[Formulajones]

Originally Posted by steve25

Sub title that "The reality street section"!

Sub title that " the old farts reality street section"

[MarkS57]

Originally Posted by Formulajones

Sub title that " the old farts reality street section"

Can't deny that one...followed by "Decrepit old farts reality street"

[Mr Anonymous]

Originally Posted by 70 bird

Didn't the Olds engines have those great windowed mains?

Not til 1976-77, and also went from 7/16 to 1/2" head bolts. Go figure.

That windowed main thing does not apply to the diesel blocks, nor the Foyt/Nascar blocks.

[PunchT37]

Originally Posted by Mr Anonymous

Not til 1976-77, and also went from 7/16 to 1/2" head bolts. Go figure.

That windowed main thing does not apply to the diesel blocks, nor the Foyt/Nascar blocks.

I had one of those. A `77 350. Maybe they thought the bigger head bolts would hold the whole engine together?

[Rocky Rotella]

As many had previous stated or eluded, the 455 was the natural progression of Pontiac’s largest full-size engine—which started at 421 and had already moved to 428—to maintain good acceleration as vehicle size and/or weight increased. And as mgarblik had so well explained, everyone else was doing it, too.

Pontiac’s official explanation can be found in the “engine changes” section of the 1970 Pontiac Engineering Manual. It states:

“This year a new 455 cubic inch displacement V-8 replaces the 428 in all applications. Its larger displacement gives it improved performance. The basic block design is the same as the 428, with the bore centers and water jackets remaining essentially the same. The additional displacement comes from a 0.031-inch bore increase and a 0.210-inch stroke increase. The crankshaft is new for the increased stroke while the heads and camshaft are modified from those on the 428.”

Additionally, I once asked Mac McKellar this very question. Why the jump to 455? His answer then was twofold and I’ll summarize.

1. Pontiac had been increasing engine displacement to improve performance ever since its V-8 was introduced in 1955. During the 1960s, its small-car 326 went to 350, its intermediate-car 389 went to 400, and its full-size-car 421 went to 428 and then to 455 (at least developmentally). Its OHC-6 increased from 230 to 250 as well. Mac said the 455’s longer stroke was an effective way at ensuring that plenty of torque was available to satisfy the average customer’s acceleration expectations, particularly at take-off and in low rpm passing conditions.

2. Pontiac’s closest competitors—Chevrolet, Buick, and Oldsmobile—had each stepped up the displacement of their largest engines at that time, and Pontiac—who celebrated most of the 60s as the nation’s third largest automaker—wasn’t prepared to be left behind, especially when GM opened the 455 to the intermediates (A-body). So Pontiac’s Sales department was also pushing Engineering for a 455.

Ironically, the continuous displacement increases at Pontiac (and really with all GM brands) ended around 1970 when emissions and fuel economy became significant issues, and ultimately led to the stark displacement reductions of the later 1970s.

While the explanations above mirror what many had already stated, it gives insight into Pontiac rationale as a company and from an key insider.

[steve25]

You younger guys need to understand that if it was not for us so called by you "older guys " you would not have these cars today to enjoy because we where the original target market they made them for!

I myself was blowing up Pontiac motors looking for more power before many of you where even a twinkling in your parents eye's if you will, lol!

Also as you can see by my photo I had 650 HP street car that could be driven anywhere in 1979" the year that this photo was taken as seen here!

[RocktimusPryme]

Originally Posted by Formulajones

Sub title that " the old farts reality street section"

"400 HP is enough dag nabbit!"

Joking aside, while its certainly an older crowd (Im 36, this might be the only place left where I get called young) there are plenty of very progressive minds on this board in the name of making horsepower. Especially if you hang around long enough to pick out the names you should be listening to, you will generally get steered in the correct direction here.

Im part of other hot rod groups that are waaaaay worse on the old guy mis-information speak. Which people can think what they want, but I hate when someone who genuinely doesn't know gets influenced by that "3/4 race cam!" mentality.

Back to the topic, Considering pretty much everyone who can afford to adds that stroker crank in their 400, I would think the reason to go bigger than the 428 is obvious.

[MarkS57]

Originally Posted by steve25

You younger guys need to understand that if it was not for us so called by you "older guys " you would not have these cars today to enjoy because we where the original target market they made them for!

I myself was blowing up Pontiac motors looking for more power before many of you where even a twinkling in your parents eye's if you will, lol!

Also as you can see by my photo I had 650 HP street car that could be driven anywhere in 1979" the year that this photo was taken as seen here!

Yeah, I happened to be driving my 69 428 Bonneville in 79. Newer cars were really struggling with any level of performance back then. Mine looked like the attached except it had parchment interior. A car I regret selling, but I kept the engine

[77 TRASHCAN]

Mark, Still got that engine???

[Formulajones]

Originally Posted by steve25

You younger guys need to understand that if it was not for us so called by you "older guys " you would not have these cars today to enjoy because we where the original target market they made them for!

I myself was blowing up Pontiac motors looking for more power before many of you where even a twinkling in your parents eye's if you will, lol!

Also as you can see by my photo I had 650 HP street car that could be driven anywhere in 1979" the year that this photo was taken as seen here!

