Finally took my maiden voyage have after swapping in a mildly built 360 in place of the old 273. Engine runs great, but I seem to have transmission issues that were not present before.
Any significant throttle seems to cause it to start slipping on the 1-2 shift. Let off the throttle and the shift completes. The first trip around the block was with a low fluid level, my fault for checking in park and not in neutral. It took 2-3 quarts to bring it up to level. The second trip was maybe 1-2 miles, but no better.
Now one issue may be the kick down linkage. I switched to cables, but the ratio on the Holley carb is off. So I have 100 percent kick down at WOT, but at idle to 1/3 throttle the cable stop isn't even contacting the linkage. Now I've seen conflicting info. Some say the linkage is critical to part throttle shifts, others say it does nothing except at WOT.
Finally, I drained the converter when I pulled the motor. I topped the system off with AutoZone STP Dex/Merc.
So, what's the most likely cause of my issues? Kick down adjustment, fluid, driving while fluid is low, or just exceeded the horsepower limit of a 50 year old trans.
Note: Trans previously handled WOT with the 273 no issue. I did not exceed 1/2 throttle after the swap. No more than 3k RPM.
