FernyGT

Hi my name is Fernando, my dad and i just rebuild a mustang gt 4.6 engine but i am having this problem. when rebuilding we cheked clearences and we were between .015 to .020 with main and rods even installed a? mechanical gauge, when i fired it up the presion started on 50 psi and with a rattling noise at idle, presion was ok but when the engine got hotter presion droped to almost 20 to 15 psi and oil volume was ok. should i change the oil pump or check compression????

uberstang1

As long as the bearings are withing spec and you checked the oil gallery plugs I would lean towards the Oil pump, you did use assembly lube when installing the bearings and caps correct?

FernyGT

I used Lubri-plate as i guess that is the brand name am i correct???

FernyGT

what is the clearence for the 4.6 romeo engine for main and rod

ctgreddy

this is normal. my buddies engine which has a brand new ford oil pump has pressure around 50-60psi when cold and drops down to about 15 once the oil's warmed up. it's just because of how thin oil gets when it's hot. as long as you have roughly 10psi of oil pressure for every 1000 rpm then you're fine. so if you've got 10psi at idle you're good to go.

FernyGT

well thats good news to hear from this reply, i am surely scared cause the oil pump i have is old so i just ordered a melling pump that should arrive tomorrow. But know the question is why is there a rattling noise??? the noise comes from the front cover i used a water hose as a stethoscope or hearing device

FernyGT

i mean acceptable tolerance for clearence

WannaBeGearHead

That's why Ford put in a "dumby" oil pressure gauge. People would always think something is wrong as the oil pressure fluctuates much more than people think.

My oil pressure when cold is 80-85psi and when warm at idle it's around 15-20psi. Other than the rattling you describe the oil pressure seems normal.

ctgreddy

for the rattling you're gonnna have to pull the front cover off and take a look. might be a bad tensioner or something.

FernyGT

the good thing than is that i have good oil pressure than i was scared since i thoughtj that was a minimum measure and maybe blow the engine... again!!! JK. ill check the cover and keep u guys posted, hope this problem gets solved as soon as posible