? about DCR for my 350 sbc
 

I was pokeing around a few sites and read a little about DCR which im not fully sure about. I know my 350 sbc, has 9.0:1 SCR, but i dont know what the DCR is, which is what i want to learn more about. It is to my understanding that its suppose to be in the range of 7.5 to 8.5 for a street motor. I dont know what mine is, and would like to know if anyone could tell me. The motor is a 350 sbc, with stock crank and rods, plus KB120 .030 hiper flattop pistons= .007cc valve reliefs, that are .010 in the hole. The heads are WP S/R torquers = 75cc, beehive springs, 2.02-1.60 valves, and 170cc intake runners. The head gaskets are GM Performance .028 composset to give me a .038 quench. The cam is a retro-roller from Comp = EX270HR = 495in-502ex = 218in-224ex = 110 LSA. When i dialed the cam in, i used a 9 keyway timing set which was set on the (0) mark. If my motor is not in the 7.5 to 8.5 range, what could i do to change it. Please Advise :thumbup:

According to the calculator I use you have a DCR of 7.51. You can read up on it here

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

Change the heads to a 64cc chamber volume.

Thanks for the link (gregb) It tells me that im atleast within range, and if i wanted to change out to a set of 180cc Dart Iron eagle 72cc heads milled down to 70cc i believe would yield 9.5:1 cr should'nt hurt me much but might be better. :thumbup:

The 180cc Dart Iron Eagles are a inferior outdated design when stacked up to the comparable competition. They don't flow well
for a 180cc port head. They are not like the newer improved Dart Platinum/Pro 1 series 200+cc ports. There is no improved 180cc "Platinum" IE head. Pick a better 180ish cc head. Every other popular 180cc head and many smaller 170ish port heads flow better than these heads in stock form.

The Intake port only flows 208cfm @28". Thats weak for a 180cc port SBC head.
Thats why you see them advertised for cheap(er).
Nothing against the Dart Cylinder Heads in general. It's just that these specific heads are a bit of a dissapointment.
It takes a good bit of hand porting to get them up to what the other competitive 180cc heads flow in "out of the box" form. Now the port is 180cc++ volume.
You might as well start with a stock or "S/R Torker" or "S/S" head and port them.

If it was my engine I would Fully port your WP S/R torker heads and mill them to 68-69cc chamber volume. They respond very well to this.

Point well taken :thumbup: The S/R 76cc heads i bought could only be milled a total of .021 which was on the spread sheet that came with the heads. I had them milled .007 because they needed cleaned up, yes they where whorped. So if i do anything i'll just get another set of bare castings with 67cc chambers, and have them ported.

If you are going to spend the money to get another set of heads get a head that flows the numbers you want. You can mill a S/R head down to the intake valve seat edge and or the spark plug hole boss. Which ever comes first. That is the physical flat mill limit. Should be able to get to 69cc with that.

"and have them ported" Porting S/R cast iron heads is time consuming and labour cost prohibitive.

These heads, like most stock heads are not worth paying someone else to port them. Its a do it your self thing or else its just not cost effective.
Unless you do the porting yourself and pay some one just whats required to finish them up with required machine work, its cheaper and more cost effective to just buy a aftermarket head that flows the numbers you want.

:thumbup: Point well taken :thumbup: I probebly could mill them, more than what they are, but i plan to leave it alone for now. Maybe in the not so distent future, i'll be able to land a set of alluminum heads and i'll go from there. :thumbup: