Originally Posted by stefan

Hi Uriah,

below is a question that I also posted in the Siro thread, but I figured that you are probably the best man to ask this question, since you"ve worked a lot with Sirio engines:

"I just received my very first Sirio engine,a .12 Evo4 STI.

I took it apart and everything looks very nice, but one thing caught my attention.

The head button sits very loosely in the sleeve and has some considerable play.

Is this normal?

I am used to Picco and NR engines, where you can only pull the button out of the sleeve when the plug is removed, and even then the stick pretty tight.

Also, the Sirio head button has a groove around the part that goes into the sleeve. Is that there to seal?

I can only imagine,that the button expands so heavily that it"ll seal correctly once the engine is hot, otherwise I would expect major blow by.

Thanks for your input."

Thanks buddy!