Thread: 350 4 bolt build ????s

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I will try to load up the calculator that tech originally gave to me

http://kb-silvolite.com/calc.php?action=comp

Now I will calculate the compression ratios both static and dynamic for two different head and cam combinations, but using the same basic block configeration. If you compare results you will see something interesting.

Combination 1

cylinder head volume cc 76

Piston head volume cc 6

Gasket thickness inch .039"

Gasket bore diameter inch 4.030"

Deck clearance inch +.010"

stroke inch 3.48"


STATIC COMPRESSION RATIO 8.889

Aditional information

Rod length inch 5.7

Intake closing point deg ABDC at .050
lift plus 15 degrees 36 + 15 51 deg

DYNAMIC COMPRESSION RATIO 7.796


Combination 2

Now the basic short block is left the same what will change is I will go for the 64cc double hump fuely heads 462 castings and a lunati solid lifter 00013 cam The catalogue says fair idle good performance street cam, great for saturday night drags.


Cylinder head volume cc 64

Piston head volume cc 6

gasket thickness inch .039"

gasket bore diameter inch 4.030"

Deck clearance inch +.010"

stroke inch 3.48"


STATIC COMPRESSION RATIO 10.068

Additional information

Rod length inch 5.7"

Intake closing point degrees ABDC at .050" lift
plus 15 degrees 56 + 15 71 deg

DYNAMIC COMPRESSION RATIO 7.642

So as you can see two totally diferent heads, cams and static compression ratios, but the dynamic compression ratios are the same. So this exercise derinitely points out cam and cylinder head relationships. you have the calculator available try swapping the heads and cams around and you will see how things drastically change to soggy bottom extemely low compression or detonation extremely high compression.

It is worth noting that the dynamic compression ratios cars run on pump fuel is at 7 to one and the long duration race engines run at a dynamic compression ratio of 9 to one.