Olds Man

I have the choice to rebuild a 1970 455 with "C" heads, or a 1967 425 with the original 1967 heads (not sure what heads they are). I have read a bunch of articles on the pros and cons of each, and I was wondering if anyone had any advice on which one would be better to build. It is going into a 1972 Cutlass Supreme to be streetable with hopefully around 450 to 500 horse power. Thanks...... Olds Man.

70 cutlass s

Buy another Olds and build both. One for a dd and the other for a hot rod.

I would build the 455 if it was mine. Mainly because it is going into a 72 Cutlass.

citcapp

I would go with the 455 as well also because of the year of the car

cutlassefi

X3

jaunty75

Yes the 455 is correct for the year.

But you guys are dissin' the 425! Check out this comment from that bastion of knowledge, Wikipedia (I've bolded the relevant part):

The 425-cubic-inch (7.0 L) big-block was the first tall-deck "big block," produced from 1965 through 1967. It is arguably the best engine Olds made in the muscle car era, although it never made it into a "muscle car". It used a 4.126 in (104.8 mm) bore and 3.975 in (101.0 mm) stroke. Most 425s were painted red, though the 1966-67 Toronado units were light blue. All 425 engines were fitted with forged steel crankshafts with harmonic balancers.

I'm not saying I agree or disagree. I'd be curious to hear anyone's reaction to this.

66ninetyeightls

Thats right. 425 RULES!!!!!!!!!!!!!! I am bias though!!!

rocketraider

A 1967 425 should have C heads as well. A 1970 455 should have E's, which makes me wonder if it is in fact a 1968 or 69 engine.

I like the 425 for a nice high-revving BBO build, but you have to deal with the obtuse cam bank angles. That's the biggest negative about the 425. Paint it blue and most people wouldn't know the difference anyway.

The 455 OTOH is ultimately easier to source parts and you got 30 extra cubes off the bat.

Either will make a fine streetable engine, and at least our friend here is sticking with Oldsmobile power!

425olds

The 425 in my oipnion is the stronger engine, forged crankshaft and rods. That engine is very durable too! I put one in a 1984 cutlass ,and it was pretty quick too! Just my opinion.

jaunty75

Yes, but your opinion is no surprise given your username!!

geckonz08

.amen

Quote:

The 455 OTOH is ultimately easier to source parts and you got 30 extra cubes off the bat.

yep and the parts are less expensive

joe_padavano

???

Other than pistons and potentially cam and lifters, the parts are the same.

Texas Jim

I'd drop the 455 in the Cutlass, like the other replies stated, and f/ sure keep that 425. IMO, the 425 is an engine to hold on to even if you don't have a body to put it in at this time. As time goes on, the 425 would be a great engine to put into a car that coinsides w/ it's year or something older, to preserve another great design.

mugzilla

I have some nice c heads and would like to put them on a 400 ...

Should I look for an E block ...

What year ?

425olds

I guess i,am a little bias towards the 425. The torque and rev monster of the big block oldsmobile. When i had one ,at first i was not too impressed with its performance. I thought that the buick and pontiac,s were a lot stronger ,but i changed the intake and used a quadrajet and a recurved distrubitor and some 1965 starfire exhust manifolds. That woke up that engine ,and i beat my trash talking bro-inlaw,s 1967 grand prix. I know a guy that i repaired a few cars for, that has a 425 -out of a 1967 -98 thats for sale,i think he wants $200 or $300 for it. Any on interested ? Call him at (773)287-7771 ask for George.

442much

From what I've read either one would be a good source of power on the street. However, for full racing mode the 455 is the "best recommendation" according to the book I have. I'd say the only thing against the 425 would be that it wasn't made for the A bodies. If that doesn't bother you, then whichever you pick, 425 or 455, you can't really loose out on either one.

380 Racer

Guys are using the forged steel 425 cranks and stroking their BBs out to 482, 496 or bigger cubes. Of course this can be done with a 425/455 block whichever you choose. Since I'm a SBO guy you will have to ask a BBO guy what the strokes figure out to .

Warhead

When we ran our car years ago, we tried both engines.
The 455 was launch, shift, shift. 5300 rpm-anything higher and it slowed down. Most 455's with stock heads slow down around 4400 rpm.
The 425 wanted to run up to 6200.
The 425 pulled harder in our car, and was more FUN!!!!!
Jim

captjim

Unfortunately, most guys who have ever driven 425s did so in big, heaby cars. I drove one in a 65 F-85 with some gear, man talk about fun!!

66ninetyeightls

Hey I have a 425 in my big car and I still think its a bag of fun.

425olds

I have more idea,s than money , so this is just a wish. A 425 with Edelbrock heads W-30 type roller cam tuned-port fuel injection ,4-80e overdrive trans. Hi-compression forged pistons, hi-rev valvetrain. 3:42 gears in a 1970 cutlass. I think low 13sec-hi 12sec car.Any idea that this combo would do?

Warhead

Mine was in a stripped down G body with too much gear (4.56), and a 3500 converter.
It launched hard, ran the same et with 28 inch tire, and a 29.5 inch tire.
What a gas.
Nick,
The 425 has a 3.975 stroke, and a 7 inch rod.
The 455 has a 4.25 stroke, and a 6.735 rod.
Jim

geckonz08

what I meant joe --guess you are right--OVER AN ENTIRE BUILD it is negligible --apologies--

mike