The V8 Owners Forum -

Wilts289 wrote:Hi Pocketrocket,

already have the Hardcastle book - didn't realise they are so valuable! Very useful as a starting point, but no specifics on headwork, whereas I understand the Hammill book has lifesize pictures of what to aim for re ports and combustion chambers. Anyone confirm that or prepared to post up photos?

I have both books and I prefer Des's one!

It does have full size drawings, I never have any luck bunging up pictures on this forum!

Wilts - apologies for the wrong link - too much haste and not enough speed

Pete - I already know about your fetish for Des

Hello Guy's - sorry its been a bit quiet on the porting front I am, as is typical, getting involved to too many other activities and commitments drawing on a limited time resouce.

Been spending time trying to get to the bottom of the flow issues on the Stage 3 and will be in a position to report back soon.

Purchased a couple of new die grinders off e-bay that look reasonable and I will give an opinion on these quite cheap items when they arrive.

If looking for Xmas stocking fillers - Peter Burgess Speedpro book on cylinder head mods - and if you can get one cheap enough the Guy Croft books - Vizards book on Cylinder heads is also a worthy read. And the handbook for the Superflow benches is excellent - I have it on PDF if anyone wants a copy - I may even have a link. ...... bear with me

manual download

Cant get the code to work - cut and paste this into browser

http://www.freewebs.com/jawa634/superfl ... 20ocr).pdf

Anyhow - will be back with some more results soon

Andrew

That's a very interesting document although im going to have to read it a few more times!
tom

Darkspeed, id be happy to loan you an 80's ported TVR head to evaluate. I travel all over the country for work so dropping one off wouldn't be a problem.

The head in question had throats 91% of valve size for both inlet and exhaust which is way above the ~86% most experts seem to recommend. I'd be interested to see what this does to flow and what dropping a big (1.63) valve onto the existing seat would do.

Ben

Will drop you a PM - will be nice to have another type for the datbase.

Andrew

Its been a while since doing any head work as I have been really busy building a Fisher Fury and working on my Ginetta G15 - the G27 V8 really has taken a back seat and absolutely no engine work.

However the recent posts and digging out the bench to test a head has encouraged me to complete what I started.

Shrouding.

Pictures below show the level of shrouding when the valve is at .4" lift which is the 0.25 dia figure - the white stick is on the edge of the valve at right angles and is 8mm long providing the 0.2 dia figure

The 0.25 D curtain and the 0.2 D annular being the figures that indicate full valve flow area.









This is a 3.5 deep chamber head - the shallower 4.6 heads have a different chamber shape not only due to the depth of the chamber but it also has less "shape" The shallow chamber reduces the chamber shrouding and gives an increase in available flow.


As can be seen above over 90 degree of the valve area is compromised by the chamber and the bore wall and there are good improvements to be made with careful reshaping of the chamber.

The bigger valves the restriction to the curtain area is enlarged and further work is required in the chamber to reduce the shrouding.

If you carry out the work to remove and shape the chamber to reduce the shrouding as much as possible on the higher lifts you also make greater gains at the intermediate lifts.

Cracking! Thanks for posting this mate. Do you take it right up to the bore /gasket line? What about loss of he quench band? And is it 1/8 valve diameter or there abouts that should be clear/flat around the valve? I think when I eventually test my 300 heads with you, it will be the shrouding that will need the attention- diamond