Think Im going to be sick. brand new flathead siezed.

OK.



I have a definitive answer to the problem now, so here goes, its fucking obscure, but I take full blame..

keep the paragraph below in mind, it becomes important later.

This engine was a military motor out of a WW11 tracked vehicle called a Bren Gun Carrier. the engine was mounted amidships and difficult to get to, and as is typical with military stuff, they improved upon the civilian stuff, in this case adding a FULL flow oil filtering system. Now '39 mercs on the other hand, had NO filtration.

As i pulled it down it was obvious there was no oil at all reaching the front two main bearings, and consequently also the front six conrods bearings, so at this point Im convinced something has blocked the main gallery.The rear main is fine as it is fed by its own direct drilling from the oil pump gallery.

Now the frustrating thing about the design of this engine is that the main gallery tube ends at the fuel pump pushrod bush, wraps around it ,and then carries on to the rear of the block where there is a plug, so you cant actually see straight thru it without somehow removing the fuel pump pushrod bush(which is close to impossible)
SO my thoughts were ,'something has blocked the area around the pushrod bush' so i worked out how to block all the other passages and blow carb cleaner thru with air, and that worked fine, nothing but clean fluid came out. Damn. thats not it.
then I thought about the supply to the end of this tube and traced all the passages back, thinking there must be a direct passage back to the oil pump cavity, but no, there isnt! the main oil supply goes up thru the little hump above the bellhousing, where you screw in an oil pressure gauge,then travels back to the centre of the engine, and down the main gallery.

Deep inside this little hump is another gallery plug, that is placed there on Military engines to direct all the oil out thru the filter and then it re-enters on the other side of the plug. This plug is in place on my engine. I put it back in, assuming it was part of the way the oiling system worked, but of course with no external filter to bypass this blockage, no oil reached the front of the engine.
Lack of understanding of the differences between '39 military and civilian engines killed my motor, Making it one of the last casualties of the second world war!!



The damage is as follows..

Main bearings-toast
conrod bearings-toast
bore and piston Cyl 1 are fucked.I think this is due to bearing material being thrown into the bore from no1 main..its pretty ugly.
the rest of the pistons show some wear, which has me puzzled, i will post pics of these on a new thread..
lifter faces scored, can resurface.cam looks ok.
rods are all fine.that moly assembly lube is good stuff! its all that saved them.
the crank should be fine with a polish.



if it wasnt for the piston and bore i could have this thing back together in a week.

Im halfway contemplating a set of Ross forgeds and going out to 0.060 whats another fucking thousand dollars right??


Im angry at myself for missing this, but it at least proves i didnt make any obvoius cock ups, just a pretty fucking obscure one.

 

Oh and yes I am damn lucky to have this car..And the fact I can pull it from a complete vehicle to a piston in my hand in an afternoon (with a little help..Thanks Rob!!)is one of the awesome things about early cars...

 

Get some 'XXXX' into ya ,you need it......

 

....as if things aren't bad enough.

Glad you got to the bottom of it Ben, but, shit that is a fairly extensive list. The No1 bore is the only real concern though...the rest is just time and money. Chin up

Pete

 

Sorry to read about your motor, but at least you found the issue. Guess this makes two of us trying to get engines in roadsters for Summer.

 

Hey mate glad you got it understood.. Would have been a shocker to think it was something else, put it all back together then have it again.

As for driving it.......It was pissing down all day anyway....

 

Shit Ben, sorry to hear about the dramas...

At least you got the problem solved...chin up mate.

 

Dont kick yourself for not knowing that. Be it a model T or a 2010 Bmw they are all bitches. And its a beautiful car

 

That is great that you now have a definative answer/cause. Good luck to you, and thanks for keeping us updated.

 

sorry to hear about your motor but the good thing is you found out what really happened!!!!just think how bad it would have sucked to fix it all and have the same thing happen again.

 

This is the same way we modified our civilian 50 Merc engine to add a remote filter. My screw up was to reverse the lines to the filter. I remember vividly smoke coming out the crankcase breather just before I stopped it and then it would no longer crank. This was about a month before Speedweek which we had been working towards for three years. I have a whole set of Ross pistons that look like that. Don't remember all the parts we changed but I will always remember the sinking feeling when I realized something was terribly wrong.

 

Well at least your on track now. If "misery loves company"...I had a similar experience this past spring. I thought I would be smart and run a freshly prepped motor on the floor, before putting it in my wagon... well, I did`nt have any gauges connected and was unaware of the NEW oil-pump not working... result: trashed motor!

 

Good luck with the rebuild mate...thats a stunning roadster you have there
Best wishes. HRD

 

Sorry for your problems. Glad you found the problem and shared the diagnosis.
I guess there's another lesson here. If you modify for full-flow you have to watch out for clogged filters, because full flow means there is no flow if the filter is clogged. It now makes sense to add an oil pressure gauge on the return side of the filter!

