And again, since the bore on both the 425 and 455 are the same, all that does is give you a 425 in the 455 block. Why bother swapping if you get exactly the same motor? And again, you need to swap the rods and pistons in addition to the crank. If you really think you need a forged crank, build the 425, but frankly for a street car you'll never see the difference. I'm not aware of anyone who's ever broken a nodular Olds cast crank.
olds 425 1.69 r/s ratio mopar 413/426/440 1.80 r/s ratio mopar 426 Hemi 1.83 r/s ratio wanna try that again?
I like hearing all these opinions, they all have validity. The 425 is a great motor, the downside is the flywheel MUST remain with the crank, flywheels don't interchange with 455's. Next pistons are expensive compared to 455's. I have 3 425's and need a forged .060 flat top piston for one and it's tough to find. There are also different lifter sizes or lifter angle I forgot which. As has been said the rev higher and with the right heads (Edelbrock makes aluminum) you will have a great motor. Pat
I ran a 425 in my stock car back in the '70s and it was a torque monster, nothing beat me out of the corners. Love those motors.
It may not matter to you but 425 cranks rarely are drilled for a pilot bearing, the one I own included. Only a concern with a manual transmission.
This rebuild Marine 455 with C heads, is for sale $1800 Located in North Western North Carolina. This one has the threaded boss for 4 speed bell crank ball.
I see 425 parts hard to get and expen$ive. But they were strong engines. Couple of buddies had them, one a '67 Delta 88 and another with a '65 Olds 98.
I bought a 65 Malibu two door wagon in the early 70's that someone had swapped a 425/Muncie in, not sure why but the thing was a dog, it ran out of steam about 5k rpm's.
olds 425 has 7" rod/3.975" stroke= 1.76 r/s ratio not 1.69 ratio near same as a pontiac 400 at 1.77 which is damned good
I know this is old thread, can't resist...1968 and up is 455, 1967 and back is 425 Olds hit the 455 mark 2 years sooner than Pontiac or Buick....that's what's cool about them. I lucked into a '68 Hurst/Olds 442 engine 455 w/D heads and split center port exhaust manifolds, and original carb, for 75 bucks once, found it apart in a barn. it may ? have had a forged crank too ? can't remember...it belonged to a friend. I sold it on Hemmings Motor News for $1500 when I found out what it was...it would probably be worth 10 grand by now. this was pre-internet days early 1990's... just picked up a 455 and 425 from a local junkyard that were sitting for decades...the 425 turns and has B heads, from a Toronado 1966. the 455 is seized, cracked bore from water, and has J heads from a '73, gave 450 bucks for both package deal. 425 has original carb, flywheel, both have a/c compressors, all brackets. the scrounger will continue..to scrounge !! cuz I always was a closet Olds guy...drove 2 Cutl***es as DD for years...
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