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Thread: 425 block 455 guts

  1. #1
    biggraypig
    I have a 455 olds with a cracked block. Does anyone know if I can use a 67 olds 425 block for a rebuild of the 455?
    Thank you

  2. #2

  3. #3
    biggraypig
    I have decided to build the 425 instead.
    Does anybody know a good place to buy an engine kit?
    Thanks

  4. #4
    ghittner
    Yup, these are the guys. When I build my Toronado 425, this is where I'll go!
    http://www.mondellotwister.com/

  5. #5
    LakesOnly
    I have a 455 olds with a cracked block. Does anyone know if I can use a 67 olds 425 block for a rebuild of the 455?
    Thank youThe 425 and 455 Oldsmobile blocks are identical all the way down to the factory boresize.
    The 425 Olds all came with a beautiful forged crankshaft. If you have not yet seen one of these cranks, you will love looking at it. I think you should use the 425 crank, absolutely. By the way, they have huge rod journals and you can offset stroke these Olds 425 crankshafts and have a nice forged stroker crank. Aftermarket piston/rod combos will need to be figured out by you, then stroke the crank accordingly. By the way, I'd recommend using fully-grooved bearings in your Olds boat motor so as to establish continuous oil feed to the rod bearings.
    LO
    p.s.: All 455 Ols cranks are cast. Supposedly, some say there were 30-40 forged 455 cranks out there, but this seems to be a mythical motor of sorts....

  6. #6
    biggraypig
    I do like the steel forged crank, and it is how you say beautiful. I have decided to build the 425 instead.
    Could I Use any of the 455 parts that I already have to build the 425?
    Thanks for all the input.

  7. #7
    SmokinLowriderSS
    Since the block is the same:
    Heads, Intake, Exhaust, Distributor, etc, etc, etc.

  8. #8
    uselessgrant
    go to oldsfaq gives all specs and even casting numbers. your questions will be ansewered.

  9. #9
    Senior Member
    Join Date
    Feb 2009
    Posts
    2,626
    Couple things to watch out for.
    The 425 lifter bores are machined at a different angle than the 455 lifter bores. This requires the use of a 425-specific cam. Using an off the shelf 455 cam will not work.
    The crankshaft flange bolt pattern is different on the 425. The 455 PTO will not work. Looks like Glenwood Marine still has a 425 PTO in their catalog.

  10. #10
    oldselmn8tr
    I was told the lifter bore angles were different in my 67 425 when I called edelbrock for my cam and they said they didn't make a cam for it, I then called Engle cams and he said that was b.s. and shipped me cam and lifters. Worked great and no probs. So I am not sure if some did and some didn't or??? I do know I like my 425 and it screams for an Old's motor. The crank flange bolt pattern is definately different.

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