WHy did pontiac Discontinue the 428?
 

Just curious my mother had a Grand Prix with a 428 and it was probably one of the fastest cars I ever drove from the factory.

Because the next step was to increase the bore and stroke and build the 455.

Legendary.

If you haven’t experienced driving a 455 powered Pontiac you really should.

Olds was already at 455, Ford at 460 & Chrysler at 440 before 1970, so in 70, Buick went 430 to 455, Chevy 427 to 454, and Pontiac 428 to 455. My recollections of the 428 were memorable too. Courtesy of a Bonneville that would happily chirp its 1st to 2nd shift when mashing the loud pedal. :D

What sucked was that we could not get a engine like the 390HP 428 in a Firebird or GTO. What we had were a bunch of 400s. While some ran good Chevy had the 427 then 454.
They did try, what was left became the 73-74 SD 455. But it was low CR.
The plan was to build a 10-1 CR SD 455 in 1970, but did not work out. Chevy the cause ?
It was to be a 10-1 455 with a big cam, adjustable valve train, 850 Q Jet on aluminum intake, forged rods and pistons with the 455SD block.
There were 2 sets of the 10-1 round port heads made, down to the pushrod tubes like the SD 455 had. Casting number 96. Whittmore had a set in his hands.
But all we got was the cast rod D port 10-1 455 with 64 heads.
If PMD could have pulled it off in 1970 that engine would have rules the street.
What was left of the program was Pontiacs last gasp. SD455, still a great engine but it could have been so much more.
Its one of the reasons I hate Chevy.

Main advantage the 428 had was that it had more compression than the '71-up 455's.

I think that 390hp 428 may have been a little overrated, or the 360hp GTO 455 engine was underrated.

But, some do like the compromise 4" stroke of the 428. Something for everybody.

One of those #64 head 455's, with no change except an 041 clone cam/Rhoads lifters, ran 12.40's in my '68 Bird bracket car. The Bird had 3.55 gears & a stock 13" converter. I think the 455 had around 75-80K miles when I got it. Had never been apart. A lifter had come apart. Owner thought engine was about to blow. So, he paid me to replace it with a junkyard 400, & he gave me the 455. Got a real good deal on that one. Ran it in 3 different bracket cars. We won lots of races with it. Never ran a 428 on the strip. 455's were much easier to come by, back then. LOTS of early '70's big Pontiacs came with one.

I have never been I fan of an under square engine.

Stan

I think that 390hp 428 may have been a little overrated, or the 360hp GTO 455 engine was underrated. [/QUOTE]

There’s no way the ‘70 455 GTO was the dog it was made out to be.

One of those #64 head 455's, with no change except an 041 clone cam/Rhoads lifters, ran 12.40's in my '68 Bird bracket car. The Bird had 3.55 gears & a stock 13" converter [/QUOTE]

....and right there; ‘70 GTO 455, had it been offered as a RAIV would have been up there with LS6 and Stage 1 (at least in stock form). Shame that.

They did try, what was left became the 73-74 SD 455. But it was low CR.
The plan was to build a 10-1 CR SD 455 in 1970, but did not work out. Chevy the cause ?
Its one of the reasons I hate Chevy.[/QUOTE]

I’ve seen this referred to on a few occasions - what was the deal there? I get that Chevy was supposed to be the performance division, but what happened?
421s were a genuine competitor to Max Wedges, I don’t think 409s were. (I may be wrong!)
I’m pretty sure Pontiac were dealt a sh*tty hand but what was going on behind the scenes?

Car s where getting heavier all the time as more options became available, especially in the big B body line that had station wagons !

The 455 was already beginning development when the 428s first showed up as a production motor.

A new motor does not just come along in one production season that basically started very August for the new year cars.

The 428 is very similar to the olds 425 on bore and stroke. 425 was made 1965-1967, with factory forged crank and 7.0" forged rods. Same argument, some say its better than the 455 which came later. Whether pontiac or olds, or whatever, its a good bore/stroke combo!

While 428 sounds cool (maybe piggybacking off CJ fame) just like I always thought a 427 sounded cooler than a 454. The correct answer is almost always more CI. Modern forced induction solutions aside, the easiest way to increase power while maintaining reliability/driveability is to make it bigger. Im sure Gm engineers knew that.


a 450hp 400 is going to be harder working than a 450 hp 455.

Don't forget about the '71-'72 455HO engines. Hey, with forged rods/pistons & a bigger cam, those engines would have been bad, even with their lower CR.

There have been LOTS of those engines run in Stock & SS over the years. Many of those cars were ordered specifically for drag racing. Still some out there today. Scott Underhill recently held the NHRA E/SA nat record with one. Thru the years, those engines have powered LOTS of record holders. Brad Burton just won Stock, at the AZ Nats with one. :)

Unfortunately the head flow capability that the Olds heads had be it 425 or 455 cid sucked when compared to even a stock D port high comp head of the era, no less the RA4 heads!

The 4" stroke combo's are my favorite. Pressure to be cool for more cubic inches from the street crowd made the 455 a reality. Nobody cared about fuel mileage for emissions, just give me a big gas burner was the mindset.
If we could have seen a 428 with Ram Air II/IV heads or the later Ram Air V's heads, Along with a factory aluminum Intake and a Holley 800 in 67/68/69 Firebirds/GTO's it would have been a game changer.

How would a RAV Intake had worked on D port or RA4 heads Mike?

Steve,
I think you misread-
If we could have seen RAII/RAIV or the later RAV heads with an aluminum intake.
There is a comma between the head part and intake.
I have owned RAII, IV and V parts I understand they are not the same.
But I edited it to make it more clear.

