Posted on: July 29, 2016

Originally published as “Your Tiger’s Other Serial Number” by Keith Bettencourt in the January 1993 RootesReview:

Keith sends this, noting “it is a way to determine the approximate assembly dates of the Tiger at Sunbeam and the engine at Ford-it can’t guarantee the engine in the Tiger is the right one but it can guarantee if it is the wrong one!” Thanks to Keith for researching and sharing this information.

Want to know if the engine in your Tiger is not original?

Need a sure fire method of telling if your engine was made AFTER your car was assembled?

With the astronomical escalation of the value of Tigers in recent years, cars that are original can command a premium price. Part of this originality is if the car has its original engine. Since Tigers have their serial numbers on the firewall identification plate AND on a sticker on one rocker arm cover, it’s real easy to swap the rocker arm covers of the original engine and a replacement engine and pass it off as original.

This tip will prove if an engine was built AFTER your car was built thus proving the engine is not original. What it CANNOT prove is the engine is not original if it was manufactured before the car was built.

There are two parts to the puzzle:

  • the build date of your car by Sunbeam and
  • the assembly date of your engine by Ford.

This tip will show you how to learn the approximate month your car was built and the exact month your engine was assembled.

There is a small (1/2″ x 1/4″) casting boss on the front, left (driver’s) side of your engine block. It’s to the left of the distributor, behind the original oil filter and located right at the junction of the block and the head. See it? Clean it off and you will find a code stamped in it with three numbers and two letters.

The first character will be a number and stands for the year the engine was assembled. A “6” means 1966, a “4” means 1964, etc. The next character will be a letter of which represents the month of assembly, starting with “A” for January and continuing through “M”. The letter “I” is not used because it is too easy to confuse with the number 1.

So a code “7M13W” means the engine was assembled in December of 1967!  If you found this engine in your Mark I Tiger you would have reason to be VERY suspicious!

The next piece of the puzzle is knowing when your car was built. This gets a little tougher because Sunbeam didn’t stamp each car with anything by a serial number, so we have to use that number to extrapolate the probable build date.

On the assumption that a factory produces vehicles on a regular monthly schedule, it’s possible to fairly closely estimate the month your car was built.

TigerDatesDurationSerial NumbersProduction Rate
Mk I6/27/64 - 11/31/645 monthsB94700001 to
B9471649
330 / month
Mk I1/1/65 - 8/6/657.3 monthsB9471650 t0
B9473762
290 / month
Mk IA8/9/65 - 12/31/654.8 monthsB382000001 to
B383000908
190 / month
Mk IA1/1/66 - 12/9/6611.3 monthsB383000909 to
B382002706
160 / month
Mk II12/23/66 - 12/31/660.25 monthB382100001 to
B382100129
25.8 / day
Mk II1/11/67 - 6/27/675.8 monthsB382100130 to
B383100633
87 / month
(Source: CAT Shop Notes, Fourth Edition, Pages II-5)

My car has the serial number B382001008 and was probably assembled in January of 1966. It has the engine code “5K14H” which means the engine was assembled in October of 1965. Since I’m the second owner of a documented vehicle, I can tell you this is an original combination.

My engine was assembled just three months before my car was probably assembled. I would guess there will be shorter and longer spans between the engine / car assembly dates depending on how fast Ford delivered the engines. It is just speculation as to how far ahead Sunbeam might have ordered the engines and my assumption that Sunbeam built cars on a regular schedule is speculation also.

As a final caveat, all this information will not help you if the serial number on your car is not original, so use this tip with a healthy dose of your own common sense.

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