Head Mods
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beak affects the swirl more surely? Squish is a factor of the squish band generally - keeping the combustion away from the bore walls and towards the centre of the piston?

Either way, it's a line between a nice chamber shape and reasonable boost, or an open chamber and lots of boost. I know which i favour!

lots of bosst ............. yeah

Everyone knows that instructions only have to be read if the thing doesn't work....

Rock on Mr Hybrid turbo!

bling bling ,
rock on tommy ,
to me , to you , to me ..

Everyone knows that instructions only have to be read if the thing doesn't work....

AlexF

Sure?

fairly...

unless my understanding on what squish achieves is wrong... which like anything is possible!

The way I understand it:

Squish is an area trapped between the cylinder head and the piston that DOESN'T form part of the combusion chamber.

So you want the actual volume to be very small to prevent detonation in this area which can be caused by cool cylinder walls, the advancing flame front, and the trapped end gasses.

To make this volume small you run the pistons very close to the cylinder head (ie small clearance) and this pushes most of the end gasses into the main combustion chamber.

The BIG advantage to this is that as the piston comes up the bore the squish area forces the gasses at high speed towards the centre of the combustion chamber... this movement can be used to create swirl... which is a shole subject in itself... but the A-series certainly has very high swirl for a production engine!!

Alex

AlexF

Swirl is when gases are coming into the cylinder from the inlet. Tumble or bounce are similar.

arr yes... I mean turbulance I think...

alex

AlexF

Yeah not too worried about the sqish so much.


Anyway pretty much finshed now, check out the ports let me know your thoughts on it as it is.


Exhaust port

No iain, not sandblasted it yet it is gray primer you can see just so it made the gasket line easier to mark out. Gonna sandbast it before painting. Needs surface gringing aswell

Edited by mikemph on 17th Mar, 2005.

Middle 2 exhaust ports





Inlet

What tools are you using to do the work ? and how much time and cost have you got into the head sofar.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Have you got the guides in there??

Just using air die grinder, seletion of burrs to rough out and grinding stones to ploish out, with flapwheels to buff.

Taken about 8-10 hours in all

No guides yet, got to press them in once they arrive.

I'm going blind.. :( Sorry Mike.

Edited by Doodmeister on 21st Mar, 2005.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

I thought I just did!!!!

Tunstung carbide burrs, mostly ball ended type and just grinding stones shaped to a ball shape

yep its in the right direction , but ultimately the most volume and chamber depth needs to be around the plug , maximise squish according to what pistons you are using with a +0.005 " thou deck hieght, and maybe deepen the piston dish if ness

I measured my head and it has about 12 mm deep chambers. That´s 0,47" to you imperial lot.

I'm not sure that many on here use 'pounds, shillings and pence' Jukka!

I'm in a fun phase of working with Americans who are meant to be designing in metric - but are cheating by doing it all in imperial with the intention of convering it when the design is all finished. I can see silly dimensioned drawings coming up with two or more decimal places on random numbers.

Sorry havent updated for a while I will take some pictures soon as I have had the unleaded seat s fitted. Should I go with the sodium filled valves or go stainless? Either way I will have to buy the valves as it was a NA head

When I chose the valves for my head I went for stainless steel. At the time i had heard storys of sodium valves dropping heads, But I dont think anyone on here has atually experianced this.

+ The soduim valves are so thick im sure they do not flow as well as other racing stainless valves, but I have no proof or technical data to back this up.

The stanless valves I use are 30mm in size, I think the metty turbo uses 29mm, again not really sure how much difference this makes tho

Think stainless is the order of the day then. About the same price if not cheaper than sodium filled anyway

I use stainless valves, I will never use sodium filled again, I have seen too many failures

Team Racing

I was thinking rimflow exhaust and normal stainless inlets. Think the sharp edge of the inlet might get hot and cause detonation any thoughts??