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Discussion Starter #1
Got some room in the garage finally and was looking at these again. They code to 75-79 Truck or Van 4bbls. Doing a little research lately I see some people call them Orange or Blue blocks with the Orange being stronger. Don't know if there's any truth to that? I also read a Machinist say that his machine boring tool (Whatever it is they use, I'm not an Automotive Machinist) dulls quicker when boring out 509's compared to other blocks. I believe the 010 stamp is 1% higher Nickel content, not sure what the other numbers/letters mean if anything.
 

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The high nickel content deal with the 010 marking is a myth.

The only blocks that GM ever made/sold with high nickel or tin content were aftermarket "Bowtie" blocks. They are not hard to machine either.
 

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Discussion Starter #3
Might very well be. Don't know for sure never had a block tested. Have heard it for years and seen people for or against it. Vizard has a few paragraphs in "How to Build Max Performance Chevy Small Blocks" on the "desirable" 010 or 020 blocks. Would be interesting to know where he got his info. Can't say I haven't had my doubts. I was never on the hunt for one but both these 400 rebuilders I bought and also the 350 in my Nova have the 010 stampings. My luck isn't good enough just to keep stumbling across these "desirable" blocks. Curious as to what the 010 denotes as it seems to be the only common denominator of all the casting numbers under the timing cover.
 

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The last discussion I read about the marks under the timing cover was that they were casting mold numbers used to ensure that the right molds were used together. It was nearly impossible for the mold makers to know which blocks were to get a "higher tin or nickel" metal batch if there even was one. Chevy engineers and bean counters were not going to use any more of any metal that was absolutely not necessary due to the fact that they were producing millions of these blocks.
 

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I doubt there is any difference in strength but the "orange" blocks were indeed heavier castings. The "Blue" blocks were later and GM was able to fine tune their castings with a lot less metal. Probably as much as 5 pounds lighter. That's a lot less money spent on iron. I used to always debur the blocks before assembly for looks and to remove all the sharp corners that cut hands and the later blocks took half the time.
 

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Discussion Starter #6
The last discussion I read about the marks under the timing cover was that they were casting mold numbers used to ensure that the right molds were used together.
Seems more reasonable than the 010/020 - high nickel/tin theory.

Good info guys.
 

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Seems more reasonable than the 010/020 - high nickel/tin theory.

Good info guys.
Yea, the casting numbers inside the timing cover mean nothing to me. I've never seen a solid theory on what they mean, or any evidence of a certain set of numbers being meaningful in any way.
My best guess, based on experience with various other casting operations, would be that they're nothing more than revision numbers. (And they may not even be design/engineering revisions - it could just be a mold revision for a different piece of casting equipment, or a new set of molds with no engineering revisions.)

I look at block casting numbers and VIN pad application/suffix codes. Pretty much everything else is unreliable, other than the physical properties of the block (bore, journal size, etc.).


Random data points:
I'm down to two SBCs. The one in the Nova, an '86 350 block, has only "GM" under the timing cover. I've seen this stated many times as ABSOLUTE FACT that it means it was a 'service engine' (dealer replacement). However, the block is VIN-matched to the original vehicle that I pulled it from - which I owned and knew the full history.

The 400 block (511 casting, two bolt main) sitting on the engine stand has "GM" near the crank and "6" half way up on the left side under the timing cover (right side when facing the block). That's it.
Yet again, I've seen the 511 two-bolt blocks cited as absolute fact that they were 'service engines'. But this block's history is known, with only three owners (including myself); and is VIN-matched to the original truck that was purchased new (a '72 K20) and driven for 25 years before the engine got some 'bolt-ons' and a cam, and went into the owner's Studebaker pickup.
 

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Some of the 010/020 blocks did have stronger modular iron main caps that were better. Off the top of my head, I don't remember what the casting numbers were on the caps but I think they were 2482 or 2982 or 2981( don't remember) castings and have a "N" on them.

I've never put to much focus on the blocks as I have seen plenty of cheap 2 bolt blocks live reliably at 500 HP and 4 bolt blocks up around 1000 hp properly assembled with the right parts and machining.

Personally, anything over 650 or so I'd be going to a Dart block or something equivalent where you know exactly what you are getting. I have 2 small blocks, a 400 based motor that makes well over 550 N/A and has had a 250 squeeze on it as well and in my storage a 454 small block unfinished tt project using a GM Rocket Block. The aftermarket blocks are night and day but not worth it unless you are really trying to max out your performance and wallet.
 

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We never put any stock in any of those numbers when I was at the machine shop. We went by the block casting number. The small blocks were either 4 bolts or not, pre 75 for wall thickness, and the hecho en mexico blocks. That was pretty much the deciding factors of what would be done. Otherwise, 010 or any other codes meant nothing. Even the big blocks, certain casting numbers were found to have better casting characteristics such as core shift or wall thickness.
 

