I don’t think so as it clearly still shows its a 681F.
Here is couple more 681F blocks that have been on ebay.
The pics that Paddy posted for me, thanks Pad, show a 681F L block, with SQUARE main caps, as it came from the factory. Quite unusual no? I would think that this block was one that was cast in around 1970, as Ford were going over to the 701M L block for Lotus, but the case casting number has not been changed yet.
Leslie
Hi Leslie, yes thats quite unusual, I noticed the square caps but assumed they had been changed… as we know with Lotus very little is written in stone or even cast in the same mold 
Leslie, what size welsh plug (cor plug) does that engine have in the rear face (flywheel end) I could be wrong but I seem to remember the 701M has a 2" …the same as a 711 where as the 681F is 1 5/8" same as the side ones.
Brian, I am not suggesting you have done anything suspecious, I have no reason for even thinking that you have ! 
What I am saying is that this is the first time in my 30 years with these blocks, that I see a 2737 “L”… ! On the other hand, I have never ever seen a 681 with square caps either, - unless later added -, so I may have a lot to learn still !
The “common truth” is that square caps came with the 701-block, but again, that may also be wrong. And when did the hole in the gallery for the oil pressure pipe go from 1/4 to 3/8 ??? ( - hope I remember the sizes now… )
Dag
I guess the sizes were 1/8" BSP & 1/4" BSP - as my current 681M block has 1/8" BSP and the previous 681M block had 1/4" BSP.
Good afternoon Brian,
The picture of my 681F with the square caps has the smaller core plug on the rear face. I am sure that these caps came with the block from the factory, as I have examined the block very carefully, and any markings for position of the caps, ie 1 2 3 4 & 5 have only been done once. Also any original machining marks between the block and the caps correspond.
Whilst we’re on blocks, does anyone know the definitive answer as to why on some blocks, the identifying casting number has been ground off, leaving just the 6015 BA, or no number at all. I have heard it is to get past scrutineering, if you are trying to use a later block than is permisable in a given class, for racing.
Answers on a postcard…
Leslie
- there are no definate answers , that’s for sure…
However, according to some litterature, you will find 120E, or 122E, on some Mk.1 Lotus Cortinas, and I guess S1 Elans as well. When the Mk.II Cortina Lotus came out late -66, the model was designated 3020E. I have blocks with the “120E” ground off, and the 3020E stamped on the flattened face… My very unqualified ( ) guess is that this was done in between the 120-blocks and the 681, just in order to be able to mark them. What is being done nowdays is another story, and a lot (!) of pre-65 racecars run 701 blocks with no casting numbers on. Cheating ? No, I don’t think so, but that is another discussion… ( - with no definate answers either…)
Dag
The engines were orginally assembled by JAP and then by Villiers and finally by Lotus when they moved assembly to Hethel in 1967. I have always assumed that griinding off of the Ford casting number was done either by Ford or by Lotus or the other assemblers due to some sales agreement restriction that stopped Lotus using the Ford casing number. it only appears to have been done in the 65 to 69 period from what I have seen in cars but with so many engine changes its hard to tell exact start and end dates
regards
Rohan
PS the original twin cams came on a 116E block which was the first 5 bearing ford 1500 block and strangely not mentioned on the Lotus Cortina web page. I have never seen a 122E block so not sure what they look like or where they where used versus the 120E and 116E blocks in ther mk 1 twin cams
I’m struggling with engine identification on my “new” Elan; the PO, who’s father owned the car from 1970, said that his Dad took it to Mike Spence to have the engine upgraded to BRM spec; it carries a Mike Spence plate on the orange crackle BRM cam cover with the engine number 125670/1 (which, of course, means very little, at least to me, the most cynical of cynics).
Stamped in the usual place (what kind of idiot hits an iron casting with a hammer and stamps?) appears to be: P12916L A-A although this is a little feint.
In the DVLA document the engine number is shown 036/1 (the chassis VIN number is also wrong, but that’s due to a shaky hand with the electro-engraver and can be fixed by me sending them a photo.
Any views on the engine number(s)?
edit: btw engine block is dark green.
Pete
I suspect that the engine no should read LP12916, which were fitted to Elans from July 1968 through November 1968. However that is a full year earlier than the date of first registration of your car. Was your car retro fitted with an earlier Spence engine? The LA-A refers to wall thickness of the block.
Someone posted a description of the Spence BRM engine numbering system on here a while ago. I can not find it via a quick search. I believe the 036/1 number may have something to do with that. They were stamped onto the Spence cam cover plate.
I think Mark will be able to help you more on this question.
Tim
Thanks for that Tim. There really is only just enough room to fit P12916LA-A on that boss with the large stamps used, perhaps they left out the spacing.
