I purchased a 72 Elan Sprint recently, and a more experienced eye cast over it has just revealed that it does not have it’s original engine (Where are you N25015?). Maybe I should have done a bit more homework before buying!
Instead I have what seems to be a much earlier engine, and I’m hoping someone can give me an indication of what is now sitting under the big valve cam cover.
The main block casting numbers are partially ground off, as shown in Brian Bucklands book. It is not clear if there is any Lotus overstamping on this, if so it must be very lightly done. It is an “L” block thankfully. The head has no letter on the raised boss in the spark plug well, suggesting an early head.
I have the carbs off currently and can now see the engine number clearly. It reads LF98721LBA which does not seem a standard format. Also I expected the 2nd letter would be a P but it looks clearly to be F.
Any ideas what this engine number might mean?
Thanks, Nigel
Nigel, I have never heard of a prefix “F” (although that doesn’t mean it doesn’t exist) here are a couple of other things to look for which may help establish the engine’s origin’s, have a look on the rear of the head (quite difficult) as Lotus used to stamp the block number on it on the earlier engines, also check if it is a four or six bolt crank (the sumps are different with the four bolt sump the rear two bolts are much more prominent as they stick down) although a six bolt could have been fitted. You could also check the cam markings (rings) but this involves a little more work but would give you an idea as to the spec of your engine.
Cylinder head stampings in this topic.
elan-f15/cylinder-head-stamped-with-lotus-production-numbers-t15867.html
Some engine number topics to look at
elan-f14/engine-number-location-t16005.html
viewtopic.php?t=15708&postdays=0&postorder=asc&start=15
You engine number LF98721LBA has on to many digits, clean up the area and get a decent photo or put pencil to paper over the stamped area and read the white area that didn’t get penciled over. Lotus only made 35000 Twin Cams so you seem to have one extra digit.Please let us know what you find.
Gary
Nigel
Send me a PM with your VIN and contact details and I’ll let you know if I have any additional information.
Tim
As long as it has got the “L” behind the engine mount, it is either a “681F”, or a “701” engine, probably being produced between 67 and -70. The 120 block never carried the “L”. The sump will tel you what crank you have, but both 4 and 6 bolt cranks will fit all blocks.
Dag
Dag, are you sure of that as I have a friend who had Lotus Cortina of 1964/65 vintage, the car went to the scrapyard many years ago but he retained the engine. Although the casting numbers had been ground off by Lotus it has the “L” cast into it (see pics) the engine number is LP 3719 LBA and I always assumed it was a 120E block.
The article below from the Lotus Cortina Register states:
“Of the first five blocks, with the exception of 2731 6015, all were produced as ?L? Block, i.e. letter L cast into block between right hand engine mounting bolt holes.”
The 120E is the 2nd engine listed.
Gary, do you have this engine number in your list?
From the Lotus Cortina Register:
The following article gives detailed information about
replacement Ford cylinder blocks, their history, and what to look
out for.
There are eight different blocks which can be of use to us. Five take a Lotus crank, the other three were originally used in 1600cc crossflow motors.
These are the numbers to look for:
122E 6015 Early Lotus & GT, very rare
120E 6015 1500 Cortina, Capri, Lotus, Cortina (L/C), 1500GT
2731 6015 MKII 1500 Cortina
681F 6015 MKII L/C
701M 6015 Found in the most odd places, rare and desirable
All above can be used with 4 bolt or 6 bolt L/C cranks.
681F 6015 Early 1600 Xflow, 1600E, etc.
2737E 6015 Early 1600 Xflow, 1600E, etc.
711M 6016 MKII Escort, MKIII, MKIV, Cortina, Single Wheel Transit
These three require crossflow crank and machining of top face.
Of the first five blocks, with the exception of 2731 6015, all were produced as ?L? Block, i.e. letter L cast into block between right hand engine mounting bolt holes. This normally means that they have been cast with more metal around the cylinder bores, to accommodate the larger bore of the Twin Cam as compared to ordinary Cortinas. It DOES NOT FOLLOW however that they were all used in Lotus engines, as many of them found their way into the Ford engine exchange scheme and trundled around for years propelling Granddad and his Yorkshire Terrier in the trusty 1500cc MKI. If you can find one of these, it is in effect a new L/C block, as 1500cc Cortina bore size is 1.5mm less than the L/C. For this reason, always check the engine in any scrap Cortina MKI or MKII. We have found 6 ?L? blocks in this way in the last 12 years!
In spite of the foregoing, blocks without the ?L? marking can be used in L/Cs in 90% of cases, and there is another marking to watch out for which gives a clue. This is the T number, cast into the top middle left of the block, and front right, adjacent to the distributor. As a general rule, any non ?L? block numbered T1, T2, or T3, will bore out to Lotus + .040 bore size. ?L.? type blocks carrying these low T numbers mostly can be bored to 85mm without going porous, which gives 1650cc and 150-155 BHP with appropriate head and camshaft mods. This is getting towards ?Sod the expense, give the cat another goldfish? for road use however, as 85mm pistons are rare and expensive.
