The 1965 GM Chassis Manual lists the block torque to be 50-55 foot pounds yet
the 1966 GM Chassis Supplement Manual lists it to be 55 foot pounds. Why the
change and what positive or negative benefit to set the torque at exactly 55
foot pounds? All comments appreciated...

Typically, two torque numbers represent oiled and dry thread torque values.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
65 Canadian Monza 4dr 110/PG 40k
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

I always view the two numbers as a range. So I see the block torque of 50-55 as anywhere between 50 and 55. Most all torque values are stated this way.

Dennis
Nashville area

Most torque specs vary depending fastener condition, thread pitch and type of lubrication.
Low friction lube can make a significant difference in desired fastener stretch, the ultimate goal.
Engine Oil on threads and nut contact surface and 50 lb-ft should be plenty to sufficiently clamp the block.
The use of ARP rod bolt lube may require a lower value, for instance.
Sometimes up to 15 % less.
Some basic info here for the technically minded :
[www.hextechnology.com]
Print and save if you wish, for ready reference.
The chart below is useful in a general sense, but specific applications like our rod and block bolts should use manufacturers recommendations.
In our case because for the block we are clamping aluminum.
Why is another discussion.
[www.repairengineering.com]

Bob C aka Dryenko
Dobson, NC 27017

The 11/32 flywheel bolts are something else where the Spec value changes through the years.

Jim Brandberg
Isanti, MN
CorvairRepair.com