Cc'ing a head tools?

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Not sure I am understanding this.....
"Calculate the volume of the cylinder as if it were a flattop with no reliefs, then cc your cylinder as if it were a cyl head, and compare volumes."

My H655CP pistons are below the deck. So I would drop them in cylinder to x depth, fill with fluid, measure and calculate volume. Does it matter that my pistons are dished? How does that factor?
Piston Head Volume (cc):
+11.23cc

upload_2021-7-21_13-42-24.png
 
Not sure I am understanding this.....
"Calculate the volume of the cylinder as if it were a flattop with no reliefs, then cc your cylinder as if it were a cyl head, and compare volumes."

My H655CP pistons are below the deck. So I would drop them in cylinder to x depth, fill with fluid, measure and calculate volume. Does it matter that my pistons are dished? How does that factor?
Piston Head Volume (cc):
+11.23cc

View attachment 1715769144


Anything below the deck at TDC adds to your chamber vol wrt calculating the c/r
 
If those are your pistons pictured, with no reliefs out to the edge, there is no need to cc them in the cylinder. You can just use a plate with a hole in it, seal it to the top of the piston with some grease, and cc the dish just as you would a cyl head chamber.
The cc-ing of a cylinder is usually used to find cc of a domed piston, or one with a dish that has valve reliefs to the edge that cant be sealed with a plate.
Now, that will get you dish volume, but that is only a SMALL part of determining actual compression ratio!
 
If those are your pistons pictured, with no reliefs out to the edge, there is no need to cc them in the cylinder. You can just use a plate with a hole in it, seal it to the top of the piston with some grease, and cc the dish just as you would a cyl head chamber.
The cc-ing of a cylinder is usually used to find cc of a domed piston, or one with a dish that has valve reliefs to the edge that cant be sealed with a plate.
Now, that will get you dish volume, but that is only a SMALL part of determining actual compression ratio!

He needs to know how far down the hole they are as well though.
 
Not sure I am understanding this.....
"Calculate the volume of the cylinder as if it were a flattop with no reliefs, then cc your cylinder as if it were a cyl head, and compare volumes."

My H655CP pistons are below the deck. So I would drop them in cylinder to x depth, fill with fluid, measure and calculate volume. Does it matter that my pistons are dished? How does that factor?
Piston Head Volume (cc):
+11.23cc

View attachment 1715769144
If those are your pistons, and you know the dish volume, (and you believe the numbers) you dont need to cc the cylinder. But accurate measurements need to be done if you want an accurate comp.ratio.
You need to know the cc of the heads (should cc those), how far down the flat portion of the piston is from the deck (deck height) head gasket thickness (to calculate volume), and of course, bore and stroke.
Once you have measurements, most of the piston manufacturers have c.r. calculators. I like the one at Wallace Racing Calculators.
 
Thanks guys. Yes I am calculating my CR. I have my deck height measured (.065 yuk), Bore (4.030), Dish volume (+11.23), Heads (62cc) and head gasket thickness (.028). I'll check out the Wallace calculator and also use the fluid measurement on a cylinder to compare.
 
@JoePole1, for giggles (and before i saw your #33 post,) i ran some hypothetical numbers on your combo, and i got 8.43. However! All the numbers in your #33 post were smaller than what i used, just a guess at this point, but it looks like you might be 8.6-8.8/9. Good measurements get accurate results. The calculator will tell you what measurements it wants.
 
Wallace gave me 8.88, but i added in 1cc for miscellaneous. (Wallace has a list of miscellaneous volumes that typically dont get measured)
Either one is a nice ratio for a street performance engine.
 
Thanks. I hindsight I wish I went with some better pistons for closer to 10:1 but didn't have the scratch to balance. It's a magnum and piston choices are limited but it is a street performance engine and should be fun. The cam will help.
 
Thanks. I hindsight I wish I went with some better pistons for closer to 10:1 but didn't have the scratch to balance. It's a magnum and piston choices are limited but it is a street performance engine and should be fun. The cam will help.

Don't sweat compression too much. Cam is mostly where it's at. A little bump in compression doesn't do all that much. Cam/Valve event timing does. The folks around here can talk/write about it for eons and I'm just trying to catch up.

Good luck!
 
Thanks. Here's my cam spec from Oregon but we should not turn this into a cam selection discussion. I already Hi-jacked this enough. Hahaha

upload_2021-7-21_18-38-30.png
 
Not much left to hijack of the original post. There's the high dollar proper tools.....and then there's the kind lots of us use. They both work. What else is there?
 
I still have my mine from the 80's,I think it was Crane or Comp Cams kit.Heck it's still in the box it came in.
 
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