Question about cc'ing

[126coupe]

Im doing my compression ratio measurements and what gives me the most trouble is filling the cylinder and combustion chamber w Trans fluid. I seal my plexiglass circle w grease but at the end when the combusion chamber and/or cylinder are full it always wants to leak past the grease seal. I even had the wife put pressure on the plexiglass to seal it but it still leaked.

its amazing how a few cc's changes the Compression Ratio Dramatically. I need an accurate reading concidering this will be a high compression racing engine.

I set the cylinder and Cylinder head in a vise w soft jaws and level it.

Any Advise?? Wayne????

[126coupe]

Stomski Racing has a great spreadsheet for Compression Ratio Calcs, you need excel to run it though

[Wayne 962]

If it leaks, it sounds like your heads or or plexiglass are not 100% flat?

-Wayne

[TimT]

Well when Ive done it, I just watch till the chamber is filled then close the pipette...leakage doesnt really matter.. as soon as liquid starts to enter the vent in the plate turn off the pipette

jot down the amount of liquid removed, and proceed with the measurments

[Zeke]

Can't you do the cylinder mathematically? Or is this how you figure the displacement of the piston dome less the valve pockets?

[126coupe]

Wayne the heads are not the issue( all machine work done by Ollies) the plexiglass is flat and smooth. Maybe when I added a splash of solvent to the ATF that breaks down the grease. I might try some Dow Corning 101 silicon grease its thicker and stickier that the ATF/solvent mixture.

Zeke to get an accurate measurement the cc'ing method is the only way!

[Early_S_Man]

Dow Corning 112 would be the preferred grease ... but any silicone caulking compound could be used in a pinch!

[Wayne 962]

Originally posted by Zeke
Can't you do the cylinder mathematically? Or is this how you figure the displacement of the piston dome less the valve pockets?

If you have a valve job done on the heads, the valve is typically mounted further down into the head, increasing the combustion chamber size. Unless the heads are brand new castings, cc-ing is the only way to figure this out...

-Wayne

[Wavey]

Originally posted by TimT
Well when Ive done it, I just watch till the chamber is filled then close the pipette...leakage doesnt really matter.. as soon as liquid starts to enter the vent in the plate turn off the pipette
jot down the amount of liquid removed, and proceed with the measurments

,

Same here except I use Vaseline to seal the edges and H2O with food coloring as the measuring agent. Did a bunch of engines this way, never had a problem.

[ChrisBennet]

It probably doesn't matter with the chamber measurement but when measuring piston dome volume I use a little vaseline on the top ring to make a seal. I use vaseline because I can clean it off easily when I'm done. I'm not sure that I would be able to completely clean silicone (like DC 111) off the cylinder walls.
You guys are going to razz me for this but I do my CC'ing at the kitchen table using olive oil so if I spill a little it isn't a big deal. It's a little too viscous to be ideal (suspended bubbles) but it's pleasant to work with.
-Chris
"Would you like Ranch, Thousand Island or CC oil and vinegrette with your salad?"

[silver911rdb]

Old thread but what do you guys think the max allowable volume difference between heads should be? I have a 3.4 high compression engine. I did a ton of work on the heads to bring them back from the dead. I cc'd the heads before i started. They were all approx 85cc. Now they're all around 82cc with the lowest at 81.0. I ground some material away from the spark plug hole to get it to 81. It was around 80.2 when I started. Let me know what you guys thiink. Thanks