From what I discovered, the B/RB heads did not always have 2.08" intake valves. Also be aware that the 413 was the first "B-family" engine for the 1958 model year, so the "bigger than 383" engines pre-dated it. I know this as I happened across a section containing "S.A.E. Transactions" in the Tx Tech Library in about 1974. Where Chrysler presented the paper on the design and operational characteristics of their new family of engines, which was 413 at that time, to the S.A.E. group, in 1957. The "low deck" 350 was in the Plymouth Fury with a 2x4bbl intake, a bit later in the model year. Replacing the prior "single-rocker shaft engine" with 2x4bbl carburetors.
A side note -- although Chrysler had been designing V-8s with "aircraft combustion chambers" for more power, when the Chevy 265 V-8 appeared for the 1955 model year, it certainly was "taken apart" by everybody, to see what made it work as well as it did. Light, compact, "rev-happy", easy to assemble, etc. Which also means that if you angle-nill a 906 head casting, it suddenly gets to look a lot like a Chevy-use combustion chamber, just bigger (for the larger bore sizes and longer Chrysler block). I saw that one afternoon when my late machine shop guy was angle-milling a pair of 906s. The earlier "closed chamnber" Chry heads, probably not so much. Of courfse, GM had no patent on the head design they used, I suspect, as they were wanting something that worked well.
Chevy put priority oiling to the mains. Chrysler put priority oiliing to the hydraulic valve lifters, but with a simple modification, the mains would be oiled first. The reason I suspected about that is that an elderly owner WILL hear a ticking hydraulic valve lifter before they feel a THUMP THUMP from a crankshaft bearing . . . with low engine oil level being the culprit. Chevy put the distributor at the rear of the motor, so low hoodlines could be had for the upcoming Corvette, but the level of the cowl would be higher. This also let "the new engine" be showcased rather than the distributor. Chryslers were more formal designs, so the initial front hood level was naturally higher. Smokey Yunick said he spent thousands of dollars (in the later 1950s) in long distance phone calls to Chevy Engineering ( mentioned in his book) to get them to move the distributor to the front of the motor. Why? Camshaft twist harmonics between the timing chain drive and the rear-mounted distributor, which affected engine timing as a result. So B/RB distributors were at the front. The A and LA motors still retained their rear distributors, though, probably because Chrysler did not want to do a complete re-design of those motors.
Valve sizes, 1.92 intakes on the earlier motors. 2.08 intakes did not happen until "power" became important on the drag strip, to the OEM brands. 2.02 intakes only existed in SBCs in the moer-HP engines, as 1.72 intakes in the 327/250 and 1.94 intakes in the 327/300 motor. Chevy seemed to be more open to several different cyl head castings to go with the larger intake valves and engine sizes, compared to Chrysler's "one size fits all, just machined for different valve sizes".
In ANY engine design, there will need to be some "limiting factor", by design. How much it might "limit" can be variable. In the later 1950s, it was carburetor cfm, with the bulk of 4bbls not getting past 550cfm, no matter the engine size. But back then, they were also marketed by "Cubic Inches of Venturi Diameter", with the Max Wedge Carter AFBs being the largest (which was touted in the advertisements). Also realize that it were the Max Wedges which had horsepower production above what the Chrysler 300 Letter Cars had. With those letter car engines being on-par with the Chevy Fuel Injection Corvette engines for power (the "1 Horsepower per Cubic Inch" standard) in the later 1950s.
Past the carburetor and cyl heads, the next "limiter" is the camshaft duration and lift. In those first B/RB engines, the cam duration was about 252/252 duration with .390" valve lift. Which, again, was very similar to what Chevy used, with the Ford FE engines being very similar. Those Chrysler cam specs were last used in the 1966 383 2bbl V-8s, replaced in 1967 by the 256/260 cam.
Another interesting thing is that the optimum spark advance for the SBC is 38-40* TDC at 4000rpm. Very much alike the same things for the Chrysler B/RB motor. Which can somewhat validate the two engine families' combustion characteristics and efficiency.
Now, fast forward to the middle 1980s dirt track motors. In order to get "more power" from their SBCs, in certain classes, the builders were stroking the SBC so far that the piston pin was actually behind the ring package. So they were fusing an inch of metal to the block decks to they coiuld get the rings above the piston pin for better ring sealing stability. When I heard that, I thought "They ought to use a Chrysler block made of aluminum, with a taller deck height." As I grinned about how much they were Chrysler-izing the Chevy motor in the process.
The last limiting area is the exhaust system, from the exh valve to the end of the rear bumper. Relating to exh manifold design/outlet sizing and the under-car exh system.
Were the Chrysler owners short-changed because they did not have better cyl heads? Mostly not, as they were not all drag racers or NASCAR racers. They wanted power, reliablity, and a good bit of fuel economy in their cars. Which Chrysler Corp's high placings (if not outright wins) in the Annual Mobil Economy Runs indicated. THAT probably sold as many cars as their NASCAR and drag racing class wins did. Don't need class-leadiang cyl heads to get those fuel economy issues, although combustion dynamics came into play with the emphasis on exhaust emissions (which can also relate to fuel economy and CO emissions). And from magazine accounts, those Mobil Fuel Eonomy Run drivers took their work just as seriously as any drag racing or NASCAR driver ever did! Lots of little tricks that had been learned from proving grounds testings, like using soft drings in cups "angle of the fluid" to supply information of grade angle, which then related to how much throttle to use without getting in to the "power enrichment" circuit of the carb at what speed. Which the observer in the back seat might not be aware of!
The OTHER thing is that, by observation, Chrysler built "package motors", where ALL of the components worked together to supply their trademark operating characteristics (mentioned above). Everything was sized "just right" to work with the tighter-action torque converters in their trademark Torque Flight automatics (again for fuel economy and quick throttle response), in the later 1950s-mid 1960s. In a 1965 Plymouth Satellite 383 4bbl road test, CAR LIFE took the car to the drag strip and let it "idle" down the drag strip, with a trap speed of 8mph. In later model years, the "tightness" of the torque converters were loosened a bit to decrease "creep at idle".
And, though all of these things, Chrysler Products tended to dominate the higher classes they raced in on the drag strips and were very competitive with those they raced against. Aided through the "leisure time": activities of the Chrysler engineers in "The Ramcharger" group. Which led to the various "Performance Clinics" at Dodge and Plymouth dealers in the later 1960s and the eventual emergence of the Chrysler "Hustle Stuff/Direct Connection/Mopar Performance factory-backed racing manuals and parts items.
Chrysler was not the only one playing this game. Smokey Yunick was the main Chevy guy. Several engine shops did Fords, as Holman-Moody, and even Buick had a skunkworks unit of powertrain engineers who drag raced. FUN TIMES back then, keeping up with everything!
Just my recollections from back then. YMMV
CBODY67