 

Wow, lesson are sometimes expensive. Hopefully, your woes will be lessons for us. Thanks for manning up. You have a great car and skills (enter Gloria Gainer I will survive song) Good Luck!

 

Good to know about the Bren engine! We are military vehicle nuts, and have a few Carriers we're working on. Never knew about the full flow modification! Sorry that you had to find out the hard way, though.

 

This sounds like what happens to chevy I6 inliners with the later 261 with full filtration systems. Everyone is used to either no oil filter or the optional filtration on the later 235. Thinking the filter on the 261 is optional they put plugs where the oil lines are.

There are plenty of warnings on every description of the 261 engine, so I have to believe a lot of them were destroyed this way.

Sorry to read about your mishap. Better in the shop than on the road.

 

lowsquire,
First sorry about the bad luck on the engine build. You indeed have a fine car in the build. Thanks for writing such a clear description of the problem. It made for an excellent post and I'm sure it was food for thought for many others as well. I have no doubt that you will overcome all obstacles and finish your project in style. Better luck ton the repairs.Thanks again for the posting

 

The full-flow mod came on some of all the variants of the WWII US, Canadian, and British flatheads...
British 221-21 stud 1937 style, US and Canadian 221 and 239 24 studs. I think on the British Bren carriers it actually fed a cooler, since armored vehicles have to run at high power levels much more of the time than in less cumbersome vehicles. Canadian trucks and stuff got a FF filter, and some engines continued to be built with this after the war.
This is nearly identical to the nomal more recent hotrod conversion...filters everything except the rear main, exact same setup and general plan as a 350 chevy system.
The raised circular boss for the 3rd hole was kept on non-FF wartime engines and then on the 59A after the war. History sure is useless after the disaster, though!

 

Sure is Bruce, and you may be right on the cooler, the engine was pretty much completely in the middle of the vehicle under covers, so a cooler makes sense.

The stupid thing is I kinda Knew all this..just didnt put it together, until now.
I actually slapped my head with a greasy hand when i realised it..

currently hunting bearings..anyone in oz know the guy on ebay who lists the .020 main sets regularly, of course there isnt a listing currently...

 

Wow, well it's not like it was something simple in my book. Sorry about your motor.

 

I've been following this closely as I'm assembling a '42 Mercury. Sorry it happened, but glad you at least found -- and understand-- the problem. You mentioned seeing, and questioning, 80 psi of oil pressure. Looking back, would you say the high pressure was a result of the oil only being able to escape through the rear main through the pump drive cavity instead of the oil galley tube as well?

Bob

 

If parts problems, spring for a call to Joblot Automotive in NYC. They pretty much bought out the British Army stash of the 221-21 parts.
The short circuit would indeed explain crazy oil pressure...the whole pump output going into one bearing. As I said, same design as an SBC...if you blocked the pump port on a 350 Chevy, you would have all oil trying to go into the rear main, though on an SBC you'd have to move the sender to read the pressure down there!

 

I feel your pain man. Had a friend who had the same thing happen. Bought a car with a remote filter and since he didn't like the way it looked, removed it without realizing the plug was in that passage. Same results as yours. Hope you ger her up and running soon.

 

yep it all makes sense and thats good, means I can reasemble with some confidence. about to drop the whole lot off to have the machining done..let you know how it goes.

Bruce, if the oil pressure was 80 pounds due to it all going to the one bearing..would that mean the pressure relief valve on the pump is too stiff? or should it be a fair bit above normal operating pressure..Im assuming the front (block ) relief valve does most of the regulating, and the rear (pump) valve is a secondary relief?

 

Same thing happened to me. It seems that I over torqued the rear main. I was able to slide in a new one with minimal trouble; just pull the pan and loosen the crank. It's been fine ever since. pigpen

 

Not Bruce here, but I'm following along. I'm using an 8ba pump with built in pressure relief valve in my 99A Mercury and I shimmed the relief valve in the front of galley so that it wouldn't open before the relief valve in the pump did. I don't think your excessive pressure was a result of a too stiff spring. In your case, the pump was essentially "deadheaded". There was so little cumulative bearing clearance through which it could dissipate volume, it overwhelmed the relief valve's ability to bleed of excess pressure. Once you allow the oil to go dissipate through all of the normal bearing clearances, you see that the relief is able to handle it and the pressure will be normal. Just a thought--you probably already have, but inspect all components related to the pump and drive gears very closely. The pump may have built pressure sufficient to put undue stress on those components.

Bob

 

At least you got it figured, maybe the piston scoring is from heat alone with the engine working against the bearings.
At least this is a cautionary tale for others to heed.
Best of luck to you and in the end may you jave years of pleasureable motoring.

 

Here are a couple of PDF's posted some time ago by some unknown kind soul that I saved. They describe the Canadian/military full flow system and a PCV valve.

 

I guess this is why you should test the pump pressure and flow and see that the oil is actually leaking out of the bearings before you put on the oil pan ETC....