You all are forgetting the big excitement when the BB was introduced. Since OldSStroker was the only other guy around when this occured, he is the only guy who should be ashamed of not mentioning it! It was the heads, which were described as "porcupine" heads. The intake and exhaust valves are canted relative to each other, not in the same plane. To those used to looking at valves all lined up in a row, this had an odd "porcupine" appearance. These heads inherently breathe better than stock architecture small block heads and are the main reason that a BB 396 will generally make more hp than a comparably "hot" SB 396, for example.

Rich Krause

 

Since you asked....... I have built a few Olds motors.

The 400 Olds is a big block, the 403 is still essentially a small block as it shares the same external dimensions & stroke as a 350 olds small block. Cubes mean nothing. Small/big block depends on engine design/dimensions not cubes.

The 400 olds was available in 65-67 with a 4" bore & 3.975" stroke & 7" rod.

The 68 up 400 had a 3.875 bore with a 4.25" stroke & 6.735" rod.

The 403 was a 4.351" bore & 3.385" stroke & 6" rod.

This should add to the confusion.... especially if you want to look at rod/stroke ratios as well.

For comparison of a 396 BB Chevy. I have a 402 .030 over 396 in my '68 Camaro
Made 632 RWHP no power adders
11.7:1 comp, 2.30" intake, 1.88" exh 315cc intake ports
262/272 deg @.050" .708" lift turning 7600RPM
Breathes well, eats 114 octane fuel @ 6mpg, idles poorly at 1500 & makes power from 4200rpm up. Not really a street car, but fun if you like to spend $.75/mi. on fuel.

 

Tony brushed upon one more major difference, the staggering of intake/exhaust valves. In a sbc the intakes are together, as are the exhausts. This is a completely foolish design, and because of it the sbc isn't the ideal engine platform. Strange that 95% of all race motors are a sbc and it's design is a major flaw.

Also, the cam height is raised in a bbc. Everything is bigger; rod journal, main journal, pin size, rod length, main bolt size, head bolt size.... basically they have very little in common, save for the firing order and the lifters.

 

Had to laugh at Rich's comment. Memory is the second thing to go...can't remember what's first.

One of the main reasons for the E I I E E I I E head layout was to make a cheaper 3-branch exhaust manifold. We've been fighting that until the LS1 (Gen III).

The SBC was not designed to be a race winning engine. It was designed to be a CHEAP to build, simple, reliable engine for low priced cars and trucks.

Folks like Zora Duntov got the ball rolling for increasing performance in the SBC. Today's SBC race engines are a tribute, not so much to Ed Cole's original design, which, IMO, was brilliant for it's intended purpose, but to untold hours of development of that design. You really can make a silk purse from a pig's ear.

 

Here's the simple version:

Small block and big block Chevy's are both V-8's. Everything else is different

 

Actually, the 348/409 was Chevys first attempt at a "big block" and it wasn't much to scream about. We could ask Smokey if he were still with us.

The typical sbc valve layout was changed up way before the LS. The Dart/Buick head was one... along with the SB2 which came out about 3 years before the LS engines.

-Mindgame

 

Just to throw a little more confusion on the heap....

Chevy big blocks are totally different blocks than the Chevy small block. A few things interchange like lifters and distributors but precious little else. When you alter the bore spacing pretty much you have a completely different engine, but the differences go WELL beyond that, well beyond bore and stroke, well beyond displacement. They're totally different engines.

Pontiac engines are ALL built basically of the SAME block casting from 326 to 455ci. Same external dimentions- just differences in bore and stroke, basically. The "little guy" 301 pontiac is the exception in that it uses a shorter deck height block which is otherwise STILL the same as the 326+ci blocks. The 301 is the motor used in the "Smokey and the Bandit" Trans Am in turbocharged form, for some historical reference.

Olds SORTA had big and small blocks. They had short deck and tall deck versions of the same basic V8. Short deck versions were motors like the 350 Olds "Rocket" motor and the later 403 that was used in late-70s "6.6L" PONTIAC(!!!!!!) Trans Ams that came with an automatic transmission. The bigger cube motors like the famous Olds 455 were the taller deck version of the same basic block. And believe me, a well built Olds 455 will belt it out like like God himself screwed it together!

