- Hello, I have a 1964 1/2 with a 4 barrel carb 289. Its had work done to it but I'm not entirely sure what has been done, looks to have a new cam that's larger than stock, and has been bored out 6 thousandths of an inch. It also has a new edelbrock carb. After checking the compression I came up with a low of 170 and a high of 180 psi. I was wondering if this is normal compression for this engine. It also has a constant miss in one of the cylinders, and it doesnt go away even at higher rpms. I've tried adjusting the timing and carb idle screws but it hasn't changed, what could the problem be?