Quote:

Quote:

Quote:

NO, NO , NO , NO - do NOT precoat the cylinder - that will definately skew the numbers. Besides, all that filling and draining is unnecessary!

Do as Andy said.

Pull the rockers so the valves don't open. Flip the motor so the plug hole is up and level. Bring the piston to TDC, fill the cavity using a burrette (measuring in cc's). Record that volume. Bring the piston to BDC. Fill the rest of the bore using the burrette (this will take a LONG time 'cause burrette's hold surprisingly little). Record that volume and do the math. If you screw up, empty that cylinder and then do it again on a different cylinder so that any fluid residue doesn't skew the numbers.





Why do you need to fill it twice?

Can't you calculate the cylinder volume?

Bore and stroke you know. You can calculate this with the info you already have.

  • The area the piston is down, including the area to the first compression ring
  • valve relieves
  • piston dome
  • chamber volume

are areas that you are unsure of and measured with the piston at TDC. Make sure to measure to the bottom of the Sparkplug threads and turn the motor on the stand so the bottom of the sparkplug is at the top of the chamber.




How would you figure swept volume then?
How would you know what volume is swept, from quench volume?
You need to know the volume at TDC, then any other volume or point of referance..but how will you know at what point the piston is down..Thats why it would be simple to just do TDC, then BDC...this will tell you swept, then quench..
Thats all you need.



Compression Ratio = Uncompressed volume ÷ Compressed volume


Uncompressed volume = Displacement + Compressed volume


Displacement = (Bore ÷ 2) X (Bore ÷ 2) X 3.14 x Stroke x 16.387

16.387 is the number to convert cubic inches to cc's.



Compressed volume = the volume you measured at TDC.


Quote:

Bring the piston to BDC. Fill the rest of the bore using the burrette ( this will take a LONG time 'cause burrette's hold surprisingly little).




Measuring the volume of the bore at BTC in addition to the volume at TDC just seems like a lot of extra work. With the bore and stroke you are just a couple clicks of the calculator from finding this value, just add the measurement from the TDC to it. Plus it's a big mess to clean up if you fill the bore at BTC afterwards.