Restoration of Ford M8 armoured car U.S Ordnance number 7373

[Big D]

Thanks Paul

I need to find a longer dipstick!

[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.

[SURPDLR]

Hi Paul

Thanks for that. I was curious to about the overall length of the dipstick from the block. I've just studied another couple of photos and I see there is a tube built into the dipstick hole on the block on the M8/M20 which gives it that extra reach. I thought that extra length was built into the dipstick but looking at other photos it is fixed to the block. I presume this extra length is just to make access for checking easier.

Darryl,

It took me a bit to find this old FB post, but here is more than you may want to know about dipsticks and M8's....

https://www.facebook.com/groups/3136315 ... 279604323/

And this demonstrates why I LOVE the G, and HATE FB..... If this info had been on the G, you would have seen the post back in Dec of 18 and been good to go. Instead valuable info is scattered all over the place and on FB it is HARD to keep track of as time goes by. Apologies for the anti FB rant and my tardiness in getting you this info.

Next question for you: Are you aware of the MWO for the Transmission oil pump? I will look for my copy and add it either way to this thread, because this looks to be THE thread for M8 / M20 ground up restoration!!! Please protect your photos so that we don't end up with dead links in the future, this thread is so valuable!!!

Keep up the GREAT work!

[SURPDLR]

As promised, MWO ORD G136-W6 TRANSMISSION OIL PUMP MOD - for increased oil inlet to the transmission oil pump:

http://www.flmv.net/images/M8/MWO%20ORD ... %20MOD.pdf

[Big D]

Hi Jeff

Many thanks for that. I had not seen that post on Facebook. Very interesting and that old Army Motors articles is gold! I will need to make sure I note down how much oil goes in the sump and keep an eye out for the correct dipstick.

I also had not seen that MWO for the oil pump. I will go through my photos and see how many holes my pump had in it. I have a feeling it wouldn’t have had the extra holes.

[sawbuck]

Engine looks great. Wouldn't the cooling vanes on the generator pulley face the windings?
The photos in the link show what I am thinking:

https://powderriverordnance.com/shop/ar ... 4485ae434a

https://powderriverordnance.com/wp-cont ... CF5960.jpg

[Big D]

Hi Paul,

Yes, like this. I had been playing around with the pulley to see how it was going to spin and I've set it up right since those photos. I think the pulley will be fine.

Getting close to starting up time....

[armoured_smiler]

Hi Darryl,

I see that it looks like you have a Scout Car dipstick in your M8, is it bent 10 degrees in the middle? (I assume you have the correct/this dipstick in your Scout Car).

Regards
Paul

[armoured_smiler]

Darryl,

The attachment of a Ford JXD engine (with the black weater pump), I have removed a oil dipstick & tube very smiliar to that from my Scout JXD (it was puncturing my oil strainer), if you can't get hold of one and you know the dimension I can check if this is an M8 dipstick

Regards
Paul

[Big D]

Hi Paul

Yes, this is a Scout Car dipstick and I have yet to source an M8 dipstick. Jeff advises in this FB post that the M8 dipstick is 19" long:

https://www.facebook.com/groups/3136315 ... 279604323/

Does this help?

[armoured_smiler]

You better be careful and make sure you also get the length of the tube as well, as the dipstick I have here is not that long BUT does have a 'tube' looking very close to the one on that other M8

[Big D]

Hi all,

This weekend, a friend and I fired up the M8 engine for the first time. Ed is a good engine man and he worked on British Army military vehicles in his younger days. He did most of the internal assembly and set up on the block.

I had completed the assembly of all the accessories on the engine on a tubular steel stand and I set up a wooden platform in front for the radiator so I could run that at the same time and make sure that was working okay as well. I don’t have an original upper radiator pipe so I cut a bit of pipe to temporarily use. This bit of tube is a bit longer than what the parts manual specifies but I needed the extra length so I could give the fans enough clearance from the makeshift radiator platform.

I remote wired the engine into the hull of the M8. I thought this was a good idea initially but upon reflection introducing a whole lot of other variables into the start-up equation was maybe not the best move, when all the wiring in the hull was untested. It worked out alright in the end though.

The first switch on produced nothing and we found the starter solenoid wasn’t engaging. As BCA pointed out on a previous post on the g503, the M8 is wired as such that when the ignition is switched on, 12 volts is supplied to the control terminal on the starter solenoid. When the starter button is pushed, it grounds that 12 volts which activates the solenoid and sends 12 volts to the starter motor post. I wasn’t completely sure the solenoid I had needed the 12 volts on that post grounded, or needed 12 volts sent to that post, to actually activate the solenoid.

After checking with another M8 expert (thanks Willy) I confirmed the solenoid I had fitted was the correct type. After a bit more tracing I found that the cause of that issue was a bad earth on the instrument panel, so the grounding through the starter button was not taking place. After working through the circuit diagram again I couldn’t see how the instrument panel was actually grounded, as it is mounted on rubber insulating blocks. Anyway, I ran an extra length of wire from the instrument panel body to the panel mounting bracket on the hull. This gave the ground required.

Once I had the 12 volts coming off the solenoid to the starter motor, I found the starter motor wasn’t working. After a look at that I found that one of the brush springs was shorting out against one of the nuts holding the brush pigtails to the starter casing. Those wee springs don’t like high current through them and it damaged the spring. I had to search a bit to find a spring locally but a retired auto electrician I know managed to find one in his box of spares that would do the job. We put it all together and it worked but the nut on the little screw holding the brush pigtail to the case was still very close to the brush springs. I have wrapped the nut with a strip of insulation tape in the meantime but both of us agreed that the nuts are probably not standard. I have a new set of brush springs coming from the US and when I fit those I will find a nut with a lower profile.

