New guy with a 1952 Flathead

Rembrant

Rembrant

Junior Member
Hi Folks,

I just purchased a 1952 Mercury M1 pickup with a nice running flathead V8 in it. I'm brand new to these engines, but I've been reading and learning all waking hours for the past few days. I plan to modify the truck a little bit, but I'd prefer to leave the flathead in it, and focus on other things like braking and steering, electrical, reliability, etc. I've been doing a lot of web searching, and those searches often bring me here, so I thought I'd join up. I'll try not to bug you guys with too many questions. I'm reading as much as I can so I don't have to ask;).

Basic details on the flathead: The truck is a 1952 Mercury as mentioned, and the engine is supposed to be original to the truck. It was pulled and supposedly rebuilt back in the late 90's. I'm going by some written (and mostly verbal) history. It has an Offenhauser intake on it, with an adapter plate and 2bbl Holley carb. The previous owner had to replace a head gasket a few years ago and ended up at the same time installing a set of 8CM Mercury heads. The original 8BA and 8RT heads came with the truck as spare parts.

Anyway, one of the list of items on my to-do list is to upgrade the ignition. A 12v has already been done, but I'm planning on doing some rewiring (whole new harness possibly) and was wondering what is the best bang for the buck in a more modern distributor and coil? Simplicity and reliability are key...I'm not going for power adders or anything like that. I plan to drive this thing as often as possible in the summer months.

Cheers,
Rem
 
Welcome to the barn. You have come to the right place for info on your truck. There are many gurus on here that will be able to answer all your questions, I'm not one of them-still learning. First thing you will want to do is post some pictures of the truck.
 
The Chevy point type distributor conversion works well, especially with the different carb you have on it. The original distributor spark advance will not work with a non-original carb.
The 8BA heads are a better choice over the low compression 8CM heads (larger chambers to keep the compression down to run on regular gas of the day). A cheap hop up trick of the day was to put the Ford heads on your Mercury.
 
First of all, ditch the "8CM" heads and at least put the "8BA"'s back on. The "8CM"'s have a larger chamber than the "8BA"'s since they were designed to keep the compression on the longer stroke Mercury's consistent with the Fords. I have heard that the "8RT"'s have the biggest chambers and are the lowest compression late heads. While you're at it, do a search on "quench" and "squish" on here and find out how a simple modification can add significant performance. As to distributor's the best choice is probably a converted SBC distributor with both vacuum and mechanical advance; check out "Charle ny" on this forum; he does these conversions (and much more) and it is all first class work. Using one of his distributors will allow you to move away from the stock Load-a-Matic carburetor/distributor combination, which will allow you to upgrade your carburetion. I prefer a small base Rochester 2G on an updated late Mercury manifold, but some others prefer a small 4 BBL. One thing I would suggest is staying away from multiple carbs, as they are more trouble than they are worth.

I see that "great minds run in the same circles".
 
Thanks for the welcome guys!

So I have do some reading on cylinder heads. The previous owner removed the 2 spare heads that he gave me, and 8BA passenger side, and an 8RT from the drivers side. Me not knowing any better I assumed they were different numbers because they were different sides, and now I see they are from the different engines. I assume this thing being a truck originally had 8RT heads on both left and right banks?

I’ll have to find one or the other of the 8RT or the 8BA to make up a matched set if I am to swap out the 8CM’s.

Peeling layers of a 70 year old onion I guess lol.
 
Rembrant said:
Thanks for the welcome guys!

So I have do some reading on cylinder heads. The previous owner removed the 2 spare heads that he gave me, and 8BA passenger side, and an 8RT from the drivers side. Me not knowing any better I assumed they were different numbers because they were different sides, and now I see they are from the different engines. I assume this thing being a truck originally had 8RT heads on both left and right banks?
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On the late engines (8RT, 8BA & 8CM) that have a designated RIGHT head and a LEFT head, you will find the big 8BA/8CM numbers on both heads, while you will also find a "6049" on the passenger side head, and a "6050" on the driver side head, distinguishing between left & right. DD

.
 
The Mercury 255 engine used the larger clearance volume heads to give a similar compression ratio to the smaller Ford 239 V8 engine for reliable operation. The Canadian Mercury M1 pickups came with a 239 so it would do better with the 8BA or EAB heads. The 8RT heads were developed to lower the chances of detonation while under extreme loads. The M3 and possibly the M2 would have had 8RT heads as stock from 1952 on. I'm not sure about the M1 in 1952 but they also likely had them. Earlier F1 and M1 engines would have had 8BA heads up until 1952 when they were superseded by the EAB heads for cars. Trucks likely all had the 8RT heads after 1951. Canada did do some things different but the use of the Mercury car 255 for trucks was not a standard thing even in Canada. It was usually optional in trucks larger the F3. Trucks larger than the F6 would have an engine derived from the Lincoln 337 design V8 until 1952 when the big Lincoln type Y-blocks were incorporated in the Big job trucks.

If a person put together a 255 engine by replacing the crankshaft and pistons the the 8CM heads would not be a bad thing. The Mercury had its own cam shaft and Holley 885 carb but the Ford stuff would work on it.
 
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Thanks all for the great info!

