[Mr. P-Body]

All Pontiac V8s use the same cam bearings, '55-'81, and all are the same bearing, regardless of "position" (I never understood why more didn't use the same approach, "Lima" (385 Series) Ford being one that did). The "line" from '63-on involves the older "through the stud" oiling for rockers and the later "through the pushrods". Some of the brands eliminated the two "extrra" holes that would feed pressure to the heads. Oil "oozing" out of the rockers while running is correct. Oil "squirting" indicates either worn rockers or worn pushrods or both.

Seldom does the Pontiac have a "bad" cam bore. We see it with 455s more than others, due to the excessive stroke and high stress at lower speeds (tremendous low-end torque, "flimsy" block). I can't recall the last 400 I saw with cam bore issues.

Clevite and Sealed Power bearings are okay for moderate spring pressures. DuraBond are "the good stuff". P-4 is the "standard" bearing and PP-4, the one for higher spring loads (good to 300 lbs. seat pressure).

A "sloppy" timing chain is a problem. If you're certain the block's never been align-bored or honed, there's "something wrong with this picture". Pontiacs, like Olds, were machined to very "close" tolerances from the factory. We seldom see an issue with the main tunnel, squareness of decks, etc. The most common issue we see is another shop align-honed one "wrong", when it probably didn't need it in the first place. Installing studs will NOT distort the main bore like it may in other engine families, the main caps being "doweled" instead of "registered" is the reason. This is also why the Pontiac enjoys such a strong bottom-end when quality parts are used. At very high power levels, "cap walk" is a non-factor.

Make certain your valve springs are correct for the application. Make sure to follow the break-in proceedure as outlined by your cam grinder. If that includes removing the "inner" springs, REMOVE THE INNER SPRINGS!!! Pop always said: "When all else fails, follow instructions..." What is the seat pressure? Nose pressure? You didn't, by chance, change to 1.65:1 rocker arms?

48s are not "Ram Air" heads. That name is "reserved" for large-valve (2.11/1.77), "small chamber" (72, advertised) and ROUND exhaust ports. 48s are good heads, but have "d-port" exhaust. And yes, were installed on '69 "Ram Air" engines with 366 HP. They were also on "non-Ram Air" 350HO engines and 350HP 400s, as well as 375 and 390 HP 428s. Don't worry, this is a common area of misnomer. The same is true of the 1970 casting no. 12. '68 "Ram Air II" (casting #64), '69 (744) and '70 (614) Ram Air IV engines are the only ones equipped with "Ram Air" heads. '71 and '72 had "HO" heads (round port) and '73-'74 were "Super Duty". The 455 heads have HUGE combustion chambers (101-124, depending).

Using the '69 engine, if you haven't taken steps to lower the static compression to under 9.5:1, you ARE experiencing detonation if using 93 octane or lower. We "dish" the pistons to accomplish this. Once that's done, the 068 cam is going to be inadequate. It "likes" higher compression.

FWIW

Jim

 

[Mr. P-Body]

I just went through the "exercise" of measuring all these things.

Cam tunnel holes measure 2.298" (three different blocks, all within .0003" of each other). OD of uninstalled bearing is 2.030-2.031" (stock type, same with "performance"). Installed, ID is 1.900" "on the nose". Cam journals on two NEW cams are 1.898".

When the bearing is installed, the "crush" of .002" reduces the ID to the correct size. The "interference' fit is required to keep the bearings "in place". I have never seen a Pontiac "turn" a cam bearing. Olds and Buick? Yes. A 455 Buick will wipe the cam bearings out in a couple of minutes if not properly installed or the engine is overheated.

Minor scratches on cam bearings is not a big concern. From a strictly technical POV, they're not really "bearings" per se, but "bushings".

Restricting oil to the cam bearings is not a typical "modification" done to Pontiacs. SOME builders will "block" the passage when roller cam bearings are used (lubed by "splash").

Semantics are not the "issue" with the d-port heads. It is very misleading to call the d-ports "Ram Air" because it confuses them with "real" Ram Air heads. As a Pontiac guy, I want accurate info "out there". It's hard enough to get folks over the "rod issue", much less all the misnomers.

FWIW

Jim

 

[Mr. P-Body]

I've also never seen a "loose" Pontiac cam bearing (in a factory block, that is), and I've seen a "few" Pontiacs...-

The DuraBond cam bearting tool, considered the BEST available, is just as you describe. An expandable inner ring with a "rubber collar". The metal ones are "old school" and used for tear-down in most shops today (those that still have them). Of course, in the proper hands, they still "work". We've found, if over-tightening the bearing to the tool, it WILL distort it and cause problems installing the cam. Just enough tension to keep it "in place" and not so "loose" it would drive the tool "through" the bearing is called for.

Jim

 

[Mr. P-Body]

Every shop has cam "reamers" hanging around. By cutting "flutes" (of sorts) in the end journal, one can accurately "ream" a cam bore. Cams don't "bend"... (they break!)

455 blocks seem to have more issues with cam bores than 400s. I believe the added stroke really "works" the block, even in a "big car" application. Most 421s and 428s (4") stroke) I've seen were okay.

Jim

 

[Mr. P-Body]

There are several ways to "skin this cat". Which installation tolol you're using makes a difference in the process.

First and foremost, who ever told you Pontiac takes "hours" to put cam bearings in, should be avoided at all cost in the future. Having installed cam bearings in literally hundreds of ALL types of engines, mostly American V-8s, I can say with "authority", Pontiacs are among the least "troublesome". From their "era", in particular. Ford FEs, BBCs and Buicks come to mind as "problem children". Ford "Y-block" is THE WORST... It takes, literally, about 15 minutes to install cam bearings in ANY V-8, and IF things go "well", they present no issue. About 95% go without issue. The Pontiacs that HAVE given me trouble were nearly always 455s that had been over-heated in their previous "life". MAYBE 5 blocks in 10 years have "fought".

Blocks that have the same bearing in every bore are "through bored" (in one operation). Pontiacs and Ford 385s (Lima) are two I know of. Most are, as described, bored from each end, "meeting" in the middle.

We always install them from the front, all 5 positions. "Floating" the front one (no centering cone) is the method I was taught 40 years ago. Still works for me. Takes "practice", though. Perhaps the front one is better installed from the rear in this case. Take care not to gouge the other bearings as you put the tool in.

FWIW

Jim

 

[Mr. P-Body]

Keith, check DuraBond first. May have a PP-4 "coated". I can find out Monday. PP-4 lives under 250 lbs. seat pressure solid rollers.

Main tunnel should be measured before align-hone is done. Pontiacs don't generally require it after studs are installed (doweled caps, not "registered"). If it ain't broke, don't fix it. Stock blocks are very good regarding machine work.

Jim