Will the crankshaft out of an 8R or 2U D8 fit into an RD-8 without modifying anything major, other than the bearings, which I would try to buy all new ones? I found an 8R sn 8923 that would be a good candidate. The RD-8 is sn 1H1079. Thanks, Jeremy

Can't give you the final answer but here's some info.
The 1H used a 7B9578 crank with shim type bearings.
All the 8R's used a 7B9511 crank with presized bearings and this same crank was used in the 2U up until sr. # 3825.
All the cranks have 3.750 main journals and 3.625 rod journals.

It would appear that they are interchangeable but I wouldn't want to give you any wrong info. Maybe someone can add to this. SJ....hows your memory working:)

Thanks Old Magnet. This tractor has the presized bearings in it as far as I could tell. It had no shims in it like my 30 or 60 did. They appeared to be alluminum with a bronze backing from what I could see? Thanks, Jeremy

It would appear that the crank bearings have already been updated then as the1H1079 had the shim bearings. The presized bearings did not come in until 1H6237.

1H1 to 1H2408 have gear drive fan, thus the 7B9578 crank which is used in these tractors will not accept cranks from later 1Hs, 8Rs or 2Us as they have long nose that extends through timing gear cover to mount the fan drive pully. I believe it would be difficult to make later bearings fit the early blocks that took shimed bearings as the caps were designed to be supported by the shims, and would have not support with shim less bearings and would tend to crush the later bearings. The later blocks that used bearings without shims were designed so caps seated on block with just a tight enough fit to retain the bearings. I guess on could make spacers to support the caps.

I never thought of the belt drive fans. I know the engine had been rebuilt at least once because the rods are .050 under. Also, the rods must have been changed, as they have the pins in them to hold the inserts, and it looks way to good for the old boys who owned it to do that nice of a job. Jeremy

Hi Brian,
See what you mean on the fan gear drive. Missed that.
Based on the description provided the 1H1079 has a crank with non shim type bearings (no mention of spacers). How would you achieve that?? I wonder if this unit has an updated engine or the replacement 1F8686 block.

Jeremy,
Does this engine have the gear drive or belt drive fan?

This engine still has the gear drive fan, and has the sn of the tractor I presume, but the rear tag is covered by the CCU. Jeremy

More crankshaft stuff:

From a May, 1941 service bulletin

In the fall of 1940 the hp and rpm of the D8 was raised to 110 hp and from 850 to 950 full load rpm on engines 1H6852. This change involved new oil cooled pistons and connecting rods plus the addition of an oil cooler and absorbant type oil filters.

Units prior to 1H6852 could also be upgraded (piston change not required) but if the new oil cooled pistons were to be used, new connecting rods and machining 180 degree grooves in the upper main bearing shells would be required.

Nov 1946 service bulletin

Aluminum bearings replaced the former babbit type.

Appears that engine has seen a few upgrades:)
I don't know if you could change over enough parts on the early engines to convert to belt drive fan. Anybody know?

Thanks for all the information. Haha and it doesnt suprise me that this old Cat has had a few upgrades over the years. Thanks, Jeremy