I'm on the hunt for a set of 8BA or EAB heads, and if I can find a decent set I'll swap them out this winter. The spare heads that came with the truck are a passenger 8BA and a driver's side 8RT. The 8BA head is cracked in the middle, so I don't know if it's repairable or not? Can they be welded and re-surfaced?

Can the compression be boosted a bit by skimming the heads or installing thinner head gaskets?

As it is, the engine is running quite nicely with the 8CM heads on there, but the truck will have a lot of down time this winter and I plan on doing a bunch of work to it. I will be draining the coolant for sure, so once that is done a head swap looks like a pretty easy job compared to a pushrod engine and dealing with the rockers, etc.

Anyway, I'll continue to look for a decent set of heads for it in the meantime.

Oh, and what about aftermarket heads like Offenhauser? Are they worth the trouble?...I'm not building a performance machine here, but I would like to make sure it is running it's very best by next spring.
 
I am a firm believer that the quickest and easiest thing you can do to improve performance on a flathead is to modify the heads (either stock or aftermarket) for optimum quench and increased compression. This is done by checking the clearance over the piston, either by using clay or foil balls (my preferred method). Determine the clearance and the decide how much you have to take off of each head (it may be different amounts) to arrive at a maximum of .050" clearance over the piston top. Then use the same method to determine actual clearance over several spots in the combustion chamber. Because of manufacturing irregularities, there will probably be several spots where the clearance is less. Bring these spots down to the desired clearance using a die grinder or Dremel. The heads will probably have to come on and off several times during the process. Since a compressed (used) head gasket is about .050" thick, I just coat the piston tops with grease, put the heads on without gaskets, turn the engine over a couple of times, and you will find the high spots on the heads.

You should put a foil ball on each valve as well during the initial step to check valve to head clearance. I have never had any clearance problems there with stock or even an Iskendarian MAX-1 cams, but better safe than sorry.

Because of all of this, I prefer aftermarket aluminum heads; they look better, they are easier to lift on and off the engine, and the aluminum is easier to grind and smooth.

It's kinda fun to do, and would make a great winter project.

Oh yeah, don't even consider trying to repair a stock head, as they are very common, I have 4 sets I am trying to give away with no luck. (I have already scrapped the 8RT's.)
 
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tubman said:
Oh yeah, don't even consider trying to repair a stock head, as they are very common, I have 4 sets I am trying to give away with no luck. (I have already scrapped the 8RT's.)
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Well if I was close I'd be coming by to grab a set of those heads lol. Thanks for all the info. I guess the EAB's would be the best and 8BA's if not.
 
If we knew where you are (at least the general location), I'll bet there are bunch of guys in your neighborhood that have the same situation that I do.

Adding your approximate location to your profile is generally a real good idea.
 
Done! I'm in Canada, way out on the east coast...east, or northeast of Maine. I always joke that we get Boston's weather, just a day later. I've put some feelers out locally and may have found some heads. It will take a week or so for everybody to see my ads and reply, but they'll turn up. Thanks for all the help.
 
If you are going to rework them, I think 8BA's would be as good as EAB's. It costs the same to mill .020" as it does to go .040", and after that the effort is the same. EAB's are going way up in price, just because of threads like this, so unless a great deal presents itself, I'd go with 8BA's. Actually, if you are going to rework them, the 8CM's are probably just as good.
 
leon bee said:
Denny: Regarding your post above, how much room to you need above the valves?
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You know, I don't actually know. However, when I measured my engines, the valves always had a bunch (.040-.060"?) more clearance over them than the pistons, so I didn't worry about them.

How's that for "precision engine building"?:D
 
If milling heads all the way down to .050" piston clearance and using any form of high lift cam, it would be advisable to check the valve clearance to the head during that process. The valve recess areas can be opened up a bit more if necessary with the right tooling or a steady hand with a die grinder. A depth gauge would be handy for uniformity of the recess rework if any.
 
tubman said:
If you are going to rework them, I think 8BA's would be as good as EAB's. It costs the same to mill .020" as it does to go .040", and after that the effort is the same. EAB's are going way up in price, just because of threads like this, so unless a great deal presents itself, I'd go with 8BA's. Actually, if you are going to rework them, the 8CM's are probably just as good.
Click to expand...

After a few weeks of searching, I found a nice set of 8BA heads. They had already been cleaned up and painted, but they could use a skim to clean up the faces, even if I wasn't going to cut them down (which I probably will). I've been doing some reading on how to measure the clearance with putty or foil balls...one guy even suggested body fill, and let it harden...kinda cool. I think for my intents and purposes, a planed set of 8BA heads will do the trick just fine. As much as I'd like to throw on a set of those nice finned aluminum heads, there are so many other things I need to do to this truck that are higher priority, things like fancy heads will have to wait.

I did find a set of EAB heads, but they were rusted very badly, and the spark plug threads were beyond good use, so I didn't bother with them.

Now, on to hunting for other parts!!
 
corvette8n said:
Welcome to the forum, post some pictures of your truck when you get a chance.
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I couldn't remember if I had actually posted any pics or not, but here she is at a little local car show yesterday. It was just a quick cruise in, maybe 20 cars showed up.
 

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