A friend is building a 383 LT1 engine with cc306 in a DD. Proted LT1 stocke head will go in.

If he uses flat top pistons, is it going to run on 94 octane pump gas with the cc306 camshaft. Calculated that it will have 12.5:1 CR.

What will be DCR of this setup? Can it run on 94 Octane?

 

a cc306's intake valve closing point is 73* ABDC.

http://www.rbracing-rsr.com/comprAdvHD.htm

bore 4.030"
stroke 3.75"
rod length 6"
static c/r 12.5
IVC ABDC 73
boost 0
altitude 0

DCR = 9.28

are you sure you have 12.5:1? how did you arrive at that? are your pistons flat tops of flat tops with 5cc valve reliefs? how far is your piston in the hole? what is your cylinder head chamber volume? what head gaskets are you using and how thick are they?

http://www.rbracing-rsr.com/compstaticcalc.html

try that out to get static C/R than use that in the DCR calculator.

 

If his actual Cr is 12.5:1 and he still wants to run on pump gas. What hes going to want to do is run a big enough cam with enough overlap to bleed off some of that compression. But I would duble check your number just to make sure.

 

Pistons with -5 cc dish.
Head cc 54
3.75 stroke
6.0 rods
4.030 bore
Stock block deck hight (I used 0.0060)
Stock Impalla head gasket (0.039)

So, CR came to 12.45. Tell me something is not right. I used the link you posted.

DCR came to 9.24. So, can it run on 94 octane?

 

http://www.empirenet.com/pkelley2/DynamicCR.html

I like that calculator much better. Make sure you use advertised numbers and not the @.050 numbers for the cam.

 

Thanks.

I used that and got 9.27.

My question is, can it run on pump gas.

 

Probably a typo, but the the Impala SS gasket is 0.029"

How do you get that .006 for deck height? You said "stock block deckheight" If the block is undecked then I bet they are about .020" in the hole more or less.

I punched in the same numbers but substituted .029" for gasket and .020" for deck height and come up with 12.32 SCR.
If you have the piston closer to the deck and actually at .006" then CR will be screaming at 12.81:1

Karl

 

No. You need it way below 9. Closer to 8.5 would be safer.

 

Comp cams said no larger of a DCR then 9.6-1
My DCR is 9.54-1 and is running great

 

Sorry to hijack, gixxer92, Did we meet at Cordova on Sunday? I was in the black 93 6sd z28.