Twin Cam Head dissection

[Certified Lotus]

A couple of months ago I started a topic on the water cooling and oil passage ways of the Lotus Twin Cam head.
(lotus-twincam-f39/section-view-cut-away-drawing-head-t35733.html#p244188)

Several individuals had some interesting information consisting of a photocopy of a head cut away (Rohan) and an actual twin cam head that was cut to show the casting details (Nick). Those examples raised more questions and once I realized the aluminum head cutaway was a new casting I recognized I needed to find a way to slice apart an older cast head.

So the search began for a used head that I could cut apart. Nick Stagg (AVRO) from the UK kindly offered one of his for shipping costs only. Once I received it the next plan was where to cut it.

Twin cam head

Twin cam head side view

Deciding where I wanted to cut the head to show the water cooling passages and oil passages took a bit of thought, but then it was off to my local machine shop to get the milling done.

CNC machine milling

Another pass on CNC

Now I need to bead blast the machined parts and photograph them. Stay tuned for an update!

[Certified Lotus]

This "project" of having a dissected twin cam head is not a high priority for me as I'm in the midst of rebuilding an S4 and I'm the Co-Chairman of LOG36 in Princeton (August 5 to 7, 2016) in addition to holding down my real full time job, but I do try to stay involved in my side projects that are Lotus related

Early this morning I brought out the twin cam head pieces I had cut and machined looking at them from various angles and thinking about what I was going to do next, developing a plan in my head about the finished result.

Couple of main items; need to file down all the cut edges as they are razor sharp, will media blast the entire head to clean it to a nice finish, will install valves and springs in a couple of areas, paint the water jacket and oil ways a contrasting color to show those areas as a highlight.

Anyway, its a work in progress. Here are a few shots of the stage the pieces are in at the moment.

TC Head sliced but not apart

TC Head divided

TC Head Section view 1

TC Head Section view 2

TC Head Section view 3

TC Head Section view 4

TC Head Section View 5

TC Head Section View 6

Will update when I Find the time to media blast it, When I can fit it into my schedule!

[rgh0]

Great work. Some more straight on shots of each section with a tape measure against them for dimensions would be good when you have the time.

Incidentally do you know why the head was scrapped? It does not look excessively soft or corroded

cheers
Rohan

[Certified Lotus]

Thanks Rohan. Will absolutely show a scale in the final photos for reference. The head was skimmed one too many times, that is why it was scrapped.

[rgh0]

How thick was the head? The first photo appears to show around 4 and 9/16 inch ( corrected my typo)

cheers
Rohan

[gjz30075]

I see someone entering the LOG artwork contest

[Mick6186]

Rohan,
One of us should have gone to specsavers. Looks like 4.5 to me!
Mick

[rgh0]

Problem is Fat Finger Disease rather than my eyes this time

cheers
Rohan

[Bud English]

...and the tolerance on a tape measure is plus or minus a furlong per fortnight.

[Certified Lotus]

Its a holiday here in the States (Presidents Day) and its snowing. I had a spare hour or so this morning so I got the media blaster pressurized and cleaned up the TC dissected head a bit.

Thought about how I want to configure the head for a static display and decided it would be cool to have some valves, valve guides, springs and retainers in the head. I have old intake and exhaust valves, but I didn't save the springs and retainers from my rebuilt engine.

Anyone have two pairs of old valve springs, retainers and clips they don't want? If so I would be grateful if you could mail them to me

Some photos of todays work:

The reason the head was scraped is as stated by Nick: "If my memory is correct it had suffered frost damage. If you look at the rear waterways on the head face and the back face it had been welded. When heads freeze this is one of the places they usually crack. The head also had its cam caps missing and had the head face machined a little more than I felt acceptable. Perhaps some might think it worth repairing but it would have been expensive and having frozen there would have been doubts about its long term reliability".

[Certified Lotus]

I found a spare couple of hours to work on my dissected head. Did a more thorough media blast of the entire head and then installed a pair of intake and exhaust valves, springs and keepers as well as a pair of spark plugs. It's starting to take shape in the way that I want it. I'm thinking I should add another pair of valves to complete the one side of the head. Then I will prime the water way jacket for prep of the final color.

[adigra]

Really love this. Fantastic effort and it will make a great display. If I may suggest, adding half a camshaft to one side would be pretty interesting, especially if set so it's opening the valves, so you really get the idea of how it works.

[Certified Lotus]

Adigra, glad you like my project. You have a good idea, but unfortunately I don't have a cam to cut or the bearings and caps. If someone wants to donate to my project I would greatly appreciate it. Would also like a weber carb to deconstruct and attach to the head. If anyone has one to donate

[Certified Lotus]

I'm at the stage where I've started to primer coat the water way passages in the head. The big question is do I paint these blue or red? I've looked up a number of engine cutaway's and it looks like blue is the color of choice. I'm wondering what others on this forum suggest?

Twin Cam head cutaway

[pharriso]

I'm at the stage where I've started to primer coat the water way passages in the head. The big question is do I paint these blue or red? I've looked up a number of engine cutaway's and it looks like blue is the color of choice. I'm wondering what others on this forum suggest?

image.jpeg

I would suggest Blue for waterways & a different color (Red?) for Oilways