Pontiac Engine Size Technical

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
472/479 cu.in.	4.181/4.211	4.300 Dude crank	1.58	3.000 or 3.250	2.200	6.800
482 cu.in.	4.223	4.300 custom offset Dude crank	1.58	3.000/3.250	2.200	6.800
488	4.250 sonic check	4.300 Custom offset Dude crank	**1.58	3.000/3.250	2.200	6.800
484 cu.in.	4.211 (.060)	4.350 custom offset Dude crank	1.56	3.000/3.250	2.100	6.800
488 cu.in.	4.223 Ford FE bore size rings available for this bore	4.350 custom offset Dude crank	1.56	3.000/3.250	2.100	6.800
494 cu.in.	4.250 sonic check first	4.350 custom offset Dude crank	1.56	3.000/3.250	2.100	6.800
505 cu.in	4.350 IA Block Aftermarket	4.250	1.6	3.000	2.200	6.800
511 cu.in	4.350 IA Block Aftermarket	4.300 offset crank	1.58	3.000	2.200	6.800
517 cu.in	4.350 IA Block Aftermarket	4.350 Dude custom offset ground crank	1.56	3.000	2.100	6.800
511 cu.in.	4.375 IA Block max bore w/o full blockfill	4.250	1.6	3.00	2.200	6.800
541 cu.in.	4.375 IA Block	4.500 custom crank	**1.51	3.000	2.200	6.800
571 cu.in.	4.375 IA Tall Deck Block	4.750 custom crank	1.52	3.000	2.200	7.200

** footnote..... Longer rods are available custom made to increase the rod ratio for less main webbing and crank loads.

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 and H-beam rods to keep cost down.