455 Block Choice Problem

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Old Aug 2, 2015 | 10:57 AM
  #1  
bostonstenthman@gmail.com's Avatar
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455 Block Choice Problem

I recently purchased 2x 455 blocks from a guy. They were both advertised as 1970 blocks, but one is clearly a 75' from the stamping and the other has no stamping on the driver side, but it is an F block with an F2 in the back. I have read a lot of information saying earlier blocks were stronger with more nickel, others say 68-76 were all about the same strength. My dilemma here is I need to decide which one to build up for my Cutlass. The 75' block is a bare block and in a bit better shape. The F block has the crank and pistons, but the top/drivers side trans bolt hole has been broken off. It doesn't look like it would be difficult to fix at a machine shop, but I'm not sure if it would be worth fixing over using the 75' block and the internals of the other. Any help on the subject would be greatly appreciated as I have never used a machine shop or attempted to build an engine up from the block. My goal for the engine is to make 350-400HP and around 450ft/lbs of torque. I am not trying to build an all out race engine. If the 75' block will hold up fine with occasional torture, but overall cruising and street driving then I'll probably just go with that one and save the F block for a future project. Thank you again for any and all advice.

Last edited by bostonstenthman@gmail.com; Aug 2, 2015 at 11:06 AM. Reason: Need to add a photo
Old Aug 2, 2015 | 11:10 AM
  #2  
bostonstenthman@gmail.com's Avatar
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Here is a picture of the damaged block. It looks like it could be repaired, but I don't know for sure.
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Old Aug 2, 2015 | 11:21 AM
  #3  
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As far as I know, the blocks are equivalent - that nickel content thing has been discussed at length and seems to be an Olds myth. For the build you are proposing the 75 block would work fine.
Old Aug 2, 2015 | 11:40 AM
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Backstrom's Avatar
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x2 on the '75 block.
Old Aug 2, 2015 | 12:27 PM
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wr1970's Avatar
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X 3 on 75 block.
Old Aug 2, 2015 | 12:37 PM
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jfb
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I use a 396021f block for hard usage and had 0 problems if yours is that casting go for it. 68 to 76 I believe was the dates for it. I would go maximum .060 overbore measure it by yourself or have the machine shop do it.
Old Aug 2, 2015 | 01:17 PM
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X4 on the '75 block.
It's been my experience that the later blocks are every bit as strong as the earlier ones. in fact I have every block sonic checked and typically the later ones have cyl walls that are very bit as thick, or thicker as the earlier ones.

Good luck.
Old Aug 2, 2015 | 01:25 PM
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cutlass fi I agree the blocks are one area we were blessed with for durability and most engines were ***** footed before hand so carnage was kept to a minimum and left many still around for rebuilding.
Old Aug 2, 2015 | 06:41 PM
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bostonstenthman@gmail.com's Avatar
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Thanks for all the help guys, I think I'll go with the 75' block then and have the machine shop check it out. Is the other block repairable do you think or is it an anchor now because of where that bolt hole was cracked off? I don't plan on scrapping it, but would like to know if it is worth a future build. Thanks.
Old Aug 2, 2015 | 07:44 PM
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Originally Posted by bostonstenthman@gmail.com
Thanks for all the help guys, I think I'll go with the 75' block then and have the machine shop check it out. Is the other block repairable do you think or is it an anchor now because of where that bolt hole was cracked off? I don't plan on scrapping it, but would like to know if it is worth a future build. Thanks.
Fixable, useable, Yes. I don't know if i would use it for a race eng.For a regular street car why not. You could use it just the way it is if you wanted.Not talking about a performance build for the street just a regular A B car engine.
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