Well I finally got into my 49 M68 engine to determine what was stopping it from being able to make a complete rotation and found a broken piston was the problem. It Looks like this is the first time the engine has been worked on and everthing looks original with the correct markings fo a 49 Merc. Surprisingly there does not appear to be much collateral damage to the cylinder or head and I think I can get away with a new set of pistons and rings rather than a complete rebuild which is good news. My question is where the pistons in the Mercury 239 engines the same as the ones in the Ford 239? I know the crank was different giving the Merc a 4" stroke rather than the 3.75" in the Ford and I just want to be sure I'll be OK ordering a set af pistons from one of the U.S. suppliers who provide the Ford rebuild parts. I can't see them being different but just want to be sure before I order anything.
Thanks for you feedback.

 

You need Merc pistons. The pin is higher in them so the same 8BA rods can be used with the 4" crank. But are you sure you have a Merc 255 engine? A 255 would be a C8CM engine. Merc trucks used the Ford 239 or the 337. (see below)

Hard to believe you can have a cracked/broken piston and get away with a quick hone. Sure you don't need a bore?

 

C8BA-6108-A .. Mercury flathead V8 Standard 4 ring pistons / Source: 1953 (only) Canadian Ford/Mercury Truck Chassis & Accessory Parts Catalog. Does not list a 255 flatty, only the 239 flatty & 279/317 OHV V8's.

 

Thanks for the quick replies guys.
I forgot to mention this is a Canadian built Merc. Does this make a difference? I don't think it's a 255 as it only has the standard 3 1/16 bore not 3.5 as shown in Ross's chart.
Thanks - John

 

No Mercury truck was assembled in the US, were specific to the Canadian marketplace only.

All Mercury trucks thru 1968 were assembled and sold new in Canada. Were not sold new in the US.

Ford trucks thru 1968 that were sold new in Canada were mostly assembled in Canada.

All 1961/67 Mercury Econolines sold new in Canada were assembled in Canada.

At one time there were US/Canadian tariffs, these were abolished in 1967. Mercury trucks 'went away' in 1968.

mercurypickups.com has some info.

 

Should be no problems with reguard to the engine being built at the Windsor assembly plant. That misconception with the Mercury truck and a mercury engine seems to be a common thing. The differences were in the trim and front fenders for '48-'50 mercury trucks as compared to ford trucks.
Just got my engine back from a rebuild. Parts were sourced from the USA. Good luck with the M-68.
Greg M-47

 

The "181" and "255" monikers above are the torque ratings of the motors, not cubic inches. A 239 had a 3-1/16" bore, 3-3/4" stroke. The Mercury Car 255 c.i. engine had a 3-1/16" bore and a 4" stroke. The monster 337 c.i. flat V8 is a totally different animal.

I am unclear on what a "188" (torque) engine would be; it was a 239 flat V8 but made a little more torque at a different RPM. Note the info shown is from a '51 catalog. Teapot vs. Holley 94 carb?

 

From what I know, the Ford and Mercury trucks of that time shared the same engines and drivetrains. Essentially the only differences was the trim and nameplates. The C8BA is the Canadian version of the 8BA here in the states, and that is the 239 version. Anything you need for your engine should be 239 parts. Be careful ordering parts for a "49 Mercury" because that'll confuse folks down here and you may very well get the wrong parts. You may be better off simply saying 49 Ford.

 

Exactly!
The Merc truck engines (of that year) were the same as the Fords.

Good point about calling it a Ford when ordering parts from the states, I know from experience.

 

Hey 49'er, I should have asked this in my earlier post. Is the engine in your truck the original one ? And can you see any hint of paint colour on it ? I'm just trying to get more input for the original engine paint colour.
My truck has a replacement engine so I can paint it blue or red or the "Gold seal engine" gold. I have come to find over the years that the original engine colour was an ivory/white. I've been told that packard engine white is a close colour.
Greg M-47

 

Thanks everyone for all the info. I've placed my order for pistons and rings and will pick them up in a couple of weeks.

Greg, as far as I can tell its the original engine and when you scrape off 63 years accumulation af grease and grime (which I've been doing for the last week) there is appears to be remnants of an ivory coloured paint on th block, transmission and pan. I thought from some of the reading I've found that the original colour on the Merc truck engines for 49 was a pale green and I assumed what I was finding was just the washed out remains of that but it really does appear to be more of an ivory or off white. Do you have any references for Merc using the ivory colour.

John

 

The engine colour was a light green (see pic).
Duplicolor's Detroit Diesel Green, is very close to the original.

 

Thanks 49'er. That is what I was hoping you would say. I found that white on the bell housing of my engine when I cleaned it too. Probably the only original piece left as the engine was changed and the transmission was rebuilt too.
I've talked with a lot of older merc owners and researched my own and others engines which has brought me to this conclusion.
Mercury Bluz I think the green is another mercury conclusion that some people jumped to. ( Mercury engine so should be mercury engine green )
This is only what I have found in talking with people and asking what they have seen when they did their trucks. I have been unable to find anyone that worked on the Windsor truck line at the time so have gone with what I've gathered from people.
Kind of rambling. Hope I answered your question. Good luck with the rebuild.
Greg M-47