[PontiacLars]

Why did Pontiac engineer the block like this? I do not see this design on Chevy, Ford or Chrysler..
i assume there was a thought behind this open design.

[steve25]

Why you ask?
Because it was all the strength that was needed to support a hydro flat tappet cam.

It may not seem like a lot , but that reduction in cast iron from what was needed to have made a enclosed
Lifter valley saved a lot of cast iron and in turn production cost on at least 70 to 100,000 blocks a year !
The open lifter valley also helps the crankcase vent better and also the oil to drain better and as it drains gets put to real good use in keeping the Cam lobes lubed.

Pontiac designers never in there wildest dreams thought that there lifter valley design of the block structure would ever be called upon to handle / accept roller lifters and 600 plus pounds of spring open pressure, nor handle Nitromethane fed thru a blower with hp levels being achieved of over 800 hp that would split the block right tru the main web’s which is a issue that having a solid lifter valley could have helped with.

Don’t knock the Pontiac block, as it was so well conceived from the start in 1955 with a cid of 287 that the engineers where able to stretch it up to 455 cid with out making any major outside design changes to the block.

No other GM passenger car motor that they ever made was able to grow 168 cid without coming out with a totally different block design!

In short I would have to say this, don’t look a gift Horse in the mouth so to speak!

[Steve C.]

Engineers Clayton B. Leach and Ed Windeler developed this cast-iron engine. One of the features described.....

"pressure-suction crankcase ventilation"


https://www.enginebuildermag.com/201...tiac-v8-power/

.

[sdbob]

I remember as a teenager working on his helping friends. It was a pain to remove old lifters from a chevy to install new cam by hand without special tools. Pontiac , I thought man this is easy to grab and work lifter free. Never thought as was said about lifter valley being open.

[PAUL K]

Originally Posted by sdbob

I remember as a teenager working on his helping friends. It was a pain to remove old lifters from a chevy to install new cam by hand without special tools. Pontiac , I thought man this is easy to grab and work lifter free. Never thought as was said about lifter valley being open.

You are correct. Lisle used to make a lifter puller tool. I remember seeing it at the auto parts store and thinking it was a scam. Then I helped a friend replace his lifters on his SBC and realized why one might need that tool.

[PunchT37]

Buick and Olds blocks are open like that too.

[Half-Inch Stud]

I recall that only 2 Lifter bores are weakened: Both on the Even Bore side.

All Odd Bores are plenty tuff.

[Douglas Willinger]

How much money was saved by such a design per unit.

Suppose they had instead used the RAV/SD455 design? How much cosltier per block?

Originally Posted by steve25

Why you ask?
Because it was all the strength that was needed to support a hydro flat tappet cam.

It may not seem like a lot , but that reduction in cast iron from what was needed to have made a enclosed
Lifter valley saved a lot of cast iron and in turn production cost on at least 70 to 100,000 blocks a year !
The open lifter valley also helps the crankcase vent better and also the oil to drain better and as it drains gets put to real good use in keeping the Cam lobes lubed.

Pontiac designers never in there wildest dreams thought that there lifter valley design of the block structure would ever be called upon to handle / accept roller lifters and 600 plus pounds of spring open pressure, nor handle Nitromethane fed thru a blower with hp levels being achieved of over 800 hp that would split the block right tru the main web’s which is a issue that having a solid lifter valley could have helped with.

Don’t knock the Pontiac block, as it was so well conceived from the start in 1955 with a cid of 287 that the engineers where able to stretch it up to 455 cid with out making any major outside design changes to the block.

No other GM passenger car motor that they ever made was able to grow 168 cid without coming out with a totally different block design!

In short I would have to say this, don’t look a gift Horse in the mouth so to speak!

[Tom Vaught]

There was a speed shop in the Dearborn Michigan community called Mayfair Auto Parts.

Joey Fair, I believe was the owner. He was a dirt track racer and liked Pontiac engines.
(I have posted about the following subject in the past).

Joey liked stroker engines and ran 4.5" stroke cranks when the 421 Pontiac crank was a 4" crankshaft. Whitey at Moldex Crankshaft would make the forged cranks for Joey.

One of the mods Joey would make was to add 3 cross bars between the heads to help
support the upper end of the block when using the stroker cranks.

I posted this info years ago for Dick Duclow and Tom, as well as Bob & Frank.

And Dick and Tom and Bob and Frank had the first Indian Adventures blocks cast up with a Sealed Lifter Area as well as all of the All Pontiac Blocks.

Rodney Butler ran one of the Indian Adventure blocks for years.

So there WAS A REASON why the aftermarker blocks were cast up with a closed lifter valley.

Thanks Joey Fair, Dick/Tom, and Bob/Frank for that design.

Tom V.

[slowbird]

Originally Posted by Half-Inch Stud

I recall that only 2 Lifter bores are weakened: Both on the Even Bore side.

All Odd Bores are plenty tuff.

Yes 2 weak bores found here.

[68WarDog]

Originally Posted by slowbird

Yes 2 weak bores found here.

Is that a solid roller with no bore bracing?

[slowbird]

Originally Posted by 68WarDog

Is that a solid roller with no bore bracing?

No, HR

[Dragncar]

I asked Jim Butler that very question. He said " to save 50 cents a block".

[GOAT8U2]

Slowbird, sad to see that. Is that from rpm, too much spring tension etc?

[Dragncar]

Originally Posted by slowbird

Yes 2 weak bores found here.

Which engine was this ? Sucks.
Its my nightmare to tell you the truth.

[Cliff R]

The only Pontiac engine we ever lost here took out a lifter bore and it had a brace in it. It was using a pretty hefty solid roller cam, lots of spring pressure and drag race only. It lasted 13 runs after the rebuild. The engine let-go in the lights at 6400rpm's and about all we saved from it was the oil pump and a few of the Crower connecting rods!......

[Mike Davis]

3 years ago when I broke a valve in my 421 in Fla, I had a 400 stroker build I bought from a friend to use as a spare, I threw it in the car for the Atlanta race while the 421 was getting sleeved. Thought for 1 race I would not put a brace in it since the engine was already assembled. 270@.050 solid roller.
It let go at the finish line in lights at 6700 and nothing was salvageable. Wild ride at 134MPH.

[Mr Anonymous]

Originally Posted by PunchT37

Buick and Olds blocks are open like that too.

Yup, and no discussion of them breaking. Then lightening up the main webs from 1977+ by leaving big holes in them, ugh. But I put 280,000 on a 1977 olds 350, so they do last with barely adequate maintenance and decent amounts of abuse.

[Cliff R]

"Aggressive" roller lobe profiles and strong springs are a recipe for disaster with a Pontiac block. Even with a brace in it you can still loose one as we did.

Haven't had any issues to date with "softer" roller cam profiles and lesser spring loads, so really nothing to worry about unless you are building a pretty high end or max-effort street/strip or full race engine, and even then with a brace in them we aren't hearing about a lot of folks busting out lifter bores......

[scott70]

Originally Posted by Cliff R

"Aggressive" roller lobe profiles and strong springs are a recipe for disaster with a Pontiac block. Even with a brace in it you can still loose one as we did.

Haven't had any issues to date with "softer" roller cam profiles and lesser spring loads, so really nothing to worry about unless you are building a pretty high end or max-effort street/strip or full race engine, and even then with a brace in them we aren't hearing about a lot of folks busting out lifter bores......

so I assume its the side loading of the lifter that breaks the bore?