What is the cylinder compression supposed to read on a 83 5.0 GT?

 

i believe 9.0:1

 

A stock 5.0 usually hits around 150-160 in prime form. You don't want a more than a 10% difference and you want at the very least 110psi - and thats a worn one.

 

typicals around 135-145 correct? all 8 should be very close to each other

 

should be higher than that... my 7.8:1 compression probe made 140psi

 

I'll bet your Probe had a lot less overlap on the camshaft too. That has an effect on cranking pressure.
Back when, when I raced a 10.70 440 Dodge Challenger, the best combo I ever had in the car only made 110# without any wear either........
BTW, the engine had a true 11 compression ratio.......

 

i believe its 8.5:1

 

good point... didnt think of that

 

I am talking about a compression test, not the ratio.I am working on a 83 GT with a 5.0 HO carb motor that is going into a comet. we were trying to get an idea on the shape of the motor and the test yielded between 123 and 130 on all the cylinders. If its supposed to be around 150 then it looks like we are going to bore and hone the cylinders with the rebuild.

 

I'm pretty sure your right. I have an 83 gt motor at my house, it checked out at 120-125psi all the way around during a compression test. The heads are 69cc stock btw and with a set of aftermarket heads the compression will go up greatly.