Early block/late crank question

[Shoebox]

I have a '39 Mercury Town Sedan with all original 68,000 mile driveline. Runs well just down on power. I'm considering doing a rebuild using parts from my stash intended for an 8BA build. I have a 4" crank and new rods, as I recall however vaguely, that I need some pot metal pieces to accommodate the rear seal, can someone refresh me ? THANKS GUYS.

[Brian]

19B 6336 lower
91A 6335 upper
91A 6347 packing

[Bored&Stroked]

With the assumption that it has a Mercury engine with the larger 3 3/16+ bore, you should be able to get the later 8BA rods through the bores. If it was a Ford engine with the 3 1/16 bore (221 cubic inches), then you'd have issues . . .

[Shoebox]

Brian, thanks for the part #s, looks like C & G has got them. B&S the engine is indeed Mercury, but I'll ask a question to all on this. I have an excellent 8BA block, always intended for the next Shoebox to come my way (hoped for a business coupe) but as time goes by, less likely so, how much of a pain to put into the Merc? I know there would be dist, fan, pulley and waterpump issues but I have not researched it yet, perhaps there is a combination of parts to make it more doable ? Open to any input, Thanks guys.

[Ol' Ron]

The rear seal of the 39 and the 8ba are the same, so the Merc crank is a drop in to a lat 38/41 block. However the 91A block has 3 1/16 bore, not sure it can be bored to 3 3/16. I did however bore the 37 block for this same installation, but we used the ford crank for the test. Wish we used the Merc. Ran verywell. The 37 block does need the rear seal mod which you can buy fromRed's heades.

[JSeery]

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Originally Posted by Shoebox

Brian, thanks for the part #s, looks like C & G has got them. B&S the engine is indeed Mercury, but I'll ask a question to all on this. I have an excellent 8BA block, always intended for the next Shoebox to come my way (hoped for a business coupe) but as time goes by, less likely so, how much of a pain to put into the Merc? I know there would be dist, fan, pulley and waterpump issues but I have not researched it yet, perhaps there is a combination of parts to make it more doable ? Open to any input, Thanks guys.

Believe VanPelt has these parts as well.

[Bored&Stroked]

There is nothing wrong with a 39 Mercury block/engine . . . just as good as any other 239 as far as I'm concerned. If you want to put the 8BA in it, then my suggestion is to change the front of the later engine to "mimic" the 39 Mercury . . . running the 39 style water pumps, timing cover, distributor, camshaft, cam/crank gears, etc.. This is easy to do and keeps the "style" of the engine the same as the original.

Now, if you don't care about the original style and usage of components, then you should be able to fit the later 8BA into the 39 Merc chassis, using the truck water pumps, rear-sump oil pan, etc..

I'm not an expert on 8BAs in a 39 Merc - not sure if there are any potential issues with crankshaft pulleys and the front cross-member?

If you need to rebuild BOTH engines, then why not stick with the 39 Merc one? There are no real advantages of on 8BA or 8CM over a 39 Mercury with a late Merc 4.00" stroke crankshaft.

[JSeery]

.....

[Shoebox]

B&s, Yes there is much to be said for rebuilding the original engine, and that is something I'm considering. I do have an nos 53 Merc cam and a Buba's chevy distributor that wouldn't get used though. Regarding the crank, I was of the understanding that there is no rear main seal on the 39 engine, merely a slinger affair. I have only rebuilt late flatheads with the rope rear seals, which is what my initial post was about, am I correct on this?

[Bored&Stroked]

Brian up above gave you the part numbers for the necessary components to convert the rear main sealing system to be like the later ones (actual rear main seal).

I use the upgraded seals from Best Gaskets (graphite impregnated rope in the rear) - with their complete GraphTite engine gasket package. I also put the one-piece front seal in as well (Looks like a rubber donut). I believe the one-piece front seal comes with their kit - though you should check.

If you decide that you want to part with the 39 Merc block, let me know - have a 40 Merc that it could go in.

[Brian]

I've seen 39 Merc motors with both style rear seal/slinger setups. You'll not know until you pull it down

[Shoebox]

Brian, interesting info, Thank you. With you having seen some 39 Merc engines, did any have the tin can cylinder sleeves or not ?

[JSeery]

Because it is easy to switch them out, I would think this could also occur in a previous rebuild.

[Brian]

No, I can't recall having seen 99A block with tin can sleeves. And, as JSeery points out, those 99's I've seen with rope seals COULD well have been changed out previously. Indeed, I always convert slinger engines to positive rope seals, even 21 studders.

[Bored&Stroked]

Like Brian mentioned, I've never seen a 99A (239 Mercury or WWII Industrial) type block with tin-can sleeves.

I've only seen this type of sleeve in replacement engines for the 3.0625 bore 221 Fords.

I know of no tin-can sleeves in 3.187 bore engines (239s). But hey, I've been wrong many times before . . . anybody else have comments???

[Brian]

There exists in the Canadian 'Fast Moving Parts Catalogue 1928-1949' ; 99A 6055 sleeve-cylinder [steel]- .040" wall thickness, but the application is listed as fitting tractors 39-48

[Shoebox]

Thanks guys for the continued info regarding my 39 Merc engine. I have a nice Columbia to go into this car and am really interested in doing an engine build. As mentioned earlier I have a certain amount of parts stashed for an 8BA build, but if I could use some of my goodies in building the original engine, that might be the better way to go. I would be boring out to some unknown extent, weren't the Merc blocks considered pretty robust regarding cylinder wall thickness? I know on these engines you never know for sure till checked out, but just asking in a general sense.

[flatjack9]

That is the prevailing opinion.