whats a good compression ratio that the stock bottom end of a 305 will hold? 10:1? i know that isnt the stock ratio, im waiting to shave my heads a lil and was wondering what gains id see, how much compression should i run...what gains would i see out of what compression ratio....i know its hard to tell....so lets guesstimate ... i have 416 castings ported and polished....

 

Each whole compression ratio gain will get you approx 4% increase in torque.

The compression limit will depend on the octane of the fuel you are using.

10:1 is about the practical limit for street gas. (92-94 octane)

What fuel are you going to use?

 

93 octance since i bought the car....my compression now just plat out sucks because my head gaskets are .450 heh

 

Did you use a sheet of 1/2" plywoood for a head gasket?
That would be around 4-5:1 compession ratio?

 

The overall cylinder pressure is going to be determined by not just the compression ratio but other factors like the cam timing. Generally speaking, you are looking for cranking pressures in the 160 lb to 180 lb. Much higher and your going to run into detonation with pump gas. Much lower and the motor will be soggy on the bottom end.

 

haha i ment .045 but yeah i have idle to 1500 rpm issues meaning i have like no power til i get up to 1500 then it throws you into the back of the seat....that prolly due to the porting and polishing i did...that and the 2500 stall...and its carbed.....and the 2.73s......

 

sounds like you got too big of a cam in it.. smaller cam the lesser the rpm range is for making power, but you max out quicker.. people with big cams can have such when they have a tranny built or a nice manual to keep the rpm high and make that cam come to life, for us poor poppers who can't afford a 3.73 posi rear, 700r4 rebuild with a stall, we must make power the only way we can when it comes to the cam.

2500 stall, that rear end with a auto tranny, your best bet for performance would be to get a cam closer to stock specs (if u have one already?)..

 

LT1 cam....i plan on gears soon though, thats why i have the 2500 stall