Flathead engine serial numbers

[Classic]

1.  The flathead engine serial number ranges are published in the CLC Directory.  I know the '37-'38 serial numbers are located on the left rear of the block.  But I seem to recall the location moved in later years.  Can anyone tell me where the newer flathead engine serial numbers are located? 

2.  I understand that the flathead tank engines did not have serial numbers.  Is there an easy way to visually identify a tank engine?

Thank you.  Gene

[Steve Passmore]

In wartime and later engines the number is on the right side of the block in front of the cylinders on a plinth of cast. the tank engines did indeed have serial numbers in the same place as Iv just mentioned but they do not correspond with any recorded domestic numbers.
Almost impossible to tell a military engine if just the block has been used in a car application, but if its a complete engine thats easy, 'Cadillac' cast in the heads, Water outlets in the heads all different, Watertight distributor, usually with rev counter drive.  Many with no fan positions, and no provision for the dipstick breather tube. All these differences were not apparent on all engines as the words 'Tank Engine' can be inappropriate, Cadillac made engines for many different uses from marine applications and Gun carriages to tracked armored vehicles, they were a developed accordingly.

[tozerco]

Gene,

The "tank" engines did have serial numbers as indicated in the attached extract from the US War Department Maintenance Manual. My "tank" (there were thousands of them bought to Oz for the various reasons Steve describes) is 3F4952. I am going to have a pretty good guess based on what I have been able to find to date that the "3" relates to the 75 series of the flatheads of this time and the "F" to 1941 (with "A" the first year of use of the monoblock in 1936, "B" 1937, "C" 1938, "D" 1939, "E" 1940, "F" 1941 and "G" 1942. I have a feeling that post-1942 the military engines were changed substantially and the engine numbers were moved to the front (fan end) of the block.

I still have some material to check about the four engine numbers in the two M24's that came here for testing towards the end of the war for the British War Office (the tests were held in QLD and in the jungles on Bougainville Island where my Dad spent the end of his war service) but I think they were, from memory, 3G or 4G engines.

Regards and good to see you are back focused on Caddies again!

[tozerco]

Gene,

Some more thoughts on the "tank" engines.

My '37 75 series originally came with a "tank" engine in it (the 3F4952 engine I referred to in my earlier post). This engine was all but impossible to differentiate from the outside from the '37 series 75 engine that came with my Iowa car. The engine mount catings etc. etc. were all exactly the same. The only visual difference was the additional shallow (about 3/16 inch deep) flat "rib" castings on the ends of the cylinder blocks. In every other respect, they were a car engine. That is probably the reason why our experiences here in Oz with dropping military engines into cars is so different from the anecdotal information about this swap from your end of the world.

I think this all stands to reason:

The first Cadillac engines to come here came in 1941 as Oz started up its own Cruiser Tank building programme (subsequently dropped when so many Lend Lease M5's and M24's became available from the US) as well as programmes that saw these engines put into Navy launches (I have the maintenance manual for a marinised version of the engine produced by GM Holden), search light carriers etc. etc.. The US did not enter the war until the very end of 1941 and didn't swing over to full war production until 1942.

Most of our "tank" engines were 1941 and early 1942 when they were, for all intents and purposes, 75 series car engines with few modifications while most of yours were, I suspect, post late 1942 engines specifically built for the then well established M5, M24 etc. tank building programmes.

This was a great period of history in the flathead design dvelopment that hasn't really been touched by the historians yet. I am still trying to get access to the Australian Thunderbolt Cruiser Tank that had the "Perrier Cadillac" engine in it - three (yes, 3) flatheads arranged radially around a common crankcase! There is one left here in the War Memorial Museum in my home town and I believe there is one in England. Both the history of the development of this tank and the War Office trials in Bougainville are a very interesting read.

One day we must get around to doing something about this.........

[tozerco]

.....forgot to mention:

The Oz Cruiser tank was the first tank to have a cast hull (rivetted hulls sent some pretty damaging stuff around the inside of the hull when they were hit) and three (3) Cadillac flatheads - two forward and one for reverse travel.

[Steve Passmore]

Thats interesting John, I have a military engine starting with 1G but I'm also running one in a car that has the number 404223, this one was in fact brand new and destined for a tracked Gun Carriage, these engines were wildly different in their fittings,  interesting also that you had basically domestic MOD engines in AUS, no such luck here as they take some work to make them usable, none more so than the marinized engines, Ive never seen one but a famous rock star here with large lips has a 1936 70 series convertible coupe with such an engine fitted and I'm told huge amounts of casting had to be removed from the crank case to make it work.  Sounds like someone needs to write a book on this?

[tozerco]

Steve,

A couple of views of your 1G and a description of how the 1G's and 3G's were mounted.

