|12-14-2012 02:56 PM|
Let's call the cylinder volume 727.4 cc's.
Piston crown 11.0 cc's
Chambers 59.0 cc's
Piston deck height 7.3 cc's @0.035".
Gasket (0.015"/0.016") 3.3 cc's
Total 808.0 cc's
Total less cylinder 80.6 cc's
Divide the larger by the smaller and find 10.02:1 static compression ratio with ~0.050" squish.
If I could check both decks and both heads with a precision machinist's straightedge and found that all surfaces were flat within 0.002" and I was on a tight budget, that's how I'd build the motor. I might use a cam something like this one that closes the intake valve at 42 degrees ABDC.
Crane Hydraulic Flat Tappet Camshafts 114561 - SummitRacing.com
This cam would generate a dynamic compression ratio of 8.46:1, which I feel would work with pump gas and a 0.050" squish. You'll need to use more ignition timing at the crank and curve the weights in the dizzy for max 34 degrees, all in by 2800. I think I'd use a 3500 stall converter.
If any decks were wavy beyond 0.002", I would not use a steel shim gasket without cutting the decks/heads for flat.
DanielC, you are correct, with a dish shaped like this, math won't get you there, you should pour the crown with alcohol. You do not, however, have to position the piston down in the bore by 1". This will keep you filling the burette too many times and allow an error. You only need the piston down in the bore far enough for fluid to flow across the crown, like say 0.030". Then you do the math as if the dish were not there to find the volume of that space: (.7854) x 4.03 x 4.03 x .03 x 16.387, which would calculate to 6.27 cc's. You would write that down and then pour the volume. If, for instance, the fluid required to fill the dish and crown was 17.5 cc's, then you would subtract 6.27 from 17.5 and find a dish volume of 11.23 cc's.
|12-14-2012 12:14 PM|
|gsoleski||Thanks for the help guys appreciate it. So I put 11.5 in the compression calculator and with the set up i'd have I would get 9.99:1 with piston 0.035 in the hole (lower compression distance right?) and a felpro 0.015 head gasket. Then 10.2:1 with a zero deck and the felpro 0.039 head gasket. I know 0.040 quench is what you want but would the higher compression be okay with my vortec heads and 91 octane? My heads were milled to 59cc by the way|
|12-13-2012 09:53 PM|
|12-13-2012 08:07 PM|
The valve reliefs go below and outside of the circle's diameter.
I have CC'd a piston having a 0.080" deep dish, but w/o the deeper valve reliefs like that piston seems to have (if the Summit photo is actually representative of the piston and not a stock photo). The volume for that Chevrolet production piston is 11cc.
The piston in question will have a slightly larger volume than the GM piston, if the reliefs are actually as depicted in the Summit photo. That's why I added "11-12cc" to my answer. In actuality the volume is probably a bit more than 12cc.
More: Dish volume
|12-13-2012 12:20 PM|
Take the diameter of 3.020 inches divided by 2 which equals 1.51 inches.
Square that result (1.51 times 1.51) equals 2.2801 square inches.
Take that result whcih really is the area of a square with 1.51 inch sides and multiply by pi which 3.1416 is close enough this equals 7.1632 square inches.
To get the volume; the area is multiplied by the depth so 7.1632 square inches times .080 inch equals .5731 cubic inches.
Conversion to cubic centimeters is 16.4 cubic centimeters to the cubic inch. So .5731 cubic inches times 16.4 cubic centimeters per cubic inch equals 9.3981 cubic centimeters.
This same pattern can be used to compute the swept area the piston makes in bore and stroke, it will compute the clearance volume of the piston crown to block deck, and it is used to roughly compute the volume of the head gasket. Head gaskets often aren't actually round, but the computation will be damn close.
Piston domes and combustion chambers need to be measured unless you're really adept at calculus and want to spend a day doing integrations, if not, buy a graduated cylinder and some colored alcohol.
|12-13-2012 05:19 AM|
You put the piston exactly 1 inch down in the bore, and then fill the volume with your burette. Measure the volume. Then calculate the volume of a 1 inch cylinder at your bore diameter. Dished piston will read more, domed piston will read less than your calculated volume.
Closer view of burette.
|12-12-2012 11:16 PM|
|12-12-2012 11:07 PM|
How to find piston CC? I have measurments
I would like to know how to find what the CC of this dished piston is. Says the dish is 0.080in deep and 3.020in in diameter. Can anyone help me out here? I did try contacting the manufacturer but they didn't tell me anything.
Speed-Pro Digital Diamond Profile (DDP) Hypereutectic Pistons ZH815ACP30 - SummitRacing.com