Lotus Elan and Lotus Elan Plus 2 Forums

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I have taken my cylinder head off do to low compression. Definitely needs a valve job as fuel in the chambers look less than 10 minutes to drain completely from the center to the exhaust runners.
My question is, I have a weber head with the center rib between 2 & 3. My engine number is 4670. Is this the correct head? I think it should be the non-reinforced head with that engine number.
Thanks all for any input you guys might provide!

Will

Hi,
Best info I have found is the later head type you have started to be used around engine number 7000, your head should have its number low on the back face ideally match engine No.
Ron.

As best I can tell the story line for twink head versions casting and major machining variations is as follows. if people can add any more variations or dates or engine numbers for the various changes it would be useful

1.First prototype / development heads were sand cast and had many variations including some having a centre rib in the plug well.

2.Earliest production heads were die cast and had no rib between cylinder 2 and 3 but had half moons down the centre well and square reinforcing blocks on the inlets, not known number of these produced but would only have been a few hundred

3.First sand cast heads had no rib in plug well between 2 and 3 and no reinforcing webs on 1 and 2 inlets

4.Next version added a rib between 2 and 3 I don't know when this was introduced but I have a head number LP6053 with the web but no reinforcing webs on the lets

5.Next version add the reinforcing webs on the inlets, don't know when and added the cross drilling behind no 4 exhaust port for oil drainage ( not sure if these changes occurred separately or the same time. but all versions I have seen have both) Both these changes appear to have been in place by around 1968 and the 6 bolt crank engines at least

6.Final version was mods for Strombergs and Big Valve installation

cheers
Rohan

Rohan and gents

My car, unit # 3476,# 26/0538 has engine # LP1312

There is web reinforcing between 1-2, 2-3, 3-4,

It was 50 years ago this month that I took delivery from the factory at the Vancouver docks.

Bill

Crikey! I wasn't even off the production line myself! Congratulations!

Bill wrote:Rohan and gents

My car, unit # 3476,# 26/0538 has engine # LP1312

There is web reinforcing between 1-2, 2-3, 3-4,

It was 50 years ago this month that I took delivery from the factory at the Vancouver docks.

Bill

Hi Bill
I presume your is a die cast head and by webs between 1-2, 2-3 3-4 you mean the half moon projections into the spark plug well?

If Lotus numbered their production twin cams from LP0001 in sequence then it looks like they made at least 1300 die cast headed enfgines split between Elans and Cortinas.(and the occasional Lotus 47 and 23B)
Does anyone know if Lotus started engine numbering with LP0001 or did they start with some higher number or make a jump in the number series early on as they did with Elans when they jumped to the 3000 series numbers after making a few hundred cars. I guess the listing of cars and engine numbers would give some clues ( Tim?).

cheers
Rohan

[quote="rgh0]Does anyone know if Lotus started engine numbering with LP0001 or did they start with some higher number or make a jump in the number series early on as they did with Elans when they jumped to the 3000 series numbers after making a few hundred cars. I guess the listing of cars and engine numbers would give some clues ( Tim?).

cheers
Rohan[/quote]

I believe it is perfectly fair to assume that Lotus started with engine no 1. The first prototype Elan was fitted with LP 10. The earliest engine no I can find fitted to an Elan was in Unit no 31, which had engine LP 6. The engine nos were fitted out of sequence, so for example Unit no 6 has engine no LP 159 whereas Unit 8 has LP 33. (I have purposefully missed out the 0s from these numbers, to make the point). As an aside, the ten Elans fitted with the 1500cc engine had engine nos in a different (Ford?) number sequence altogether; Unit no 1 was fitted with engine no 285621E. That was 997 NUR, used by Jim Clark.

Tim

Gents, attached are photo's of one of my cylinder heads which I believe to be an early production die cast head as described by Rohan above [except] that it has a cast rib between plugs three and four. Engine number stamped into the rear face is LP1160 and the casting numbers are on the bridge at the rear of the head. The only marking on the deck face is a date stamp 23/10/63.
Cheers, Brian.

I think that there is some confusion between die-cast and sand-cast, due to the description being a little ambiguous in Miles Wilkins' book.

My understanding is that all the production heads were sand-cast, and only the prototype heads were die-cast.

