S3 cylinder head

[(F5)]

Good grief I'd forgotten what it was like to read analog verniers.

[motopsycho87]

It's a shame the squish depth is different, then you could just machine the head and fit different inserts for different characteristics, never mind hey thank you for the pictures!

[(F5)]

Well you could machine the squish area all the same, then the head to get down to 1mm, then the inserts you could play with volume and reduction of squish area.

[Jakobi]

Originally Posted by (F5)

Well you could machine the squish area all the same, then the head to get down to 1mm, then the inserts you could play with volume and reduction of squish area.

Except the inserts and head join together to form the mating surface on the 2 O-rings, so you would have to machine each insert and the outer head itself to get the squish clearance down. End result a modified S3 head that only uses modified inserts.

Do S3 machine custom inserts? Very possible. I know another brand of after market head did/does offer the service. You could always do this after market too, but you'd be working with squish band angles, widths, volumes, etc. A bit more work than modifying a stock head.

[motopsycho87]

Actually sounds quite plausible! So skim the head to the lowest compression head, then skim the squashes to match the first.

Are the combustion chamber volumes actually different between them then, or just the squish? As surely I'd just be machining them all the same in the end?

[Jakobi]

Chamber volumes are the same.

The compression increase just occurs by reducing trapped volume as the insert closes the squish up (sits deeper into the cylinder).

[motopsycho87]

Wow that's rubbish, so what compression do you get if you go for 1mm squish as it should be?

[Jakobi]

Depends on how many base gaskets you need, which head insert you need, etc. Based on variables for your particular engine..

I have notes somewhere from when I ran an S3 black insert on a stock 2010 300cc barrel. Can't recall the exact setup and figures though.

[motopsycho87]

I've got 1.5mm base gaskets. So if I were to get the S3, I would need to;

measure piston to TDC gap, lets just say 4mm

machine each insert for 3mm stepped section

skim head to suit

then ideally measure the volume of my current head, and machine the bowls of each insert 1cc less, so i effectively have 4 different compression ratios to play with?

[memphis2857]

I think Jacobi did something similar with his S3. The problem you will run into is machining the head itself AND the inserts because each price accounts for a portion of the mating surface.


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