Technical Rarity of Flathead Blocks - which to build?

Maybe not what the topic appears but I have a choice of blocks to build. All the parts(helmet dist., etc). These were dis***embled decades ago and of course would be checked first.
Not trying to impress with high HP as this is for the '27 T RPU project with Model A frame(unboxed).
Are the '39-40 blocks "rare" yet in the eyes of restorers? I also have 59 and 8BA cores as well but am looking more at the early block with late merc crank using 8BA rods.
D

 

39-40 blocks are 221 ci, and have tin can sleeves. Not rare or special by any means. The post war 59a blocks were always the hot rodders choice once available. The later 8ba's have never been proven to be better, just different. I like the 59a's with a crab dizzy

 

You might want to consider using an 8BA and installing early style heads. It's easy to do and makes working on the distributor a lot easier. You can still install the Merc crank and have lots of room for boring.
https://www.jalopyjournal.com/forum/threads/38-48-style-heads-on-8ba-flathead-question.314616/

 

One thing to keep in mind : Ford engineers weren't sitting on their hands back in those days. The 8BA series of blocks offer several advantages, a**** them is upgraded coolant flow. Since overheating is always a concern with flatheads, I believe this is an advantage. Also, while the front-mounted distributors are cool, they are kinda weird and hard to work on. I prefer the later post distributors, especially if one can find a "flattop" Mallory, which are cool in their own right. Full floating bearings are getting hideously expensive and hard to find along with other early parts.

Throw in a Merc or truck bellhousing and a set of truck water pumps, and you have the "universal" flathead block that will fit in anything. You want the later (non-mushroom) valves, an 8BA oil pump, and 8BA rods anyway, so why not run the all best stuff? (Unless it's a restoration.)

 

tubman hit the flathead nail on the head! Get out your hammer and do the same.

 

Definition of "rare" = I think I can get double the money out if it if I say it is "rare".

If you are building a hot rod engine you don't want "rare" unless your pockets have unlimited depth.
You want the common edition that everyone tends to modifiy with a flathead that being a 59A or 8BA based block. More parts floating around both used and new and more equals better deals.

 

You build the ones that don't have irreparable cracks.

 

Not all are 221's. 99A's, which were '39-'42 Mercurys are 239 and very much sought after blocks. A known good 99A Mercury block can bring big bucks. The dead give away that its a 99A block is all the center cooling outlets are t****zoidal and most have the "raised" intake deck surface.

 

This is the truth. Took 5 blocks to find one good one. Last one was a 59L that I used.

 

Great advice here.

 

JMO. The 8ba. As already said if you want the earlier look use 59ab heads.

 

Yes @banjorear , the mercury blocks were special and sought after even then. Try and find one now !

 

So true. Thankfully, I've got three. LOL

What's even odder is two are factory relieved and one is not.

 

T

The center outlets are round in Merc blocks. Fords are t****zoidal.

 

Thanks, Jack. After I posted, I ran out to check my blocks and coming back to edit my post. See you at Hershey.

 

I gave up at 6.

Someday I might have a flathead powered ride.

 

Thank you. I already had the mounts in for the 8BA. A recent windfall of blocks and parts had me considering other options. I like the idea of the older heads. May just go 8BA and mod a SBC(*gulp*) distributor to get mech advance. Great ideas!
D

 

L, Z, or X blocks are best but hard to find.

 

If I had to do it again I would use the 8BA block and swap the cams to run the earlier crab distributor and short pumps, saves a little room and I wouldnt have had to push the radiator out a few inches on my Model A. The options of bellhousings is greater with the later block and all of the early stuff bolts on, even the heads if you block off the right coolant p***ages though I prefer the late heads because of the removable water outlets / thermostat housings.

 

You shorten up the whole motor ***embly 1 1/2" by using the front mount dizzy. makes quite a difference when figgering out the fan space

 

I’m certainly out of space there! Needing a 12” fan!

 

I agree the one with no cracks is definitely the one to go with.

 

One caveat. While the early (39-48) center outlet heads are quite easily adapted for use on a later block, they compromise the cooling improvements made by Ford in the 8BA era. Plus, unless you go to the earlier cam/distributor arrangement, mounting the di8stributor becomes problematic. (I hate set screws in the timing cover tower.)

 

The rarest Flathead block is one that isn't cracked

 

So true,

 

I have been running early heads on my 8BA for over 25 years now with no cooling problems.

 

If you are building a common street engine with nothing more than port matching and minimum cylinder over bore, most any non cracked block will work. (24 stud)
The 49-53 block is the choice for reliable large cylinder over bore and maximum racing port size.
This is ***uming the water jackets are not rusted out.
Acid stripping and ultrasonic testing are essential for going big.

Most all parts will interchange with minimal mods between early and late blocks so any era "look" can be achieved.
Here is an intake ported to .090 min. wall all the way through.
This size can NOT be done on a pre 49 block without welding in steel tubes.

 

I thought all Flathead’s for sale are 48 Mercs and all
SBC’s are Corvette’s.
“Rarity” should not be used when discussing flatheads either. “Lack of non-cracked” describes it better.

 

You wanna drive it or toy with it taking all your time for first build I would have a couple of your blocks checked and take into consideration the condition of the other parts then design them together with your machinist unless your doing it all yourself . Another privelege you have is you have multiple engines and the best build is the one that that keeps you out of the garage and on the road not on the side . Put your efforts and $$$ into what's going to make you happy when it's done

 

That is true, I saw it on the internet.