So what is the difference between a pontiac 400 and 455, bore or stroke or both?

 

455
Engine Code WT, WW, ZZ, ZE
Engine RPO L75
Displacement 455 CID
Bore x Stroke 4.1522" x 4.121"
Compression Ratio 7.6:1
Horsepower @ RPM 200@4000
Torque (Lb/Ft) @ RPM 330@2800
Head Casting 7F6

Carburetor 4-bbl
Carburetor - Federal 7043273


Camshaft
Part #
Lift, I/E NA / NA
Rocker Arm Ratio 1.5:1
Duration I/E - Degrees NA / NA
Overlap - Degrees NA
Intake Valve Dia - 2.11"
Exhaust Valve - Dia 1.66"

400
Engine Code WT
Engine RPO L78
Displacement 400 CID
Bore x Stroke 4.1212" x 3.750"
Compression Ratio 7.6:1
Horsepower @ RPM 185@3600
Torque (Lb/Ft) @ RPM 310@1600
Head Casting 5C

Carburetor 4-bbl
Carburetor - Federal 7045263
Intake Manifold 495106

Camshaft
Part #
Lift, I/E .377 / .415
Rocker Arm Ratio 1.5:1
Duration I/E - Degrees 269 / 282
Overlap - Degrees 59
Intake Valve Dia - 2.11"
Exhaust Valve - Dia 1.66"

 

you can stroke a 400 to 455.. so not much

 

you can take a 400, bore it .030 and use a 455 strock crank

 

Both. But you can't just drop-in a 455 crank, they have a larger main journal size than the 400. Go check out "pontiacdude.cc" lots of cool pontiac build-up stuff.

 

I meant to say 455 stroke crank, I knew the mains were different