For many years hotrodders passed around the information that "010", "020", or both cast into the timing chain area and/or the rear bellhousing area of rhe SBC block meant "percentage of nickel", "high nickel block".
Fact was, it was all a myth...someone dreamed it up, a magazine hack(writer) glommed onto the "info", printed it in Hot Rod or Car Craft or some such magazine and spread the idea to the masses. From that it became the shade tree gospel.....a good old fashioned old mechanic's tale("old wive's tale").
Problem, was, it has no basis in truth....there is a big long thread over at the Speed-Talk web site, in the Engine Forum where a lot of top people in the performance industry hang and help out others and pass along info....that goes into great detail about it.
One set of info was from a former upper level shop employee at the GM Flint Engine Plant, where the blocks were cast. He explained exactly what those numbers mean....that they are just core plate identifiers for the casting mold...so that after the iron is poured and the mold sand is removed from the casting they would have a way of knowing exactly which mold pattern parts were in that mold...so if they have a run of blocks with a problem, they have a reference to the mold parts/patterns used, for QC tracing to locate the problem.
Second big thing posted was a metallurgist took up the task of gathering as many samples as he could reasonable test, even had others send him used block samples, so he could do an electron mocroscopy of what metals were in the cast Chevrolet blocks.(off the books, on his own time, stay after at work kind of thing)
Not a single stock block showed any more than a random trace of nickel, just what you'd see just from materials handling cross-contamination traces is all, less than a 1/10 of a percent..
Chevrolet never built a single SBC "high nickel block", not a single 1.
There were some very early 427BBC blocks, and of course the BBC and SBC Bowtie performance blocks made of a better grade of cast iron....but nickel stil isn't a noted alloy element in the mix.
The minite you add a measurable portion of nickel to cast iron...it becomes a steel, and is no longer iron.
The only thing special about any 70's 350 4 bolt main block will be if it had the 3 center caps with the numbers "2482" cast on them, these are nodular iron, rather than plain old grey cast iron like standard caps. These are factory HD caps.
The blocks are of course just plain grey iron, regardless of what caps are on it.
Sorry to burst your bubble, but that's the truth of it....
Yes many people look for the better caps. I had 3 blocks and not one had the better caps. HOWEVER, 40 years ago when these were being used as race engines they did just fine regardless of what they were. The internet has forgotten history of what and how stock stuff was used and made it now that you can’t build a high performance engine unless you have the top of the line stuff and a pot of gold.
Ericnova, thank you for posting that, it was a great read de-bunking what most of us thought was gospel regarding the "010 special high nickel blocks" lol. I admit I was taken as a sucker back in 1981 by a guy with a "special" 010 block, I'm sure I paid double what it was worth, then brought it to the machine shop with pistons to be bored, told the guy be careful because it's a special block, he looked at the poor young kid (me) with a strange look. But either to appease or be sarcastic he wrote "bore block .030....be careful because it's special" on the work order. I'm sure they were all laughing at me as soon as I left. Sometimes wish I was still that naive 15 year old kid again, life was much simpler.
Don't feel bad, I believed it too, up into the late 1990's until I was having a couple 400 SBC's with those "010""020" numbers on them and I mentioned "high nickel", my machinist told me he never noticed any real difference in how SBC blocks sounded as the boring bar cut them. Right about the same time I got a little more professional info from engineers and designers I was freinds with who worked for the Eaton Corp Proving Grounds near my hometown.
It started to really get confirmed as BS info when the Web took off and everyone could share info for all to see. The guy doing the Electon Microscopy finally put the nail in the coffin for everyone who wanted to search for the truth...
A lot of less serious guys and street rod types still beleive it though, because they heard it for so many years you just can't change their minds with the truth, they refuse to open their eyes to more recent facts.
Funny part about the whole thing was the next door neighbor of the guy that screwed me on the block had a 55 Chevy with a 4-sale sign, loved the car and didn't even have my learners permit yet. Convinced my dad to go over a week later with me and look at it, car was an arrow straight Cali car, 6 cyl ran but smoked, faded factory yellow paint but not a spot of rust anywhere. My dad loaned me the 1500.00 I paid for it, still own it to this day although looks nothing like it did when I bought her so maybe it was meant to be.