Re: Help Identifying 70s Tractor/Backhoe

[Grown_in_gravel]

Bore is 4.420”. Strange indeed. Unless they used some oddball pistons, the shorter stroke wouldn’t give you as much compression for the diesel. I’m guessing? I’m planning on getting the block sleeved back to standard size but I want to get this all figured out before I ordered the crank.

The shop said the stroke is 4.2” based on the wear pattern on the cylinder and the spacing between the top and bottom rings. Perhaps that was measured incorrectly, I guess I better get a hold of the crank again and measure it by the offset of the rod journals from the mains. The part number on the crank is illegible.

Thanks for the confirmation, wanted to make sure I wasn’t crazy. This might be some kind of a Frankenstein tractor….

 

[Destroked 450]

4.2 stroke crank used in a 4.4 bore block makes a 192 ci engine
This combination was used in the 65-68 4000 series gas engines but was not available as a diesel until 1983 in the 3910 model
Since you need a crank just get one with the 4.4 stroke and a set of 201 diesel pistons, the rods are the same length

 

[Grown_in_gravel]

Destroked, thanks for that! Yes, I just did that calculation now that you mentioned it (193.3). As a bit of an academic question, wouldn’t the compression ratio be too low if you use the 4.2 stroke with the same connecting rod length and piston designed for 4.4?

 

[Sean in PA]

Destroked, thanks for that! Yes, I just did that calculation now that you mentioned it (193.3). As a bit of an academic question, wouldn’t the compression ratio be too low if you use the 4.2 stroke with the same connecting rod length and piston designed for 4.4?

That's what I was thinking, but they did use a 4.4" bore x 4.2"stroke on the 4 cylinder 256 ci engine in the 5000, so maybe it has the pistons from a 5000, or from the later 3910 engine.

 

[Destroked 450]

Destroked, thanks for that! Yes, I just did that calculation now that you mentioned it (193.3). As a bit of an academic question, wouldn’t the compression ratio be too low if you use the 4.2 stroke with the same connecting rod length and piston designed for 4.4?

Yes if you use a 201 piston with the 4.2 crank the piston will be .100 down in the block, to low for even good gas engine compression
As Sean mentioned the 4 cylinder 256 had a 4.4 bore using a 4.2 crank, it's piston pin hole is located .100 farther from the crown thus moving the piston crown back to the top of the block.
The 193 diesel can be built using the 4.4 bore 4000 block with a 4.2 stroke 3000 crank and 3 pistons from the 256 4 cylinder
One can not use 3910 pistons unless you use it's new design tapered rods