Head ID Please

[tonyabacus]

Can anyone tell me when this head was produced or how old it may be and what it may have been fitted to please
LP7841.Supposed to be a Sprint head.

Also where is the source that people use for this information and for engine numbers etc, whenever the question is asked someone always comes up with chapter and verse, but from where?
Thanks
Tony

[Billmack]

That sounds too old for sprint. Not sure where info like that is but some time with Mr Google ought to turn it up.

[jonsered 11]

Hi Tony, it was fitted on the 5th of December 1967, probably to an S3, hope that helps.

Jonsered

[Andy8421]

A ‘genuine’ Sprint head will have a Z or N (depending on which way you look at it) stamped on the round casting boss in front of the front plug.

It is of course possible your head has been machined to Sprint spec and had bigger valves installed which is all pretty straightforward.

[tonyabacus]

Thanks guys, Jonsered I have another head so will look out the number and see if you can identify that one
Tony

[tonyabacus]

Jonsered

As you seem to have access to head numbers, can you tell me anything about the following three heads I have please

1.LP1738
2.LP1485
3.1735 (this head has an indistinct mark but the markings on it in different places are as follows, WM9403, L406, A26E311, BD16L and what looks like 1735

The last one does not appear to have an LP number except the 1735
Thanks
Tony

[elated]

My understanding is that the first Mk 2 engine was LP7800 and this was introduced in March/April 1967 so i am a little surprised that LP7841 was so late in the year. I suspect that it was probably SE spec.
Gordon

[trw99]

Tony,

Neither LP1738, LP1485 nor Engine No 1735 appear against any of the early Elans, so were likely fitted to LoCorts.

Tim

[tonyabacus]

Hello Tim
Thanks again for your investigations, having thought about it, one of the heads I now recall came from a guy that had raced Lotus Cortinas. It was a very long time ago and I had forgotten how I had ended up with these items, but you prompted the old grey matter.

What is interesting is that the head 1735 does not appear to have a prefix like LP which the others have, although the number is not very prominent or clear, so I am wondering whether this may be a very early head, any thoughts?
Tony

[tonyabacus]

Gordon
From the information between you and Tim it does seem as though the numbering is in question, but I think this is something that those with greater knowledge than me, may need to speculate on as to what may have occurred. Tim seems to have pinned it down very specifically in date terms, presumably from some sort of factory records one would think, I leave it for him to comment further, but thanks for the input.
Tony

[rgh0]

Hello Tim
Thanks again for your investigations, having thought about it, one of the heads I now recall came from a guy that had raced Lotus Cortinas. It was a very long time ago and I had forgotten how I had ended up with these items, but you prompted the old grey matter.

What is interesting is that the head 1735 does not appear to have a prefix like LP which the others have, although the number is not very prominent or clear, so I am wondering whether this may be a very early head, any thoughts?
Tony

The "1735" head also has the number BD16L so I doubt its an early head. I presume this BD16L was on the rear face of the head. These numbers started appearing in 1968 when Lotus took the engine building inhouse and the LP numbers ceased being put on the heads. As best I can tell the first letter in the AAXX number appears to be a year code with B corresponding to 1968 ( C=69, D= 70 etc). A letter after AAXX, in your case L sometimes appear and may correspond to it being a low compression head ?

Not sure what the 1735 or the L406 represents I presume they are on the bottom face. I see these various types of numbers on the bottom face of some heads and not sure if from the factory or from later machine shop work or both. The other numbers are the William Mills ( WM9403) and Lotus part numbers (A26E311). If the numbers are cast in then they are from the factory. If stamped it may be from the factory or done during latter servicing

Photos of the head from all sides and of the numbers close up would help pin down its date a little more as the casting and machining details changed over time.

cheers
Rohan

[geni]

Where did you get all this good information from? Could we share the document with our Lotussians!

[rgh0]

I have published this some ago on Lotuselan.net and continue my investigations when time and a chance to look at more cylinders heads in detail arise. It comes from looking at heads in detail and analysing what others have observed and written about but sometimes not interpreted fully.

See the attachment below. I really must update this sometime when I get a chance, but working on my Lotus' and working to earn enough to pay for what the Lotus need consumes to much time

Any information on heads especially with detail photos is always welcome especially if it appears inconsistent or adds to what is in the attachment. There is a lot still to learn. Somewhere the original design drawings for the various versions must still exist and whoever holds them will have the best information but whoever that is does not want to go public unfortunately and no one who worked on the heads during the original production years appears to have published much either

So reverse engineering and speculation is the best we can do currently

Lotus Twin Cam Head version History.pdf

(1.24 MiB) Downloaded 310 times

cheers
Rohan

[111Robin]

Regarding head stamping, can anyone post a photo showing a head with factory letter stamped on the boss infront of #1 plug please. I've wire brushed mine but can't make out anything obvious. Are there any other numbers on the head to assist with identification ?

[Andy8421]

Regarding head stamping, can anyone post a photo showing a head with factory letter stamped on the boss infront of #1 plug please. I've wire brushed mine but can't make out anything obvious. Are there any other numbers on the head to assist with identification ?

As mentioned above, it doesn't take much to turn a 'normal' head into a 'big valve head', so your head could easily be big valve spec without having come out of the factory that way. With Lotus you can never tell, but I believe all factory big valve heads had the Z / N stamp. Picture below:

https://lotuselan.net/lel/28004/0/20130926_212004.jpg