Technical Turbo 1108 or 1242 cc which?

[Fivehundred]

Yes, but we started out making a rough and ready estimate of the compression ratio of your engine with 2 x 1.9mm head gaskets and an additional 4-5cc of combustion chamber volume. We now know the chamber is bigger than 22cc and your method is less rough and ready than my initial rule of thumb.

Using the new formula that implies:

Volume of 35.3 cc less the original gasket at 5.9cc makes 29.9 without a gasket. Add 2 x 1.9mm gaskets at 7.5cc each gives 44.9cc plus 4.5cc for the chamber enlargement makes 49.4cc.

310.5 + 49.4 divided by 49.5 gives a ratio of 7.3:1 Makes me wonder if you can afford to lose one of the 1.9mm gaskets?

Following this example one gasket would give 8.4:1

 

[Asteris]

From the total 35.3cc, you have to deduct the gasket volume (about 6cc) and the dished volume at the face of the piston. The 8V pistons are about 2-2.5mm dished on the 70-80% of their face, which deducts another 5-5.5cc from the total. Finally, the piston does not travel all the way to the face of the engine block, but stops about 0.2-0.3mm from the top, which is another 1-2cc less. And that leaves the head chamber at about 22-23cc...

Anyway, my mechanic has an 1242 8V head lying on the bench, and i am going to fill the head chamber with oil using a scaled syringe, so we can roughly see who is right.

Cheers.