I rigged up a fuel supply to the newly built fuel pump and with Ed on the engine and me on the instrument panel, the engine ran on the first touch of the starter button. It sounded very nice and seemed very responsive. The NOS fuel pump which I had put new neoprene diaphragms into worked well.

There were a couple of minor issues during our various tests, like one of the water pipes coming off and spilling water everywhere. I have been advised that I will receive the ‘Golden Screwdriver Award’ for not tightening the screw on the clamp enough. There was also a slight leak in the gasket in the thermostat housing, which I’ll sort out when I actually fit the thermostat.

After a number of starts we found the battery was starting to slow. I did a few voltage checks and it didn’t look like the generator was feeding the battery enough so I will check that and the regulator out.

I have a new calcium type N150 battery but I don’t have a compatible battery charger here and I wasn’t super confident it was being charged fully prior to us starting the engine. It certainly looks like that is the case now so I will order a new calcium compatible battery charger tomorrow.

It’s a great feeling seeing and hearing the engine run and knowing most of what is attached is operating correctly.

I will fit the clutch assembly and gearbox next and then fit the correct ignition lead terminals now that they have arrived (thanks Brian). They need a little ferrule at the end to stop the wire coming out which I have not seen available so but I might have to come up with an alternative for that.

After that, my next step is to fit the newly rebuilt brake hydrovac into the hull and complete all the plumbing on that. I will then pressure bleed the brake system and that should get the hull pretty much prepared for fitting the engine and gearbox assembly.

Here are a few videos of us running the engine, testing the generator and regulator etc:

https://youtu.be/sOCfMGhI3mU

https://youtu.be/VUlI76GAZBE

https://youtu.be/If3TuDe7TIQ

https://youtu.be/dMuRJgVTYV0

[armoured_smiler]

I congratulate you on your first 'run', great job

[Big D]

Thanks Paul

I’m getting there!

[brian in denver]

Hi all,

I have now learnt (thanks to Willy) that the conduit that runs around the hull actually carries the 12 volt power supply for the terminal box on each sponson, as well as the CO213 cordage that links the BC606's for the commander and the loader. The conduit terminates at the terminal boxes and then there is a short length of cordage to each BC606. This fits with what I was seeing in the plans.

What I was confused about were photos of some restored M8’s that had the cordage on the firewall inside the hull connecting the commander’s and loaders BC606’s. I understand now that this is the early design. I’m going the later design with the conduit around the hull behind the firewall beside the fuel tank, providing I can get my hands on enough of the conduit!

I’ve now connected up the four BC606’s and the FT237 radio tray using the CO213 cordage. Preparing the cordage was a bit of a tedious job. Seperating the shield on the outside is time-consuming as it is very tightly wound around the internal wires.

I wired in the cordage for the driver and co-driver BC606’s in situ, only because I wanted to be sure of the lengths of the cable required. I wired the BC606’s for the commander and loader out of the vehicle and that was a darned sight easier. I’d have to say, that despite all the drawings and plans, without knowing exactly how it was all laid out, I still needed to do lots of research and have a good think about the layout and how it was connected both before and during the installation.

I was (and still am) a bit confused by the layout of the BC606’s. The plans show that the BC606’s for the driver, co-driver and commander should be positioned with the INT/RADIO switch and Volume Control side of the unit down. I setup the BC606’s for the driver and co-driver in this way as per the drawings.

I placed the loader’s BC606 as per the drawings with the INT/RADIO switch and Volume Control up. As I say, the drawings say that the Commander’s BC606 should be positioned with the INT/RADIO switch and Volume Control side down though, which didn’t make much sense to me.

What was the logic to how these BC606’s were fitted? I have seen numerous variations in the setups in restored M8’s, and a number of pictures of M8’s during wartime also showed variations. Why not keep them all in the same layout with the INT/RADIO switch and Volume Control upwards where the crewman can see it and change it if required?

In the end, I positioned the Commander’s unit with the INT/RADIO switch and Volume Control up, as per the Loader’s unit. I guess someone will correct me if it is wrong.

Along with the radio stuff, I’ve been trying to progress the gun. We haven’t been able to remove the two screws holding the recoil system in place. These screws have an allen type head on them but they were pretty knackered and corroded. I had been soaking the screws with penetrating oil for several months but the heads weren’t good enough to get a decent bite on them with the allen screw bit. We tried welding a bolt onto one screw but even then we couldn’t get the thing to budge. As a result, I will be taking it into a metal specialist next week to get the screws removed by spark erosion.

I got the boys in the engineering shop to profile cut a tool for removing the big nut on the barrel. This will allow me to remove the sleigh. Again, this nut is stuck and I’m better off having a tool that fits it properly before trying to lever it much more. l will give this tool a try next week and see if that will shift the nut.

yah the commanders box is wired different, the later boxes had spring loaded toggle switches, because if crewman leaves his switch in the wrong position then you cant broadcast out. (we have that problem in our stuart). our sherman will have spring toggles so we wont have to mess with it. um the assistant drivers box is supposed to be in the lower position, the upper position is for the SCR-506 squawk box, and do me a favor flip all them clips over so the wire is against the hull, and not standing out for stuff to get hooked on it, thats bothersome to my fung shawy