 

A little off topic but...what the heck.
Olds came out with several "strange" combos. I once owned a Dynamic 88 with a high compression 425ci 2bbl. I was parked in the driveway of my cousins house and was blocking-in a 455ci Trans Am 4speed. The guy (now a Jefferson Parish police officer) told me to "move that piece of junk" which I replied that I'd blow the doors off his T/A. He said let's go for $100 from a dead (stop). We pulled it out on blacktop and went on three. All he did was spin and tried to stay in a straight line. I walked him like a dog! He never stopped to give me my $100, and I never saw him again to this day. Just a memory that popped in my mind talking about ol' Smokey and everything...

Why would Olds put a 2bbl on a high compression 425 anyway?...

 

In pre-emission days OEM's had literally scores of engine/transmission/axle combos available.

A 425 2 bbl high compression was one way to get good fuel economy along with decent torque which equals decent acceleration. Remember this was before OD transmissions, when there were 2.41 and even 2.29 axle ratios. Of course a 3.23 with a 4L60 is 2.26 in OD.

I recall some engineering tests where Pontiac used a 428 high comp. dual exhaust 2bbl with a 2.41 or 2.29 axle. It ran the same 0-60 as a 400 4-bbl dual exhaust 3.08 or 3.23 axle, but got better level road fuel economy than the 400. Second gear was good to about 110 @ 5000 shift point and 70 cruise was 2100-2200, about the same as now. I don't think it was marketed heavily, but you could probably have it built for you by just checking off the correct blanks on the order form.

 

Yes the Buick 455 is a Big Block, one of which I love, it has a great bore to stroke ratio 4.3125x3.90 and is very light, almost the same weight as a small block chevy (625 without aluminum intake or heads) The light weight is due to the fact Buicks were already heavy and so they wanted a lighter block, they used nickel in the block which gave strenght but reduced weight, with pure cast iron you need it to be thicker to be strong. This engine put out more torque, and at a lower rpm than any engine, except the Cadillac 500 ci which had slightly more tq but at a higher rpm. I always thought it was expensive to build this engine, until I got an LT1 which doesn't seem any cheaper.

 

thanks for the info, the olds 455 is my favorite engine, expept the for 69 and 2001 concept ZL1 engines, and i always thought about this "And believe me, a well built Olds 455 will belt it out like like God himself screwed it together" i am very glad it is true

 

The bb Olds 455 is a good motor. Edelbrock/Mondello finally made a head for the thing, so that's good to know in case you want to try to put out some more serious power. The competition has about 20 years of head development up on the Olds, so it can be a little tough keeping up with the Chevys, Mopars and Fords.

Main thing with the Olds is the oiling issues.... the Olds needs some work in that area. Mondello and other Olds builders like to use restrictors in the main registers along with modified main bearings. A windage tray and modified/blueprinted oil pump would also be a necessity as I see it. Yeah, they can make some good power, especially if you're a torque lover.

-Mindgame

 

While we are on this topic....Can someone please explain to me what constitutes a "MOUNTAIN MOTOR"?

I was told its a very strong block that can be bored and stroked well over 500 cubic inches and is used a lot in drag racing.

Is this true and can someone please shed some more light on the details of what makes a Mountain motor.....well...a Mountain Motor?

Thanks for any insite,

 

i dont beleive there is an exact definition but i'll take a stab at it:

632/638ci engine is sometimes called a 'big cheif'
that would be the largest displacement on a tall deck (10.2) big block chevy

4.6 bore 4.75 stroke

aftermarket blocks come in decks even taller like 11.625" which allow strokes in excess of 5", displacements in the 700 cube range (i think i've heard of 800ish cube ones)

so... i beleive it is those 700+ cube engines that are 'mountain motors'

 

Are you sure that the lifters are the same?? My dad's friend has a 454 in his Chevelle that ate a camshaft, and I got to see one of the lifters afterward (the face was pretty chewed up ). I compared it to a lifter we had out of a 350, and I remember it being slightly larger (both diameter, and height).............since everything except the number of cylinders, firing order, and manufacturer are different (aka: larger) in a BB, why would they use the same "small" lifters from a SB??

Something that I've heard about comparisons to 396 BB's, is that most 350's could be made to beat 396's since they were a "small" big-block, and the difference in displacement between 350-396 wasn't that great compared to the difference in weight between the SB and the BB. My dad said that he had no problem beating Camaro SS 396's with his '69 SS 350, but if guys had 427's or 454's, he'd have a much harder (or impossible) time beating them. Now, his 350 wasn't exactly "stock", but the 396's weren't always stock either!?