Engine "Squish" ?

[wombat457]

I thought I had pretty much everything under control and laid out for my bike; however, I am now told that something called "squish" can effect the performance of an engine in both a good and bad way if not adjusted properly.

I understand (to a minor degree) that squish refers to the amount of room between the top of the cylinder and the head where gases get compressed when the cylinder is at top dead center. It is said that less "squish" (a smaller gap) will/can improve engine performance.

Please someone correct me if any of this sounds wrong or slightly off.

It is said that one way (the easiest way) to adjust the amount of "squish" is to use thinner head gaskets, thereby moving the bottom of the head closer to the top of the piston. The other option is to get the heads shaved .......

If that sounds right, then can I ask the following:

1. what thickness of head gasket is recommended?
2. Is there any possibility of something going wrong doing this?
3. How much of an improvement running an Andrews EV27 Cam should/could be expected?

Lastly - I will not be doing this myself - this will be done by my mechanic, I am just interested to know what is happening with my bike

 

[Frenchie]

What compression ratio do you have now? If you want to bump up the compression ratio why not use high compression pistons. Do you have adjustable push rods? If you start machining the heads and you use smaller head gaskets yes the compression will bump up but you will have to go with adjustable push rods as the hydraulic lifters can only accommodate.010 to .015 travel change and if you use non adjustable push rods you can overshoot that limit and end up with valve train failure.

 

[wombat457]

What compression ratio do you have now? If you want to bump up the compression ratio why not use high compression pistons. Do you have adjustable push rods? If you start machining the heads and you use smaller head gaskets yes the compression will bump up but you will have to go with adjustable push rods as the hydraulic lifters can only accommodate.010 to .015 travel change and if you use non adjustable push rods you can overshoot that limit and end up with valve train failure.

Thanks Frenchie now to try and answer your questions -

1. Have no idea what compression the bike is running at the moment - whatever stock is I am guessing. How do I find out?
2. Yep - will be changing the stock pushrods for S&S Adjustable Quickee Pushrods and Tappets
3. High compression pistons and head shaving "might be" on the list for next year or 2024

 

[wombat457]

Frenchie - just dug up about the compression test. Not something I want to delve into but might talk my mech about checking it when he does the camshaft stuff, unless it would be beneficial to do one now?