i was wondering if there was a calculator on the internet for DCR or if everyone is just using the formulas and doing the math, either way if someone could provide me with a link that would be great. im going to try and figure how much i need to enlarge my combustion chamber in order to get a compression ratio low enough to run 91 octane. thanks guys

 

Mine is Performance Trends and it's about 50 bucks.
Now-- bring your chambers to 56CC's and 5CC's valve reliefs ya get 11.64 static and 9.089 DCR which is a tad over max.
Making your chambers back stock(54) and 8CC's of valve relief'(4 eyebrow) ya get 11.20 static and 8.98 DCR.
The chambers at 56CC's and 8CC's of valve relief ya got 11.23 static and 8.77 DCR well within the limits.
Myself I would get a larger cam and leave the rest alone with 4-5CC's of valve relief(2 eyebrows) I think if ya build a 383 the small cam ya got,ya will be disappointed with.

 

the stock piston is 8cc's?

 

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

 

in that calculator what do i put in this blank?

Intake Closing Point (degrees)
ABDC @ 0.050 lift plus 15 degrees

 

Use 68* the actual closing point.

 

what should i shoot for, as in optimal but on the safe side for 91 octane? with 57cc chambers im coming up with 8.716 static with -7cc pistons. hows that?

 

That's good but I hope the static is higher.The 8.71 is DCR.
I don't know where you are coming up with the 7CC pistons. Are they 4 eyebrow?
The 2 eyebrow I use from Probe have 4CC's and are clearanced for 2.100 valve and .800 lift (big reliefs)

 

the pistons are KB and they say they are -7cc, now its just a matter of seeing if i can get them in stock bore. o and i mistyped my static is 11.15, the DCR is 8.176. how hard is it to get enough material out with a home porting job to make the combustion chambers 57cc? would that me a lot of metal having to come out? thanks

 

8.17 is low but 8.71 is safe.
Why not put a set of forged piston's in it. The hyperucraptic are not very good for performance work.

 

okay im also dyslexic. haha seriously. anyways its 8.71 assuming i can get my chambers to 57cc, i looked at a BUNCH of head porting sites but i cant find anywhere to show where the "extra" aluminum is in the combustion chamber, 3-4 cc's doesnt really seem like that much to take out but i definately dont want to get near anything like waterjackets or other hidden goodies that need to be left alone.

 

It's in the smog lump by the exhaust valve. If ya do it yourself be carefull,ya will hit water in a hurry. Ya need to CC them now and grind to 57CC's and make them ALL the same shape and CC'S. When ya measure make sure ya install the plug ya are going to run and the same plug in every hole. If ya don't have a burett don't try it. Ya can't do it by sight.

 

haha

here is mine

STATIC COMPRESSION RATIO 14.934

DYNAMIC EFFECTIVE COMPRESSION RATIO 11.568


so what does the dynamic do for me?

 

If ya got a 11.5 DCR ya better run it on nuclear fuel.

Contact Iran,they got it cheap.

 

That's a good one!

Rich