I'll admit that it could well be possible that the moly rings, Tri-Metal (i.e. Clevite 77) bearings, and double-roller timing chain could well have been items added with the change to 8.2 CR in the 4bbl HP motors as they were running hotter, generall, with the higher temp thermostat, slightly retarded timing, and lower compression ratio (on my parents '72 Chrysler 400-2bbl, the exhaust temp at the end of the tail pipe was significantly hotter at idle than that of the '66 Chrysler 383-2bbl). The chrome/moly rings and double-roller timing chain (all metal sprockets) would have been long term durability items.
When the change to 8.2 CR was done, the timing events of the camshafts were lengthened a few degrees with added "overlap". This did two things--it tried to recoup some of the power loss due to the lower CR and also provided a little more residual EGR in the cylinder at lower speeds, but aided higher rpm power. Score one for Chrysler! Not major differences, but just enough.
In the diagrams for the chrome/moly rings, there is a machined inset in the vertical surface of the ring, about 1/2 of it's total contact area to the cylinder wall. Might be about .010" deep? That's where the molybdenum was added. The next progression upward from that style of compression ring is "plasma moly" where the contact surface of the ring is impregnated with the moly via a high temp "plasma" process. More costly and supposedly better, but much more "high end" than the regular chrome/moly rings.
The other thing about chrome/moly rings is that they need a much slicker cylinder wall surface to contact than the lower level rings. Hence, so long as the cylinder walls are not scored and piston clearances are not an issue, they work just fine with the existing cylinder wall surfaces without any honing ("dingleberry" or stone) operations. I've seen that work, although it tends to go against some service manuals, and was suggested by my machine shop associate.
The 440-6bbl cam was always suspected to be "bigger" when the vehicles were introduced, due to the added power output of the engine. The specs were the same as the regular 4bbl HP motor, though, but with the lower taper on the lobes (as mentioned). This resulted in a greater contact area for the lifter to the lobe, yet still was enough taper to spin the lifter in its bore during operation. 6bbl motors did have heavier valve springs too and a larger oil pickup tube for the oil pump and usually a baffled oil pan. I did score a new 440-6bbl oil pan for a Sport Fury 440 6-bbl from my Dodge dealer parts associate while they were still available new.
At one time, there were some "276 degree" numbers being published for that 6bbl cam, but if you average the 268 and 284 durationsm, intake and exhaust, it comes out to 276. Not sure why that number crept into things, but it was in some publications.
The Tri-Metal bearings are mainly durability items, as mentioned, but do have some downsides if there are dusty conditions, oil filter, or maintenance issues. Other than bearing types, the main issue with B/RB main bearings is the oil grooves in them. Factory, they came with a set that had one grooved and one non-grooved. The "hot trick" for high rpm use (back then) was to put a full-grooved set in their place.
The 4160 Holleys, Chrylser spec, seemed to have much worse service problems than the Carter AFB or AVS carbs. Usually, it was their many cork gaskets. When they worked, they were fine, but they usually took an annual rebuild (to basically renew the gaskets). After looking at Holley exploded views for years, when I finally saw the inside of an AFB from a '60 Chrysler, I wondered where the extra parts were--no comparison. As mentioned, the local Chrysler dealer swapped out many Holleys for the more troublefree Carters. The same dealer would not order any car that had a Holley on it, unless it was a "normal" car and not a factory hot rod.
In the more recent times, the bulk of the Holley issues have been addressed with much better gasket materials. Funny thing is, though, that I never heard any of the GM or Ford people complain about their factory Holley carbs. When I was in Lubbock in the early-mid 1970s, I posed the same question to the owners of the old Speed Equipment World (Lee and Jan Hefley, who were Chrysler people) and they had no answer either, just that the Chrysler factory Holleys were ____.
The Holley 4160s were 600 cfm units with 1.56/1.56 pri/sec throttle bores (except for the 1971 383/300 750 cfm Holley 4bbl I mentioned earlier). Normal issue stuff. The AFBs usually had 1.56 primaries and larger secondaries, just as the AVSs later did. Some of the middle 1970s ThermoQuads for the 440HP motors had 1.50" primaries instead of the normal 1.38" items.
