Lotus Elan

Mystery Head

PostPost by: Pistonempire » Tue Jul 15, 2014 11:59 am

I have just imported a large quantity of Twin Cam, FF and FF2000 spares from California. They were part of an old friends race shop, Tom Rust Racing based up at Sears Point Raceway. There's this Twin Cam head that looks very early to me, plus one other. I have been advised by a Lotus racer at Brands last weekend that you are the guys who will know. Anyone got any ideas?

http://www.pistonempire.com/Twin-Cam-ex ... 07642.html

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PostPost by: rgh0 » Wed Jul 16, 2014 12:26 am

There were a number of protoype and pre production heads make by Lotus during the devleopment program for the engine for the Elan and Cortina and for use in racing. How many i dont know but i would think many more than three.

These prototype and pre production development heads were sand cast by Birmid as i understand it from the Wilkins book and they had many variations as you would expect.

e.g.
No 5th half bearing for cam at rear
Thermostat housing on inlet side
No breather vent gas oil separation chamber
Varying legnths of inlet tracts
No centre web in spark plug well

The intial production heads were then die cast with some futher variation in design the most notable was the half moon intrusions in the spark plug well and then they returned to sand casting again with further variations in the design

Yours certainly looks like one of the development heads before they added the breather oil knock out chamber. Does it have an engine number stamped into its rear face?

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Last edited by rgh0 on Wed Jul 16, 2014 7:56 am, edited 1 time in total.
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PostPost by: rgh0 » Wed Jul 16, 2014 2:15 am

I just spent an hour looking for a thread that discussed the twin cam head development history in more detail a couple of months ago. I cant find it despite use of both Google and the forum search function. Found a lot of other earlier stuff on head identification I had forgotten about but not this particular thread. Did anyone keep a reference to it. I saved the summary listing of the development history I posted in that thread in a file on my PC but cant find that either !!!!!

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PostPost by: holywood3645 » Wed Jul 16, 2014 4:00 am

I have a similar head on my 1700cc QED spec motor in my elan, The main difference with the one in the picture is mine does not have the steel liners in the buckets,
Rest look the same. I dont think they are anything special, however Tony Thompson told me they were good for a few extra HP because the were more ridget,

I really don't know, Tony has kissed the Blarney Stone...

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PostPost by: rgh0 » Wed Jul 16, 2014 5:08 am

Found the link after going back through my posts one by one :roll:

lotus-twincam-f39/correct-head-t31049-15.html

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PostPost by: rgh0 » Wed Jul 16, 2014 5:17 am

The interesting thing about this head is that it appears to be sand cast by Williams and Mills and is early as it does not have the breather vent oil knock out chamber

Wilkins in his book said the prototype and development heads were sand cast by Birmid and the die cast and later sandcast heads were done by WM. I have updated my summary of the cylinder head version history to reflect this and will start a new thread so I can find it next time I want to do an update

One more piece for the puzzle
I guess it is possible that WM did some development heads around 1966 when they were moving from die casting back to sand casting but why would they delete the breather vent oil knock out chamber?

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PostPost by: jabingb » Wed Jul 16, 2014 12:54 pm

LW head6.jpg and
LW head3.jpg and
LW head9.jpg and
LW head3.jpg and
LW head9.jpg and
LW head10.jpg and
LW head5.jpg and
LW head4.jpg and
LW head2.jpg and
LW head1.jpg and
It appears identical to the head that came on my '65 Lightweight that I bought at Summit Point in 1973. The head was not the original on the car but had been re-purposed after the original head went missing during an SCCA race evening when it had been pulled off the engine for inspection. 4 cap cams, longer runners, no vacuum port, no bucket sleeves, no breather box, etc. Mine has obviously been milled more than the Rust sourced head but must be from that same production run?
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PostPost by: rgh0 » Wed Jul 16, 2014 1:13 pm

Hi jabingb

Great photos of another variation of the pre- production heads used in competition engines.

Makes me wonder of the 5th cam cap on the Rust sourced head was a later addition as everything else appears the same.

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PostPost by: jabingb » Wed Jul 16, 2014 1:23 pm

Rohan,
Good spot, the Rust head also has a couple little pins in the 5th cap area that might indicate a later addition? Also seem to have bucket bore sleeves but those could have been retrofitted?
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PostPost by: rgh0 » Wed Jul 16, 2014 1:45 pm

Hi Jerry
Yes the pins on the 5th cam cap location versus the normal collets around the cap bolts on the other 4 suggest a later addition. The cam follower sleeves and half moon scallops at the top of the follower bores versus yours without also look more like a later addition in the style of later heads.

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PostPost by: jabingb » Wed Jul 16, 2014 3:21 pm

Rohan/Jeff,
Can we get this moved to the engine/head grouping where you have posted other head history, not sure how it got stuck in +2, guess the original by Steve?
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