Rebuilding XPAG 9204

[SteveW]

Having finished the tub I have moved on to stripping and rebuilding the engine, so I though that I would start a thread and keep adding progress. No doubt there will be specialist things that I need to farm out, but I want to do as much as I can myself. By way of background, when I bought the car I was told that the engine had been stripped by the previous owner and then reassmbled for sale to ensure that all of the parts were present.

This sequence shows the engine on the bench ready to start stripping and the first couple of pictures of progress. As you can see from the inlet manifold, some restoration has been started and the masking tape to cover the ports whilst painting is still on. No core plugs and it looks as though the water ways have been cleaned out

The rocker arm looks to be in good condition, but one of the rockers has surface rust on the contact surface maybe suggesting that something was stuck

The timing chain cog looks to be in good condition. The smaller cog was in a box that came with the car.

Because it was previously disassembled it's coming apart quite easily and is quite clean, which is good

[SteveW]

Next step was taking the oil pump cover off. Although you can see that the plate is polished where the gears turn, it's not worn and the gears look almost new.

The main body of the pump was stuck to the block and took a bit of getting off. Maybe because there was not gasket.

The gear shaft was very stuck in the block and I had to jack it out by placing an old socket and some washers over it and then gradually tightening a bolt that I screwed into the end. One end of the shaft has a threaded hole for that purpose. If you put the shaft in the wrong way around so that you cannot screw a bolt into the thread you will never get it out again!

[SteveW]

Next step was to take the cyliner head off. I'll come back to the condition of the head in another post. Interestingly, it seems to have new pistons and they have 0.060 written on them, so it's looking as though the engine has been rebored to +60 thou. Hopefully the staining on the tops of the pistons is superficial and will just clean off.

On taking the end plate off I found more writing which confirms that the engine has been rebored. I'll have to get the pistons out to look at the condition of the bores and to see if they have been properly honed, but it's looking as though more work has been done on the engine that I thought. Not sure what the '?main caps' is about

Next I turned the engine over and removed the sump. I had been told that the previous owner had crack tested the crank shaft and one end of it has 'ok' writen on it which seems to support that theory. The crank will not move, so I'm not sure what I'm going to find when I take it out.

Also, I cannot get the cam shaft out. I've taken off the lock screw that holds the middle bearing and I can pull it out a little way but then I hear a tapping noise that sounds like something on the cam shaft is hitting the block as I slide it out. I'll get a better look when I remove the crank and con rods, but any thoughts would be appreciated.

[Tom Lange, MGT Repair]

The cam problem is easy - assuming you have the lifters out! The center bearing is a split bearing, and once tapped forward from the center cam bearing journal can be separated and removed. That allows the cam to be removed; be careful not to knock a lobe against the front cam bearing on removal.

Tom Lange
MGT Repair

[Tom Lange, MGT Repair]

There is a good description of what is needed to rebuild the oil pump in the Moss Motors information sheet. Look at their on-line catalog for the rebuild kit, and click on the small logo that will lead you to the information sheet with the specs.

Tom Lange
MGT Repair

[Tom Lange, MGT Repair]

Your oil pump driven gear shaft is correctly installed, and is supposed to be quite tight in the block. You removed it properly! I had to take a sharp pair of pliers to the one shaft that had been incorrectly installed; it quite ruined it (but it needed replacement anyway).

Tom

[frenchblatter]

Steve, if you need any special tools or help, just shout. I'm "safe" having had the virus in March.

[SteveW]

Hi Norman, thanks for the offer. I was wondering how I was going to do it without calling on your engine building knowledge. I'm really glad to hear that you recovered from the virus. Unfortunately, I know others who were not so lucky. I think that I would prefer to have more confidence that those who have caught it cannot catch it again before being the reason for exposing you to more risk though.

[SteveW]

Back to the strip down...

