Thanks for the info. Nope, not planning on anything other than a great production engine rebuild. But as conversations at the cruise in (or at the bar) usually go, there's a lot of know-it-alls. The horsepower from the 400 over the years varies greatly. You want 335 hp? You want 180 hp? All can be done with a build up of a basic 400 block. Obviously, this is due to all parts of the engine so I'm trying to nail down what the crank contributes to the that variance. Do all 400 cranks have the same throw? Are there other design variances in the crank that would affect performance (not just strength)? Or all 400 cranks the exact same except for materials or production process?
They are all basically the same and depending in year, can have a different metal composition with some claiming to be a better material than others when used for hi-performance applications - meaning HP you are probably not going to see on the street.
The stroke & dimensions are all the same, 3.75" stroke to include the 389, 350, and 400. Not all will have the hole drilled at the rear of the crank for the use of a pilot bushing when using a manual transmission - seems this would be some of the later 1970's cranks. Most do, but a few did not, so something to check if using a manual transmission. And as bigD
pointed out, the flywheel register where the flywheel bolts on can be different with some of the mid-to-late 1970's cranks.
I have read that the snout on the 389CI cranks are a bit shorter, but never personally confirmed this. It does appear they are shorter on the earlier 1963 and older cranks. Many will upgrade the 1964-1966 389 to the later and more available 11 bolt timing cover and water pump which would indicate these years having the same snout length as the 400CI.
I have read that the 350 crank is lighter than the 400 crank. Again, never confirmed this and if it were lighter, then I would think many Pontiac builders would be jumping all over the 350 cranks as the 350 engines go for peanuts and are often just junked because no one wants them. So may be another Pontiac arm chair myth.
Most all Pontiac cranks are cast. Forged are found in the the early Pontiac's of 1955- 58, Super Duty engines, and Ram Air V. Forged cranks are also heavier than cast.
Armasteel cranks are said to be the better cranks for high HP drag engines. Found in the 1964-1966 389 engines. I found this reference, "Armasteel cranks were Pearlitic Malleable Iron (PMI), with enhancements, are not drop cast poured, but are centrifugal spin cast. Armasteel is less prone to cracking and pounding damage from detonation, not much, but a little more, and is more dense in its basic structure. After the main casting process is done and the basic machining is completed, the fillet radius and main/rod journals are rolled in a hydraulic former, to make those areas stronger (about 10 to 15 percent stronger) than either drop cast or machined areas of the cranks."
Next is the Nodular Iron cranks produced in the 350/400 CI in the 1960's. The Ram Air engines are said to use a crank with .001" more clearance than standard cranks.
The Nodular cranks are good cranks up to about 1976 when they are not as desireable with thinner counter weights.
Check out this chart - Wallace Racing - Crankshaft numbers
So don't listen to the arm chair engine builders who are the experts on Pontiac engines and crankshafts. Pontiac cranks are some of the best in the industry.