Early Mercury block vs 59A
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rotorwrench
Well-known member
The first two years of the 239 were in a time where there was little issue about using more materials in the casting of the blocks. That all changed in 1941 with the beginning of wartime production for lend lease and the inevitable build up for the US as well. Ford found several ways to use less material in the casting process and they never looked back after that. The 59 series 239 engines were the latest of war production in mid 1944 when Ford was allowed to manufacture both 221 and 239 replacement engines for the home front effort to keep agricultural and manufacturing concerns functioning smoothly.
The term better may not really apply. They made the cylinder walls just a little bit thicker to compensate for core shift and they still had core sand clean out ports on the pan rails. That practice stopped for 1941 and they used less material at the top of the block on the intake deck area. These changes really didn't affect standard usage of the 239 engines that much. Hot rodders were disappointed that they couldn't safely bore the cylinders out as far they could those 39 and 40 blocks so this could have affected how some folks looked at the situation.
The post war engines changed the valve angles a bit in the design but I don't know how much that change improved the design in the long run of things. The 59 series are decent enough that I wouldn't trade a good one just to get one of those early ones.
The term better may not really apply. They made the cylinder walls just a little bit thicker to compensate for core shift and they still had core sand clean out ports on the pan rails. That practice stopped for 1941 and they used less material at the top of the block on the intake deck area. These changes really didn't affect standard usage of the 239 engines that much. Hot rodders were disappointed that they couldn't safely bore the cylinders out as far they could those 39 and 40 blocks so this could have affected how some folks looked at the situation.
The post war engines changed the valve angles a bit in the design but I don't know how much that change improved the design in the long run of things. The 59 series are decent enough that I wouldn't trade a good one just to get one of those early ones.
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Thanks on the info.
That make sense.
I notice hotrodders later 40’s did go 3.75” cranks and bore max.
So with that knowledge even if the later 59 blocks did perform ( the same ) even if they might could be bored that much as the Mercury it’s cool to has a early Mercury.
I has one and about to get another block ( I think I has one to go, I know soon.
That make sense.
I notice hotrodders later 40’s did go 3.75” cranks and bore max.
So with that knowledge even if the later 59 blocks did perform ( the same ) even if they might could be bored that much as the Mercury it’s cool to has a early Mercury.
I has one and about to get another block ( I think I has one to go, I know soon.
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Brian
Well-known member
My take is somewhat different...disclaimer, I am talking Canadian sourced blocks here....
In my experience the pre war blocks are cast in a 'better' cast iron, higher nickel content. I don't really 'play' with 59A blocks, but whenever I've built a big bore flathead, I've always used a particular Canadian block a 'C69A', these seem to have been manufactured between C59A and C8BA blocks as they share some features of the 8BA series. The reason I use 69A blocks is because they have REALLY thick cylinder walls.however, the cast iron is definitely of an inferior grade, and often seems to have carbon inclusions within the cast, usually discovered when I'm just about finished my porting job, rendering hours of work a waste of time!! That iron doesn't weld the same as the prewar blocks either. My thinking is that after the war there would have been a shortage of nickel, so FoMoCo modified the recipe so to speak....
In my experience the pre war blocks are cast in a 'better' cast iron, higher nickel content. I don't really 'play' with 59A blocks, but whenever I've built a big bore flathead, I've always used a particular Canadian block a 'C69A', these seem to have been manufactured between C59A and C8BA blocks as they share some features of the 8BA series. The reason I use 69A blocks is because they have REALLY thick cylinder walls.however, the cast iron is definitely of an inferior grade, and often seems to have carbon inclusions within the cast, usually discovered when I'm just about finished my porting job, rendering hours of work a waste of time!! That iron doesn't weld the same as the prewar blocks either. My thinking is that after the war there would have been a shortage of nickel, so FoMoCo modified the recipe so to speak....
I have three 99 blocks. Two of them have the same crack in the # 3 intake right into the cylinder. I'm assuming due to poor timing making them run hot.
I also wonder about the higher nickel content and makes sense that post-war it was scarce.
Debating whether or not I should fix them. The other block also may be junk too and it came with a bunch of parts and was not stored well. I need to knock it apart. Two of the pistons I needed to drill holes into to relieve the rust pressure in order to remove.
Looking into the water jackets and comparing them to my 59L, the cylinder walls on the 99's seem to be thicker. I would really like to sonic test the bores to confirm this visual.
Funny story about one of them. The motor ran, didn't smoke or knock. All of this with a crack in the valve seat into the bore. A severely out of round crank journal that was so bad, it split the floater into two separate 1/2's for each rod and the journal was oval shaped when looking at it. Seller was amazed when I showed him and he gave me my money back as promised. Great dude.
I also wonder about the higher nickel content and makes sense that post-war it was scarce.
Debating whether or not I should fix them. The other block also may be junk too and it came with a bunch of parts and was not stored well. I need to knock it apart. Two of the pistons I needed to drill holes into to relieve the rust pressure in order to remove.
Looking into the water jackets and comparing them to my 59L, the cylinder walls on the 99's seem to be thicker. I would really like to sonic test the bores to confirm this visual.
Funny story about one of them. The motor ran, didn't smoke or knock. All of this with a crack in the valve seat into the bore. A severely out of round crank journal that was so bad, it split the floater into two separate 1/2's for each rod and the journal was oval shaped when looking at it. Seller was amazed when I showed him and he gave me my money back as promised. Great dude.
