Altering the squish on a DR177 head

Is this recommended? I’ve measured the squish on my DR kit and its a whole 3 mm. Is it safe to remove about 1.5mm of material on the head of the kit to get a squish of about 1.5 mm and a higher compression?

My compression is about 130psi cold, and I suppose thats about right, but I would like some more if it is possible.

Thanks in advance.

Thanks for the advice. The polini head helped quite a lot… My compression is now almost 170 psi cold and about 160 psi warm!

I also got a noticeable increase in power throught the revs. Do I need to change my jetting after this?

When I compare the two heads it looks like the squish band on the DR head is wider than on the Polini. Now, what if I would remove enought material on the DR head so that the squish clearance on both is about the same. How would the performance differ? Would the DR head give more low end or more top end?


yes you could do it, or you can buy a Polini 177 head that works nice in combination with your DR kit.


you could need to change the jetting of your carb, it depends how you were running before. If you were running slightly rich now it could be ok. Check your spark with the plug chop technique or just give it a try if it any better with bigger mixer tube or main jet. (if you have SI style carb. )

As far as the comparison between the Polini head and a modified DR, I cannot answer since I have never did it and I don’t like to speculate a theoric possible result, I only do it if it is my thing and my money that I risk.