Can anyone tell me how to find out what compression ratio my engine is. It is a 350 cu in-with flat top pistons, 1965 camel hump heads,194 intakes and 150 exhaust. Thanks
griffman300
G
Geez, Gimmie a break!
10 to 1 like stock if you have 4-notch flat-top stock type pistons!!
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
10 to 1 like stock if you have 4-notch flat-top stock type pistons!!
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
actually, more like swept volume and all the rest added together divided by the chamber volume and all the rest added together.
Nominally, a flattop 350 with 64cc heads is about 10:1.
it's easier to get the swept volume by doing this calc: bore x bore x .7854 x stroke.
.7854 is pi/4.
the deck clearance volume is calc'd by: bore x bore x .7854 x deck clearance
the gasket volume is calc'd by: bore x bore x .7854 x gasket thickness.
you can use 9cc for 350 head gaskets that are .039 thick
cu. in. x 16.4 = cc's
cc's ÷ 16.4 gives cu in
valve notches in a typical stock type 350 piston will run around 6cc
the only way to get accurate cc's on a chamber is to measure it with a burette or syringes. Veterinarians have 50 and 100cc syringes.
here's a sample calc for a .030 over 350. round everything off to two decimal places. the bore x bore x .7854 is re-used, so figure it first: 4.03 x 4.03 x .7854 = 12.76
12.76 x 3.48 (stroke) = 44.39 cu in
12.76 x .025 (deck clearance) = .32 cu in
12.76 x .039 (head gasket) = .50 cu in (this is a little small if you think about it)
64cc (chamber) ÷ 16.4 = 3.90 cu in
6cc (valve notches) ÷ 16.4 = .37 cu in
So, the volume with the piston at BDC is 44.39 + .32 + .50 + 3.90 + .37 = 49.48 cu in
the volume with the piston at TDC is .32 + .50 + 3.90 + .37 = 5.09
CR is 49.48 ÷ 5.09 = 9.72
displacement is 44.39 x 8 = 355.12
It's nominal because deck clearance can vary from .030 to -.010, head gasket thickness varies from .020 to .060 and the bore hole size varies too, most are not round. Nominal 64cc heads are found to be from 58cc to 68cc depending on how much has been milled off and how far the valves are sunk by valve jobs.
Or, google "compression ratio calculator" and pick one of the many. They will vary some due to different assumptions about the head gasket bore diameter and whether or not the programmer remembers to add the valve notches to the BDC volume.
Nominally, a flattop 350 with 64cc heads is about 10:1.
it's easier to get the swept volume by doing this calc: bore x bore x .7854 x stroke.
.7854 is pi/4.
the deck clearance volume is calc'd by: bore x bore x .7854 x deck clearance
the gasket volume is calc'd by: bore x bore x .7854 x gasket thickness.
you can use 9cc for 350 head gaskets that are .039 thick
cu. in. x 16.4 = cc's
cc's ÷ 16.4 gives cu in
valve notches in a typical stock type 350 piston will run around 6cc
the only way to get accurate cc's on a chamber is to measure it with a burette or syringes. Veterinarians have 50 and 100cc syringes.
here's a sample calc for a .030 over 350. round everything off to two decimal places. the bore x bore x .7854 is re-used, so figure it first: 4.03 x 4.03 x .7854 = 12.76
12.76 x 3.48 (stroke) = 44.39 cu in
12.76 x .025 (deck clearance) = .32 cu in
12.76 x .039 (head gasket) = .50 cu in (this is a little small if you think about it)
64cc (chamber) ÷ 16.4 = 3.90 cu in
6cc (valve notches) ÷ 16.4 = .37 cu in
So, the volume with the piston at BDC is 44.39 + .32 + .50 + 3.90 + .37 = 49.48 cu in
the volume with the piston at TDC is .32 + .50 + 3.90 + .37 = 5.09
CR is 49.48 ÷ 5.09 = 9.72
displacement is 44.39 x 8 = 355.12
It's nominal because deck clearance can vary from .030 to -.010, head gasket thickness varies from .020 to .060 and the bore hole size varies too, most are not round. Nominal 64cc heads are found to be from 58cc to 68cc depending on how much has been milled off and how far the valves are sunk by valve jobs.
Or, google "compression ratio calculator" and pick one of the many. They will vary some due to different assumptions about the head gasket bore diameter and whether or not the programmer remembers to add the valve notches to the BDC volume.
Compression ratio if I recall is the ratio of the volume of a cylinder (bore and stroke) over the volume of the head gasket, the combustion chamber and any dish or valve reliefs in the piston.
The volume of the head gasket may be strange to think about but its there.
The volume of the combustion chamber is whatever its measured at. Th mfgr stated size often varies.
Since its a circular, er, thing we're looking at first calculate the area of the circle. pi*R^2 (pi times the radius squared (radius is diameter divided by 2)).
For head gasket volume multiply the above by the thickness of gasket to get the volume of the head gasket.
Similar math can be used for the volume of a cylinder.
Measure the combustion chamber volume or guestimate from mortec.com.
Or, just scrap the heads and get aftermarket or Vortec heads from GM...
The volume of the head gasket may be strange to think about but its there.
The volume of the combustion chamber is whatever its measured at. Th mfgr stated size often varies.
Since its a circular, er, thing we're looking at first calculate the area of the circle. pi*R^2 (pi times the radius squared (radius is diameter divided by 2)).
For head gasket volume multiply the above by the thickness of gasket to get the volume of the head gasket.
Similar math can be used for the volume of a cylinder.
Measure the combustion chamber volume or guestimate from mortec.com.
Or, just scrap the heads and get aftermarket or Vortec heads from GM...
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