Squish-did I do this correctly?

[husley]

I have done many 2T top ends in the past (including one GG) but never worried about the Squish.

2010 300. No modifications to cylinder or head.

I used the RB Designs instructions on measuring squish. Again, this was the first time for me.

At first I had all three base gaskets that were included in the top end kit in place, the squish was nearly 3.0 mm.

Eventually I ended up having just one (the medium thickness gasket that I believe to be 0.5mm +-) base gasket in place with a squish approximately 1.8-2.1 mm.

Does this all sound to be in the ballpark/reasonable?

Thanks

J

 

[Fred1956]

I believe the 3 gasket thicknesses are .15, .3 & .5mm. Theoretically if you started with one of each and subtracted the 2 small ones (.45) you would have dropped that amount. Just go through RB's direction carefully as it is pretty straight forward.
If your 'nearly 3mm' (BTW "nearly" isn't real accurate) was in fact 2.55 then your math would add up pretty close.

 

[swazi_matt]

I am also interested in this. I believe that Playing with base gaskets has a trade off effect on the exhaust port height. I have also done a few top ends without paying attention to the squish (because I only had one base gasket anyway!) but will be doing my top end again in a few months and have pile of gaskets now so want to do it better

I know the correct way is machining the head to get correct squish and correct compression etc but for those of us without access to reputable machine shops what is the second-best way to do it?
What are the trade offs of exhaust port level and squish. Wich should hold preference?

 

[Jakobi]

Not only does it trade off your power delivery due to the port timing, the compression ratios also work in the same way.

Remove base gaskets = higher compression = ports timed for bottom end. High comp boosts the bottom end too and kills over rev. You end up with a bike thats a beast off the bottom but signs off early. Good for some, but a waste of an engine.

Going the other way you end up with low comp and a massive inefficient squish clearance which makes it a pain to tune.

Ideally you want both to be in a set range, and then use port and powervalve timing to determine the curve. Squish should be around 1-1.3mm ideally. 2.5mm is considered large enough to drive a bus through. 3mm is obsurd.

 

[Fred1956]

Not only does it trade off your power delivery due to the port timing, the compression ratios also work in the same way.

Remove base gaskets = higher compression = ports timed for bottom end. High comp boosts the bottom end too and kills over rev. You end up with a bike thats a beast off the bottom but signs off early. Good for some, but a waste of an engine.

Going the other way you end up with low comp and a massive inefficient squish clearance which makes it a pain to tune.

Ideally you want both to be in a set range, and then use port and powervalve timing to determine the curve. Squish should be around 1-1.3mm ideally. 2.5mm is considered large enough to drive a bus through. 3mm is obsurd.

Ideally you set port height with base gaskets then set squish by measure/machine method for optimum results