Oil filter O ring blow out.

Porsche 2 · 07-09-2017, 11:56 AM

I have a '77 911 2.7 ltr. engine just installed in my 914. My oil filtering, front cooling and storage plumbing includes AN12 stainless steel braided hoses and fittings. I re-installed a remote after market oil filter bracket that worked well with my Type IV four cylinder, which has 1/2" female oil inlet and outlets (like most of them). It also has 1/2" nipple to screw the filter onto it. My 2.7 makes oil pressure very quickly but has blown about 1" of the oil filter O ring out (K&N brand with large not very secured O ring) three times causing major oil dumps!

The scavenger oil line is connected directly from the engine to the remote oil filter. I am guessing that the 1/2" nipple on my used oil filter bracket is too small for the oil pressure/flow. So I will be installing a new bracket that has a 911 size - 3/4"- nipple along with a new 911 Mahle oil filter from our host. I have a mechanical oil pressure installed on the engine (temporarily in place of the oil light switch) and will be watching it carefully - what is an acceptable high oil pressure with cold engine at say 2000rpm? I have about 20lbs/square inch at idle.

Any advice will be most welcome, including comments re the possibility of the engine oil pressure relief valves failing and not limiting the maximum pressure. Seems to me that if they are failing it is more likely that pressure would be too low not too high?

manbridge 74 · 07-09-2017, 12:57 PM

1/2 inch fittings? 3/4 inch?

I'd keep the ID the exact same as factory spec or larger. Questioning the original engineering will lead to nothing but headaches.

Porsche 2 · 07-09-2017, 01:25 PM

Correction: The old filter bracket has 3/8" NPT ports with 3/4"-16 nipple. New bracket just received has 1/2" NPT ports with corresponding larger internal plumbing diameters, but with the same 3/4' nipple for spinning the filter onto the bracket. After much searching on the internet, can't find a bracket with a 1" nipple to match the 911 Mahle filter thread size(?) I need to get AN 12 male connections to this new bracket tomorrow and will try this larger flowing bracket.