[Stan Weiss]

If under square was the way to go why did Pontiac use the Olds 403 - 4.351" x 3.385"?

Stan

[Mr Anonymous]

Originally Posted by Stan Weiss

If under square was the way to go why did Pontiac use the Olds 403 - 4.351" x 3.385"?

Stan

Simple. 403 came out in 77, replaced applications that used the 455. They needed 400ci +/-, and all small block olds cranks were all 3.385. Only way to get it big enough as a small block was to take the bore out huge. A friend in FL just stuffed an aftermarket 4.00 crank in his 403, its 484" if memory serves. My 350 diesel with 4.00 425 crank and 0.197" overbore ended up 454ci. Still small block.

The olds motor from 1968 to 1976 only had two different combustion chamber sizes, and two different piston dish sizes. They were durable, inexpensive, and did the job. That meant 442s, land barges, jet boats, irrigation pumps, etc. Eight years of production with few changes (besides w-30 specific parts) means that they're quite plentiful, unlike the 455 Pontiac.

I'd love to see two cars of similar weight and gear, one with 428 Poncho and one with 425 Olds, and let them go at it. I'd bet theyd be close.

[67GP428]

I miss driving my 428 GP. It ran very strong. The 428 was a unheard motor outside the Pontiac world.

[hurryinhoosier62]

Originally Posted by Stan Weiss

If under square was the way to go why did Pontiac use the Olds 403 - 4.351" x 3.385"?

Stan

Stan, you are making this too easy. It was already EPA and CARB certified for CA and high altitude areas. The Pontiac 350 and 400 were NOT. Look at the cam specs, carb jetting and ignition timing of the 403s. Then, consider the 403 had an air pump, catalytic convertor and was designed to burn unleaded fuel.

[Schurkey]

Originally Posted by hurryinhoosier62

emissions. Under square engines produce few emissions than over square or square engines. The first emissions control protocols were already in effect in CA.

From the perspective of the times, this is true.

Given the decades of additional research, not so much. But also consider, Chevy was cutting bore size and increasing stroke by 1965 compared to the engines designed in the '50s. The 409 "W" Chevy had a much shorter stroke than the 396/402 "Mk IV" Chevy; the 348 W" had a much shorter stroke than the 350 sbc. Even the '66 Buick 401 had a shorter stroke than the '67 Buick 400.

Originally Posted by PAUL K

I thought they added stroke to make up for the loss of compression. I also think they did a lot of bad guessing when diving into the emissions part.

They were scrambling like mad. They made many bad choices, but I think Management had a hand in that also--by insisting everything be as absolutely cut-rate cheap as possible. It took a couple of decades and on-board computers to even begin to bring power numbers up. If they'd made better choices then about compression ratio, quench distance, in-cylinder turbulence, restrictive pellet-type catalysts instead of monolithic/honeycomb, and a host of other factors, we'd be remembering much nicer cars to drive.

Buick, Olds, Cadillac each built larger engines in the '67--68 time frame, just as the switch-pitch feature was getting deleted from the TH400 and TH425. It was cheaper to enlarge the displacement than to fancy-up the torque converter.

Originally Posted by steve25

First and foremost it was the switch to the open chamber heads that got most manufacturers in compliance with the Fed's limits on emissions!

Followed by Bigger motors stroke wise made for increase Torque which allowed less rear gear.
Lower rpm and less emissions go hand in hand!

But open-chamber heads tend to have poor turbulence, slow burn, and need lots of spark advance. They mitigated one problem, but caused two more: Low power and crappy mileage.

"Stroke" doesn't increase torque. Increased displacement increases torque. The Buick 455 was a torque-monster; and it had the shortest stroke of all the GM 454-455s.

Originally Posted by napster

Think about it. Bunky Knunsen (SP) was at Ford and they had the BOSS 429 and chevy had Delorean and they came out with the 454 LS-6. All Pontiac guys that were gear heads.

Bunkie Knudsen left GM to go to Ford. Later, he was fired from Ford.

Henry Ford: "History is bunk!" 1916
Henry Ford II: "Bunkie is history!" 1969

Originally Posted by Formulajones

I tend to believe it was more along the lines of cost. Due to limited bore spacing, the only way Pontiac could increase the CI comparable to other brands was to simply shove a long crank in it, otherwise they would have to spend more money to completely redesign and cast a new block.

The Pontiac block and the Olds block have similar bore-center measurements, along with the FE Ford. I've heard that the same raw forging can be machined into Pontiac, Olds, or FE crankshafts just by altering the way it's machined.

Pontiac "could" have siamesed the cylinders like Olds did with the 403, and had a significantly larger bore (or just gone paper-thin like Ford did with the 427). I wonder if Pontiac management/engineering ever considered that.

