[steve25]

The factory info that I have and have posted up here in the passed in regards to 1970 motors clearly states that the 4 bolt caps where all Armasteel!

[Rocky Rotella]

Steve,

I don't doubt that 1970 info. I believe I have the same brochure you're referencing that from.

Let me go over what I can say with absolute certainty based on some of the internal engineering info I uncovered while preparing the Firebird books.

The early Super Duty engines aside, Pontiac was constructing its 3- and 3.25-inch main caps of the same gray iron as its blocks during the mid-1960s. Even the first 4-bolts caps for the midyear 1967 Ram Air 400 (9792506 block) were gray iron.

Going into the 1968 model year, particularly when nearing the release of the R/A II program, Pontiac began constructing its 3-inch 4-bolt caps of a special-alloy (malleable iron) for certain applications. These same caps continued on into the RAV program and the 1970 Ram Air IV.

It seems that Pontiac had high hopes for the 1970 455 and decided for 4-bolt applications to construct the main caps of a special alloy. Most 1970 455s were equipped with 2-bolt caps, however. The 4-bolt 3.25-inch caps, both before and after 1970 were constructed of typical gray iron. The SD-455 is the obvious exception.

So the 1970 info you found is certainly correct. That’s why I carefully chose the wording in my original posts.

[Tom Vaught]

My Favorite FACTORY Brochure is the one with the 64 Service Package) "Tube and Plunger Tri-Power Linkage" (Center Carb to Rear Carb installed on a 65 and later engine in a 65-66 FACTORY Brochure and the "Tube and Plunger" are installed incorrectly on the wrong model year engines. So I take any Info read in a Factory Brochure should be assumed to be advertising info and not as totally correct "valid engine info".

Tom V.

[avman]

When I had my wife's 421 rebuilt I used ARP studs in all but the end cap on the flywheel end of the crankshaft. It didn't "like" the studs. I was very happy to see 4 bolt caps! The motor wasn't stock when we got the 65 GTO, and I added a number of additional go fast goodies to it.

[Tom Vaught]

With the intent to go studs it is usually a good idea, in the machining of the block process, to at least verify that the block main bores are still round. Main Beatings (as well as Rod Bearings are retained in place by bearing housing 'crush"). To little crush and the bearing shell will slip. The little bearing tang locators are only that, Locators for which way the bearing shells are installed.

I have not seen any recent info, (maybe Paul and others can provide) on dimensions with today's bearing material and shells.

Tom V.

[steve25]

A question here on align honing a block with dutile iron caps .
When I port Buick heads that are cast with dutile iron they are a bitch as compared to remoning gray iron so how when doing the machining to you deal with how fast a Hone will remove gray iron as compared with dutile?

[hurryinhoosier62]

Originally Posted by steve25

A question here on align honing a block with dutile iron caps .
When I port Buick heads that are cast with dutile iron they are a bitch as compared to remoning gray iron so how when doing the machining to you deal with how fast a Hone will remove gray iron as compared with dutile?

Most diesels have ductile iron caps. They can be a little contrary, but hone just about like gray iron.

[steve25]

Avman, that's the nice thing about 421 blocks in that they where all 4 bolt!

[jamaca85]

Originally Posted by hurryinhoosier62

You got lucky...

racegto65 has run into the nines with his pontiac for years with no failures, i think it has to do more with knowledge than luck. i know him for years