85stangman

What are thecylinder compression for a stock 302 in lbs.

MrMiracle

A minimum of 101 psi. There's actually a chart that correlates a minimum and a maximum based on a pressure check.

paulstang

howdy bro

paulstang

Out of couriosity what should be the lowest for my cobra motor

85stangman

So running 110 - 120 per cylinder is normal. Thanks.

lxman1

They should all be within 10% of each other.

OneFastEclipse

I would say 110-120 would be a bit on the low side. Around 140-150 all within 10 of each other would be good numbers.

MrMiracle

I don't have a repair manual for the Cobra, sorry.

An engine with 9:1 compression, with perfect volumetric efficiency will yield a 132 psi pressure (ambient multiplied by compression). However, setup can really provide perfect VE. Pressure varies from day to day, and location to location. There's also a small amount of pressure loss to the rings as well.

110-120 falls within the specs of the Haynes chart. The point isn't necessarily to have the highest number, but the most balanced. The close readings on all cylinders means that the intake setup is providing roughly similar amounts of airflow to all cylinders, and that there isn't much loss in any one cylinder compared to any other. I'd say this engine in quite healthy in those terms.