'70 Toronado Engine
Trying to remember member
Joined: Oct 2005
Posts: 4,112
From: Ohio
I had a place in Tennessee do that in 1998,with 5 random blocks.A 68 F3 block,69 F1 block,70 F5 block,71 F4 block,and a 72 F(no number) block.They all came out about the same.Nothing stood out more than the other.The 70 F5 block is what we used for the 507.After sonic testing all of the cylinders,that one had the least amount of core shift,and the thickest cylinders,but not substantially thicker,just the best choice to bore to 4.211".It did have a slight amount more nickel than the 69 F1,which was supposed to be the best,but again,the amount was so minimal,it wasn't worth getting excited about.
What I look at is the cylinders.If you look at the cylinders at the deck surface,you will notice that about 1/2" down from the deck,the cylinder steps in,or tapers,resulting on a thinner wall.I have seen blocks with more or less step,and some with no step at all,leaving a nice thick wall all the way down.I have found no relation to the F-number & the wall thickness either.The 70 F5 block was like this,and the 72 F(no number) was also like this.I have had others like this as well.I have also had some with no step on one side,and a step on the other.The block I am using for the 517 is of all things,a 1976 F6 block.Never would have thunk it,but it was real meaty,so the choice was made.I brought another 70 F2 block up with me,thinking it would be better,and it was good too,but not quite as much after the sonic check.
Conclusion: It's all random.
What I look at is the cylinders.If you look at the cylinders at the deck surface,you will notice that about 1/2" down from the deck,the cylinder steps in,or tapers,resulting on a thinner wall.I have seen blocks with more or less step,and some with no step at all,leaving a nice thick wall all the way down.I have found no relation to the F-number & the wall thickness either.The 70 F5 block was like this,and the 72 F(no number) was also like this.I have had others like this as well.I have also had some with no step on one side,and a step on the other.The block I am using for the 517 is of all things,a 1976 F6 block.Never would have thunk it,but it was real meaty,so the choice was made.I brought another 70 F2 block up with me,thinking it would be better,and it was good too,but not quite as much after the sonic check.
Conclusion: It's all random.
What we recently "discovered" (thanks to Brian Ehlers) is that the single digit number next to the distributor also "above" the ordinal date code is the "mold number" (I won't go into what exactly the "mold number" is here). Verified by
a 1970 document. Previously this single number was "widely believed to be" the number that denoted the year the block was made, starting with 1 being the first year the block was made. There *appeared* to be that kind of relationship (with good reason, as it turns out), but the point here is that the "year of the block" is *not correct*, and was nothing more than a good guess based on looking at a lot of blocks and trying to come to a conclusion.
Thread Starter
Registered Thread Killer
Joined: May 2011
Posts: 192
From: Wisconsin
Well, here it is. Fresh off the spectrometer.
0.08% Ni
3.05% C
2.29% Si
0.73% Mn
0.29% Cr
0.10% Cu
0.041% P
>0.12% S
Balance Fe
I'm no Metallurgist, but I imagine .08% is negligible.
0.08% Ni
3.05% C
2.29% Si
0.73% Mn
0.29% Cr
0.10% Cu
0.041% P
>0.12% S
Balance Fe
I'm no Metallurgist, but I imagine .08% is negligible.
Trying to remember member
Joined: Oct 2005
Posts: 4,112
From: Ohio
Please give me the block #. And the the date code and mold numbers (by the distributor) so I can add this to my database.
You can email them to me at wmachine@shubes.net
Yes, the nickel is negligible, but notice the chrome. That is not negligible, and is probably an add. That is too high to be incidental. And as I've said before, if they were going to add anything to an iron block, it would be chromium, not nickel.
Thanks again for stepping up. There are a lot of things that went on back then the we can't validate, but this nickel issue *isn't* one of them!
Administrator
Joined: Oct 2009
Posts: 42,386
From: Poteau, Ok
Damn, now I suppose your going to tell us there is no tooth fairy or santa clause! Good info here! I would be curios to know what the other gm blocks are made of!! I would also be curios to know how they compare to other manufacturers, ie ford, mopar, etc...
Thread Starter
Registered Thread Killer
Joined: May 2011
Posts: 192
From: Wisconsin
I had to check too,
[Some of the Gen.1 smallblock motors used blocks with an additional 1% tin and an additional 2% nickel added to the cast iron alloy. These desirable blocks can be identified by looking at the block face under the timing chain cover for "010" AND "020". These designators can also sometimes be found on the rear face of the block inside the perimeter of the bellhousing mating surface. ]
...But they can try to debunk that themselves.
[Some of the Gen.1 smallblock motors used blocks with an additional 1% tin and an additional 2% nickel added to the cast iron alloy. These desirable blocks can be identified by looking at the block face under the timing chain cover for "010" AND "020". These designators can also sometimes be found on the rear face of the block inside the perimeter of the bellhousing mating surface. ]
...But they can try to debunk that themselves.
Last edited by mfgusa; Sep 2, 2011 at 09:56 AM.
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