James Hupy wrote on Fri, 05 June 2015 08:58

<snip>

It will run with the 455 very well, with the exception being at the bottom of
a hill when I let the RPM's fall below 2000. In the 1800 to 2200 rpm range,
the 455 will out torque the 403. But not above 2800 - 4000 rpm. No prudent
person will drive a GMC above 4000 rpms on highways with traffic anyway.

Jim Hupy
Salem, OR
78 GMC Royale 403

Yes and those with an stock torque converter shouldn't be lugging down below 2200 as it is below the stall. Heat can build pretty fast.

I have a Switch Pitch which when not in switch it has a stall that must be around 1700. On a hill my 455 is as poopy as the next at 2000 RPMs. We are tugging a lot of weight. 2400-3000 makes it much happier.

Good point about 4000 RPMs. Lost my governor and it wouldn't come out so I drove home in low on country roads at 3800-4000 and while you get used to it, things sound they they are going up and down pretty fast in there.