This is what I classify as a "late" WWII Block. It has the 3 bosses (undrilled and untaped) for the M24 series block mount oil filter. I do believe that this late bock has all the correct bosses on it for a 3G engine. So you would need to drill and tap as necessary, for M24 3G or 4G LVT application. Biggest problem being the 3G oil fill location. Again this is a educated guess, not fact. Also as a side note I think this engine/block should have the "late" "Cadillac Motor" heads


1G Engines

​M5 Stuart Series

M24 LT   -   M37 HMC   -   M19 GMC   -   M41 HMC

I would appear that the heads off the 3G, 4G, and 5G engines are the same.

Cadillac Flathead V8 - 346 cubic inch displacement - Model 44T24 - 42 Series

The front engine cover for the M24 series 3G engine is not used on any other engine civilian or military. The mounting for the generator bracket required a machined surface with 4 tapped holes. No provision of any kind for the fuel pump (M24 has electric in tank fuel pumps) as on the 1G or civilian engine.

3G Engines​ - M24 Series (please note this is a 4G block with 3G components, The oil fill is incorrect, This is how I bought this)

Right Head

Left Head

These 1G Stuart engines are truly Left and Right. They sit in the tank at an angle. Therefore the the mounting plate for the carb on the intake manifold  is angled to bring the carb back to horizontal.

Timing Chain Cover / Front of Engine

​Civilian Engines

This view shows the other boss or extra casting that is used on the Stuart engine for mounting the exhaust. Also note that the M24 / 3G water pump is completely different from any other Cadillac water pump. Generator adjustment and the 3 grove pulleys particular to the M24 / 3G engine.

Engine Model & Serial Number Locations

Water Pumps

This is an "NOS" 3G Engine. It has had some items removed. This is a Left engine, denoted only by the exhaust outlet direction. Unlike the Stuart engine, the 3G engines are fully swapable left to right. 4 bolts removed and flip to exhaust port to the right, is all that is required to make this a right side engine. It does have the incorrect oil pan (for a 3G). the oil dip stick should be on top across from the distributor.

     Civilian Water Pump                      1G - Stuart Tank Series Water Pump             3G - M24 Tank Series Water Pump

This is what I classify as a "early" WWII Block. It does not have the 3 bosses for the M24 (3G) series oil filter mount. It does have the boss for the Stuart (1G) oil filter with the two mounting studs (and the exhaust on the other side). This boss is on the 3G block (but wider) but no holes and no studs. 

M24 Chaffee - G200 Series of Vehicles

Nice clean photo of the correct timing cover / generator bracket for the Stuart 1G engine

Many military engines were used in cars after the war. The military items were discarded such as the intake manifold, timing cover, oil pan, water distribution pipes, water pump, exhaust manifolds, and other misc items.

Notice the two studs for mounting the oil filter. Stuart 1G engine block. These are not on the M24 3G block, but the boss is (but wider)Studs on other side also for exhaust.

Note: The size of the mounting boss on this "early" engine as compared to the "late" engine in the picture to the left.

Cylinder Heads & Water Distribution Tubes


All G Engines are Government?

1G Engines - M5 & M5A1 Stuart Tank, G103 Series

2G Engines - ?

3G Engines - M24 Chaffee Tank G200,   M37, M19, M41

4G Engines - LVT 3

5G Engines - British CPT 20 (Very late war, T-16 looking, enlarged, longer & wider) 

Civilian Engines -  

Well like everything else on this web site, its all about the information, and or the lack of it. Well Cadillac tank engines, Cadillac car engines. Early engines, late engines. Its all to much to figure out since there is VERY little info on the net, and the manuals were never made to help us figure out what was what.

So, this page will be a learning experience on available information. Subject to change and probably open to interpatation and some guess work.

Simple answers are, the blocks and heads are all different and really don't interchange, as thing won't bolt on the block or heads. From the "original" design, to the "final" design of the block, there are major differences. These will impact your restoration and ability to bolt things up.

David Levey has restored two engines for his Stuart tank, and many of the "rebuild" pictures are of his engines. His help on this page has been invaluable as far as engine data and rebuilding pictures. His rebuild photo library will be posted sometime in the future. The Before & After is below. 

​The differences we are looking to explore are the following:​

  • Block casting (holes, bosses, connections, etc)
  • Intake and exhaust manifolds and related
  • Water pumps
  • Timing chain cover / Front of engine
  • Heads
  • Bell Housings
  • Anything not mentioned above

NOTE: All references to "Left" or "Right" side of

          engine, are if you were sitting in a car.


This listing and related photos are of original heads that are / were documented to be on the related blocks​. Also note that the water tubes off the heads do not have the secondary line out of the side.


                                                   Left Head                                                                                                                           Right Head

                                                   Left Head                                                                                                                         Right Head


1G Series Engine - Application: Stuart Series Tanks M5 M5A1 - Note that water distribution tube has secondary outlet on the side, BUT in different location than for the 3G, 4G, and 5G engines.

This is factory original or "early" Stuart

                                                             Left Head                                                                                                                    Right Head

This is Replacement or "late" Stuart

                                                           Left Head                                                                                                                  Right Head

2G Series Engine - Application: Unknown

3G Series Engine - Application: M24 Chaffee Series Tanks

                                                         Left Head                                                                                                                     Right Head

4G Series Engine - Application: LVT 3 (amphibious tracked landing vehicle)

                                                            Left Head                                                                                                                      Right Head

5G Series Engine - Application: British CPT 20 Tracked Carrier, Late war, low production (similar to a T-16 except longer & wider)