Anyone cc`d the combustion chamber

[gnutz2]

I`ve just orderd a 50 cc burette and im going to work out my CR and was wondering how many other people have done this and what results did they get.

Im going to work out the standard CR on an aby before i do any modifications and i have calculated a theoretical combustion chamber of 43cc`s using this tool

http://www.csgnetwork.com/compcalc.html

to save time.
Using feeler gauges i worked out the the steel head gasket was 1.55mm thick and used a -4cc dish for the standard pistons (bit of a guess there) to work out a 9.1CR.

[Jamo]

cylinder volume = 445 cc/ml according to all.

The piston dish is 2.76 cc according to Mahle

The metal headgasket is 1.61mm new

[mcandmar]

The figure was posted the other day, i'll see can i find it. Was something like 33cc's. The thickness of a compressed head gasket is also on the forum somewhere. Sorry if thats not much use, i have them all written down at home somewhere...

[mcandmar]

Maybe it was 45cc's, http://www.s2forum.com/forum/showthr...highlight=45cc might be of use...

The answer is on here somewhere, even has a pic of the process but i cant find it

Mark.

[Jamo]

Maybe it was 45cc's, http://www.s2forum.com/forum/showthr...highlight=45cc might be of use...

The answer is on here somewhere, even has a pic of the process but i cant find it

Mark.

Heh like I said 44.5 cc

1.875 is the size of the paper gasket I think uncompressed.

[Jamo]

Another spreadsheet

[gnutz2]

I worked 1.55mm for a compressed gasget and the 60x1.2mm dish is -3.4cc but these are KS pistons not mhale, but that does`nt include the valve cutouts thats why i worked it out to -4cc (approx).

I`ll conform the actual figures when i get the burette it will be very intresting to see if it does work out to a 9.1 CR in standard trim.

[twoqu]

I agree! I'll bet the comp ratio is lower than advertised. Seems 45cc is pretty common for the comp chambers. But I think this after refacing, so I guess that they measure a bit more. Mark H definately measured then at 45cc with a tolerence of 0.2cc but his head was so shiney I am pretty sure it had been machined.
Only way to be sure is to measure as accurately as you can. They are a lot of factors. Depends whether you want an exact calculation or an approximate one!

[JariP]

I did a 7A head that had 42cc for cyl nro.1 and rising cc's from there for the rest, stopping at 44.5cc for no.5. Bad casting with shifted cores...

It takes some time to grind out 2,5cc's from a 4 valve chamber to even things out, there's not so many places where you can dig without altering the chamber shape. The head had been machined atleast once.