see if the assembly stays where you placed it or rolls to a different point and stops. If the latter, the assembly is out of balance and has stopped where the most weight is at the bottom.

Seems odd that somebody milled out some metal between the fins on that pulley on the ‘short side’ of the shaft hole. I would have thought that would have made the ‘long side’ even heavier.

David

[lynx42]

Hi Darryl, any reason that you have put the generator pully on back to front? The fins should be up against the generator face not out there where you can get caught on them. The fins are to push cooling air through the genny.

Doing a great job. I'll have to pressure feed my Lynx hydraulics to find the leaks.

Cheers Rick.

[Big D]

Hi Rick

Good spotting. I had been playing around with the pulley and its alignment at the time. I have put it on the correct way since then and it seems to spin evenly enough.

Yes, I was impressed with the pressure bleeder option and ordered one of these from the US. It seemed to have pretty favourable reviews from what I had seen and really the only drawback with it was the lack of a release switch on the output. The hydrovac should be done this week so I will hopefully have this bleeder by then and will use it to bleed the brakes.