Well, there you go. Tony, what are your thoughts on the metallurgy of them vs. post-war blocks? How they bore might give a clue if there is more nickel in the mix.
KiWinUS
Well-known member
Sorry I have zero metallurgy experience with either. I did just hit them both on a casting flashing with a machinists file and I believe the 59AB was harder to file. Both filed nice.
I had no good luck on that Mercury block, but he had a 1/8 over 59 block pro ported/relived.
It's just that 'Mercury' sounds more 'cool' and I like the raised intake ports ( but as all say ; 'who see this'.
-How hard is it today find a early Mercury and who/where to ask ?
It's just that 'Mercury' sounds more 'cool' and I like the raised intake ports ( but as all say ; 'who see this'.
-How hard is it today find a early Mercury and who/where to ask ?
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rotorwrench
Well-known member
The post war Mercury cars through 1948 all used the same 59 blocks. I looked into the water jackets on a 99 and it appeared thicker than a later 59 type but all the corrosion in there was eating a good bit of it up. A lot of owners used straight water for coolant back then.
I still like the 8BA blocks the best myself. They have advantages
I still like the 8BA blocks the best myself. They have advantages
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rotorwrench
Well-known member
The flange on the back makes it more adaptable to different transmissions and the cylinder deck coolant ports force circulation toward the front. Barney Navarro used to put collector tubes in the early blocks to force more coolant back there. He didn't have to on the 8BA design.
This is why I mentioned it. I didn't say they were better but there are a lot more of them around due to sales figures after WWII. If I were going to reproduce a new flathead block, I would reproduce the 8BA. That half bell on the early blocks makes the design more complicated. I wouldn't hang those blocks by that half bell on an engine stand due to the inherent weakness of the casting.
This is why I mentioned it. I didn't say they were better but there are a lot more of them around due to sales figures after WWII. If I were going to reproduce a new flathead block, I would reproduce the 8BA. That half bell on the early blocks makes the design more complicated. I wouldn't hang those blocks by that half bell on an engine stand due to the inherent weakness of the casting.
tubman
Well-known member
I agree with this. I have heard that the 8BA blocks are more prone to cracking than the earlier blocks, but this has not been my experience. Over the years, I have gone through 8 8BA engines. 7 of the blocks were good, and the cracked one was from an engine that I got for free because it was in such bad condition. 20 years ago, you cold pick and chose the engines you bought, and I passed on those that had obviously been neglected.
Long bells in general make an engine less desire able; a good example are the very early hemi's ('51-'53); people have gone so far as to saw off the long bell and weld on a workable flange. Early Olds and Caddy engines were popular because there was nothing else available. Their long bells make them incompatible with many transmission setups, but they were popular because they could easily be adapted to early Ford transmissions. Since both were "long bells" a simple adapter plate was all that was required.
Long bells in general make an engine less desire able; a good example are the very early hemi's ('51-'53); people have gone so far as to saw off the long bell and weld on a workable flange. Early Olds and Caddy engines were popular because there was nothing else available. Their long bells make them incompatible with many transmission setups, but they were popular because they could easily be adapted to early Ford transmissions. Since both were "long bells" a simple adapter plate was all that was required.
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Personally I'm no fan of the 8BA, but if I was going Bonneville I use one.
For hot-rods my choice is the 99/59.
Maybe it's my head not going forward in time era, but in one of my FH i has the 8 BA crank and lifters so idea is when they came ( I used my old Merc block...
After all common sense tell me of a LM7 engine. Cheap, great tech and make power easy.
Builde one this spring to a customer with a cast std crank, std block/heads and turbo and another cam and intake, rest is std = 1.000 HP easy on the rear wheel in a Volvo.
Bigger turbo and better rotating ( more boost ) it can make 1.300.
This is sneaky pete 2026.
Anyway.
Mercury sounds nice.
I did find a 41 block ( shortblock ) in California and bored 30 over but its wear, but came out as a runner ( but seller did 'not' run it so it could be cracked.
Case is the freight over here to Sweden.
300 USD but I could get a 59 block pro ported/relived and sonic testet/pressuare checked and 1/8" over std at 800 USD from same guy.
But the Merury talk to me.
-Maybe I get both just in case.
I do it as fun as FH is dead meat here in Sweden ( can never be sold.
For hot-rods my choice is the 99/59.
Maybe it's my head not going forward in time era, but in one of my FH i has the 8 BA crank and lifters so idea is when they came ( I used my old Merc block...
After all common sense tell me of a LM7 engine. Cheap, great tech and make power easy.
Builde one this spring to a customer with a cast std crank, std block/heads and turbo and another cam and intake, rest is std = 1.000 HP easy on the rear wheel in a Volvo.
Bigger turbo and better rotating ( more boost ) it can make 1.300.
This is sneaky pete 2026.
Anyway.
Mercury sounds nice.
I did find a 41 block ( shortblock ) in California and bored 30 over but its wear, but came out as a runner ( but seller did 'not' run it so it could be cracked.
Case is the freight over here to Sweden.
300 USD but I could get a 59 block pro ported/relived and sonic testet/pressuare checked and 1/8" over std at 800 USD from same guy.
But the Merury talk to me.
-Maybe I get both just in case.
I do it as fun as FH is dead meat here in Sweden ( can never be sold.
tubman
Well-known member
From bitter experience, I will tell you that the best oil pump for a flathead is a tested Ford 8BA pump with a new relieve spring. After market pumps for flatheads have almost all proven to be inferior.