I can make no sense of the 036/1 number on the reg doc, it does not tie in even with the “Spence” number on the cam cover, which, with a bit of imagination can be seen to encompass the Lotus engine number 12567? 
Although Shirley that would have been even earlier?
At some point the engine will be coming out and then I’ll be able to look on the rear of the head, to see if there is an engine number stamped there.
Any more thoughts, chaps?
The plot thickens… Andy Graham at Lotus has told me that the kit was shipped with engine number L18647.
Just spent the day stripping a 120E long engine with an L cast in at the appropriate place.
This engine came from my Lotus Elite series 1 which had had an engine transplant in the USA back in the dark ages. I pulled the engine out some 14 years ago in late 1998 and put it aside when I built and installed a Climax.
A few years ago I was moving the engine and it was then I realised the engine was built around an L block a T3.
As I now have 3 cars with twincams, 2 Brabhams and a series 1 Elan, I thought I would start the process of building a spare around this block, starting with stripping it bare. I always imagined that seeing the Elite was a Lotus they had sourced a Lotus engine and put a non-crossflow head on it. Well, first disappointment was ordinary pistons, no eyebrows. Next disppointment was 116E crankshaft and rods. Next disappointment was bore size 81 mm. Next and last disappointment was only about 3mm meat measureable in the rear wall of the rear cylinder, not enough to get 82.5 even.
So it would appear occassionally a block cast with an L was realised to have too thin a wall thickness to use as a Lotus and it was sent down the normal assemby line as a normal production block and only bored to 81mm
Almost 50 years later we learn a little more - anyone else ever found an L block with only 81mm ?
Going to list it on E-bay as might be useful to someone from an originality point of view - but it will have to be sleeved. I have searched all over it but cannot find an engine number on it. It still has 120E-6015 embossed on the side.
Ed
Yes. Info here.
lotus-cortina.com/library/block/blocks.htm
Read all the highlighted links to get a fuller picture although it’s 2005 info.
There may be something later.
Certainly my 701 L block was 81 before I had it bored to standard 82.5 twin cam bore
Also have 81mm L block on a T3 cast, came out of a 1500 corsair it’s all greased up & waiting for it’s day Curly 1964 s2 26Rrrr
Hi Ed
With offset boring it should be quite practical to get an 82.5 mm bore out of the block - the wall thickness on the front of the rear cylinder you should find is much thicker and you can bias the boring to take essentially nothing of the rear wall and maintain most of its 3mm minimuim wall thickness.
cheers
Rohan
Just on casting numbers at the late end, my March 1972 build Twin Cam Escort’s engine is built on a 710M6015LA casting with the “L” in the engine mount and is a T2 example (from memory it’s stamped LA on it’s front too) - it’s at plus 60 at the moment, tired and emotional after having done a lot of miles since it’s last rebuild.
- I’ve always presumed that the 681 blocks came in with the change from rope to lip seal. I’ve got a spare L blocked Twin Cam Escort engine (that I’ve not dissected yet, but am pretty confident it’s out of an Escort as it’s got the correct “winged” sump and is on an earlier 681F6015 N/A block and is a T1 example - I don’t know what grading stamp it carries). Edit 23 July 2012 - It’s got J 22130 stamped on the flat between the distributor and fuel pump sites. Will check for grading and head numbers in next couple of days…
How plentiful were the 116E blocks compared to the120E back in the day? I’ve only seen one 116E in the flesh, & I’ve never seen a 122E block either, though these days some people refer to any Cortina Block as as 116E, which can be misleading…
Yeah Ed, keep it and keep as much meat in it as you can, run it small bore!!!
Cheers
James
Hi James
My guess is one 116E block to about twenty 120E blocks - based on my sampling. I to have just one 116E block in my collection currently.
Never seen a 122E block either
cheers
Rohan
My guess has long been that Ford moved to 120E castings fairly early on. Racing car magazines in 1968 were referring to the standard engines for bespoke racing cars as the “116E” and that would have been years after the 120E blocks had gained wide circulation, as a stab in the dark I’m guessing that 120E blocks could have been produced in 1965, or even '64?
I presume that once 120Es started appearing, 116Es ceased production.
Hi James - despite what is written by some I have never managed to find any correllation with the T number and wall thickness in the many 1500 and 1600 blocks I have measured. To be specific I have never found any correllation between bore casting outside diameter and thus wall thickness and any of the various casting and T numbers. Bore casting outside casting diameter variation is random within a narrow band dictated by the sand casting technology used by Ford. Sample lots of blocks with an ultrasonic guage and you will always find a few of any type that can can take a bigger bore.
cheers
Rohan