Now a brief rundown on each block, its pros and cons.
(1) 122E 6015
Originally used in some early Cortina GT, Capri GT, early L/C. Very rarely seen, most have worn out or blown up. Will normally bore to 83.5mm, originally used 4 bolt crank,
has round section main bearing caps which don?t survive long about 7000 rpm.
(2) 120E 6015
The most common MKI Cortina block, basically same as (1) above although will usually bore larger if its an ?L? type block.
(3) 2731 6015
The last of the 1500cc non ?L? blocks, originally fitted with 6 bolt crank, usually bores to 83.5mm OK. Requires relieving for clearance if fitted with a Lotus crank. Round main caps.
(4) 681F 6015
The ?L? version of this block was the original fitment in MKII L/Cs and obviously takes the 3020E type b6 bolt L/C crank. Round main caps. Most will bore to 85mm if they have a low ?T? number.
(5) 701M 6015
Something rather special, reputedly of Ford Germany origin probably for the Escort T/C. Only made as an ?L? block, a meatier casting altogether, with big square main caps, the best basis for a competition engine, and much sought after. Many were used with 81mm bores towards the end of Ford?s engine exchange scheme for the 1500cc Cortina, so you know where to look!
All the above blocks can be used with 4 bolt or 6 bolt crankshafts, but you must use the correct sump, as they are not interchangeable and if fitting a 6 bolt crank in an early block you have some fancy welding to do on the oil pick up pipe.
We now come to the 1600cc type blocks, to which people are turning for a useful capacity increase and easier availability.
(1) 681F 6015
Confusing, as this early crossflow unit used in 1600Es and 1600 GTs carries the same number as the MK II L/C but is easily
![GORDONS CARS 013 [HDTV (720)].JPG](https://cdn.lotuselan.net/original/2X/6/6557bec05cf9a0092c597c8d9babf8a2301882a0.jpeg)
![GORDONS CARS 012 [HDTV (720)].JPG](https://cdn.lotuselan.net/original/2X/b/bb8d6a4e97a4a6b95fe3634727ff14286b27240b.jpeg)
I believe the “L” castings were introduced by Ford around the time they stopped making 1500 height blocks for themselves and only continued making them for Lotus. All the Ford production changed to the 1600 tall blocks. I believe the “L” enable the Ford foundry and machine shop to clearly distinguish the Lotus block castings so they would not get mixed up with their 1600 tall block castings on the production line.
As this change came in after 120E blocks stopped production and 681F blocks came in I would agree with Dag that there are no 120E blocks with the “L”.
regards
Rohan
Update on my engine number. I may have been suffering from dyslexia or double vision last week! With a bit of wire brushing and my glasses cleaned I can see my Sprint engine number is LF9872 LBA (i.e without the extra “1” I added in my initial posting. I am guessing this engine is from around 1967 but if anyone can confirm this I would be interested.
Thanks, Nigel
[quote="types26/36/74F
From the Lotus Cortina Register:
[/quote]
While this page from the Lotus Cortina register is a valuable listing of the blocks it does propagate some of the myths that are not real as far as i can tell
i.e.
The “L” block is somethng special
- The L version was only a factory identification and made no real difference to block dimensions or tolerances
Some blocks are better than other to use as the basis for a Lotus Twin Cam or a race engine or a big bore engine.
- The only crtiical dimension is the bore wall castings and all are the same basic dimensions and tolerances on all blocks. While detail differences occur in the external webbing there are no significant strcutural changes that make one block type more suitable. It is more crtical to choose a good block of any type than a particular block casting number type.
T numbers mean something in terms of ability to bore out a block
- I have never been able to correlate T numbers with bore wall thickness after testing many blocks
cheers
Rohan
Hello Nigel,
I have a late 1967 Elan - Semi Super Safety DHC. It was built in July/August of 1967 and sold in March of 1968 in the US to Lotus East/Duchess Auto. It still has the original LP8149LAA engine in it. You can use an inspection mirror and flashlight to check the back of the head to see if the head number agrees with the block number.
Your engine may have been produced in 1968 or 69. Is it a Weber or Stromberg head? A standard or SE engine can be easily upgraded to sprint specs with cams, pistons, intake valves and a careful milling of the head… It was an easy choice since all but the cams needed to be renewed when I rebuilt it.
Enjoy your Elan!
Regards,
Dan Wise
Another data point: The engine in my car (4869, built July '65) has an “L” block. I have temporarily lost track of the engine number, but I did establish that it was the original block according to the Sports Car World site (and in any case, the car has been in my family since '67). Having read in several places that this Can Not Be, I’m glad to see that information from the Lotus Cortina Register.
engine numbers easy to fake and by 67 L blocks where coming in
I am still waiting for someone to show me an orginal 120E block with an L on it. Always happy to be proved wrong
The 120E blocks external ribbing can be identified even if the casting number ground off so post some photos.
cheers
Rohan
Putting my photos where my mouth is… In these photos, the engine has been enlarged to 1700cc and converted from 4-bolt to 6-bolt crank, but it’s the original block (with the old-style oil pickup). In the original full-res photo of the right side, I can just make out the engine number: LP3831LBA. For this to be anything other than the original block, the first owner would have had to replace the block, faking the numbers, in early '67 - or the one guy who worked on the engine when it was out of the car would have had to do the same without telling me or charging for the new block.
