308 Oil Pressure

Unknown

New forum member. I have just started my newly rebuilt 308 engine. It is equipped with a full flow dual oil filtering system. I have put a oil pressure gage after the oil filters and seem to have too much oil pressure. About 45 psi at idle and in excess of 100 psi when the motor is moderately revd. I have good oil flow out of the filters into the oil gallery of the engine. We thought the bypass piston may be stuck, but this was not the case. As an experiment we removed the piston and spring and put the plug back in place. Briefly started the engine and had about 20psi at idle and more than 40 psi at higher rpm. I am not sure what is going on, but I do not want to hurt the bearings. Since the engine was rebuilt before I got it , I do not know the bearing clearances, but it turns over with no problem. Is there a big risk in altering the relief spring to control the oil pressure to something arounn 60 to 80 psi? Any help is appreciated. Hornut

[Deleted User]

Hornut, I am by no means an expert on this but I think I read in the forum somewhere that to get an accurate oil pressure reading you have to take it where the original oil pressure switch was located, by the oil pump. Not sure if this is applicable to your situation or not.
Bob

[Deleted User]

I remember reading somewhere (maybe a Clifford article or Ken Cates' site) that stock oil gallery welsh plugs on the back of the block will only hold 50 psi before they blow out. Any more than that and you have to tap the gallery plug holes and install pipe thread type plugs.

Clutchguy

Hornut wrote:

New forum member. I have just started my newly rebuilt 308 engine. It is equipped with a full flow dual oil filtering system. I have put a oil pressure gage after the oil filters and seem to have too much oil pressure. About 45 psi at idle and in excess of 100 psi when the motor is moderately revd. I have good oil flow out of the filters into the oil gallery of the engine. We thought the bypass piston may be stuck, but this was not the case. As an experiment we removed the piston and spring and put the plug back in place. Briefly started the engine and had about 20psi at idle and more than 40 psi at higher rpm. I am not sure what is going on, but I do not want to hurt the bearings. Since the engine was rebuilt before I got it , I do not know the bearing clearances, but it turns over with no problem. Is there a big risk in altering the relief spring to control the oil pressure to something arounn 60 to 80 psi? Any help is appreciated. Hornut

It really sounds like something is not lined up correct??,not for sure?. You also need to think about the pressure that is being applied to the bronze oil pump gear. If you are drag racing this may not be an issue,but if you are looking for longevity and dependibility,I think the excessive oil pressure may cause future concerns??,I personally would pull the oil pan and inspect the bearings. The main bearings could be installed incorrect and/or the cam bearings are not correct. You will not be able to check the proper alignment of the cam bearings without disassembling but the mains are easy. It is probably worth the time and effort now VS at a later date with other damaged parts as well as the original problem. A new pan gasket and oil is all that is required to inspect it currently-and of course, a day of your time. I also may not understand how you have the oil filters set up??.

Ol racer

Excessive oil pressure is not good. Do you have 'full flow' by drilling & modifying the oil pump? If so, Try installing a stock oil Pump and/or eliminate the filters temporarily then re-check the oil pressure at the block oil galley. If normal its in your pump or filter set-up

Unknown

I know the manual says the bypass is non-adjustable, but can't the spring be shortened to lower the pressure. That's assuming everything is OK inside.

Unknown

You were on the right track. The original builder piped the remote filter with copper line and ferrule type fittings. Since this was pretty ugly, I switched to #8 braided hose which was about the same diameter, but apparently the fittings and the hose were more restrictive. I changed to #10 hose and redid the fittings to replace any 90 degree fittings with 45 degree fittings. This has corrected the high pressure. With the engine oil cold I can see 80psi max. at high rpm. I think it will be OK with a warm engine and normal highway rpm. I may switch from 10-30 oil to 10-20 to get a little more reduction. Thanks for your input. Hornut