View Full Version : Olds 455 vs Pontiac 455

06-23-2003, 02:47 PM
Who can rack and stack these two engines for me?

06-23-2003, 04:13 PM
Olds is made of better metal and lighter by several pounds. It's a torque monster. Limited aftermarket performance parts support.

Pontiac 455s run hot. They should have stopped at 428 ci but Buick and Olds had 455s, so. Aftermarket performance support is good. Most had what Pontiac called an Armasteel crank which is durable and capable of occasional 7000 rpm abuse. Pontiac also has an adjustable valvetrain which Olds does not.

What is the engine going in?

06-23-2003, 04:32 PM
I'll give it a try, but I hope I don't get a lot of people mad at me.

Both have a 4.125" bore and a 4.25" stroke. Both weigh about the same(within 25lbs). Both have similar Cam profiles. I think Olds camshafts have a little more lift and Pontiacs have a hair more duration from the factory. They're both torque hogs, each capable of putting out over 500 ft. lbs on even a mild build.

Advantages for Olds: you can fit them in a more wide variety of cars. There are a lot more Cutlass bodies out there than comparable Pontiac ones which will accept a Pontiac engine. Locating a 455 olds is easier than finding a 455 Pontiac(I've been looking for a Pontiac at a decent price for a long time. I've found several 455 olds along the way). The Olds 455 block is also a little stronger than the Pontiac ones, unless you can find a really early 4 bolt main one. In fact, if you want a really stout 455 poncho, locate a decent 400 block and get an Eagle(I think) stroker crank and rods set up, bore it out to 4.125", and you'll have one better than an original(400 blocks are stronger and have smaller main bearings).

Advantages for Pontiac: They're a little better for all out performance in my opinion. The heads and exhausts are better set up for flow. They have bigger valves and better ports. They also don't have that stupid crossover from one manifold to the other. Listen carefully to this next one: Although finding a 455 olds is easier than finding a 455 pontiac, finding decent parts for pontiacs, such as heads and aluminum intakes, is a whole lot easier. I can jump on Ebay or even thumb through the paper and get an edelbrock performer for a Pontiac for inside $100 easily. I can also find heads, and at a decent price. THe more common heads for Pontiacs are still good castings. One of the most common head castings for Pontiacs are the 6X variety. For Olds, J heads seem to be the most plentiful on big blocks. 6X's are a whole lot better of a setup than J's. Even the more exotic head castings are superior. The SD 455 and some earlier GTO's got round port heads; Olds never saw these. Stock rocker arms are adjustable for Pontiac; olds never saw these either. Oh, and there's none of this big block/small block crap with Pontiac. All Pontiacs have the same block dimensions, which means one part fits all, namely intakes and heads.

A good place to learn more about Pontiacs is www.Wallaceracing.com

There are a few other things to remember about Pontiacs. For one, pre 70 blocks have a different Motor mount scheme to the later ones. Bottom line here is that pre 70 blocks will only fit into pre 70 cars without mods, while post 70 blocks will fit into just about any year. Pre 71 heads are high compression for the most part. The 72 and later have much larger chambers for lower compression, but you can use 350 or 400 heads on a 455 and have a nice street setup. I could give you the head casting numbers of some really nice heads if you'd like.

Hope I didn't bash olds too much, but there are a few things about Pontiacs that are superior to Olds. I say for a street engine, they're about the same but I choose olds just because it's not too much of a problem finding a body and a big problem locating a 455 pontiac.

06-23-2003, 04:35 PM
Sorry, but the Pontiacs didn't have adjustable valve trains. They have don't have bridges or shafts, but they are still non-adjustable. They have to swap over just like us.

06-23-2003, 04:39 PM
My 76 350 and my 71 400 both had a stud, a rocker arm, a little ball inside for it to pivot on, and a nut on the top. It did not have a fixed position. Wouldn't that qualify it as adjustable?

06-23-2003, 04:55 PM
Adjustable means you can adjust the height of the rocker's fulcrum. On Olds and Pontiacs, you torque to the factory specs, usually advertised as 20-25 ft/lbs, and double check the valve train geometry. Shims must be added to raise the rocker. An adjustable set up will have some type of set screw or other holding device so they can be adjusted and locked down, i.e. you can adjust them while running.

If you try to adjust an Olds like the typical adjustable set up, you will generally break the bridges, then tear up rockers and pushrods. A Pontiac will just start with the rockers and pushrods. Either way, valve and lifter damage is also possible.

I do believe that Pontiacs are a lot easier to switch to adjustable rockers. I haven't done that swap, so I can't say for sure. Most of my Pontiac info comes from www.classicalpontiac.com so you can go to the Q&A and Q&A archives and search for more detailed info.

06-23-2003, 04:59 PM
If my memory is right, all you really need to make the Pontiac valve train adjustable is the proper fastener (e.g. polylocks, etc.). They are machined to be held a certain height with the factory nut torqued to spec. Any machining or swapping of cams requires rechecking geometry to see if geometry changes. It's usually easier to just go adjustable though.

06-23-2003, 08:51 PM
Hey, thanks for the great info - I am replacing a 403 in my 78 TA, so either engine should fit fine (although the Olds 455 will require less accessory changes). I have found a 455 Olds already; it's in a 71 Delta 98, head casting #s 409 100 - anyone know if that's a high or low compression head?

06-24-2003, 08:07 AM
Yes, I know about the different brackets - I have found a 455 with all of the accessories, so that shouldn't be a problem; the deck height I have heard can be dealt with, but I haven't found out the details yet...

06-24-2003, 01:49 PM
My friend built a very mild Pontiac 455 for his 70 GTO. He put 6X-4 heads on (higher compression than 6X-8) with stock valves and guides. He ran the Summit version of the Ram Air IV cam. Stock bottom end rebuild with TRW pistons. He put a Performer manifold and a Edel squarbore 750 carb. Stock log exhaust, skinny 2 1/4" exhaust with crappy muffs, 3.55 rear and 4 speed. With my drag radials he ran an easy 13.7. With a nice set of header and exhaust with cross and a better carb and lauch high 12s would have been with in reach. All this at 5500 rpm. max. It idled like a puppy. Vac was a nice steady 17. Great low end torque. The Olds 455 would be comprable with less to do since you can get all the brackets. The AC box will be the issue and the shaker. All Pontiac 326/350/389/400/428/455s use the same outside dimensions for the block.

06-24-2003, 01:50 PM
I still would go with the 403.

06-25-2003, 01:10 PM
The 403 is still in the back of my mind, but way back there - I know that I can build it for good performance, but I can get more out of a 455, and the parts are more plentiful. I have some time to think it over...