Pontiac Engine Size Technical

Pontiac Engine Sizes
Year Engine Size Bore Stroke Rod Ratio Crank Main Size Crank Rod Size Rod Length
1964-67 326 3.720 3.750 1.77 3.000 2.250 6.625
1968-77 350 3.875 3.750 1.77 3.000 2.250 6.625
1959-66 389 4.063 3.750 1.77 3.000 2.250 6.625
1963-66 421 4.063 4.000 1.66 3.250 2.250 6.625
1967-69 428 4.120 4.000 1.66 3.250 2.250 6.625
1967-79 400 4.120 3.750 1.77 3.000 2.250 6.625
1970-76 455 4.151 4.210 1.57 3.250 2.250 6.625

Additional "PURE PONTIAC" Stroker and Combos available

Engine Size Bore Stroke Rod Ratio Crank Main Size Crank Rod Size Rod Length
440 cu.in. 4.181 w/455
.030 Block/Pistons		 4.000 1.675 3.000/3.250 2.200 6.700
467/474 cu.in. 4.181/4.211 4.250 1.60 3.000 or
3.250		 2.200 6.800
477 cu.in. 4.223 (.060) 4.250 1.60 3.000/3.250 2.200 6.800
482 cu.in. 4.250
sonic check		 4.250 1.60 3.000/3.250 2.200 6.800
487 cu.in. 4.223 stock block
Ford FE bore size
rings available for this bore		 4.350
custom stroke
 1.58 3.000/3.250 2.200 6.800
495 cu.in 4.185 stock block
 4.500 1.49 3.000 2.200 6.700
501 cu.in. 4.211 (.060 455 stock block) 4.500
 1.49 3.000/3.250 2.100 6.700
488 cu.in. 4.223 stock block
Ford FE bore size
rings available for this bore		 4.350
custon stroke
 1.56 3.000/3.250 2.100 6.800
494 cu.in. 4.250 stock block
sonic check first		 4.350
custom stroke
 1.56 3.000/3.250 2.100 6.800
511 4.250 stock block
sonic check		 4.500
 **1.49 3.000/3.250 2.200 6.800
505 cu.in 4.350 IA Block
 4.250 1.6 3.000 2.200 6.800
511 cu.in. 4.375 IA Block
 4.250 1.6 3.00 2.200 6.800
517 cu.in 4.350 IA Block
 4.350
Custom stroke		 1.56 3.000 2.100 6.800
535 cu.in. 4.350 IA Block 4.500
 1.49 3.000 2.200 6.700
571 cu.in. 4.375 IA Block
 4.750
 1.41 3.000 2.200 6.700

** footnote..... Longer rods are available depending on application.



The above combo's can be run with a Big Block Chevy wrist pin diameter of .990 (Stock Pontiac is .980) for a better pin selection. The longer rods used are based on basic Big Block Chevy rod lengths also.
The Factory Pontiac 455 cranks are turned on the rod journals to a .040 positive offset to achieve the 4.250 and then use the new BBC rod diameter (2.200) bearings for fit.

The Factory and Cast aftermarket cranks can be offset ground for a SBC rod size of 2.100 for even greater cu.in. choices. The total rod side clearance is an additional .010 with a BBC rod.
I would recommend however keeping the rotating weights as light as possible to maintain less load on the lower weaker Pontiac block area.

This is a benefit to help oil exit the rods for better cooling with no drastic wear or side load noticeable.
These combo's can be run with a 455 block as well as the 400. You can cut the mains down on the 455 crank to fit the 400 block and use my main bearing conversion kit listed in the Part/Catalog section.
Keep in mind that there are dozens of combo's, but these are readily available with current cores and reasonable "Now available" aftermarket Cast & Steel cranks. Now available: Quality overseas H & I beam rods to keep cost down.