sorry but the engine builder is not sure, and says since the heads are mill it is: x, but the heads are not milled as per: y, so there is no definitive answer.

things i do know:
my engine is a 383 gen 1 roller block
achieved from i think from the increase in the stroke and i don't know about the bore i'm assuming they at the very least went 10 over??

afr street eliminator heads, let say they are not milled ( jesus christ)
they are 65cc

my 113 heads were 58cc's?

there are flat top malhe pistons with valve reliefs like 2 eye brows,
supposedly they are 007 in the hole as per y and build sheet says deck: clearence is 1 thru 8 is -.007 is this the same?

i don't even know what thickness head gasket they used, could it be .041? is the standard unless there is a reson not to?

is that enough info to determine with accuracy?

how about these mumble jumble numbers:
sv 48.08 swept volume? is this the stroke of the motor?
hv 65 head cc? seems like they figure this as a non milled head....
edv-5.0 piston edv? what is edv?
gv9.1 gasket cc? this would give away the thickness i presume...
dv 1.46 deck cc? does this match a -.007 deck?
total 81.56

do you really need all this stuff to figure it out? how do they know how?


the builder believes the heads were milled, i am 99.9 percent sure they are not (jesus christ)

let just suppose they are not, is there enough info here to get a close figure??? please assist and thanks!!!

 

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

 

In that case I would CC the heads to be sure; Comp Cams sells a unit to do just that.

Wow, that's a slick site; got it earmarked...

 

I would be concerned ; basic engine machinist stuff.
383 is 3.750 stroke x 4.030 bore
48.08 is the swept volume in cubic inches
-5.0 piston is the cc volume of the valve reliefs in the piston.
9.1cc gasket is the cc volume of the area between the head face and the top of block where the gasket is. 1.46cc deck is the volume above the piston to top of block

Everything listed above plus the head cc is added together to give the total volume above the piston at TDC .
This figure divided into the swept volume gives your CR.
On your numbers above
48.08ci =788cc
80cc above piston assuming 65cc head
788/80 =9.85 CR

 

so the numbers don't jive, he says 10.7 to 1 you say less, i plug the numbers to the above calculator and get 12.2

i have mahle pistons and they are flat, when they say -5cc, is the affect on the cumbustion chamber size (add) +5cc ( take the cc of the head and add an negative number?)because of the reliefs, so in the calculator do i plug in -5 or plus 5 ?

 

If you are using the linked calculator, enter -5. Some calcs make it more clear i.e "Enter positive number for domed piston, negative number for dished or valve reliefs."

 

Slickfx3,
If your pistons state 5cc's for eyebrows ,then you enter +5 for the silvolite formula.The requested piston volume is just that. Air Space volume the same as for head volume listed.Dome pistons will be negative numbers. For example,If you put in 0 as if no eyebrows existed. the compression will go up because you have reduced the total chamber volume of air.
Rick