The main feature between the heads is that the early (Type '1') head, fitted up to mid 1966 or so, had the half-moon projections / pillars in the plug well, and the Type '2' didn't have them. All the production heads I've seen have the bridge between plug 2 and 3, and it's only the prototype ones that don't have that. Certainly LP006 has the bridge, but doesn't have the strengthening pillar at the front of the plug well. LP127 and LP168 are fitted to friend's Lotus Cortinas, and both have the bridge.

The prototype head looked quite different, with no bridges in the middle or at the rear, and no half moon pillars. And a very strange place to put the thermostat !...photo below.

Mark

Updating the time line for cylinder heads based on the last few posts

1.First prototype / development heads were sand cast ( or maybe diecast ??? but it seems strange to invest in die casting for prototypes which are constantly changing) and had many variations including some having a centre rib in the plug well, differrent length intake runners, only 4 rather 5 bearings per cam and the thermostat housing on the inlet side.

2.Earliest production heads (lets call type 1 heads) were die cast ( or maybe sand cast but the surface finsh and mould detail is very different from the later type 2 heads that were defintely sand cast). They all had half moons down the centre well and square reinforcing blocks on the inlets, Not known number of these produced but would only have been a few hundred to approx a thousand maybe. Examples exist of these heads with and without the centre rib between cylinders 2 and 3.

3.First sand cast heads ( let call type 2 heads) had no rib in plug well between 2 and 3 and no reinforcing webs on 1 and 2 inlets. All type 2 heads did not have the half moons down the centre well and had larger diameter intake runners than the type 1 heads

4.Next version added a rib between 2 and 3 I don't know when this was introduced but I have a head number LP6053 with the web but no reinforcing webs on the lets

5.Next version add the reinforcing webs on the inlets, don't know when and added the cross drilling behind no 4 exhaust port for oil drainage ( not sure if these changes occurred separately or the same time. but all versions I have seen have both) Both these changes appear to have been in place by around 1968 and the 6 bolt crank engines at least

6.Final version was mods for Strombergs and Big Valve installation

cheers
Rohan

Good stuff Rohan, but I can see you're still to be convinced by the sand-cast vs die-cast stuff.

I'm not 100% convinced myself....but here are my findings and conclusions.

Here's what Miles Wilkins says in his book 'Lotus Twin-Cam Engine' (page 25).

Prior to JAP taking on the production contract, the heads were sand-cast by Birmid but were unsatisfactory. At the time, William Mills were trying to develop die-casting as an addition to their established sand-casting business, which included producing heads for Jaguar. They submitted an amazingly low quote of ?2000 for patterns (next lowest was ?10,000).

JAP's task was to machine the heads and assemble trhem on the built-up blocks from Dagenham. The first engine with a die-cast head arrived at Cheshunt on 21st February 1963, and promptly leaked water everywhere. A second die-cast head was used on 25th February with better results. Now at least, the engine was beginning to be produced, although the rejection rate for heads was still incredibly high (up to 8 out of 10 at one time).

The die-cast saga continued until Lotus thought that enough was enough, and Steve Sanville had to try and sort out the problem.

Eventually, John Standen persuaded William Mills to sand-cast the heads, which they did, and all the problems were solved immediately, including the head gasket failures, which, with hindsight, were realized to be caused by a combination of two things.

Firstly, the original heads from Birmid were not stiff enough and moved around under load and expansion.. Secondly, the original gasket material was not up to the job.

The only other later modifications made to the head were to add a bridge piece between nos 2 and 3 plugs, and a stiffening web to the inlet tract. William Mills sand-cast them to the end. No records exist of how many die-cast heads were made.

So, the write-up isn't definitive on when the change happed from die-cast to sand-cast, but it does say that 'the only other later modifications made', which in the context I take as being after the change to sand-cast, the bridge between Nos 2 and 3 plugs was cast in.

The picture below shows the head from LP006, and that has the bridge between nos 2 and 3 plugs, so I would conclude that the sand-cast head (if defined by it having the bridge) was brought in very early on, if not for all production engines. It also has the stiffening web to the inlet tract (if I'm understanding what that is correctly!!)

Note with this head...it doesn't have the front half-moon pillar...I don't know when that was introduced, but again, it must have been very early on.

