45 Flathead Belly Numbers

[Chris Haynes]

Great picture Paps, That looks just about where I found mine.

Ok…. I get it. It’s an apple and orange’s thing.

To bad that list, matching belly numbers to VIN numbers has been lost. -Steve

It is not lost. It is in the H-D Service department. It is only available the H-D dealers and law enforcement. It is a numerical list of line bore numbers with the serial number applied to that case next to it.

[Paps]

Their are folks still pursuing that list Bro. I really believe the list will become public one day. If not via the MoCo...via the military.

[Ohio-Rider]

Great picture Paps, That looks just about where I found mine.

Ok…. I get it. It’s an apple and orange’s thing.

To bad that list, matching belly numbers to VIN numbers has been lost. -Steve

[Paps]

Steve, This particular case half is from one of my 42wla case sets. All my case sets have matching belly numbers. The vin for this particular engine is a low un altered 5 digit 42 early type III wla. Earlier 42 wla's only had a 4 place vin after the year designation. Note the 5 place belly number. It is still a 42 machining job though. IMHO....since your vin is a 45 and your belly numbers are 45*****, then you have a pretty perfect match. I don't believ your cases to be replacement cases. Paps

[BEK]

belly numbers

Steve (Ohio-Rider),

I believe that in 1945 they made a lot of 45 motors that never got VIN's, that were used as replacement motors. I used to own such a motor that had 5 digit belly numbers, from '45, and no VIN.

[Ohio-Rider]

Sorry for the confusion. Its not something I read, rather it is something I own. I have a 1945WL with matching five digit belly numbers and a four digit VIN number.

[cdndewey]

Now I’m a little more confused than normal. How could an engine have a five digit belly number with a four digit VIN number? -Steve

I don't see where you read that...can you point me in that direction.

[Ohio-Rider]

Now I’m a little more confused than normal. How could an engine have a five digit belly number with a four digit VIN number? -Steve

[Steve Slocombe]

On the VLs the belly numbers are within a few hundred of the VIN numbers, showing the level of engine cases held in intermediate stocks. The exception is 1930, where the first 2000 cases were recalled and replaced (we think) with new cases with the same engine numbers. The case numbers therefore run a couple of thousand ahead of the engine numbers (plus or minus a couple of hundred as above) for this season only.

For the 42WLAs, these were built until 1944, so you can find them with 1942, 1943 and 1944 belly numbers but still with 42WLA engine numbers going up over 70,000. Not all will have five digit belly numbers, as the first 9000 each year presumably have belly numbers in the 1000-9999 range.

It would be nice to think the factory records survive linking the engine and belly numbers, so we can retrieve the original engine number from a good belly number. I've never had any luck finding these. It's possible the military bikes are better documented, with records in Army possession even if cleared out of the Harley archive. Keep asking.

[Paps]

Something is a miss if your vin number is older than your belly numbers also. Low vin numbers would indicate low belly numbers, provided the vin numbers are original. Especially on type III and earlier wla's. IMHO Paps

[bmh]

The numbers you refer to only tell us the year in which the case halves were mated and machined as a set and what their place in the machining order was. They were marked to insure they remained a set during production and also to help the police in the event of theft to verify the VIN. The Factory kept records of which motor # was built with which set of cases, but those files are long since gone. there is no real relationship between the serial number and the case numbers, it was a matter of which parts got grabbed from stock at what time to build a machine. The only real thing I can think of is that if your belly numbers are older than the casting date codes inside, something is amiss.

[Ohio-Rider]

I’ve been researching information about belly numbers on the flatheads and haven’t found much useful information, so I figured I ask you guys. Here are my top three questions I’ve been trying to find info on.

Do the belly numbers on a flathead tell us more than just the year they where assembled together?

What can the five digit number following the year the cases where stamped tell me?

Is there any relationship between the belly numbers and the VIN number stamp on the left pad?

Thanks in advance. -Steve