I'm no spring chicken anymore but I also refuse to grow old, least that's what I keep telling myself. Hell my dad is well into his 70's and I think he has one of the more radical street engines in this forum and he's not afraid to drive it. To him it was just another street build to have fun with and it goes everywhere a stock engine goes and does everything just as well, except maybe pass a gas station

So when I refer to old farts in here It's more about poking fun at those that feel they need 25 inches of vacuum and a baby smooth idle or otherwise it just can't be driven. Because to me that doesn't sound like a real car guy, it sounds like someone that needs a Cadillac. It's all good Steve, don't take offense to it

[Formulajones]

Originally Posted by RocktimusPryme

"400 HP is enough dag nabbit!"


Back to the topic, Considering pretty much everyone who can afford to adds that stroker crank in their 400, I would think the reason to go bigger than the 428 is obvious.

Exactly!! The only reason I build a 428 more than 20 years ago is because we simply had the parts laying around, and back then aftermarket stroker cranks weren't readily available like they are today.

Doing engines today I generally look at 455 and larger. Prefer cubic inches. Especially considering the costs involved are nearly the same.

[MarkS57]

Originally Posted by 77 TRASHCAN

Mark, Still got that engine???

Yes I do, its followed me around through a few houses etc since about 1983. I pulled the engine & replaced it with a 72 400 prior to more or less giving the car to a relative.

[77 TRASHCAN]

Originally Posted by MarkS57

Yes I do, its followed me around through a few houses etc since about 1983. I pulled the engine & replaced it with a 72 400 prior to more or less giving the car to a relative.

Good thinking!!!

[Mike Davis]

Originally Posted by Formulajones

So when I refer to old farts in here It's more about poking fun at those that feel they need 25 inches of vacuum and a baby smooth idle or otherwise it just can't be driven. Because to me that doesn't sound like a real car guy, it sounds like someone that needs a Cadillac. It's all good Steve, don't take offense to it

Funny.
I agree. I drive my 66 GTO a good bit. While not a radical build it does run 9.85 at 3750lbs and I race it hard.
Drove it 25 miles last weekend to grab some lunch.

[Douglas Willinger]

During the time of Pontiac's engine development from the aborted LS-1 SD400 (Ram Air IV headed Ram Air V short block) engine development,what was the rationale for the piston valve relief design of the SD455? Was told by a gentleman who sold me an SD455 piston that such was for high compression, yet the SD455 was ow compression. Was it for superior resistance to engine knock, say with an SD400/428 or 455 with high compression, and perhaps some superior octane fuel?

Originally Posted by Rocky Rotella

As many had previous stated or eluded, the 455 was the natural progression of Pontiac’s largest full-size engine—which started at 421 and had already moved to 428—to maintain good acceleration as vehicle size and/or weight increased. And as mgarblik had so well explained, everyone else was doing it, too.

Pontiac’s official explanation can be found in the “engine changes” section of the 1970 Pontiac Engineering Manual. It states:

“This year a new 455 cubic inch displacement V-8 replaces the 428 in all applications. Its larger displacement gives it improved performance. The basic block design is the same as the 428, with the bore centers and water jackets remaining essentially the same. The additional displacement comes from a 0.031-inch bore increase and a 0.210-inch stroke increase. The crankshaft is new for the increased stroke while the heads and camshaft are modified from those on the 428.”

Additionally, I once asked Mac McKellar this very question. Why the jump to 455? His answer then was twofold and I’ll summarize.

1. Pontiac had been increasing engine displacement to improve performance ever since its V-8 was introduced in 1955. During the 1960s, its small-car 326 went to 350, its intermediate-car 389 went to 400, and its full-size-car 421 went to 428 and then to 455 (at least developmentally). Its OHC-6 increased from 230 to 250 as well. Mac said the 455’s longer stroke was an effective way at ensuring that plenty of torque was available to satisfy the average customer’s acceleration expectations, particularly at take-off and in low rpm passing conditions.

2. Pontiac’s closest competitors—Chevrolet, Buick, and Oldsmobile—had each stepped up the displacement of their largest engines at that time, and Pontiac—who celebrated most of the 60s as the nation’s third largest automaker—wasn’t prepared to be left behind, especially when GM opened the 455 to the intermediates (A-body). So Pontiac’s Sales department was also pushing Engineering for a 455.

Ironically, the continuous displacement increases at Pontiac (and really with all GM brands) ended around 1970 when emissions and fuel economy became significant issues, and ultimately led to the stark displacement reductions of the later 1970s.

While the explanations above mirror what many had already stated, it gives insight into Pontiac rationale as a company and from an key insider.

[John Milner]

I'm kind of partial to 428's. They just build tons of torque and love to rev. I wish Pontiac could have made a Ram Air IV 428 in '69. That really would have been a great engine for a GTO or Firebird.

[tom s]

I have a RA V 434 sitting on the run stand im my garage.It is replacing the 455 in my 69 bird.The 455 replaced my 366 RA V engine.Because of the trans and gearing,im bettting I could not tell the diff in street driving!Tom

[Douglas Willinger]

Thread on my 434 Ram Air Iv build:

http://psp.aquacomp.net/topic.asp?TO...TOPIC_ID=13682

[Nicks67GTO]

My 4" stroke 400 block, 312cfm e heads, T2, sft cam combo absolutely rips. There is TQ everywhere, it likes to rev and I beat the **** out of it autoXing. Glad I went 4" stroke.

[72LuxuryLeMansLa.]

Originally Posted by Douglas Willinger

Thread on my 434 Ram Air Iv build:

http://psp.aquacomp.net/topic.asp?TO...TOPIC_ID=13682

Doug,
The link brings me to the log on page.... Guidance to find the thread?