The original 440/375 cylinder heads did use larger exhaust valves (1.75") than the regular 2bbl and 4bbl motors (1.60"), but made the 1.75 exhaust valve standard across the board in 1968 with the new "open chamber 906" heads. The earlier Max Wedge style motors used something like a 1.88" exhaust valve. In 1967, the previous 256/260 4bbl cam replaced the 252/252 degree cam (which dated back to the '58 Sport Fury 350 V-8 2x4bbl motor?) in the regular 2bbl motors too. It seemed that everytime something came up that would hurt power output per se, Chrysler found a way around it.
As was mentioned, the B/RB exhaust manifolds were first used in the 1967 440/375 engines, but later used on all of the B/RB 4bbl engines, standard or HP cam, at one time or another. There are specific ones depending on the body series and model year too. Hot air stoves for the hot air air cleaners, exhaust pipe flange angle and orientation are some signinficant issues regarding where they were originally used, for example, as are the casting numbers.
Interestingly, the LT1 Chevy 350 engine uses a smaller size exhaust manifold that looks like a copy of that 1967 Chrysler HP manifold. Other than the reverse flow cooling system and intake manifolding issues on the Chevy motor, it suddenly gained a good bit of horsepower from the earlier versions.
I guess the key thing was that even as emissions issues (lower CR, included) tended to beat down high performance engines and vehicles, Chrysler was still building basically the same HP/HO B/RB engines that they built in the later 1960s, just updated as they needed to to remain some semblance of their earlier orientations. GM and Ford (to a lesser degree) pretty much threw in the towel and had very few, if any, real high performance engines (much less real dual converter exhaust systems) as Chrysler did until 1978. Another reason that Chrysler police cars were favored, I suspect, as they still had power back then.
One thing to keep in mind, whether it's Chrysler, Ford, GM, or otherwise, all of the initial batch of sales brochures, Data Books, service manuals, and the first parts books were printed in a July/August time frame (before the October time frame new vehicle introduction date) as most of the approvals for the final vehicle were already made. That's why some of the chrome trim might not align as good as it was on the production models as the vehicles being used were pre-production vehicles. That's also why some of the illustrations in the service manuals might appear a little dated compared to what you might normally expect. As time went on, if there were any production changes, they might not be reflected in those publications (unless something of the order of a hand-written note was added, as mentioned in the ModTop Imperial comments recently). The parts books were usually updated with the separate part number change
book that was supplied quarterly (usually) to the parts department. These things are why the fine print on the bottom of the rear cover of the brouchure (usually) or at the bottom of the specs section about changes might be made after publication being possible is important (operationally and legally).
The Data Book could well have been updated for the spring time of the year too, but from what I saw back then (1975 time frame), not too often. Much less expensive to send out notification/modification letters to the dealer, I suspect.
In the realm of Mopar Muscle Cars, and restorations thereof, finding a verifiable "unmolested" vehicle is good. During restoration, documenting all of the production marks/paint daubs/ink stamps is highly important so that they can be reproduced after the particular part is cleaned and rebuilt/refurbished, and then correctly repainted/refinished. This extra care and documentation will take into account how the particular car was built specifically instead of how it "might should have" been according to the build instructions. The proof of those items rests with the restorer. At this point in time, many of the high level judges (i.e., Mopar Nats) are fully aware of those things too, unlike in prior times. Even if the build instructions were the same for a particular vehicle and assembly line, it was up to the people on the line to put the correct markings on the vehicles--the human factor. Hence, markings from one shift might be
different than the particular way another shift applied the same markings, not to mention if more than one plant built the same model of vehicle. The database of known knowledge on these issues and similar issues is humongously greater now than it was 30 years ago (back when only the Corvette people used to be worried about "numbers match" or correct paint stamps on the frame or the correct screw in the correct hole or the correct date code or casting number on something).
Back then, I wasn't keyed on those sort of things, but did notice new Chryslers come into the dealership back then that had grease pencil messages scrawled on the k-frame and the answer written on the rear portion of the car's undercarriage somewhere. A friend got a new 1968 Satellite 2-dr hardtop, 383-4bbl, car for high school graduation. In the trunk, under the mat, in the thick layer of sound deadening mastic (that was later painted body color) was the message written with a finger in the mastic "Vote for Little Vic" before it dried and was painted. A few of the messages I saw on the Chryslers could not be repeated, even now, in certain company.
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