The next two photos show an early head with the half-moon projections, and a later one without.

I can't see any difference between the 'grain' of the cast surface between the early heads and the later ones. They are both quite an equally coarse grainy finish, and surely a die-cast finish is quite smooth?

Incidentally, the earliest 'Type 2' head that I've found was on LP 6075, which is the first (prototype) Elan Coupe S/E, made in July 1966 (that was owned by Tim Mees) . Tim and I spent a fair time contacting owners of cars around this period that still had their original engines / heads, and it seems that this is pretty much the change point to the later head. That doesn't guarantee that all later heads than 6075 were Type 2, and all earlier were type 1! Lotus didn't seem to believe in any sensible method of managing / using inventory, and using stuff in sequence was definitely forbiden!

Mark Kempson

The top 2 photos of type 1 heads are interesting - one has a boss in front of No1 cylinder like later type 2 sand cast heads and one does not --- but both have the half-moons. Is one sand cast and one die cast and the boss reflects the sand casting like the later type 2 heads? Do you have pictures from the bottom for these heads to see the details around the inlet runners.

Further Updating the time line for cylinder heads based on the last few posts -- be good when we have the Wiki for this sort of stuff

1.First prototype and development heads were sand cast by Birmid and had many variations including some having a centre rib in the plug well and some not, different length intake runners, only 4 rather 5 bearings per cam and the thermostat housing on the inlet side. First prototype ran October 1961 and versions were developed for racing and as part of Elan and Cortina development programs

2. Type 1 Heads ? First production heads, by now the same for the Elan and Cortina were die cast by JAP and introduced February 1963. They had half- moons down the centre well and square reinforcing blocks on the inlets and a centre rib in the spark plug well between cylinders 2 and 3, Not known number of these produced. At some stage Lotus changed to back to sand casting but it is not clear if this occurred with the change to the type 2 heads at around engine LP 6075 in 1966 (earliest engine number type 2 head located?) or prior to that time within the types 1 head production run.
3.Type 2A heads- Earliest versions of type 2 Heads had no reinforcing webs on 1 and 2 inlets, when these webs were introduced is not clear.. All type 2 heads did not have the half- moons down the centre well and had larger diameter intake runners than the Type 1 heads.

4. Type 2B heads The next version added the reinforcing webs on the inlets, (not known when) and added the cross drilling behind no 4 exhaust port for oil drainage and / or sand removal from castings (not sure if these changes occurred separately or the same time). Both these changes appear to have been in place at latest by around 1968 and the 6 bolt crank engines introduction.

5. Final versions were variations on the type 2B heads with the Stromberg version in 1968 and machining changes for the Big Valve engine in 1971 and modification for Twincam Europa with the extended inlet cam installation driving the alternator in 1971 .

cheers
Rohan

I think your definition is about as close as we can get currently, Rohan. I just spent 10 minutes comparing the head on my S4 (a Type 1 early half moon one, converting Stromberg to Weber) with my S3 (Type 2).
Having them next to each other I can see that the casting is quite a bit smoother on the early head, especially around the inlet tracts, and the Type 1 has no boss in front of No. 1 cylinder.

If this is the case, then surely it would make sense to incorporate the modifications (get rid of the half moon pillars) when changing to sand-casting?

So when Miles talks about the 'only other later modifications made.......' he means after the initial design, rather than after it went back to being sand-cast. His statement can be taken either way!

Mark

Hi Mark

Yes Miles' statements can certainly be interpreted in different ways.

I think the remaining significant question is did Lotus go back to sand casting at some time during the Type 1 head production run. If the die casting was so problematic i struggle to see them continuing for 6000+ engines and 3+ years of production.

I would like to see some detailed photos of the last type one heads from anyone ( say from a late S2 elan engine number somewhere in the 5000's) to see if the casting shows differences from the the early type 1 heads that could indicate a change back to sand casting while maintaining the half moon type 1 design.

I am racing at the Winton Historic meeting this weekend and will see a friend there who has an S2 , Not sure if he has the orginal head but i will have a look and see

cheers
Rohan

I suppose it depends when the failure of the casting showed up....after casting, after machining or after build. If it was the earlier two, Lotus wouldn't have minded!

Having it fail on the built engine would help to explain why engine numbers are all over the place though.

Mark