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

[Big D]

Hi Barry,

Many thanks for that. I feel like things are progressing at a good rate now.

Yes, the manual shows another follower in the coupler end of the recoil system which sits over the top of these parts: gasket-gland-packing-housing (in that order) in the cylinder. I think those would be the parts you are referring to.

That is interesting about what you say about the oil in the recoil system and is good advice, thanks. That does change my plans about how far I go with restoring the cylinder. This gun will only ever fire blanks, but that in itself is reliant on me finding all the parts for the breech. At this stage I have a bare breech block and not much else! On that note, if anyone has any bits and pieces for the breech, I’d be very keen on them.

[Big D]

Hi all,

I am still waiting for the axles to be done which is getting quite frustrating now. If it is going to be too much longer, I’m inclined to go in and pick them up and do them myself now that my hand is right.

As well as doing a few odd jobs on the M8, most of my time over the last week has been spent stripping the three engine blocks. All three blocks are pretty tired with quite a bit of pitting on the tops of the block in and around the valve seats. The pistons and valves are all stuck so there is some work to break them all down. I’m not sure if any of the blocks will be up to the job but my aim is to get them all apart so that they can be assessed by someone with more knowledge than I have.

I have taken out the other two crankshafts that were still in the blocks. One crankshaft looks quite good and still had plenty of oil on the surfaces, but the other two will need some tidying up. I’ve had the pistons soaking with penetrant for some months in these blocks and now that I have all the crankshafts out, I’ve started the process of giving the pistons a good smack with a big hammer and a solid piece of wood shaped to fit in the bore. Out of the 18 pistons in the three blocks I’m working on, 1 piston has moved about 10mm so as I expected, this is going to be a long process.

As you can see, the tops of a number of the pistons are actually so badly pitted they can’t be saved so I am experimenting with another method of piston removal recommended to me. This involves drilling the top of the piston with the aim of breaking up the piston and or getting to the rings. I have plenty of valves and pistons and these are easily obtained, but good bores are not, so if I can get the pistons out and save the bores from anymore damage it maybe worth a go. I’ve been told an air chisel is the way to do this but I don’t have that so I will progress with a drill and die grinder and see how that goes. I need to get peneterant into the rings which will be what is sticking in the bore.

I’ve tidied up the bellhousing, engine mounts and timing cover along with a few other parts in preparation for a rebuild. It took me a couple of go’s to get the paint to my liking. I think it looks pretty close now.

For Oz and others rebuilding Hercules JXD engines, one of the photos shows the two seals for each end of the block. One seal has the unique rubber ring that goes around the seal in the block. I got these from Linda and Jerry at Hercules Parts, along with some other engine parts.

That's all for this week.

[17thAirborne]

Hi all........For Oz and others rebuilding Hercules JXD engines, one of the photos shows the two seals for each end of the block. One seal has the unique rubber ring that goes around the seal in the block. I got these from Linda and Jerry at Hercules Parts, along with some other engine parts.

You are doing great work. Thanks for posting the engine data. Every pic and story helps us with our projects, even if it is two years from now.

[tankanic]

Great job! It will be a looker when its all done! I do have a non-shootable barrel sitting around if you need one.

[Big D]

Thanks Oz and Tankanic,

I wondered if the thread might become a bit of a 'bible' on the M8, and it looks like it might end up as long! I've been trying to focus on photographs of parts and installations that I hadn't seen before when I started gathering up M8 photos. Hopefully it will continue to be a useful resource for a lot of people.

[Big D]

Hi all,

A little bit more progress on the engine side of things which might interest Oz and the other guys looking at doing Hercules JXD’s.

I’ve cleaned up and prepared a few more parts for the engine rebuild. It looks like there are a couple of types of thermostat housing as I have two types here. I haven’t worked out which one I’ll use yet.

I’ve been working on the fan pulley assemblies. One of these has a broken pulley and is seized. The other one was completely rusted up and I had to soak it in molasses some years ago when I first got the project. Neither is going to come apart easily but I’m hoping I’ll get one good unit out of the two. I have another good fan pulley on the way to make up the two required.

I checked out all three cylinder heads I have here and I see there are differences in them. I picked out the one that looks the best and cleaned it up with a wire wheel. The thermostat housing was a bit of a dog to get off as the internal nut and the stud in the cylinder had corroded and become one. I used a die grinder in the end to knock off the side of the nut and that has saved the stud. I think this head should be okay and I can’t see any obvious defects with it. There is a bit of pitting on the surface so it will need to be planed. It is ready now for a dip and closer inspection by the engine reconditioner.

I’ve attached some pictures of the other cylinder heads I have. The one pictured with the head that I cleaned up is off a scout car engine but I see it has a fine crack through to where the thermostat housing bolts on. This head appears to be the same as the other head I have which has some damage to one of the head bolt holes. Are there differences between the M8 and Scout car heads? Is there any difference in the compression ratio? Is the one I have cleaned up for an M8 and the others are for Scout Cars? I will have to investigate further.