Originally Posted by Skip Fix

So I'll throw a slightly related but tangential question -why did most of the jet boats in the 70s early 80s use Olds 455s vs Chevy 454, Pontiac , Buick 455s?

Originally Posted by PAUL K

Tons of torque from the long and relatively small intake tract.... IMO

Originally Posted by Stan Weiss

Unless I am thinking of something else jet boats were not high RPM.

Far as I can tell, the Olds management made engines available to the Berkeley Jet company cheap. Olds also sold engines to companies producing agricultural irrigation pump systems. Maybe the Olds engine plant(s) had excess capacity and needed a way to dispose of a heap of engines. Every time I saw a jet-powered ski boat with a white painted (Berkeley) jet drive, there was an Olds engine powering it. Every time I saw an Olds engine in a jet-powered ski boat, it had a white Berkeley jet drive. There were other brands of jet drives, but Berkeley was "the" main player in the market I was exposed to.

Ever driven a jet boat? The L-A-S-T thing you need is big bottom-end torque. Low-RPM torque is TOTALLY WASTED. A jet pump is a centrifugal pump. At 2K rpm, they barely move any water. I think a Techumsah lawn-mower engine could spin one at 2000 rpm. It takes ~600 horsepower to spin them 6000 rpm, and probably 400+ horsepower to spin one 5000 rpm. The power absorption of the pump is VERY non-linear. (i.e., it takes much more than double the power to double the RPM.)

So lots of Olds/Berkeley power packs ran 4500--4800 for hours on end, 'cause that was WFO and all the engine could do. The torque curve of the engine intersects with the torque absorption of the jet pump; and that's it for RPM unless the boat hits a wave and the pump sucks air.

Originally Posted by steve25

Other then the Olds motor bring lighter then a BBC for use in a Boat I can't see why Edelbrock made the needed water cooled Exh Manifolds for them.

I think Mondello was twisting Vic's Arm a lot to do that!

Edelbrock made marine parts for heaps and piles of different engines. Marine engine mounts, timing covers that could mount a cam-driven marine water pump, and water-cooled aluminum exhausts for Ford small-block, Ford FE, Ford 460, SBC, BBC, Olds, Pontiac, Mopar B-RB-Hemi...Edelbrock made lots of marine stuff. Far as I know, every bit of it was discontinued decades ago.

Originally Posted by chiphead

Yeah, now we understand the concept of crevice volume and how much unburned hydrocarbons hide there. This is one reason there are precious few modern engines over 4" bore. The unburned HC emisions go up along with bore size. Top ring placement has an impact on crevice volume, so even that affects emissions. They didn't undertand any of that yet in the late 60s.

There was also the idea that large-scale production machine tooling couldn't control tolerances very well. The quench distance was huge. Part of that was the machining engineers telling GM they couldn't hold tight tolerances, and they had to go big because going small could result in things hitting each other. The other part of it was LIES told to the upper management. Example: There was a problem with certain Chevy engines not making advertised horsepower. Engineers grabbed several engines from a warehouse, and measured them. The cylinder blocks were too tall, leading to the piston being way "down in the hole" which lowered compression. Why? It cost less to leave the blocks too tall rather than spend the machining time and tool wear to cut them lower. The plant manager probably got bonuses for increasing production and lowering the wear on the tooling, while at the same time he was sabotaging the power, efficiency, and emissions output of the engines he was making.

Originally Posted by chiphead

There were no overdrive automatics in 1970s american cars, so the only way to move a heavy car around with freeway gears is to put a larger engine in... ...The emission laws of the early 80s caused a slaughter of engine families, Pontiac, IHC, Caddy, most Olds and Buick, among others ,were discontinued by '82

Yeah, the outright failure of GM and the competition to produce a REAL automatic transmission with additional gear ratios was a stunning mistake. The TH400 and variants was a great trans, but it needed another gear. This happened in '91 or '92, but only in trucks, and only with computer control. They needed it in '73 or earlier, with no electronic controls beyond the kickdown. Same with the TH350. It was sort-of replaced with the 700 a decade or more too late; but the 700 was a piece of crap for the first three or four years, and wasn't really right until...1988? And even then, it was at best a "light-to-medium duty" trans, and at worst it was a hand grenade.

'Course, we could see what was happening in '67, when GM killed the switch-pitch TH400 for the '68 model year. They were carving money and utility out of the transmissions even then. The Powerglide was even worse. Had GM spent a little more, a little earlier, they'd have eliminated untold problems in the '73--'90 timeframe; and they'd have pissed-off fewer customers in the process.