compression with 274cam

I would say about 9 to 1 and the 274 xe would do good ,that's what I had in my 340 with a 4 sp,3.91 .You are not gaining much hp upping the comp. ratio ,for a street car anyway compared to the problems ,pinging, more fuel cost per. gal.ect.Been down that road! 100 horse spray would be cheaper and more h.p.,more fun too! Herb McCandless mopar expert said in his sem. you don't need more than 8.5 -9.0 the very most to make power in a street motor !Get the cam that your heads will flow ,not much more. I had yrs. ago a 340 with the old H. E. 268-454 lift comp. cam that ran great with 3.23 's ! Excellent cam in a mild street 340! :D