I have made some progress in removing the pistons with three out of the bores so far. I certainly recommend the option of cutting out the top of the piston and attacking the rings from in behind, providing the piston is expendable and the pistons are at TDC. I can see now that five of the six pistons are pitted on the top so they’ll need replacing anyway. I see also that these pistons are .060” so the engine has been rebuilt at least once before. I wonder if the fact that it is at maximum oversize now has contributed to one of the cylinder walls collapsing? Anyway, the three bores where I have removed pistons look good. We’ll see how bad the others are. I can only see one hole in one of the bores so hopefully there is enough meat there for the cylinder sleeves.

That’s all for this week.

[Big D]

Hi all,

Here are a few photos now that I have the pistons out of the block. I’m glad that the pistons were not reuseable as it was a real battle getting them out and as expected, the pistons are now a sad sight! Four out of the 6 bores are not too bad. As you can see cylinder 5 has quite a hole in the cylinder wall. You can probably make out in the photos that the cylinder wall is actually quite thin there and as I said in my last post, I wonder if .060 thousand oversize is pushing it on these blocks. Cylinder 6 has a bit of damage from where the rings and the bore had become one. Structurally though, this cylinder and all cylinders bar cylinder 5 are sound.

I guess the reconditioner will determine whether the condition of that cylinder makes it a viable option for sleeving. I can’t see any reason why not providing the sleeve seals around that hole in the wall, but then I am no expert. Hopefully I haven’t wasted about 2 days work in getting it apart so far!

I am almost inclined to get the reconditioner to assess the block first before I try to get the valves out as I can see these are going to be a battle as well. All are stuck in the guides and I suspect there will be plenty of pitting around the valve seats once I get the valves out. I doubt whether any of these valves will be reuseable and I will be replacing the guides and springs anyway, providing the block can be rebuilt. Does anyone have any bright ideas on the most time effective way of getting the valves out?

The engine sump holds oil but is a bit of an eyesore and I am debating whether to repair it or not. It has several internal baffles so getting access to the dents is impossible without cutting the bottom off the sump, panel-beating it and then welding the bottom on again. I am a little hesitant to go that route though, as cutting through the sump without seeing what is behind the sump wall might be risky. Alternatively I guess I could drop it off to a panelbeater and get them to try pull out the main dents.

I have seen worse sumps than this though and I’m confident that the majority of the oil would drain during engine change. However, it does look ugly. Thoughts anyone? Has anyone done such a repair?

That's it for today.

[Big D]

Hi all,

A bit more progress on the engine block side of things. We had a close look at the spare block from the Scout Car rebuild now that all the pistons are out of that.

The crankshaft from this block has some wear on it and the crank I took out of the M8 block I was working on will be a better option.

The good news is that the bores in this block are STD size and are all intact. The bores actually don’t look too bad, and may be good enough with just a hone, but if not they will be bored out to 0.20” oversize.

Like the other block, the valves in this block are all stuck as well. There is some pitting around the valve seats but from what I can see, it is a lot less than the M8 block.

Overall this block appears to be a better rebuild option than the M8 block I have been working on. I will finish stripping it and then get it back to the reconditioner for a crack test etc, just to be sure, but I'm fairly sure this will be the one.

As an aside, here are some pictures of the manifolds for the Scout Car and the M8 which shows the differences between them. The pictures of the M8 block and the scout car block show the two studs missing at each end for the different manifold that the M8 uses. If I use this block, I will need to drill and tap the ends and fit some studs to mount the M8 manifold.

I’ve completed the gearshift and linkage assemblies. I had an original of the shorter rod for the linkage but didn't have the longer one. I’d seen NOS rods for sale but the freight cost of getting what was basically just a length of 7/8” solid rod sent here versus making one just didn’t warrant the expense, so I ended up fabricating the longer rod. In the end, I didn’t even use a solid rod, and went with a hollow pipe with heavy walls on it instead.

I stamped my data tags and fitted the ones to the gun side plate. One of the letters I stamped is not flash but overall not too bad.

That is all for this week.

[Big D]

Hi all,

I’ve continued working on stripping this engine block over the last week. A couple of the valves came out relatively easily, but most haven’t been easy to get out and appear to be rusted into place in the top of the valve guides. One valve was broken at the head, and at least one was bent and most looked pretty rough. Almost all the valves were in the down position, so even when I got the valve spring keeper out, I couldn’t get the spring off the valve. Access to the top of the guide on most of the valves was only possible through the ports, and it isn’t easy to get penetrant into the top of the guide from the port.

The valve pushrods, apart from two or three of them, were also stuck in their guides, so I couldn’t get the camshaft out either. With the pushrods stuck and the valves stuck, I had to scratch my head for a while about how to progress things. In the end, and considering the condition of the old valves and the cost of new valves, I decided to cut the valve springs, cut the keeper end of the valve off, and work penetrant into the valve guide (from the underside), while tapping on the cut end of the valve with a drift to see if I could loosen them up.

