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.