Having taken the crank, con rods and pistons out this morning, I returned to trying to get the cam shaft out. It turned out that the central bearing had seized in the block and was not sliding out. The tapping noise that I heard was the adjacent cam shaft lob pushing against it as I tried to pull it out. With the crank removed I managed to get a drift against the bearing and tap it out without damaging the cam. This is the cam, it looks good to me, but would it be obvious if it was too worn??

[SteveW]

On removing the crank I found that the end bearing shell was marked with 0.030 which means that it's 30 thou over sized. What I don't know is whether the crank has been ground to match so more investigation needed.

The pistons came out with a satisfying pop as they were withdrawn and the pistons and rings look new. However, the big end bolts have obviously been stretched so will all need to be replaced (which I probably would have done anyway). You can just about see where the start of the threaded bit is thiner than the rest. I reckon any attempt to tighten them back to the required torque would have resulted in immediate falure or even worse, failure in service and a destroyed engine.

Interestingly, the mating face between the block and the sump has been stamped with "A A +3 +2 +2 +2" does anyone know what that means?

The final job today was to clean out the sump oil strainer and reassemble it (yay, I've started to put the engine back together already!). Don't forget to check it as they can get virtually completely blocked.

[Steve Simmons]

Fun stuff! I re-used big end bolts once. Upon tightening, one snapped right off. I definitely recommend replacing both big and small and bolts.

[timberstone]

Very thankful for this new thread on rebuilding this XPAG engine because now doing the same for engine XPAG 1498 (taking it back to factory specifications as much as possible from the repair shop indications of 1954).

MGTC 0820 Repair Shop Tag 1954.pdf

(115.22 KiB) Downloaded 278 times

Cannot answer many questions, but see that the real experts are looking into this thread (such as Norm Vernon and Tom Lange) so that this will all be very correct.
I would NOT rely on any marks written or stamped into the metal of the block, or parts of it, without independently measuring and verifying, then writing down on paper the results. The reason is for future reference without the need to tear down again, as well as also trying to determine whether any tags, stamps or plates are correct. Also question whether any marks on the crankshaft mean that it has been magnafluxed properly or balanced.
This is definitely not one of those projects where "Assembly will be the reverse of dismantling.........."

[SteveW]

I'm relying on the experts to give advice. Although I'm reasonably good with spanners, I've never rebuilt a whole engine from scratch before so I'm going to need it. Here is my first list of questions that I hope someone will answer - some might be so naive as to question the wisdom of what I'm embarking on!

i) engine block core plugs. Two types are on offer. In one type the material is not specified, in the other they are brass. The brass ones are a little more expensive but is it best to go for them. Also, is there a specific sealing compound that I should be using with them
ii) The books talk about a camshaft core plug at the rear end of the cam. Is this just like a normal core plug (the reason for asking is that there was nothing like that on my engine as received)
iii) Little end bolts (on con rods). Two types are available - original design and Allen head. The Allen head ones are cheaper and I've heard that they are easier to install. Do people go for the more expensive more difficult to install ones just for originality, or am I missing something?
iv) TC Forever and other sources recommend locking the big end bolts/nuts with lock wire in pairs. Is there any reason not to use split pins?
v) Is there something special about rebuild oil/lubricant, or will normal engine oil do?

Any and all advice gratefully received.
Steve

[stephen stierman]

#1 I suppose brass is best from a rust issue, but I have never had a core plug rust away in many years of working on cars. I recommend JB Weld without hesitation, used to work for a Cat dealer and that is what they used.
#2 From memory it was a standard core plug.
#3 I don't see why con rod bolts would be difficult to install, mine are original.
#4 I used split pins, again not sure why this would be a problem
#5 Standard engine oil has never been a problem for me, always build oil pressure on the starter prior to starting engine.

[Steve Simmons]

My take...

