3782870 Iron Alloy

[Peter L.]

I was recently told that the iron used in Corvette 3783870 blocks was different (higher strength alloy) from the iron used in all other blocks. The person who told me said he did a lot of research and was very confident of his statement. Does any one know if there is any truth to this? THey made engines for all cars in the Flint plant, and I can't image that they had two different irons melts going in one plant, especially when they had no idea where any particular block would go while they were casting them.

[Kenneth B.]

Re: 3782870 Iron Alloy

I was recently told that the iron used in Corvette 3783870 blocks was different (higher strength alloy) from the iron used in all other blocks. The person who told me said he did a lot of research and was very confident of his statement. Does any one know if there is any truth to this? THey made engines for all cars in the Flint plant, and I can't image that they had two different irons melts going in one plant, especially when they had no idea where any particular block would go while they were casting them.

I don't know for sure but I beleave you are right that all blocks were cast from the same iron. the foundry would need to have furnaces to pour more than one kind of iron & why would they only cast 870 blocks from a different grade of iron. As far as I know they be the same class of gray iron.

[Clem Z.]

Re: 3782870 Iron Alloy

A block's alloy content is denoted by two figures cast into the front face, just above the main bearing bore, in the area normally concealed by the timing cover. Many production small blocks have the numbers "010," "020" or both cast into their front face, just above the main bearing bore. If both numbers are present, one above the other, it indicates that the block alloy contains 10% tin and 20% nickel. A single number, either a "010" or "020" represents the amount of nickel and indicates negligible amounts of tin.
No numbers, other than the casting numbers that are typically found beneath the timing cover, translates to only minor amounts of tin and nickel being present in the block alloy. (Tin and nickel are two metals that are commonly alloyed with cast iron to improve durability, hardness and heat dissipation)

[Joe L.]

Re: 3782870 Iron Alloy

I was recently told that the iron used in Corvette 3783870 blocks was different (higher strength alloy) from the iron used in all other blocks. The person who told me said he did a lot of research and was very confident of his statement. Does any one know if there is any truth to this? THey made engines for all cars in the Flint plant, and I can't image that they had two different irons melts going in one plant, especially when they had no idea where any particular block would go while they were casting them.

Peter-----


Virtually all Corvette small blocks were cast at the Saginaw Gray Iron Foundry and were therefore of gray iron material. At the time that the 3783870 blocks were being cast I don't think there were any different types of cast iron being poured at Saginaw. Certainly, there were not different types being used for Corvette and non-Corvette 3783870 blocks.

There were other types of stronger cast iron produced by GM foundries including malleable, nodular and ductile iron. However, none of these were used for cylinder block or head castings and none were produced at Saginaw Gray Iron.

The 3783870 blocks did use nodular iron main bearing caps but these were not cast at Saginaw Gray iron.

Beginning about 1969 there were supposedly some higher strength gray iron alloys used for some cylinder blocks including the 3970010 and, possibly, some others. However, I've never been able to confirm that even this is true.

[Bob J.]

Re: 3782870 Iron Alloy

A block's alloy content is denoted by two figures cast into the front face, just above the main bearing bore, in the area normally concealed by the timing cover. Many production small blocks have the numbers "010," "020" or both cast into their front face, just above the main bearing bore. If both numbers are present, one above the other, it indicates that the block alloy contains 10% tin and 20% nickel. A single number, either a "010" or "020" represents the amount of nickel and indicates negligible amounts of tin.
No numbers, other than the casting numbers that are typically found beneath the timing cover, translates to only minor amounts of tin and nickel being present in the block alloy. (Tin and nickel are two metals that are commonly alloyed with cast iron to improve durability, hardness and heat dissipation)

Its been rumored for years that EARLY 870 blocks had a higher nickel content.

[William C.]

Re: 3782870 Iron Alloy

When I was attending GMI in the '63-68 timeframe, had many classes with the "sand pounders from the foundries and the guys from Flint engine. Not a peep about special castings or anything special for engines other than the SHP models.

[Michael W.]

Re: 3782870 Iron Alloy

That's a new one- never heard that one before.

There's also an old myth and legend that blocks that have 010 and 020 under the timing chain cover are somehow special featuring increased percentages of tin and nickel. This, according to legend makes them 'better' and therefore more valuable.

Truth is that the 010 and 020 markings are nothing more than mold numbers for the front portion of the blocks that they were suitable for- the venerable 3970010 and 3970020 casting numbers used extensively in the 70s and 80s.

[Mike E.]

Re: 3782870 Iron Alloy

I'm having trouble sorting out posts #3 and post #7. Is it just me, or are they conflicting, and at the core of the decades-old debate?

[Clem Z.]

Re: 3782870 Iron Alloy

That's a new one- never heard that one before.

There's also an old myth and legend that blocks that have 010 and 020 under the timing chain cover are somehow special featuring increased percentages of tin and nickel. This, according to legend makes them 'better' and therefore more valuable.

