I recently replaced my timing chain/gears in my 65 300 engine, and installed neoprene lip seal in front cover. I am contemplating switching over to synthetic oil, but am worried about leakage starting at the rear rope seal. Does anyone have any experience with this?
lol, I'm sorry but I had to laugh while thinking to myself …."It's a Buick, it leaks oil no matter what"....lol, seriously, I run Synthetic Mobil 1 15-40, it leaves little drops just like it did with conventional 30 w. mainly from the rear main seal.
You will get more seepage with synthetic. Just how that oil is. Try a blend first. See if its a problem
I have been running Mobile 1 for over 20 years in my motor and it never leaked oil I got more coming out the valve cover than the back of motor, I need to change the 20 year old gaskets I guess. As long as you are driving it, no leaks. This motor was rebuilt in 1994. The front trans seal on a 350 trans will leak before the engine does so if you have that trans out you might as well get that seal changed first. Especially if it sits for long periods like over winter, then it quits once you start to drive it. I have notice the 2004r trans does not leak on the front seal after sitting a long time. I would run the 10-30 Mobile 1 oil and add 1 qt of 15-50 with your 3 qts of 10-30. The 15-50 has the zinc in it. I run 4qts 10-30 and 2 qts. of 15-50 and this puts the oil pressure at 50 lbs at 3000 rpm. You may have to add the zinc to the oil for the cam so keep that in mind when switching to synthetic. I think that Joe Gibbs synthetic has the zinc in that oil they have it at Summit Racing.
