As some of you may know, I need new heads.
So as part of the process of getting new heads, I decided to have my old heads cc to make sure I staying the 10.5:1 compression range with the new ones.
My current heads: 67 cc closed chamber.
All the heads I have evaluated to date.....63 or 61 cc chambers....that won't be to good I thought.
So on a whim I decided to investigate what my total compression really is....keep in mind it is suppose to be 10.5:1.
So I call up Speedomotovie who built my kit, they don't know.
So I call up Ross Racing you custom machined my pistons, they don't know unless I have a number.
So I call uo my machine shop and get the number.
Call back up ross, give them the number, and they pull the work order.
Ok.....Custom pistons.....etc etc....specs.....built for 10.5:1.....with a 78cc head.
A 78 CC head!!!!!!.....that's a 4v open head....I have 4v closed heads...and told the stoker manufacturer that I have 4v closed heads...but somehow they built it for open heads.
My current total compression 11.56:1
Ugh.
So now I am faced with a choice. Purchase a set of 4v closed with an even smaller combustion chamber (63cc) and ahve my nice pistons further modyfied to lower the compression, meaning I will also need the whole thing re-balanced, or go to 4v open heads and actually maintian my 10.5:1 compression which is what I wanted.
4v open heads are historically less pricey, but I have heard that they cost lotsa torque in the low end. Will this still be true since I have a piston designed for 10.5 with their chamber or will I get similiar performance from a 4v open with 10.5 as I would with a 4v closed with 10.5?
So as part of the process of getting new heads, I decided to have my old heads cc to make sure I staying the 10.5:1 compression range with the new ones.
My current heads: 67 cc closed chamber.
All the heads I have evaluated to date.....63 or 61 cc chambers....that won't be to good I thought.
So on a whim I decided to investigate what my total compression really is....keep in mind it is suppose to be 10.5:1.
So I call up Speedomotovie who built my kit, they don't know.
So I call up Ross Racing you custom machined my pistons, they don't know unless I have a number.
So I call uo my machine shop and get the number.
Call back up ross, give them the number, and they pull the work order.
Ok.....Custom pistons.....etc etc....specs.....built for 10.5:1.....with a 78cc head.
A 78 CC head!!!!!!.....that's a 4v open head....I have 4v closed heads...and told the stoker manufacturer that I have 4v closed heads...but somehow they built it for open heads.
My current total compression 11.56:1
Ugh.
So now I am faced with a choice. Purchase a set of 4v closed with an even smaller combustion chamber (63cc) and ahve my nice pistons further modyfied to lower the compression, meaning I will also need the whole thing re-balanced, or go to 4v open heads and actually maintian my 10.5:1 compression which is what I wanted.
4v open heads are historically less pricey, but I have heard that they cost lotsa torque in the low end. Will this still be true since I have a piston designed for 10.5 with their chamber or will I get similiar performance from a 4v open with 10.5 as I would with a 4v closed with 10.5?