Most of the valves were pretty rough, and I’d already decided I would be replacing these along with the springs so it just made sense to do it this way. This has been relatively successful and I have 7 valves out now. The other 5 valves are proving to be a challenge. I can tell by the sound when tapping on the cut end that the valve and guide are now one so I will need to come up with another strategy to get these last ones out.

I have tried applying some heat around the guides from the ports but it is little hard to apply evenly from there. I may yet look at somehow cutting off the top of the valve. This will give me good access to the guide so I can get penetrant in there. Failing that, as a last resort I may just punch out the guides with what is left of the valve stem in them. The guides are removed by punching down out of the block (with the piston side up), so I would still need to have taken the top of the valve off to do this though. These guides will need replacing anyway, so that could be a quick way to deal with the problem valves. Most of the valve guides had some corrosion in them so I will probably just replace the lot.

Once I had cut the keeper ends of the valves off, I was able to turn the block over and get some penetrant into the pushrods, and start tapping away on these. After a bit of work of penetrant, the pushrods were free enough to be able to fully tap down so I could get the camshaft out. A bit more penetrant later and out came all the pushrods.

The pushrods are pretty rough even after a soaking in solvent and with replacements costing $20 each, it just makes sense to replace these as well. I’ll also check out the pushrod guides after the block is cleaned up to see if any need replacing.

The camshaft has cleaned up nicely. It has a bit of pitting in a few places but the lobes are clear. The crankshaft from the M8 block is the best one I have so I will be using that. It has a bit of pitting here and there but overall is pretty good.

Now that I have some of the valves out, I can see that most of the valve seats are in pretty good shape. A couple have some deep pitting but overall these look better than the other block I was working on. Hopefully my engine reconditioner can work his magic on these seats.

I’ve removed the broken manifold studs. I still need to retap a couple of these, along with drilling and tapping the extra holes for the studs to hold the bigger M8 manifold.

I’ve attached a picture of the various shims used in these engines. They are easily bent when trying to clean them.

That’s about it for today. If anyone has any other bright ideas about the valves, I’m all ears!

[laurent]

great work !

[Remy]

Hi Darryl,

I am about to put on my front axle but forgot to mark down the spring leafs. There is a long and a short side to them (measured from the center bolt)
Which side goes were?

Thanks,
Remy

[Big D]

Hi Laurent

Thanks for that. I am getting there.

Hi Remy,

I will need to check in the workshop. My springs were all in one piece so I didn't have them apart. From memory, the shorter lengths of the spring leaves are towards the front but I will double check the next time I am there.

[Big D]

Hi all,

I’ve finally completed stripping the scout car JXD engine block. The valves tried my patience but I got them all out, albeit one taking a guide with it.

As I expected, it made a big difference being able to access the top of the guide where all the corrosion was. I got a bit creative and came up with the bright idea of using a mag drill and hole saw cutter to cut the top of the stuck valves off. That worked out good as it gave me access to the top of the guide and I was able to first scrape away and clean off the corrosion and then get some penetrating oil into the guide.

The block is now with the engine reconditioner for cleaning and crack testing. We’ll see then what the bores are like. He took a quick look at the valve seats and felt that two of them may need new seats inserted, but will confirm once he has had a closer look. He also thought that the main bearings and big end bearings might actually be fine, but will also confirm later. I see the big end bearings are already 0.060”.

The M8 manifold is blasted and painted now, although I’m not overly happy with the paint. It is just too flat and some surface rust is showing on the manifold already, so I’ll need to find something a bit heavier. I’ve pre-drilled the holes on the scout car block for the two extra studs required for attaching the M8 manifold. I’ll tap these once the block is confirmed as ‘good to go’.

I did a bit of panel beating on the sump but it still has a number of dents in it. Now that it has some paint on it, it doesn’t look too bad.

I’ve also continued some work on the recoil system. I will need to get some new strips of brass folded up to replace the damaged ones on the top of the cylinder. These strips are held into place by small brass pins. They almost look like an extrusion of some sort so I might try some of the surplus scrap dealers to see if it is something they might have on the shelf. I’ll also need to make up another brass bush for it to sit in the cradle as this only has one. I’ve re-tapped all the mounting holes on the cylinder and all are in good shape. I have also cleaned out the bore and it is nice and shiny. I am taking Barry’s advice and won’t be putting any oil in the tube.

I will need to make up a tool to get it all back together though. With the aid of a neighbour who is a retired mechanic, we spent a bit of time on it today trying a bit of muscle power, to see if we could compress the spring enough to get the coupler on the end. We weren’t able to do it though and I’d suggest it would be a three person job to be able to hold enough weight on the spring while screwing the coupler on the end.

I have in mind to use some steel plate at each end connected by half inch threaded rod. There are enough fixing points on the cylinder that I can attach it to and I’ll simply wind down the plate on one end and compress the spring. That’s the plan anyway…
I’ll photograph what I make up next week.

That is all for this week.

[seacon]

Dacci dentro che sei quasi arrivato!!!
M

[Big D]

Buongiorno M,

Progresso!