1CM Merc Crank In A 40?

[Bored&Stroked]

Fordestes: What you mention is more of an issue if you're trying to get to a cast piston - not so much with forged pistons - where the big determining factor is do they have a forging blank of the right size to work from.

Now they may charge you more to do the machine work (as it is not a typical high-production stocking piston), but the process really is no different for whatever bore size, ring package and compression height you require.

If I was into the world of 221 blocks, I'd check with a few piston manufacturers to see who has a good forging blank that can support your needs and not end up with a piston that is too heavy, too short, etc.. This usually requires a basic CAD drawing of what you're looking for - so they can check with Engineering to see what they have to work from.

[Bored&Stroked]

Hey Gary - I think you meant 3.228 at the start of your post --- .040 over the stock 3 3/16 bore (3.1875 + .040).


Good info on the big-end sizes of the SCAT rods. They will not work in this 221 world - so it is back to the 91A or 21A rods for the smaller bore sizes - 3 1/16

[philipswanson]

Originally Posted by 42merc

Stock '40 Ford rod bearings will not fit. Wrong size.
Must use Mercury bearings. They are compatible.

Didn't know there was a difference...….

[philipswanson]

Originally Posted by Ol' Ron

The 40 engine comes in two sizes 3 1/16 and 3 3/16. The crank, rods and pistons will drop right in. The 221 block must be bored an 1/8 to fit the rods. Or the crank turned to 1.998 for the floater's. However, if you select to bore, better off using a later block and make 276. I've found that a "STOCK" 276 with EAB heads milled for .045 piston clearance, is a toque monster.

So are you saying that if I run the 1.999 rod journal size on the Merc crank, I won't have to bore the 221. Right ???

[Ol' Ron]

That is correct 1.998 is the stock size for the 91A/21A Rods. However I dn't know where you'd get the pistons?? also you have to consider balancing the assy??sounds like a very complicated and expensive project?? For what purpose??

[philipswanson]

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Originally Posted by Ol' Ron

That is correct 1.998 is the stock size for the 91A/21A Rods. However I dn't know where you'd get the pistons?? also you have to consider balancing the assy??sounds like a very complicated and expensive project?? For what purpose??

I am going to build an NOS military engine for my 40. I was hoping I could use the pistons and rods in it. All parts NOS. Hoping to just switch cranks and that's it.

[JSeery]

Pistons have to match the crank stroke. All of the rods are the same length so the piston pin location has to move up to accommodate a larger stroke.

[Ol' Ron]

You could use french rods. 6 3/4 length. Or use a set of OFFY heads and recess the pistons, creating a much higher CR. Boy wouldn't that be a torker.

[frnkeore]

About a week ago, we determined in a thread that I started, asking for the deck height of the FH, that the deck height, is 10.440 - 10.445. So, I will use 10.442 for the following:

1/2 Stroke = 2"
Rod length = 7.0"
Piston CH = 1.527 (this measurement is from my piston)
--------------------
10.527

10.527
- 10.442
---------
.085
- .070 (Cometic SS headgasket)
---------
.015 Piston above head gasket

My piston is .250, to the top ring so, it's still well below the cylinder.

You can chamfer the corner of the piston, .060 at 30 deg and then assemble and check the clearance, to the head with clay. If there isn't enough clearance, in the inboard area, modify the chamfer angle.

Just a suggestion but, it wouldn't cost much to modify a junk piston to find out.

Frank

[philipswanson]

Originally Posted by Fordestes

If you use 3-1/6'' bore block with 4'' stroke 1CM crankshaft .Where do you find 3-1/6'' pistons to fit the 4'' stroke merc. crank without ordering custom pistons ?

Eggie (Custom).

[Ol' Ron]

One way to install 8BA rods into a 3 1/16 bore is to install the rods from the bottom. Then install the pistons and wrist pin from the top. Using a ring instillation tool install piston and rod on crank, WE gota see this engine get built!!!!

[philipswanson]

Originally Posted by Ol' Ron

You could use french rods. 6 3/4 length. Boy wouldn't that be a torker.

That's a great idea. 6 3/4" rod would make up the difference if I use a 4" Merc stroke and allow me to use stock 221 pistons, right? Are those rods available?

[frnkeore]

The engine will have very little compression with a 6 3/4" rod. You would have to run the 4 1/4 crank to get the piston up to the stock deck clearance.

Frank

[philipswanson]

Originally Posted by frnkeore

The engine will have very little compression with a 6 3/4" rod. You would have to run the 4 1/4 crank to get the piston up to the stock deck clearance.

Frank

Will the 4 1/4 crank work in a 3 1/16" bore with the French rod and stock 221 pistons? How good would it run?

[frnkeore]

As far as running strong, it diffidently would but, I know nothing about the French rods but, assume the crank will fit in a post '40 block. Internal, crankcase dimensions should be the same as the 3 3/16" bore Merc blocks.

I would think the French rods would be very rare in the USA.

[KiWinUS]

The French rods are for 2.138 crank journals the 4 1/4 stroke cranks I have seen ( scat eagle welded merc )have 2 inch rod journals

[JSeery]

Originally Posted by frnkeore

I would think the French rods would be very rare in the USA.

The French military used a version of the Ford flathead for many years after production stopped in the US. Some years back they sold off all of the surplus FH stuff, complete engines, blocks, cranks, rods, etc. A lot of the surplus came to the US and is still available.

"The Ford flathead V8 was licensed to other producers. It was used by Simca in France until 1961 and in Brazil until 1964 for cars and until 1990 in the Simca Unic Marmon Bocquet military truck. In the United States, the flathead V8 was replaced by the more modern overhead-valve Ford Y-block engine in 1954."

The dates for production in France are all over the place, I have no idea what the last production date was, but all surplus now.

http://www.reds-headers.com/html/ffh.html

http://www.btc-bci.com/~billben/french.htm

[frnkeore]

But, the Speedway 4.25 crank, that I posted about earlier, is 2.138 on the rods. It's a little pricey at $750 though. But, it is a Scat crank.

https://www.ebay.com/itm/Scat-9-239-...ss!97502!US!-1

[KiWinUS]

Excellent. I did not know.
Good luck

[JSeery]

I happen to have a Scat 4 1/4 crank laying around, just measured it and it is 2.000". Interesting.

Just looked at their site, they have both throw sizes listed for a 4 & a 4 1/8, but not 4 1/4. Shouldn't be much of an issue to produce a larger dia throw on a 4 1/4 though.