Sectioned Lotus Twin Cam Cylinder Head

[rgh0]

The attached pdf file shows a picture of a sectioned head in two planes done of a photocopier so true to scale with no disortion plus a couple of chapters out of the vizard book on head porting modifications so you can relate what he says to the actual head casting.

You will note in the sectioned head the small gap between the bottom of the inlet spring pocket and the inlet port. When porting the head this is the area you need to be careful with and one of the critcal areas to work on to get good flow without breaking through

cheers
Rohan

[john.p.clegg]

Nice one Rohan,that will save Bill having to get the hacksaw out....

John

[bill308]

Rohan,

What a great piece of information.

The first x-section is a plane through the valve centerlines. The piston side is down and left. Do you recall if this cut also down the center of the exhaust and inlet ports?

The second x-section appears to be a plane between head bolt locations, showing threaded fitting on the far left side. I believe the piston side is upper left? Is this midway between cylinders 3 and 4?

Do you have any more sections?

Was there a reason you copied them at an angle?

Thanks Rohan. I this this is important stuff.

Bill

[rgh0]

Rohan,

What a great piece of information.

The first x-section is a plane through the valve centerlines. The piston side is down and left. Do you recall if this cut also down the center of the exhaust and inlet ports?

The second x-section appears to be a plane between head bolt locations, showing threaded fitting on the far left side. I believe the piston side is upper left? Is this midway between cylinders 3 and 4?

Do you have any more sections?

Was there a reason you copied them at an angle?

Thanks Rohan. I this this is important stuff.

Bill

Yes first picture is as you describe it and cut on the centre line of the ports and valve guides
Yes second picture also as you describe not sure which cylinders the cut is between but probably between 3 and 4 as you say

I got these pictures many years ago I have never actually seen the sectioned head itself. I dont have any more sections. I do have a old soft head that probably has no chance of ressurection and I have been thinking of sectioning it myself just been reluctant to do it as it is in good conditon apart from being to soft and I have heard people say that with the right heat treatment you can reharden them so dont want to cut it up until I can test that theory more.

They were copied at an angle just because that is what fitted on the platten of the photocopier

cheers
Rohan

[mini64]

Great info to have here.

Rohan,

do you happen to have the cross section diagram that I believe is in that same book of how to lighten the flywheel?

[elansprint71]

I've got an old soft head too and my wife is thinking of having me Sectioned.

[john.p.clegg]

These help?

John

[dougal9887]

Hi all,
The David Vizard article copied in this post describes a 'radius valve seat tool' and holder. The holder seems pretty straightforward but can anyone described in detail how to make the cutting tool out of a centre drill please. No doubt a similar procedure can then be used to produce the boring tool also described.
Thanks.

[bill308]

Years ago when I did my head to Vizard's specification, the local machine shop showed me a piloted tool that could be chucked in milling machine. This tool held 2- opposed ceramic cutters, maybe 3/8 inch square by 1/8 inch thick each. I found a local tool maker who was able to grind the specified radiused notch by removing one corner of the ceramic cutters. He was also able to put a back cut relief on the non cutting edge of the radius so it would cut on only one edge of each cutter. The valve seats were hardened (Stellite). The cutter worked well but dulled toward the end of the job. I don't think we got the back cut on the cutter perfect, but it was good enough. I guess my point is seek the advice of a good automotive machine shop and ask their advice if this is what you want to do.

Since those days, flow technology has moved on. In Vizard's latest book on porting, "How to Port & Flow Test Cylinder Heads", He advocates multi angle valve jobs. It seems discrete boundaries between the multiple angles encourages the fuel air mixture to shear, helping vaporization, IIRC.

Bill