Steve,
I read that as a reference to the heads and then after the comma some other ideas.

Stan

Mike,
I know because of the bore spacing that they could not go really big bore, but they could have gone 4.2" bore and 4.11" stroke and gotten the same cubic inches.

Stan

Because Pontiac had to do something to try and keep up with the other brands

:D

Agree. Very limited by bore spacing.

I am currently running a 4.050 stroke in my 421 and feel it is a great combo.
Have a few 421/428's as back ups and they all ran as well as expected.

Interesting that you've bench flowed Olds stock B, C, D, & F heads & they flowed less than a '67-70 big valve Dport head's 205-208 cfm. the peak flow data I've consistently seen on many untouched Olds heads with good valve guides is they flowed between 230-240 cfm at .500 lift (28" depression). No port work. From flow sheets all performed the same day on my own round ports that's in the range of the best stock flow '71 HO's to stock 722's.

And what of the exh side of the Olds heads?
On the Exh side there down 15 to 20 cfm @ .200" lift as compared to a high comp D port head with a 1.77" valve.

Don't the Olds have like 2.072" and 1.625" valves?

Stan

Approximately but there is ample room to use bigger valves.

A race ported factory Olds head will flow around 290 @ 700.

Gentlemen, you are missing a major point in the development of the 455: emissions. Under square engines produce few emissions than over square or square engines. The first emissions control protocols were already in effect in CA.

Haven't you ever seen an Internet thread road map... It zig zags all over the place. Kinda like one of those spaghetti maps that predict the path of a hurricane :D

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.

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!

One thing you have to remember are the people who replaced DeLorean after he left Pontiac and went to Chevy. None of them starting with James McDonald were car guys. That is why Pontiac got caught with their pants down with the 455. Also, the idiot that was the division manager during 1973 was against the SD455. That is part of the reason why it was late on top of the EPA issue.
These non gear heads screwed Pontiac. That is why I always think of what Pontiac might have been if Delorean was the division manger through the end of the 1970 model year.

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.

If that is the case why was the Pontiac 301 so over square?

Stan

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.

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?

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

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

Stan

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

Stan

Hmmm, all the jet boats and mini off shore racers I ever saw or rode in were mainly BBC's with a few exceptions. My buddies jet boat ran a 460 ford with a tunnel ram. I don't ever recall seeing one with an Olds.

The old 403 has terrible flowing heads which was ashame since it had a great big Bore size.

Buick wise other then the nail head motors they have quite poor oiling systems even for just a steady 4500 rpm, so they out of all of these motors would never survive!

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!

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 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. Think of how fat these cars got by 1975-77. A 8:1 400 with 2.76 gears can't get out of its own way. They also didn't know how low the octane was going to go in the lead free gas. They figured a low compression, lean burn, low RPM tractor motor would get the job done until things got sorted. I assume they killed the 455 after '76 because it was too thirsty and they couldn't lean it out to overcome the crevice volume and pumping losses. The 350s and 400s that were left were woeful weak sauce. 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

Most of the ones her in Texas were Olds motors. My best friends could pop 3 of us up at once skiing! We had a powerplant lake you could ski on so even into the fall after summer jobs or school go out and ski until dark!

There were a lot of Olds powered jet boats in the early 80's were I was in CA as well. As a mechanic at a general shop (worked on every make) from the late 70's through the mid '90's, I saw a lot of the old large-bore V8's. Of them all, the Oldsmobile 455 was the most durable, and would put up with the most abuse/neglect. So running an Olds in a boat at high load most of the time would make sense, as there would be less down time. BBC's had valve issues, Cadillacs liked to toss rods, and Pontiacs liked to spin bearings. The old FE Fords were durable, but by then, the 427's were a lot of money. Used Olds 455's were cheap and all over the place...and they held up.

1968 Catalina 2-door sedan 4-speed
 

Check out Post 182 of this thread. A 428 setup like this would possibly make even more power with a 744 or ra iv cam.

I really wanted to get into jet boats in the mid 70's and likewise, those blue 455 Olds jets seemed to be everywhere.

My friend was really into the W30 455's in those days and had some trouble keeping the rod bearings from spinning.

Because no one would care if the boats sank :D

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.

Olds 403 was a decent engine. If your TA came with one they can be built to put a smile on your face.

I have 3 455 powered cars; I love the diesel like torque. The TA is just a low mileage, low compression, unopened (sans timing chain) 1971 455 but the torque is unreal. Even the 75 GV I have with a 200 horse smogger will light up the tires anytime.

Olds V8s are pretty durable but had a flimsy weak bottom end if you plan on pushing them unless you use the diesel block or girdled it.

Precisely, Paul. The Big Three were already aware that unleaded fuels were coming. The extra displacement was to compensate for the drop in compression ratios that had already been mandated for 1971. Yes, the bureaucrats at EPA really should have left the engineering to the engineers. It's odd: we are coming full circle. In order to conform with more stringent environmental and fuel economy standards we are returning to high compression engines. I read an article a few weeks back that stated that 87 octane unleaded regular will soon disappear because many of the engines powering hybrid vehicles utilize engines with 10:1 or higher compression ratios. The new grades will be 89 octane unleaded regular, 93 octane mid grade and 100 octane premium.

A 4" bore and a 3" stroke isn't that over square, Stan. Think about it: the 301 also had an air pump, catalytic converter, altered carburetor jets and ignition timing plus it was designed for unleaded fuel from the get go.

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.