Stripes, Funny that you should mention the 455 SD engines.
In the early 70s (before 1973 and 1974), I was at a university located a few miles from my uncle's Pontiac Dealership. I was talking one day with a couple of college age guys and they said they worked for Pontiac Engineering in the summers as engine dyno operators.
They were Dyno Operators on the 455 SD Engine Program!
They mentioned a bunch of engine failures they saw on that engine.
Said they were blowing those engines up left and right.
Now in my research job we ran engines to failure too. Several times we had 2800 hours on the engines and no failures. Other times the engine's parts just failed from fatigue.
The people I was talking to told me about other failures.
Oiling failures, connecting rod failures, distributor drive failures (gears on the distributor and camshaft), to mention a few. Pontiac Engineering changed MANY things on the 455 base engine to give the 455 SD engine durability. See list below:
So Pontiac Engineering went to Teledyne - Continental (located on the western side of lower Michigan) and had them make the first 455 SD "A" Forged Connecting Rods.
Pontiac Engineering redesigned the Pontiac block to use the larger distributor gear and a camshaft to use the smaller distributor drive gear.
Pontiac had Melling Tool (Melling Oil Pumps) come up with a higher pressure oil pump.
Same gear set just a different contril pressure (80 psi) for the 455 SD engine.
I could list many other changes to the 455 SD engine to make it live.
Here is a quick summary: (info from a Hemmings Article)
The most expensive SD replacement item is the block itself. It's a unique casting, identifiable by the "132" (corresponding to its casting number of 490132) found on the driver's side of the block (1). Prices for the scarce few used and Service Replacement Super Duty short- and long-block assemblies that make it onto the market have exceeded the five-figure mark. Regular production 455s will have the displacement, instead of the casting suffix, marked on the driver's side (2).
Through the years, Pontiac included reliefs at the bore edges on those engine castings destined for use in high-performance applications with larger valves. The SD blocks are among those that received this treatment to unshroud the valves.
While not as much of an issue on stock-specification engines, those modified for performance with high-lift camshafts and high-rate valve springs running higher rpm often cracked around their unsupported lifter bores (4). The SD addressed that issue with added cross bracing between the lifter bores (5). The main bearing saddles were also thicker, as were the engine mount bosses on the torque side of the engine.
Four-bolt mains with nodular iron caps are another Super Duty trait. The SD engines did not come with windage trays, though this example's caps have been modified to accept one (6). A baffled oil pan came into use in 1973 to control slosh and prevent oil starvation during hard cornering. Standard 455s came with two-bolt main caps, usually equipped with a windage tray mounted on studs on the caps (7).
The 1973 SD engines were cast without an assembly-line transfer lug, also known as the "mountain" or "pyramid" (8). Super Dutys assembled for the 1974 production run had the transfer lugs used to move the blocks down the regular production lines (9).
A larger distributor gear was intended as a solution to issues with camshaft gear wear in high-performance applications. Getting the distributor with the large gear to fit into the block required an oversize distributor hole (10). This was also a feature found on the 303, 366 and Ram Air V 400s. The standard production block's distributor hole is shown for reference (11).
Rather than utilize a new distributor core casting to accommodate the oversize gear, the SD distributor was fitted with a sleeve. Accordingly, the corresponding cam shaft gear was undersized to match.
The rear of a regular production 455, or just about every other Pontiac block for that matter, is a rather nondescript affair. (Pontiac Engineering slipped in a hidden dry sump oil system designed into the 455 SD blocks.
To accommodate the dry sump system, an SD block's backside is a rather busy place. The spur-gear-style oil pump was designed to fit in the oversize opening around the cam bore. The pump was driven at half engine speed by a keyed protrusion on the back of the spur gear, which slotted into the back of the camshaft. The spur gear fed the oil into a unique oil galley, seen at the right upper part of the opening; this galley led to the oil filter mount pad and needed to be drilled out at that end to open it up. The large flat area around the opening was pre-machined relatively flat for the pump cover.
This rare-as-hen's-teeth spur gear system pumps the oil to the SD-unique galley, which leads to the oil filter mounting pad. An intermediate keyed stub rides in a bearing installed in the block. The bearing opening must be precisely machined in relation to the cam bore. The stub then interlocks with the back of the camshaft, with the gear system itself fitting into the large central opening.
Here's the cover plate for the pump gear. To complete the installation, you have to drill and tap the cover's mounting holes. At the filter mount, an adapter/bypass block is required to route the oil to and from the sump tank.
At the front of the SD block, there isn't much different from the regular production 455 with the exception of the oil plug holes. These were tapped and fitted with threaded plugs to avoid leaks and potential blowouts. The SD's 80 p.s.i.-rated oil pump (compared to the stock 60 p.s.i.-rated pump in the standard 455) did cause some issues during cold starts early on: Some folks blew out their oil filters during the first start of the day.
The full casting/part number is also found at the top right rear of the block.
There are four possible engine codes for Super Duty engines: XD and ZJ denoted automatic and manual transmission-equipped cars in 1973; Y8 and W8 are the corresponding codes for 1974.
(Ken Crocie was involved in putting the article together for Hemmings writers)
I will not post the Pictures from the article but here is the link:
https://www.hemmings.com/stories/art...side-the-glory
So knowing Tom Nell on a personal basis, (RIP Tom), and talking to Herb Adams for hours at different car shows you get the real story on the 1972 455 engine vs the 1973 & 74 455 SD engines.
So to answer your question, if you did not use the Pontiac Engineered 455 Oil pump drive system you could have excessive wear on the camshaft and distributor drive gear.
Drag Racers or car show people would never see the difference in wear.
Tom V.
ps Stripes, you ask a lot of good questions and voiced your opinion on the subject.
I posted facts. Pontiac Engineers changed stuff on the 455 SD engine vs the normal 455 engine for REASONS.