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Debbie Harris's 1969 Grand Prix

2022 September
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1971 455 Block


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You'll probably want to elaborate more, post pictures maybe of what you mean, etc... right now this is very vague and you probably won't receive the answer you want ;)


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I have a 1971 455 block, YG code, when I removed the heads I see a stamp at the top of block next to the piston chamber. stamp "M" on most cylinders but there is a "P" and a "S".

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Here are some pics. I bought this motor a few years ago with good intentions of doing a motor swap. Things are too demanding currently for me, especially time and money. I want to put this in someone's hands that will do something with it as it will just sit in my garage forever.

post-1938-0-55753400-1383506746_thumb.jp

post-1938-0-85215900-1383506766_thumb.jp

post-1938-0-53794100-1383506794_thumb.jp

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455 block,early year which means better metals.i just sold a couple blocks a 74 and a 73 one bare No crank,the other was block crank pistons (original) i got 800 for the both as a package deal.Put it on CL start at 1500.00? do you have a complete asm?


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I have the entire bottom assembly, it has .30 over aluminum pistons, I have a set of 6x heads with it. Block and heads were hot tanked and pressure checked for cracks, all good. 2 valve seats were installed in one head. Comes with a Edlbrock street dominator intake and old holley 750 double pump. I have another set of heads #15 stock with lalves and springs.

I will not be doing anything with it so someone else should.

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The stamped letters next to each bore represent the correct piston to be installed at the factory. It was my 1st job with Pontiac Motors! New pistons come down and the ears on factory pistons need adjusting. After adjusting it falls into a letter catagory, M-S ect. They are then loaded into stock bins and sent to the assembly line. I also "STUCK" pistons in the blocks on the assembly line. Each bore in the block is done at the same time with 1 machine. But the machine has 8 different bits = 8 slightly different bores. Measured N stamped on the block. The Block is read, and that person grabs the correct piston for each bore. They would then insert bearings and hang on the engine rack each correct piston above the correct bore. I would then grab the 1st piston, align The notch in factory pistons (points to the front of the engine) and insert guide, drop through ring compressor and insert into block with a sliding swing arm. Completing all 4 pistons on my side of the block, grab my guides and push my swing arm back to the starting point of my work area. (roughly 6ft of working space) 1 engine every 16 seconds. 10hrs a day, 7 days week. I've EARNED my stripes! FOREVER Pontiac........


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When he got behind the wheel with his heavy right foot. That's how he usually breaks his motors!!! LOL! :lol2:


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Seriously, stratman and JUSTA6 are spot on with the information they've given you. The date code D051 near the distributor shaft says when the block was cast, which was April 5th, 1971. So the motor was produced in the spring of 1971 - for use in either a late 1970 or an early 1971 model year vehicle.


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So when did you break in the engines..LOL

Never made it to engine test, 1st start up.

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