i opened up the 351 trying to see what i am looking at,

everything inside looks brand new except the tops of the pistons(carbon build up)

down side looks like allready bored 40 over, and the weird thing is i have never seen a piston shaped like this see pic

is this a standard cutout for a 351 piston?


see how shiney new the side looks, like it just came out of casting is this normal for a 5000 mile motor?

 

that looks like the top of the pistons that came with my 351w out of a 84 f250. i replaced them with flat top pistons.

 

Those are dished pistons used to lower compression. The sides should stay shinney for the whole life of the motor.

 

but basically low compression naturally aspirated means loss in power correct? versus if i have just notched or flat top pistons,

 

yes

 

Higher compression can make more power from better thermal efficiency, you can also run a larger cam. You need to have an engine that'll run with the fuel you have available though. Many of the newer n/a EFI engines are running 10.0-11.0:1, some as high as 11.5....but I'm sure the knock sensor triggers frequently at low rpm.

 

i will probobally get some flat 9.6-1 pistons these are a 7.6-1 cr

 

7.6:1 is great compresion......for running 18psi of boost on pump fuel.[&:]

 

You must consider the heads you are going to run in conjunction with your pistons.

We are running dished pistons (-15cc) with 60cc chamber heads on the 408 to come up with a little more than 11 to 1 CR..

Head gasket thickness and piston deck heightare CR factors as well,,,, these will both tend to lower it a little..