Posted By: The Sphinx
oil pressure issues - 04/30/13 11:30 PM
I've rebuilt a few small blocks in the past and never had an issue like this. I primed the oil system and fired up the engine and it maintained (cold 75PSI) (hot 40PSI) at 2000 RPM. Now my issue is at idle my pressure drops down to 15PSI regardless of it being hot or cold.
I use a snap-on 1200 RPM drill on an old distributor that has been lengthened to reach the oil pump as a priming tool.
What I noticed that is strange is:
1) When priming it, it takes about 3 seconds to feel any resistance in the drill. If you stop and start the drill again a few seconds later it still takes about 3 seconds to feel any back pressure on the drill. Like the pump is loosing its prime.
2) When I prime it and get the oil pressure up to any pressure and then stop, you can hear the sound of oil pouring into the pan. It sounds more like pressurized oil dumping.
I've checked the gallery plugs, they are all in. The oil pump pick up is just shy of 1/4 off the bottom of the pan.
What else should I check? I'm down to thinking it's either a bad pump (Melling M72), gasket between pump and main cap poo pooed on my, or a leak between the pick up and the pump.
Any other guesses?
For the heck of it I primed the system on an old 360 I rebuilt several years ago and noticed once It's primed and I reprime I get instant pressure and resistance on my drill.
Once I stop priming you can hear a slight trickle of the oil back to the pan.
I use a snap-on 1200 RPM drill on an old distributor that has been lengthened to reach the oil pump as a priming tool.
What I noticed that is strange is:
1) When priming it, it takes about 3 seconds to feel any resistance in the drill. If you stop and start the drill again a few seconds later it still takes about 3 seconds to feel any back pressure on the drill. Like the pump is loosing its prime.
2) When I prime it and get the oil pressure up to any pressure and then stop, you can hear the sound of oil pouring into the pan. It sounds more like pressurized oil dumping.
I've checked the gallery plugs, they are all in. The oil pump pick up is just shy of 1/4 off the bottom of the pan.
What else should I check? I'm down to thinking it's either a bad pump (Melling M72), gasket between pump and main cap poo pooed on my, or a leak between the pick up and the pump.
Any other guesses?
For the heck of it I primed the system on an old 360 I rebuilt several years ago and noticed once It's primed and I reprime I get instant pressure and resistance on my drill.
Once I stop priming you can hear a slight trickle of the oil back to the pan.
