Here's some information and comment on a subject related to the one I started regarding big block dipsticks but enough different that I thought I'd start a new thread for it.
During the 65-74 period, there seems to be a lot of confusion regarding just how much oil a big block is supposed to have in it when the oil is at the "full" mark on the dipstick.
We can glean some information from the AIM's since the oil fill was done at St. Louis and the volumes are given in the AIM. These are as follows:
1965--------------------------not shown
1966--------------------------1.5 gallons (6 quarts)
1967--------------------------1.5 gallons (6 quarts)
1968--------------------------1.75 gallons (7 quarts)
1969 (start of production)---1.75 gallons (7 quarts)
3/18/69----------------1.12 gallons (4-1/2 quarts)
8/19/69----------------1.375 gallons (5-1/2 quarts)
1970--------------------------1.376 gallons (5-1/2 quarts)
1971--------------------------1.376 gallons (5-1/2 quarts)
1972------------------------"approx .25 gallons" (1 quart)
1973--------------------------1.375 gallons (5-1/2 quarts)
1974--------------------------1.375 gallons (5-1/2 quarts)
As far as I know, there was no change in the configuration of the oil pan over the 1965-74 period that would account for any difference in volume. Of course, GM could have changed the point that they considered the pan to be "full" and that could account for some change in volume. Such a change would have necessitated a different oil dipstick and/or dipstick tube. However, there were only 2 dipstick tubes used---1965 to E1970 used one and L1970-74 used another.
There were 4 KNOWN dipsticks used, though, and, possibly, more.
There was one other factor, though, that could have affected oil SYSTEM capacity and that is the volume of the oil filter. So, I did some calculations to see just what the capacity was of the various oil filters used over the 1965-74 period. To do this I just calculated the volume of the canister or spin-on cartridge shell. For the canister, I subtracted the volume occupied by the center bolt but I did not calculate the volume occupied by the filter cartridge inside either the canister or spin-on cartridge. The only way to do this would be to do it empirically and I just don't want to go that far. However, I feel that the space occupied by the filter cartridge components would be quite small relative to the volume of the canister or filter shell. Here's what I came up with:
GM #5574538 (63-67)----1.268 quarts (0.317 gal)
AC PF-29 (68-E69)--------0.88 quarts (0.22 gal)
AC PF-25 (L69-74)---------0.70 quarts (0.175 gal)
To some extent, the above difference could explain the different system capacities shown. However, the 1968-69 period is the real "head scratcher" and, especially, 1969. Curiously, that's also the period when a "mystery dipstick" and a "mystery oil pan" were used. I have little information on the GM #3959158 dipstick (as mentioned in my previous thread). I also have no information on the GM #3955106 oil pan used for 1969-E70. However, I have no reason to believe that its configuration differed in any significant way from previous or later oil pans.
One more thing: one would expect that if the oil filter capacity differences resulted in a change in the oil system capacities, then there would have been commensurate differences for the AIM-specified fill capacity for SMALL BLOCKS, too. The exact same oil filters were used for small blocks for any given year. However, all of the 1965-74 AIMs for base engine small blocks call for 1.25 gallons (5 quarts) of oil fill, the same capacity that we have all used for years.
During the 65-74 period, there seems to be a lot of confusion regarding just how much oil a big block is supposed to have in it when the oil is at the "full" mark on the dipstick.
We can glean some information from the AIM's since the oil fill was done at St. Louis and the volumes are given in the AIM. These are as follows:
1965--------------------------not shown
1966--------------------------1.5 gallons (6 quarts)
1967--------------------------1.5 gallons (6 quarts)
1968--------------------------1.75 gallons (7 quarts)
1969 (start of production)---1.75 gallons (7 quarts)
3/18/69----------------1.12 gallons (4-1/2 quarts)
8/19/69----------------1.375 gallons (5-1/2 quarts)
1970--------------------------1.376 gallons (5-1/2 quarts)
1971--------------------------1.376 gallons (5-1/2 quarts)
1972------------------------"approx .25 gallons" (1 quart)
1973--------------------------1.375 gallons (5-1/2 quarts)
1974--------------------------1.375 gallons (5-1/2 quarts)
As far as I know, there was no change in the configuration of the oil pan over the 1965-74 period that would account for any difference in volume. Of course, GM could have changed the point that they considered the pan to be "full" and that could account for some change in volume. Such a change would have necessitated a different oil dipstick and/or dipstick tube. However, there were only 2 dipstick tubes used---1965 to E1970 used one and L1970-74 used another.
There were 4 KNOWN dipsticks used, though, and, possibly, more.
There was one other factor, though, that could have affected oil SYSTEM capacity and that is the volume of the oil filter. So, I did some calculations to see just what the capacity was of the various oil filters used over the 1965-74 period. To do this I just calculated the volume of the canister or spin-on cartridge shell. For the canister, I subtracted the volume occupied by the center bolt but I did not calculate the volume occupied by the filter cartridge inside either the canister or spin-on cartridge. The only way to do this would be to do it empirically and I just don't want to go that far. However, I feel that the space occupied by the filter cartridge components would be quite small relative to the volume of the canister or filter shell. Here's what I came up with:
GM #5574538 (63-67)----1.268 quarts (0.317 gal)
AC PF-29 (68-E69)--------0.88 quarts (0.22 gal)
AC PF-25 (L69-74)---------0.70 quarts (0.175 gal)
To some extent, the above difference could explain the different system capacities shown. However, the 1968-69 period is the real "head scratcher" and, especially, 1969. Curiously, that's also the period when a "mystery dipstick" and a "mystery oil pan" were used. I have little information on the GM #3959158 dipstick (as mentioned in my previous thread). I also have no information on the GM #3955106 oil pan used for 1969-E70. However, I have no reason to believe that its configuration differed in any significant way from previous or later oil pans.
One more thing: one would expect that if the oil filter capacity differences resulted in a change in the oil system capacities, then there would have been commensurate differences for the AIM-specified fill capacity for SMALL BLOCKS, too. The exact same oil filters were used for small blocks for any given year. However, all of the 1965-74 AIMs for base engine small blocks call for 1.25 gallons (5 quarts) of oil fill, the same capacity that we have all used for years.
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