cylinder head question

[georgesgiralt]

Hi !
I've just got a pair of second hand heads for my R65.
I intent to have them totally refurbished and use them in my "new" motor (I'm preparing my retirement....).
Both heads have an SDS port filled with a plug. But, if both have the big valves seats, one has no squish band.
Both are "R65" molded and from Kolben Shmidt.
Questions :
How come one of them has no squish band ?
Is it possible (easily) to cut a squish band ?
What consequence on the engine, having only one squish band ?
As you can see, I'm at loss here !
Many thanks for your help and advice !
P.S. one has valve guides machined for the big engine valves, not R65 valves. But of course, the guides are same outer diameter.

[Tony Smith]

The only way to know how it will behave is to measure.

You can get a good idea of the combustion chamber shape by lightly gluing lengths of soft electronic solder to the top of the piston and then bringing it up to TDC with the head correctly torqued in place with a new gasket. This will tell you the shape of your combustion chamber and give you a rough idea of the internal clearances - you don't necessarily need much of a squish band, depending on the overall shape and the actual compression ratio.

To work out compression ratio - remove head and remove  strips of solder then put the head back on and torque correctly. Using a pipette fill the combustion chamber at TDC with alcohol, keep a record of how much you put in.

Then calculate the volume of the cylinder at BDC (or use a lot more alcohol) and then calculate the compression ratio. For a long and happy life I would seek to keep it below 9:1, preferable in the mid 8's.

You can still buy decompression plates/spacers if your combustion chamber shape is OK but the compression ratio is too high.

There is no practical method to reinstate a standard looking squish band and metal has been removed if it isn't there anymore and putting the metal back is not really an economic proposition.

But don't sweat the squish band too much - if your CR is within reasonable limits dual plugs will largely overcome poor flame front propagation as a result of no squish band.

Or, unload those heads to an enthusiast and buy yourself another set of stock ones.

[georgesgiralt]

Thank you Tony,
But is it feasible to put a squish band where there is none, copying the one on the other head ?
Is it easy or a very hard job ?

[Tony Smith]

Thank you Tony,
But is it feasible to put a squish band where there is none, copying the one on the other head ?
Is it easy or a very hard job ?

No. It is not feasible, it would be cheaper to have a new head cast from scratch.
And it is vtial that the heads are the same

[georgesgiralt]

Thank you Tony, now i know ;-)
I wonder if I have heads with squish bands on the 1982 ? As it should be the "most powerful" R65 ? Does somebody knows for sure because I do not want to pull a head to check ;-)