My .02, I would leave it all as they did it,---- probably Don tells you that too. Why in a second.
Don is the source of all solid info on this, but original 300 letter car weights are smaller, so have to spin faster for outputting a given governor pressure, = higher RPM shift ..guess 5300 - 5500? I brought Don two NOS governor packs (mopar bags!) for two 60 CI F trans he did for me that had the wrong (heavy) weights in the trans in a 300 F . These trans were often replaced by Dodge or Plymouth AAMCO rebuilds back then. They do die , if beat on in a 300. (or in my case back then , a D500) . Don might have even made some lighter weights at one point. Stock WOT up shift , guessing here about 4800 in a NYer or Dodge non D500, , North of 5200 in a 300 hemi . (loads of variables in that, 10-15% variations too) ; there might be something in FSM on TF diagnostics on this too. (WOT upshift speeds, but in MPH not RPM )
Now, why leave it alone:
I had a 300J that I put a LOT of work into the engine maybe 20-25 years back. I also built up the 727 Torque flight in it with all Turbo Action parts..fast shift and higher line pressure etc So ended up with a very fast car that shifted hard, and had more torque than stock, maybe. Up to a point. . As in break tires loose at 60 downshift. BUT , having both 300J weights and the shift kit, despite my thinking it would help a higher duration cam hustle even more, , caused it to shift at maybe 6000-6500-+ Rpm . It would Hang at the top of first or second very unhappy and not pulling, ignition hurting too. . And then bang a truly violent shift . And when that happened it would toss all the fan belts off about 1 in 5 times, wrecking the fan and radiator most times. = tow home. Not pretty, It (or I) destroyed in my mind a perfectly balanced car. They really knew what they were doing, we must give them that ,to stay objective. . Big job to undo all that, depressing to me in the day ,----after a lot of $ in. . So sold the car as is, to a guy who we expected restored it to sanity.(I explained all this) . 300J rams got 390 HP out of 413, remember even 440 six pack barely got that 6 years later and ~ 30 cu in more. .
But , and implied in Marshall’s excellent question--- is a question I have….the shift RPM is one number , but all the trans itself knows is road / governor speed and regulated line pressure, not engine RPM,--- but slip in the converter is how much?? At WOT? .I have tried on this many times, the so called stall is only true when at stopped output turbine,..it apparently sort of slips less as RPM of converter output shaft rises. But, it DOES slip. (why later converter clutch) But a big torque (say stroked engine) would seem to me to make it slip some more…at any speed you floor it. So ?? result = engine speed rises with power, even if trans shift RPM program / weights does not change. = Engine RPM gets higher. (back to 300J issue!) I have no idea if 300 converters are special, parts number guys might look at that,.. I suspect very special, as the C300 and 300B had 280 degree cams. If you put a 280 cam in a 440 you have to get a loose converter, or it stalls when you engage D –or no vacuum in D . 280 is really a pretty hot cam even today. Purple Shaft B block is 284 , can hardly drive it on street,. I think J had 268? They had backed it down, (smart!!) but J had a special 727 converter what we would call a hole shot, because at the time people were looking for those. And J/K is the fastest “regular” 300, but not the biggest top end cam by a long shot. = C300 and 300B are top end , high speed cars….
I expect it must slip 500-1000 RPM at WOT ? No one knows.
Key to acceleration is torque , especially with long rams,= that works (F way faster than E) but only if you shift up keeping torque high before the rams crash, and stop pulling ..which is not a very high RPM on F,G ? 4500-4800? Yet they had the light weights; but maybe different line pressures. ..or converter slips with rams more? You can see why J short rams attacked this auuugh feeling at 4800. And the thinking in 400HP F, 300H non ram. Or 405 HP. Hi slip converters waste power and gas, get hot going uphill. . So lots of compromise in all this. If you have an unmolested 300 , leave it alone, but it does need the light weights. Part of what it is, higher upshifts, but can rapidly be diminishing returns….let alone damaging things if trans changed more than that. .
Hope this observation helps….really interests me too, Marshall.
Maybe someone with digital tach has measured this….stock tach a joke.
(PS, Dead Stock, 340’s beat 440’s 440s beat Hemis, you get it; 12 sec 289 Studebaker larks beat all of them. relates to all this )
I am wondering about this subject of governors as well. On my C I have long felt that my 2-3 shift in particular is occurring before my hemi is tired of winding. The cast iron TF is now on Don Verity's bench, and we have discussed moving to lighter weights on the governor. I don't want to mess too much with the shift points for normal driving, but just want a bit more rev for "spirited acceleration". Does someone out there have experience with having done this? Did you like the result and would you recommend it?
Does someone know what the standard shift RPM is and what is available for higher shift points? Also, what is the weight of the governor weights for standard and optional weights? Thanks in advance for any help given.