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Got lucky this weekend, Part 2

Discussion in 'The Garage' started by madmike, Mar 3, 2003.

  1. madmike

    madmike 1/2 ton status

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    OK, now that I know my 305 will not be of this earth much longer (see Part 1), I decided to tear down my 402 bbc, to see just exactly what I'm dealing with as far as rebuilding goes. This engine was driven daily in my '80 Chevy winter beater till about three years ago when I parked it on my Dad's farm. The engine had been swapped in by a previous owner, so I didn't know anything about it, except that it ran, didn't knock, did smoke and leak oil, and had dismal power for a big block.

    Things went pretty well. All of the bores looked good, no damage, and only a slight ridge at the top. The bore measured 4.125", so it was definitely a factory 402, not a 396. Connecting rod bearings were all scored pretty badly, one rod had spun a bearing, and it looked like another one was ready to go. Some of the rod bolt threads were stretched, as if overtorqued, and every rod nut seemed to be tightened differently. The main bearings looked ok, except for one which was also scored. Some of the pistons had the oil control ring seized to the piston, which helped explain the smoking. Amazingly, this engine didn't knock, unless the headers drowned it out! The cam was severely pitted from metal fatigue and the surface hardness was gone. All of the lifters were dished on the bottom. Lucky huh?

    Now for the good part. The block casting number (3999289) indicated that it was a 1972-1979 454 block, even though it was only bored to 4.125 (402ci). At the bottom of the bores, the block was factory cast with clearance notches to run a 4.00" stroke crank, indicating it was meant to be finished as a 454ci. 402 blocks can be bored up to 4.25", but this block is already a 454 casting! 454's can be bored 0.060" over safely. I checked the head casting number (6272292), and it came up as 402 or 454 large oval port open chamber. /forums/images/graemlins/cool.gif

    It seems to me that I could build a 454 out of this engine by boring the block to 4.25" (std 454 bore) and installing a 4.00" stroke 454 crankshaft. A guy here at work even has a forged steel Eagle 454 crank in good condition he'll sell me for $300! /forums/images/graemlins/cool.gif

    I hope that 305 can hold together a few more months! /forums/images/graemlins/thumb.gif
     
  2. madmike

    madmike 1/2 ton status

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    OK,Maybe not so lucky... I called a few machine shops, told them I had a block casting number identifying it as a 454, and asked them if I bored it to 4.25 and used a 4.00 stroke crank, could I turn it into a 454? Both shops said no, you can't use the casting number towards the bellhousing alone, you also have to use the number stamped into the pad at the front of the head to correctly ID it. Both shops said my cylinder walls aren't thick enough to support that much boring.

    I still feel lucky though, big block power and all, so I'm still happy! /forums/images/graemlins/grin.gif
     

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