[Jakobi]

Well its been a long day and I've been reminded why I'm not a mechanic! No issues faced. Just a lot of back and forwards measure this measure that.

I managed to measure up the current setup I was running (Stock 300 cyl, S3 Head, 1.3mm base gasket stack). It seems my squish was even larger than I remembered measuring it at last time. I did several measurements and settled on 1.95mm. The trapped volume was 23cc. Both top and bottom ring gaps measured in at 0.55mm. The piston has been warm enough to lightly glaze some oil on the underside of the dome. The top burn pattern is as expected from running a big squish (ie all over the shop). There were only a few areas where the carbon had built up and most was just a light oily coating that wiped off without much effort. I will post some pics later.

For the S3 cylinder, it appeared to be very much the same as the stock for the port locations. The casting is much cleaner as my stock has quite a lot of slop in one side on the transfers. Both cyldinders required a 1.3mm gasket stack to set the port timing, piston top flush with the exhaust port at bottom dead center.

The 250 top end with the ports timed as above and the S3 head with the black insert measured up very similar to the 300. Squish at 2.05mm. Trapped volume 16cc (however I was getting a bit mentally tired and ready for a beverage by then so it could be out by a mm. I did measure twice but still not certain so will get Dave to crunch the numbers for this one just to be safe).

After quickly doing a few numbers it seems the black insert boosts the compression ratio up big time on the 250.
S3 EC300: (23+293)/23 = CR 13.7:1
S3 EC250: (16+249)/16 = CR 16.5:1
Even if I missed a cc or two the 250 would still have a CR of 15.6:1/14.8:1

Note: Identified errors with viewing the fluid level at the base of the plug. Trapped volumes incorrect. Updates further ahead.

Pics coming soon.