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Twin Cam Head dissection

PostPosted: Fri Jan 29, 2016 2:53 pm
by 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.

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Twin cam head

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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.

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CNC machine milling

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Another pass on CNC


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

Re: Twin Cam Head dissection

PostPosted: Sat Jan 30, 2016 10:45 pm
by 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 :mrgreen:

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.

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TC Head sliced but not apart

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TC Head divided

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TC Head Section view 1

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TC Head Section view 2

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TC Head Section view 3

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TC Head Section view 4

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TC Head Section View 5

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TC Head Section View 6


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

Re: Twin Cam Head dissection

PostPosted: Sat Jan 30, 2016 11:00 pm
by 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

Re: Twin Cam Head dissection

PostPosted: Sat Jan 30, 2016 11:41 pm
by 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.

Re: Twin Cam Head dissection

PostPosted: Sat Jan 30, 2016 11:44 pm
by rgh0
How thick was the head? The first photo appears to show around 4 and 9/16 inch ( corrected my typo)

cheers
Rohan

Re: Twin Cam Head dissection

PostPosted: Sun Jan 31, 2016 12:10 am
by gjz30075
I see someone entering the LOG artwork contest :-)

Re: Twin Cam Head dissection

PostPosted: Sun Jan 31, 2016 8:55 am
by Mick6186
Rohan,
One of us should have gone to specsavers. Looks like 4.5 to me!
Mick

Re: Twin Cam Head dissection

PostPosted: Sun Jan 31, 2016 9:26 am
by rgh0
Problem is Fat Finger Disease rather than my eyes this time :lol:

cheers
Rohan

Re: Twin Cam Head dissection

PostPosted: Sun Jan 31, 2016 4:49 pm
by Bud English
...and the tolerance on a tape measure is plus or minus a furlong per fortnight. :lol:

Re: Twin Cam Head dissection

PostPosted: Mon Feb 15, 2016 7:49 pm
by 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:
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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".

Re: Twin Cam Head dissection

PostPosted: Sat Apr 23, 2016 7:49 pm
by 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.
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Re: Twin Cam Head dissection

PostPosted: Sat Apr 23, 2016 7:57 pm
by 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.

Re: Twin Cam Head dissection

PostPosted: Sun Apr 24, 2016 1:30 am
by 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 :D

Re: Twin Cam Head dissection

PostPosted: Tue May 03, 2016 12:41 pm
by 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?
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Twin Cam head cutaway

Re: Twin Cam Head dissection

PostPosted: Tue May 03, 2016 12:51 pm
by pharriso
Certified Lotus wrote: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?
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I would suggest Blue for waterways & a different color (Red?) for Oilways