It looks like you are correct and it is a 120E casting with an L on it. I must look more closely at other early elans to see if I can find more the same. Glad to be proven wrong 
Just for reference I have attached photos of a range of different type spare blocks I have. 116E, 120E, 2371, and what I believe is a 681F L block casting but the ground of numbers have —E 6015. This last block is a mystery as only the early blocks (116E, 120E, 122E all of which had screw in oil pickups) had an E suffux to the number and this is definitely a later 681F style casting as far as i can see including the press in pick up. It has the provision in the casting for a rear oil dip stick which suggests it was a casting done around the time of twin cam escorts
cheers
Rohan
Andrew, as I said in my previous post, my friends engine number is LP 3719 (L Block) some one hundred plus before your LP3831 and I am also sure my friends has not been doctored.
I do not know if it is a 120E or what it is but to the best of my knowledge it pre dates the 618F Block as it came from an early Lotus Cortina.
Unfortunately I cannot examine the block closely as it it is in South Africa and I no longer reside there but I will try to get more info on it.
It would be interesting to hear if anyone owns an “L Block” or has seen one with an earlier number then LP3719.
Here is a little more to add to the “L” debate, a couple of pics of a 2737 E block and its an “L” block.
Both the Lotus Cortina registry and the Dave Bean book list the 2731 E as a 1500 used by Lotus and they list the 2737 E as 1600 XFlow yet this has the “L” casting.
Quote: "2737E 6015 Early 1600 Xflow, 1600E, etc. "
Idea’s anyone? I’ve heard the theory that the “L” has nothing to do with Lotus…will we ever know?
I find it strange that something that “everyone” have judged as “never existed” , all of a sudden appears out of the sky.
This item has been discussed pages up and down over the last twenty years, and still something quite new pops up…
Proven wrong Rohan ? - not quite sure…! They fly people to the moon, and it may have been “usefull”, - cos it’s not difficult -, to put an “L” onto anything to achieve a better price. These days people pay ?1500 for a MkII Cortina airfilter-box, so why not…
Still, - yes, I may be wrong…!
Well we keep learning new things - so what do I believe I know about the topic now
- Ford made at least some 120E 6015 style castings with an L but not all Lotus Mk1 twin cam engines made with 120E blocks had the L
- Ford made at least one 2737E 6015 style tall block casting with a L
- Lotus Mk2 Twin Cam engine block castings from Ford all had the L ( 2731,681F 701M) – but as I have not seen all Mk2 engines maybe some did not have the L - does any one have an porginal Mk2 engine block without an L?
- Ford made at least one 681F style casting but with a ground off engine casting number xxxE 6015 and this was used by Lotus in a Mk2 engine
- We dont know what the L stands for but it may not have anything to do with Lotus specific castings
- The L castings appear not to have significant differences in dimensions or tolerances than the standard non L castings of the same casting style.
- Across the years while the casting syles changed in details of external ribbing the key dimension of Bore Casting OD did not change and no block style or casting number including L castings are thus preferred for boring out or appears to have any preference for use in a bored out Lotus Twin Cam
- I have never seen a 116E or 122E style casting with a L but that does not mean they dont exist
Can anyone dissprove any of those statements or can add any more true stratements to the list ? Are people adding the L to castings to get more money ? I guess its possible but its not that easy to do so it cant be seen.
cheers
Rohan
I am not quite sure if I am being accused of something underhand here but if that is the case I take exception to the insinuations 
I cannot vouch for the authenticity of the 2737 pics as they were sent to me by another forum member who was considering buying it and wanted my opinion, in the event he did not buy it but as far as I remember it was being sold as an XFlow (see the pin in the front main bearing cap for the timing chain slipper) and not a Lotus engine (so not commanding inflated Lotus prices)
As regards the moon landings …well that’s a whole new subject and there will always be the “Flat Earth Society” and the conspiracy theory’s of the crackpots 
BTW its not about proving anyone wrong, its about all of us learning about the origins of Lotus and I am surprised that there is no one around who worked in the foundry and can give some definitive answers as this and the “T” number which has been tossed about on many forums for years…but I digress…
Just to throw a little more into the melting pot, I found some more pics of my friends “L” engine LP 3719 LBA from his Lotus Cortina (and it was a 1965 C registered) he has had it more than twenty five years, long before ebay created a thriving market for anything Lotus.
Although I assumed it was a 120E I am now having doubts as this pic shows an “L” at the end where Lotus ground off the casting number! I cannot think of any casting that had the L as the last digit unless I am missing something…this is interesting stuff (IMHO)
