I have two stock crankshafts. One is a 1970 model with about a raised 1-inch tall character “N” cast into it, and the other is a 1976 model with no “N”. Is there any significant difference in the strength or durability of these two cranks? I remember a number of discussions about whether or not the presence of the “N” meant “nodular” cast iron and the absence of it meant “regular” cast iron (which implied that castings with the “N” are better, stronger, etc. than those without it). Other discussions centered on whether or not the marking was simply used to identify the manufacturer. To my knowledge, all else being equal, the general concensus is the presence or absence of the “N” does not indicate that one crank is any better than the other one. True or false? Thanks in advance,
From the Dennis Manner seminar at the BPG Nats and referenced from buickperformance.com Buick cranks with "N" cast onto the first counterweight are exactly the same as ones without the N. The reason for the N designation was for cranks cast at the Defiance OH plant. Previously, all Buick engine parts/blocks/heads were cast in Flint by Buick
I don't want to confuse my GM divisions, but the Oldsmobile cranks with an "N" or a "CN" are made from nodular iron instead of plain iron. A definate quality advantage. Why would a plant in Defiance, Ohio, put an "N" into a crankshaft? I mean, wouldn't it have made more sense to use a "D" for Defiance, or an "O" for Ohio, or maybe an "NF" for Not Flint? I'm not disclaiming your information, it just doesn't make much sense to me at this point?
I think it has something to do with the fact that the Ohio plant produced both nodular and normal crankshafts and put an N on the former to identify them so the weaker cranks weren't mistakingly sent out with the nodular ones.
Regarding Steve's comment ("I think it has something to do with the fact that the Ohio plant produced both nodular and normal crankshafts and put an N on the former to identify them so the weaker cranks weren't mistakingly sent out with the nodular ones."): That that could imply that the Ohio plant produced both normal and nodular Buick 350 and 455 crankshafts, which I believe is not the case... for a few of reasons: 1 - Dennis Manner's statement indicating that all 455 cranks were nodular cast iron. Since he was a powertrain Engineer on the Buick big block project, he should know. 2 - Even though the American automobile industry was entering sort of a dark ages in the '70's, and quality suffered as a result, it seems illogical that they would reduce the strength of their crankshafts... especially when they apparently improved the strength of the 350 rods (capscrews) and 455 block (higher nickle content). 3 - Although I'm not an expert in the field, I doubt that anyone other than the Buick division of GM would be purchasing Buick cranks, especially substandard ones. I doubt, for instance, that some automotive aftermarket company was producing cheap rebuild kits for those engines. Maybe so, though. Anybody know of any? Anyway, that's my opinion (and yes, I know what they say about opinions being like a certain body opening). Another point: Over the past few years I believe both Jim Burek and Mike Tomaszewski have stated that the cranks are the same, regardless of whether or not they a marked with an "N". I guess the only way to know for sure is to cut a chunk out of each type of crank (i.e., one with an "N" and one without), take them into the appropriate test lab and ask them to determine whether or not the chunks are nodular (ductile) iron. Any takers?
Dan, I never thought it meant that they produced nodular and non-nodular Buick 455 cranks. The 350 cranks I have no idea about what it is produced from. Just that the plant produced cranks for other divisions and that was the current standard of identification for the other divisions. Also possibly it was the plant standard to denote nodular cranks with the "N" no matter if it was the only way they were produced where as Flint saw different. If Dennis, Mike and Jim say they were all nodular then that is good enough for me.
No big deal, Greg. My interpretation of your comment probably was a pretty long "reach", but I figured that if I was able to read that into it, then maybe someone else would, too. This subject comes up enough that I recently felt compelled to ask Jim Burek about it (again). Luckily, he's a patient man. I made reference to Buick 350 cranks because there's a thread about an "N" on some of them over on the 350 engine section of this board. I guess the only way to resolve this question once and for all is to sacrafice a couple of Buick crankshafts to some metallurgical lab for testing, and post the results on every Buick-related website in existence. All we need is two scrap crankshafts, a testing lab and a handful of money.
My opinion It was just a way for GM to identify the manufacting location. N for in house, nothing means outside vendor, or the other way around. Either way, that would be a big waste of money to test that because all the racers would already know by now which was weaker. :Brow:
