ok so i picked up a 5k this weekend and the guy tells me that the head has been decked and so the motor has prity high compression. which should be good but when i pulled the head off tonight i had a look and the two small cut outs on the under side of the head which you can usually use to lever it of are prity well gone! you can still see them but only just feel them with your finger nail. how much have other people decked these heads in the past and still had success? without pingging all the time?

Do you know how to measure the combustion chamber volume?? Not hard, you just need a burette or pipette, and once you know how many cc there are in the head it is easy to get the compression ratio.

Does the engine have dished pistons and does the head have lugs under the number 1 and 4 spark plug tubes?

 

Thinking it may be a flat top piston head shaved down to be used on a dished piston bottom end.

Basically, to summarise what altezzaclub and slo030 are saying, there is NO way to answer your question accurately with just the information you've provided. The indicator marks are simply indicators, and don't determine anything other than 'has this head been machined.

 

First up, you need to know what your compression ratio is; this will tell you how likely it is to ping etc.

 

You will need the following:

 

1. Volume of the head in CC

2. Volume of the piston (dished or domed has either a positive or negative volume)

3. Bore Diameter

4. Stroke

5. Head gasket info (thickness etc)

 

Punch these numbers into this:

 

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

 

This will tell you the static compression, then let us know your results. Sounds like a lot but it's very straightforward.

thanks guys yeah it does have lugs under 1 and 4 and does have dished pistons. ill give the measuring a go and see what we get ill let you know when we have results :yes:

Quick question - whats the head from ? Just cause the block is a 5k doesn't fully mean the head is a shaved 5k, it could very well be a 3k thats been heavily shaved just to bring the compression back up.

Since you have the head off, cc the chambers like the others have said.