Butler Performance • Pontiac Tech
400 Compression Calculator
Static compression ratio & displacement for the Pontiac 400 block. Enter your build below — results update instantly.
Static Compression Ratio
10.5 : 1
Total Displacement
400 ci
Per-Cylinder Volume Breakdown
Swept volume819.3 cc
Chamber volume72.0 cc
Deck volume0.0 cc
Gasket volume8.7 cc
Piston volume+6.0 cc
Total clearance volume86.7 cc
8-cylinder Pontiac V8. This is a static (geometric) compression ratio for build planning. Verify chamber volume by cc’ing your actual heads and confirm deck height after machining. Questions on your combination? Ask a Butler Tech ›
400 Block — Cubic Inch Chart
Bore 3.75 4.00 4.21 4.25 4.50
Stock  4.120400427449453480
+.030  4.150406433456460487
+.035  4.155407434457461488
+.040  4.160408435458462489
+.060  4.180412439462467494
+.065  4.185413440463468495
Build Note • 1975–76 “557” Castings

When upgrading to a stroker kit in the 400 block, blocks with casting numbers ending in 557 should be limited to 4.000″ stroke and under 500 hp due to thinner main webbing. These can tend to break under the higher stress of a larger stroke.

Pontiac 400 557 casting block main webbing
Build Note • Early 1967 400 Cylinder Chamfer

Early 1967 400s may have a deep 389–421 style chamfer in the cylinder. If the chamfer is deeper than .250″, you may need a piston with a lowered top ring groove to keep from exposing the top ring at TDC. Butler offers a piston designed specifically for this block with lowered oil rings and an oil rail support.

Early 1967 Pontiac 400 deep cylinder chamfer
Building Your 400?
Dial in your compression with the right pistons, gaskets, and a matched rotating assembly.
Shop Pistons Shop Head Gaskets 400 Rotating Assemblies

400 Compression Calculator

Bore: (diameter)
Stroke:
Cylinder Head Volume:
Effective Dome Volume:
Butler Ross Flat Top 8cc
Deck Clearance:
Compressed Gasket Thickness: .040 is standard thickness
Number of Cylinders:
Compression Ratio :  
Total Displacement (in.3) :  

400 Block Cu In Chart

400 Block Stroke
Bore 3.75 4.00 4.21 4.25 4.50
Stock 4.120 400 427 449 453 480
+.030 4.150 406 433 456 460 487
+.035 4.155 407 434 457 461 488
+.040 4.160 408 435 458 462 489
+.060 4.180 412 439 462 467 494
+.065 4.185 413 440 463 468 495
1975-76 400 557 Casting numbers- When upgrading to a stroker kit in the 400 block, blocks with Casting Numbers ending in 557*** we recommend limiting to 4.000" Stroke and less than 500hp due to thinner main webbing. These can tend to break under higher stress from the larger stroke.

 

Early 1967 400's may have deep 389-421 style chamfer in the cylinder. If the cylinder chamfer is deeper than .250 you may need a piston that has a top ring groove that has been lowered to keep from exposing the top ring when the piston is as top dead center. We have designed a piston specifically for this block with lower oil rings and an oil rail support.