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Discussion Starter #11
Interesting. He does say that WAS the original plan with those numbers but then they realized that the blocks couldn't be tracked. He also says that they did change the casting part number to correspond with the metallurgical content on pre 71 blocks. It is hard to see how Vizard. Jenkins, Mortec, Chevy DIY and other numerous people/sites claimed this to be true all off somebody making up this "myth" years ago. Either way not too concerned about it just find the history of stuff like this interesting. I just did what Ray said on my last motor. Had it sonic tested, the walls were think enough for the next bore size up and went with it. Didn't really pay much attention to those numbers.
 

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Discussion Starter #12
Some of the 010/020 blocks did have stronger modular iron main caps that were better. Off the top of my head, I don't remember what the casting numbers were on the caps but I think they were 2482 or 2982 or 2981( don't remember) castings and have a "N" on them.

I've never put to much focus on the blocks as I have seen plenty of cheap 2 bolt blocks live reliably at 500 HP and 4 bolt blocks up around 1000 hp properly assembled with the right parts and machining.

Personally, anything over 650 or so I'd be going to a Dart block or something equivalent where you know exactly what you are getting. I have 2 small blocks, a 400 based motor that makes well over 550 N/A and has had a 250 squeeze on it as well and in my storage a 454 small block unfinished tt project using a GM Rocket Block. The aftermarket blocks are night and day but not worth it unless you are really trying to max out your performance and wallet.
Yeah, originally I bought those to pick the best one and build a drag motor. Current thinking is just go with a Dart block when I get around to building one. I figure it will take at least 600hp to get where I'd wanna be. After sonic testing, studs or caps and all the machine work I'd be over halfway to the Dart block already. Sell one 509 to put towards the Dart and keep the other if I ever want a 406 build for my Nova. Who knows, The best laid plans.....
 

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I picked this one up and we always looked for the 509 two bolt castings. I have had a 511 2 bolt which was a replacement 511 as originals were 4 bolts. This one I mic'd it at .004"-.005" wear and am gonna order some .020" pistons for it. I just bought a Scat forged crank and their profiled I-beams with the 7/16" cap screws, King bearings, Pioneer SFI flexplate, timing chain, balancer, etc.. Those rods are 6", but I'm running the same in a 5.7" and they clear up to a 3.800 stroke crank so no small base circle cam needed. I run a .600" standard base circle in my 383 with the same rods.
 

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My buddy built his with the stock two bolt block and hammered on it with a 250 hp of nitrous and he drove it street/strip for a few years. It typically ran some 9.40's in the quarter, but had ran a little faster under ideal conditions. It was in his Chevy Luv truck which he probably had about 6 of those.
 

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Discussion Starter #15
Nice! I see the block has an 010 WR stamp. Whatever the H the means.:D I put a bore gage on mine and got .004"-.005" on one and .002"-.003" on the other. Was surprised to see how little wear. I was checking out some of those Scat R.A.'s with the 6" rods the other day. Post some pics when you start putting it together. I can pick up some tips on these 406 builds.:)
 

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I have one of the "Holy Grail" 010/020 truck 4 bolt blocks. Every bit of information I have found is the "010/020" signifies them as the CORE set that is used when that block is cast. Historically the 010/020 cores have displayed less shift when casting.
 

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to the original poster : the block you show has way too much core shift for any performance use,In my humble opinion , a Grenade :yes: don't waste your time or money.
 

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Nice! I see the block has an 010 WR stamp. Whatever the H the means.:D I put a bore gage on mine and got .004"-.005" on one and .002"-.003" on the other. Was surprised to see how little wear. I was checking out some of those Scat R.A.'s with the 6" rods the other day. Post some pics when you start putting it together. I can pick up some tips on these 406 builds.:)
3 Novas back I did the 6" rod in the 406 I built it. Had to bump the oil pan rail in 3 places if I remember right and all the bottoms of the cylinders, but I used Eagle H beam rods. These I beam Scat should do better, but you never know. I just dirty one rod and piston running it down thru both sides, clearancing, vacuuming shavings out one at a time, then when thru pull the crank and clean everything real good. I didn't have to clearance any oil pan rails with any of my last 3 383's using the Scat I beams, only the bottom of the cylinders.
 

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to the original poster : the block you show has way too much core shift for any performance use,In my humble opinion , a Grenade :yes: don't waste your time or money.
How do you identify core shift visually? I thought only sonic testing was the only way to tell.
 

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How do you identify core shift visually? I thought only sonic testing was the only way to tell.
From what I have always understood the quick and dirty visual is the centering of the cam shaft. Who's to say, the cam boss could not be perfect. The picture does show a considerable amount of what could be shift. You are correct, in order to get the full story you would need sonic testing to determine wall thicknesses of the cylinders walls in relation to the water jackets.
 
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