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So I want to start this post off by saying that I got my 49 Mercury flathead running last week. I pulled the fuel line off from the tank and rigged up a jerry can temporarily. I cleaned out the remaining fuel lines to the carb, fuel pump and fuel bowl and once I got some fresh fuel in the carb it fired up after about 6-8 attempts. I would like to post a video but I am not sure if it's possible on this site or not. Anyways, on to the question. How does a person determine if my flathead is the Mercury 255 or the Ford 239 motor? Is there a simple answer to this or does the motor need to be dismantled in order for me to tell?
It would need to be at least partially disassembled. 255's were only installed in Canadian F-6's and only in '52, no other trucks (Ford or Mercury) had them stock. Do you think someone swapped one in? What is cast into the heads, 8RT, 8BA, or 8CM? The only sure way to tell is to measure the stroke, which requires either removing a head, or dropping the pan.
Punched .120" over, Isky Jr. cam, Jahns pistons, Evans heads, Offy triple w/97's, Pertronix, etc.
Very nice. I have a ways to go before mine will look like that. But on a positive note, when I finally got it running it sounded amazing. It idles very smooth also. I was a bit nervous since it hadn't ran in a while.
It would need to be at least partially disassembled. 255's were only installed in Canadian F-6's and only in '52, no other trucks (Ford or Mercury) had them stock. Do you think someone swapped one in? What is cast into the heads, 8RT, 8BA, or 8CM? The only sure way to tell is to measure the stroke, which requires either removing a head, or dropping the pan.
Here's a pic of the head. I am a bit confused now. From what I can find, the numbers stamped on the head would indicate a later model year. The truck is a 49 so I am thinking that maybe the motor was swapped at some point. My father said that he thought he remembered the motor being rebuilt sometime back in 60's or 70's. But maybe it was just a motor swap or they installed different heads on it. I thought I had read somewhere that the 255 engine was the Mercury engine and that it was available in more then one model. I am new to this stuff so forgive my ignorance. I appreciate all the positive feed back I always get from the great bunch of people on this site.
Yes, you have (at least one) 52-53 Car head on the engine. Not a problem, my whole engine is a Car EAB. They are the best stock heads, especially compared to 8RT heads.
Is your truck a Canadian Mercury truck? They all used the same Ford 239 engine as Ford trucks, with the single exception I noted above (which is pretty rare). Mercury cars from '49 to '53 (Canadian and US) used the stroked version of the 239, the 255. Stroking an engine increases its compression ratio, so Mercury engines had 8CM heads that kept the overall C.R. the same as the 239 Fords. But people would put Ford heads on Mercs for a quick CR bump. LOTS of parts were swapped around during rebuilds.
Could the stroke be measured through the spark plug hole?
Not really, the spark plug is over the valves. Even doing it from the bottom (pan off) is kind of difficult. Merc crankshafts have some markings but in typical Ford fashion there are enough exceptions that direct measurement is the only sure way.
From what I see in the pictures, I'd be surprised if it's a Merc. I'd be curious to know what's marked on the dipstick, see below. Also, does the oil pan have the large (truck-style) cleanout?
Yes, you have (at least one) 52-53 Car head on the engine. Not a problem, my whole engine is a Car EAB. They are the best stock heads, especially compared to 8RT heads.
Is your truck a Canadian Mercury truck? They all used the same Ford 239 engine as Ford trucks, with the single exception I noted above (which is pretty rare). Mercury cars from '49 to '53 (Canadian and US) used the stroked version of the 239, the 255. Stroking an engine increases its compression ratio, so Mercury engines had 8CM heads that kept the overall C.R. the same as the 239 Fords. But people would put Ford heads on Mercs for a quick CR bump. LOTS of parts were swapped around during rebuilds.
Yes the truck is a Canadian made Mercury truck. That's why I love this site, I have learned so many things from this site that uneasy aware of.
Not really, the spark plug is over the valves. Even doing it from the bottom (pan off) is kind of difficult. Merc crankshafts have some markings but in typical Ford fashion there are enough exceptions that direct measurement is the only sure way.
From what I see in the pictures, I'd be surprised if it's a Merc. I'd be curious to know what's marked on the dipstick, see below. Also, does the oil pan have the large (truck-style) cleanout?
I will have to take a look and post some pics for you tomorrow. I'll check the dip stick and the oil clean out. I will have to speak to my great uncle and find out a bit more about the truck. Hopefully he will be able to tell me if it was ever rebuilt or replaced completely. I will keep you posted as to what I find out.
It's a Canadian thing. If we can get a picture of the lines to/from it, we can confirm whether it is a factory full-flow system or not. I don't think it is, but there is also a Canadian bypass filter that is taller than the typical US type. I believe it was a Canadian military thing, to standardize on filter elements.
09-26-2016, 03:02 PM