Truth is that the 010 and 020 markings are nothing more than mold numbers for the front portion of the blocks that they were suitable for- the venerable 3970010 and 3970020 casting numbers used extensively in the 70s and 80s.

you can argue with this guy. http://www.enginebuildermag.com/Arti..._engines_.aspx

[John H.]

Re: 3782870 Iron Alloy

I'm having trouble sorting out posts #3 and post #7. Is it just me, or are they conflicting, and at the core of the decades-old debate?

Mike -

I have been at this one from both ends for many years, and there are strong opinions on both sides of the argument. In all those years, I've never found one single shred of Chevrolet information to support the "010-020" high tin-nickel theory, but there is clear logic from the foundry folks that the 010-020 identification in the timing cover area simply indicates a common pattern for that portion of the block shared between the 3970010 and 3970020 blocks. I'm not a foundry expert, but I know enough about it to believe there's no way on earth that a high-volume casting operation like the Saginaw Grey Iron Foundry would dedicate a single cupola and holding furnaces to a special iron alloy just for certain 3970010 blocks, which were cast continuously from 1969-1979. If there was any truth to it, Chevrolet would have documented it somewhere, and it would probably have been mentioned in the Colvin books, as Alan had complete access to all of the detailed engine engineering records.

[Stuart F.]

Re: 3782870 Iron Alloy

Back in the day, I read and was told by many that the finished blocks did go through a "grading" process designating the best as "A", then "B", and so on. The legend had it that the "A" blocks were assigned to Corvette applications and were therefore the most suitable for high (SHP) performance applications, and over boring, etc. Any truth to that one? I guess the concern was for core shift or consistancy of bore wall thickness or something like that.

Stu Fox

[William C.]

Re: 3782870 Iron Alloy

Refer to Jon Hinckley's post above. Saginaw was a HIGH VOLUME operation, as was the Flint Engine plant, and GM runs on PART NUMBERS. I saw Truckload after truckload of blocks coming down I-75 over the years, and they all got dumped into one pile and were run thru the same machining equipment. Never had anyone at school refer to any special processing/sorting/machining for Corvette applications.

[Clem Z.]

Re: 3782870 Iron Alloy

Mike -

I have been at this one from both ends for many years, and there are strong opinions on both sides of the argument. In all those years, I've never found one single shred of Chevrolet information to support the "010-020" high tin-nickel theory, but there is clear logic from the foundry folks that the 010-020 identification in the timing cover area simply indicates a common pattern for that portion of the block shared between the 3970010 and 3970020 blocks. I'm not a foundry expert, but I know enough about it to believe there's no way on earth that a high-volume casting operation like the Saginaw Grey Iron Foundry would dedicate a single cupola and holding furnaces to a special iron alloy just for certain 3970010 blocks, which were cast continuously from 1969-1979. If there was any truth to it, Chevrolet would have documented it somewhere, and it would probably have been mentioned in the Colvin books, as Alan had complete access to all of the detailed engine engineering records.

john we need one of these !! http://www.kemet.co.uk/product.asp?p...ness%20Testers

[Bill M.]

Re: 3782870 Iron Alloy

I was recently told that the iron used in Corvette 3783870 blocks was different (higher strength alloy) from the iron used in all other blocks. The person who told me said he did a lot of research and was very confident of his statement. Does any one know if there is any truth to this? THey made engines for all cars in the Flint plant, and I can't image that they had two different irons melts going in one plant, especially when they had no idea where any particular block would go while they were casting them.

It is possible. The raw iron would all be the same, but the alloys may be added to the iron in the ladle.

I watched different alloys being added to the molten iron at another casting supplier, not Chevrolet. They used significantly different iron for different parts.

[Kenneth B.]

Re: 3782870 Iron Alloy

Mike -

I have been at this one from both ends for many years, and there are strong opinions on both sides of the argument. In all those years, I've never found one single shred of Chevrolet information to support the "010-020" high tin-nickel theory, but there is clear logic from the foundry folks that the 010-020 identification in the timing cover area simply indicates a common pattern for that portion of the block shared between the 3970010 and 3970020 blocks. I'm not a foundry expert, but I know enough about it to believe there's no way on earth that a high-volume casting operation like the Saginaw Grey Iron Foundry would dedicate a single cupola and holding furnaces to a special iron alloy just for certain 3970010 blocks, which were cast continuously from 1969-1979. If there was any truth to it, Chevrolet would have documented it somewhere, and it would probably have been mentioned in the Colvin books, as Alan had complete access to all of the detailed engine engineering records.

You are right John. Most of the cores that make the block are common to more than one casting #. As I have said before most of the block is made from cores & not the pattern that has the casting #. As you say there is no reason to have a cupola & holding furnace to pour a small amount of blocks. Also many alloys require different gating systems than gray iron ie. ductile iron. I think we hashed this out a few years ago.