1) I don't think there is any real world difference between steel or brass, although in the long term steel will eventually rust. No sealer should be necessary. This is a non-sealed system and therefore zero pressure. The only way you should get a leak is if the block has a lot of corrosion. In this case you could use a little sealer of your choice, or some people have filled the pits with epoxy and then installed the plug as normal.

2) There is indeed a plug at the rear of the block, upper left behind the flywheel. It installs the same way as the others. This plug is known to leak (has full oil pressure behind it) so install it well. Mike Goodman recommends double plugging this one not only to prevent leaks, but also to reduce the risk of the plug coming loose.

3) The main advantage of allen head bolts on the little ends is so you can use a torque wrench on them. You can't easily get a socket on the original hex head bolts, and a crow's foot is awkward.

4) I wonder if you're referring to the main caps? I always safety wire these. A split pin will keep the nut from coming loose on the stud, but there is nothing preventing the entire stud from loosening in the block. Neither is likely to happen but you can't be too safe. On the big end bolts, you can use split pins, nylok nuts, lock tabs or a combination of more than one. Whatever you're comfortable with.

5) There are specific break-in oils and they do work as advertised. They are expensive so a lot of people don't use them, but many won't use anything else. I just used some on a 1098 I re-ringed with good results. If you use regular oil, don't use synthetic or anything extra slippery or your rings may not seat.

[bloodysalmon]

... reading comments through with interest ... may I ask if anyone knows where rust is more or likely to break through from any water gallery on the block and or head? Known water leak areas and oil leaks from the block casting?

[SteveW]

I've continued with my examination of the engine as I take it apart. Two areas of concern have came to light

i) The front camshaft bearing has a big groove in it. You can see in the picture that it runs from almost the oil way to out of the block. I'm guessing that this might be a source of a future oil leak if I leave it as is and should be replaced - what do you think. If I do have to replace it (aside from having to buy a set of three when I only need one), I read somewhere that if you replace the front one, it has to be line bored to make sure that it's in line with the others as it's thin walled and easy to install out of true - is that correct? It also has paint in it which is just plain wrong, but could be cleaned off if the rest was servicable.

ii) On closer examination of the pistons, two of them have scratches next to where the gudgeon pin comes through and particularly on the side of the top. This presumably means that the pistons have been rubbing against the side of the bore which either means that the con rods are bent or were slack on the big end bearings as it is the faces 90 degrees around from this that should almost touch (pistons are oval, not round). Given this scoring, I guess that I am now looking at new pistons? Interestingly, there is no sign of damage to the cylinders and measurements suggest that the crank has been reground, so this seems to support the latter theory.

Any thoughts on the above would be appreciated.

[stephen stierman]

I assume your goal here is a rebuilt engine. Those cam bearings need to be changed, all of them and a machine shop should do it as the front bearing does need to be honed or reamed to fit. Worn cam bearings often are a cause of low oil pressure. I don't know what caused your piston scuffing, perhaps some overheating, a stuck ring, likely not a bent rod. i would want to use new pistons and would certainly want the bores checked for wear and probably a re bore to clean up any issues.

[Steve Simmons]

The rear cam bearings seem to last forever, but the fronts wear much faster and I always replace them no matter how good they look. There is a factory bearing reamer (I have one but I'm a bit far from you) but I'm sure a machine shop can rig something up to do the job.

The groove in the bearing is suppose to be there, see photo below. It supplies oil to the cam gear thrust bearing. There were some bad bearings out there a few years ago, I think they were County brand. They had a straight seam. The ones with the seam that are shaped more like a puzzle piece are the good ones. The others were too tight and were very difficult to install without ruining them.

[SteveW]

That's interesting. I guess that the groove is there to help with lubrication, but it still looks like an oil leak waiting to happen to me. I guess that I always knew that I needed new pistons as well, but my wallet was fighting back - I've put it in it's place now.
My problem is turning into one of trying to find an engine shop with a good reputation that is still open. I'm not sure what it's like in the USA at the moment, but many such places are closed at the moment due to the coronavirus.