SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: 2savage4you on August 22, 2007, 08:16:57 PM
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Will it fit? Is it gonna change my stroke? I found a new 425 crank and thinking about it if it fits. The 455 crank i have i think it needs to be turned. Any advice here?
2sav
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turn the "Olds" one ...maybe just a polishing will do it. It keeps everything simple and
cheap. :)
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Does the 425 have a shorter stroke than the 455, or are they the same?
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Does the 425 have a shorter stroke than the 455, or are they the same?
I dont know, Thats why im asking you guys. I found one cheap and brand new.
But im not gonna waste my $$ on chance it wont fit. Now if it gave me a shorter stroke i would have to change my rods. But then i could get more rpm's.
Hell i dont know.
2sav
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My Desktop Dyno doesn't even show a 425 ???
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My Desktop Dyno doesn't even show a 425 ???
Well it just hit $100 bucks and its climbing, so much for that idea. I will have mine turned instead .
2sav
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I dont know, Thats why im asking you guys. I found one cheap and brand new.
But im not gonna waste my $$ on chance it wont fit. Now if it gave me a shorter stroke i would have to change my rods. But then i could get more rpm's.
Hell i dont know.
2sav
There's no replacement for displacement, that's my .02 on which crank I would use.
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There's no replacement for displacement, that's my .02 on which crank I would use.
It was at .99 cents last time i looked i figured if it fits i can pick it up and save some $$ its only 30 miles from me. But then again i dont want to piece together a motor, i would be right back where i started from.
2sav
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You saved yourself some trouble. The 425 crank is a shorter stroke than the 455 and also has a different rear flange bolt pattern.
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I have a 455 w/425 crank it will fit fine, my motor turns 7,200 rpm with no issues
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There's no replacement for displacement
A man after my own heart O0
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Will it fit? Is it gonna change my stroke? I found a new 425 crank and thinking about it if it fits. The 455 crank i have i think it needs to be turned. Any advice here?
2sav
The 425 and 455 Oldsmobile blocks are identical all the way down to the factory boresize. The crankshafts are interchangable.
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....
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Olds V8
Engine Bore Stroke Cubic Ins HP CCs Bore mm Stroke mm
215 61-63 3.500 2.800 216 - 3533 88.90 71.12
260 1972-'83 3.500 3.385 261 - 4271 88.90 85.98
303 1949-53 3.750 3.438 304 - 4979 95.25 87.31
307 '80-'86 3.800 3.385 307 - 5035 96.52 85.98
324 1954-56 3.875 3.438 324 - 5317 98.43 87.31
330 '64-'67 3.938 3.385 330 - 5406 100.01 85.98
350 '68-'80 4.057 3.385 350 - 5739 103.05 85.98
360 4.116 3.385 360 - 5907 104.55 85.98
371 1957-73 4.000 3.688 371 - 6077 101.60 93.66
394 '59-'64 4.125 3.688 394 - 6463 104.78 93.66
400 '65-'67 4.000 3.975 400 - 6551 101.60 100.97
400 '68-'70 3.870 4.250 400 - 6556 98.30 107.95
403 '76-'87 4.351 3.385 403 - 6601 110.52 85.98
425 '65- '67 4.125 3.975 425 - 6967 104.78 100.97
455 '68-'76 4.125 4.250 455 - 7449 104.78 107.95
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...
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....
I read somewhere that there are 455 cast cranks and 455 nodular cranks (which still may be cast?)... what's the difference between cast and nodular?
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I read somewhere that there are 455 cast cranks and 455 nodular cranks (which still may be cast?)... what's the difference between cast and nodular?
There are 4 different cast 455 cranks. All have the same casting number. There is the plain one, with no mark, then an "A", "N", and "cn" marks.
Nodular iron has higher carbon and nickel, and lower manganese, compared to malleable, and has magnesium, which malleable iron doesn't have.
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The 425 and 455 Oldsmobile blocks are identical all the way down to the factory boresize. The crankshafts are interchangable.
The blocks are not "identical". Can't recall if all, or only early 425s had a different lifter bore angle. Not a major difference but one that should be considered if expecting the most out of a cam choice.
The crankshafts are NOT INTERCHANGEABLE. There is a .275" difference in stroke so they obviously wont "interchange". Perhaps you should have said that either crank will fit either block(although the 425 may require clearancing at bottom of cylinders for a 455 crank/rod combo), but displacement will be determined by the crank chosen, and that the appropriate piston/rod combination will have to be used. The rear flange of early(1965?) 425s has a different bolt pattern. The 455 PTO will not fit this different pattern. I think Glenwood still lists the 425 item.
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.
Great idea if one is building a motor from scratch, but it is a pricey proposition as it will require a non-stock combination of rods and pistons. For someone just trying to put a 455 back together as a 455, the 425 crank isn't going to work without being offset ground to the 455 stroke. This will still require the use of non-stock pistons/rods. If just using the 425 crank as is, it would still require the use of 425 rods/pistons.
Its too bad that the Olds strokers were never as common as the Ford or Chevys. I always wanted to build a bigger Olds based on an offset ground 425 forged crank or even an offset ground nodular iron crank(had one in my 455).
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... what's the difference between cast and nodular?
First off, both are cast iron. The nodular cast iron is more ductile/less brittle than the the "standard" cast iron. This is the result of controlling the way that some of the carbon turns to graphite in the alloy. In "nodular" the graphite comes out as small spheres or nodules, hence the term "nodular" cast iron. In the standard iron it tends to appear as "flakes", which interrupts the grain structure.
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Good info Oldsquirt !! here a interesting link for comparisons" Tom
http://www.classicoldsmobile.com/tech/95.shtml
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Rod's should be(Center to center)6.9950,for 425 olds crank forging #384722 4.250 stroke in 455 block, but there are clearence issues that your machine shop can take care of. Tom carries the PTO, Mondello carries the flywheel, If you built one of these olds you'll love the power!!!