i have ny choice of either a 455 olds from a 70 delta 88 , or a 425 from a 67, which would be the better of the two and what is the difference?  

First of all, either one is an excellent engine.  You can't go wrong.  The 1970 455 is one of the best of the 455's, but if you have the 425, in my humble opinion your best engine is there.  The 425/455 blocks are generally the same.  The cranks and rods and pistons can be inchanged between blocks, so say if you had the 455, but wanted the 425, you could have it by installing a 425 rotating assembly.  The rods and pistons are different however.

For me, the 425 would be the prize.  For one, forged cranks from the factory.  The second advantage is that the engine is over squared - meaning that the bore is larger than the stroke.  This allows the 425 to rev up faster than the 455, or the late 400's found in Oldsmobiles 1968 and beyond.  425 engines were only made between 1965 and 1967, so needless to say they are getting harder to find.  I just laid down some big money on a 425 that has some new parts on it, but I still am going to have to go through it to make sure everything is right.

Parts you can still get like from Mondello like forged pistons.  I have never mounted an all out search for any in more conventional places like Summit.  You may be able to find some there (maybe not).  My 425 came with a new set of forged pistons, so I'm good to go on those.

I have a bunch of identification numbers listed in my notebook.  If you get the engine numbers off of them I can probably find what they are for you.  The engine number you want to look at is just to the right of the oil fill tube where it goes into the block.  It will be like a five digit number followed by a letter.  The other casting mark is on the block behind the flywheel.  There will be a single capital letter (A,B,C, or D) there that will further help identify the engine.  Finally what color is the engine?  That can be a loose indicator, but is a good one say 50% of the time.  The crem de la crem would be a 425 out of a Toronado.  They were built with all kinds of internal goodies that go well on build ups.

Just get back to me.  I can probably help with a proper ID.  As I said, you can't really loose either way, but the 425 would be the best between the two.

Bowser

I would just like to add that the 425 block has very high nickel content. Even more than the 70 455. And as Bowser said that 425 crank is like gold. They are getting very rare these days. Nice piece. Also the 425 has 7" forged rods (all Olds rods are forged) that give you a killer rod to stroke ratio of 1.75. The same as a 327 chevy, and we know what kind of revers they were/are. The 425 can certainly be a rever with the right oiling mods and some lightening to the rotating assembly, although the strong suit of this engine is torque. The best of both worlds. Also you will see less side thrust and friction on the cylinder walls with the 1.75 R/S ratio.I would suggest getting the lightest pistons you can afford and recondition the stock rods and crank. The TRW pistons are way to heavy. If you plan on going over 500 hp I would suggest ARP studs and a main strap kit.Also use oil restrictors in the mains to restrict oil to the topend. Restricted pushrods are a good idea too. Use the biggest oil pan you can use in your car with a HV oil pump. Another problem area with Olds is the drain back of oil in the heads. Make sure you grind out any flash that is in the oil drain backs and enlarge, contour and smooth the holes. Let us know what you are going to do and we can help. Bowser and myself are the unofficial  Olds residents.

BTW you can get Olds parts from BTR Performance, M & J performance, Rocket Racing, FCR and D-i-c-k Miller Racing. These guys specialize in Olds. Bill from BTR runs a N/A SBO into the 7's and going faster!

Edited 7/1/2006 6:00 am by analogkid455

I might add that the torque made by the 425 is at a lower RPM range than most others - meaning you are getting  thrust faster.  Absolutely agree about putting on main studs and straps.  That alone is probably one of the best things one can do.  The main straps are relatively inexpensive and an easy add on when having studs installed.  High volume oil pumps are a standard on all my engines, and I always use at least a true roller timing set.  There is a gear drive out now that is available through both Mondello and Summit, but I haven't used one yet.  The standard valve set up on those engines are pretty good, but have the normal limitations that standard sets do.  With standard springs and rockers I think most Olds engines would be good to about 4,500 to 5,000 RPMs before you get valve float - heavier springs are a good start.  There are lots of valve improvements out there. 

I would also recommend that the engine be balanced - especially if using aftermarket slugs.  I am assuming that the 425 would be bored about .030, so new slugs would be in order. 

I can't think of anything to add that you haven't hit so far.   Bowser

well the best part is the 425 is free, in fact the whole car is the daughter says i can have it when her dad dies.  it will be going into a 79 cutlass supreme brougham.  

Cool - the trick is going to be putting all that torque onto the pavement.  If your Cutlass is equipped with the standard 3.08 peg leg ten bolt that most of those cars were, then blasting the third member out of the car is a firm possibility.  Be prepared to upgrade to a 12 bolt and to put in boxed control arms in the back at least.  They are available from a number of places so don't sweat getting the stuff.  It's around and for the most part at a reasonable price.  I purchased all new springs, poly graphite bushings, and an oversized sway bar for my '67 Cutlass for about $400.  I would have purchased adjustable arms too, but I am going to try boxing in my old ones, or finding some off of a 442 since doing my own may or may not work.  I figure it's worth a try - all I will be out is a little time.

Let us know how it goes.  Sounds like you have some good parts and a good project planned.

Bowser   

Not to mention Bulldog, and don't forget the Edelbrock heads.  

go with the 455,  the saying goes "there is no replacement for cubic displacement"  

Like I told him - either engine is an excellent choice and if he could get both of them, he should for trading stock if nothing else.  In this case, the 425 will be the better engine based on the make up of the rotating assembly all by itself.  It's hard to beat a factory forged crank, and factory forged connecting rods.  Also, those 30 cubes don't really mean squat when you can put almost identical toque down on the pavement quicker.  It's a fact that 425's can rev quicker and faster than a 455. 

In the world of Oldsmobile engines the three that reign supreme (in my book) are the 425's, 330's, early (pre 67) 400's, and the early (68 - 69) 350's.  The first three of these all have factory forged cranks, rods, and high nickel content blocks.  The absolute best of the three are the early 400's, but good luck finding one.  They only came in 442's and are rare as hens teeth.  I want one for my Cutlass, but will run what I got for now.  Also, anything (425 or 455) out of a Toronado is a good find.  They had all sorts of stuff in them that the others didn't.

Bowser

Yeah the Toro 455s had forged cranks. All others got the cast crank of varying degree.  

They also used the 39 degree cam bank angle with larger diameter lifters.  Most had oil scrapers on them, and deep sump pans that held a full six quarts of oil.  The Toronado engine was absolutely the cream of the crop.  They put out more horsepower than similar engines of the same displacement.  I think it was because the Toro was the top of the line.  Engines in 98's were similar, and so were the pre-66 425's that were put into Starfires.  It's all interesting.  This guy with the 425/455 dilemma is sitting in the catbird seat.  He is going to have a screaming engine either way he goes.

Bowser