So Mick has a '36 caddy???

[Steve Passmore]

It would seem we have created just as many questions as answers for Gene, I can see a lot of similarities with your picture John and the engine starting with 40 that I'm running but there are differences, it had the casting for the standard engine mounts but their not used, a very large timing cover incorporating a bottom mounting took care of that and exhaust manifolds exited from the back and upwards, The IG engine is vastly different    On two of the engines the casting is there but never milled out for the side engine breather/ filler, and there are differences with the enlarged sump filler spout.
Most of these differences are with auxiliaries so are not insurmountable unless you find a marinized version which is more of a problem.  I'll print the information sheets you supplied there John and keep them in my records, I have never seen anything like that here, probably has something to do with the agreement the US government had with Britain after the war that all these surplus MOD engines were destroyed to prevent them being used in domestic cars, although many slipped through, its possible all this literature went the same way.   Seems each country needs a book of its own.

I remember a story told to me about 25 years ago by a guy I met on a building site in Norfolk, as a boy he worked with his father in his scrap metal business just after the war. His dad had bought at a surplus auction 200 landing craft moored out in the 'wash' at Norfolk and the condition of the sale was that all the engines had to be removed and thrown overboard before the rest of the metal could be salvaged, he remembers cutting them out and doing this with his father but I fancy many found there way to shore if only for the scrap.

[tozerco]

Steve,

I had no luck with the engine numbers in the two M24's tested on Bougainville Island - the test reports give tank numbers but no engine numbers.

The "Cadillac Marine Engine, V8 Series 75" Instruction Manual says "The basic power unit is a standard Cadillac V-8 sries 41-75 petrol engine fitted with a standard low compression head".

It says "This power unit has been developed from available materials to meet an urgent need ...for a readily available power unit suitable for light craft, work boats and general purpose launches...".

The Manual contains a Power Test graph for engine number 3F-4057 carried out exactly 70 years ago on 30 October 1941 indicating a power curve top-out at 120 BHP between about 3000 and 3350 RPM. I'll try to scan a couple of photos of the unit with massive water cooled exhaust manifolds on top.

[tozerco]

Steve,

A couple more tank photos of the later 3G series.....

[tozerco]

....and the photos of the marinised 41-75 series engine.

[Steve Passmore]

Ah, that 3G engine is much more like one I had a few years back, I still have all the auxiliaries. Very interesting.

[tozerco]

Interesting engine number on this:

http://www.ebay.com/itm/1937-Cadillac-LaSalle-Flat-head-V-8-engine-complete-/150685899394?hash=item2315945a82&item=150685899394&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

On my theory of Engine Unit Numbers, the 2K154 would make this a 1946 engine. The six bladed fan doesn't quite ring tru for a La Salle either, does it?

[Steve Passmore]

I think he may be looking in the wrong place John, I can just see the flat casting in front of the right hand bank, should be a number on there??

[tozerco]

Yep.

That's where his ENGINE number should be I think. I was interested in the Engine UNIT number which is what I think he is quoting.

[Steve Passmore]

I think your theory might be a little out John, I have got this vendor to check properly and the engine number starts with 487 making this engine a 1948 from a 75 series I believe.

[tozerco]

I will get to the bottom of the Engine Unit numbers one day! That at least explains the six bladed fan that (as far as I have been able to determine) was pretty well reserved to the 75 series engines.

[Warren Rauch #4286]

   Engine unit number prefix 2K is for 1948 series 75,76 (CC) with standard transmissions.This from 1948 shop manual.All other standard models were 8K and all Hydra matics 9K. !947 used the same numbers and J for the letter. 1949 same numbers and L for letter.It got more complicated in later years. Warren

[tozerco]

Warren,

I think my theory on CAR Engine Unit Numbers is still intact but still needs some testing:

A - 1936
B - 1937
C - 1938
D - 1939
E - 1940
F - 1941
G - 1942

H - 1946
J - 1947
K - 1948

assuming no CAR prefixes were used during the war years when no CAR engines were produced and assuming "I" was not used as a prefix because it looked like a "1".

To be sure I need either owners with original engines in their cars or Workshop Manuals that give Enine UNIT Numbers for:

1939, 1940, 1946. I have the other years covered.

Regards,

[Warren Rauch #4286]

 You do have it right as far as the letters are concerned.I seem to remember the topic was covered on the war engines awhile back. I checked out 1939,1940 and 1946 . The parts books use the unit numbers in the engine section. This makes the letter easy to pick out . What is hard is prefix number for the series and other considerations. By the way the letters for 1949=L, 1950=M. 1951=N , 1952=R, 1953=S, 1954=T, 1955=V and 1956= X are a continuation of this series. 1957 starts a new series where the first number is a reflection of the year 7.Warren