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The question of oil and filter capacity has been asked a couple times here in clarifying the correct amount. The confusing part is that some will say 5 quarts in the pan plus 1 for the filter making it a 6 quart system. BUT, another person may say that the correct amount is 6 quarts in the pan and 1 for the filter making it a 7 quart system - and they would be right based on the year of their GTO and/or the dipstick pulled from their engine. This conflicting info deals with the 1965-67 model years.
With the introduction of the 400CI, all Pontiacs seem to use 5 quarts in the pan and 1 quart for the filter. I have not compared the 389 to 400 heads with regards to oil return holes/passages which may have been redesigned when the new 400CI engines/heads came out, and thus the fix for the extra oil that was being held up in the top end of the engine.
A service bulletin was issued by Pontiac in 1966. It clearly states that the oil capacity is 6 quarts in the pan and 1 quart in the filter. GTO owners will tell you that their dipstick clearly says 6 Quarts at the fill line. Yet when a 5-quart dipstick is set side-by-side with a 6-quart marked dipstick, they are identical in length. There is no difference in the pan, they are all seemingly the same. Hmmm, so what gives?
I believe it was a PY forum member who stated that he had talked with Milt Schronack of Royal Pontiac fame and Milt said that Pontiac was replacing a lot of 1965 GTO engines under warranty and it was found that the engines were being burnt up due to lack of oil. The owners were pushing the engines hard and at the upper RPM's much of the oil was being pumped up to the top end and not leaving enough in th pan to oil the bottom end - especially if the oil level fill level had been allowed to get low. So Pontiac issued a service bulletin to fill all engines with 6 quarts plus 1 quart for the filter. They also used a dipstick having the 6-quart fill mark. This extra quart helped keep enough oil in the pan and prevent the engine from running out of oil and burning up.
So this bulletin and change was for 1966, but owners of 1965 and 1967 GTO's have also found the 6-Qt stamped dipstick. It is quite possible that when the car was brought to a dealership to be serviced and the oil/filter changed, the 5-Qt dipstick was replaced with the 6 Qt stamped dipstick so as to protect Pontiac from having to cover warranty engine work.
So it boils down to that Pontiac used a 5 quart pan and a 1 quart filter for 6 quarts, but increased the pan fill on their earlier cars to cover them from having to do engine warranty work due to those individuals who ran their engines hard, or raced them, and burned up the bottom ends due to low oil levels.
Pic #1 is the Pontiac bulletin.
So how high is the fill level of oil when it is in the pan? Nobody seems to know. BUT, now you do!! I used my 1973 factory pan having the oil baffle to see just what the oil level is within the pan. The pan was made level for this test. I filled and measured for 3 Quarts, 4 Quarts, and 5 Quarts. Keep in mind that this is at rest and once the engine fires up, oil gets pumped through the engine and the 5 Quart fill level will drop.
I will have a few follow up topics covering the factory oil baffle and my hand at extending the 1973 baffled oil pan in the photos for more oil capacity and adding the extended oil pump pick-up tube/screen to match. Got it all done and it was a ton of work, a lot of hours, and I would not recommend anyone doing this as I can assure you it would be easier and much simpler to just order an aftermarket oil pan having the additional oil capacity. Me?, I'm cheap, can do the fabrication work, and wanted to keep with "old school" practices that were done when a good aftermarket pan wasn't available or it was too expensive for the average car guy - like me when I was younger.
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With the introduction of the 400CI, all Pontiacs seem to use 5 quarts in the pan and 1 quart for the filter. I have not compared the 389 to 400 heads with regards to oil return holes/passages which may have been redesigned when the new 400CI engines/heads came out, and thus the fix for the extra oil that was being held up in the top end of the engine.
A service bulletin was issued by Pontiac in 1966. It clearly states that the oil capacity is 6 quarts in the pan and 1 quart in the filter. GTO owners will tell you that their dipstick clearly says 6 Quarts at the fill line. Yet when a 5-quart dipstick is set side-by-side with a 6-quart marked dipstick, they are identical in length. There is no difference in the pan, they are all seemingly the same. Hmmm, so what gives?
I believe it was a PY forum member who stated that he had talked with Milt Schronack of Royal Pontiac fame and Milt said that Pontiac was replacing a lot of 1965 GTO engines under warranty and it was found that the engines were being burnt up due to lack of oil. The owners were pushing the engines hard and at the upper RPM's much of the oil was being pumped up to the top end and not leaving enough in th pan to oil the bottom end - especially if the oil level fill level had been allowed to get low. So Pontiac issued a service bulletin to fill all engines with 6 quarts plus 1 quart for the filter. They also used a dipstick having the 6-quart fill mark. This extra quart helped keep enough oil in the pan and prevent the engine from running out of oil and burning up.
So this bulletin and change was for 1966, but owners of 1965 and 1967 GTO's have also found the 6-Qt stamped dipstick. It is quite possible that when the car was brought to a dealership to be serviced and the oil/filter changed, the 5-Qt dipstick was replaced with the 6 Qt stamped dipstick so as to protect Pontiac from having to cover warranty engine work.
So it boils down to that Pontiac used a 5 quart pan and a 1 quart filter for 6 quarts, but increased the pan fill on their earlier cars to cover them from having to do engine warranty work due to those individuals who ran their engines hard, or raced them, and burned up the bottom ends due to low oil levels.
Pic #1 is the Pontiac bulletin.
So how high is the fill level of oil when it is in the pan? Nobody seems to know. BUT, now you do!! I used my 1973 factory pan having the oil baffle to see just what the oil level is within the pan. The pan was made level for this test. I filled and measured for 3 Quarts, 4 Quarts, and 5 Quarts. Keep in mind that this is at rest and once the engine fires up, oil gets pumped through the engine and the 5 Quart fill level will drop.
I will have a few follow up topics covering the factory oil baffle and my hand at extending the 1973 baffled oil pan in the photos for more oil capacity and adding the extended oil pump pick-up tube/screen to match. Got it all done and it was a ton of work, a lot of hours, and I would not recommend anyone doing this as I can assure you it would be easier and much simpler to just order an aftermarket oil pan having the additional oil capacity. Me?, I'm cheap, can do the fabrication work, and wanted to keep with "old school" practices that were done when a good aftermarket pan wasn't available or it was too expensive for the average car guy - like me when I was younger.
