low oil pressure?
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Senior User
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low oil pressure?
happy memorial weekend gents 
whats considered low oil pressure? I have a 390 with 10w40 oil and when the engine is hot and idleing the oil pressure is 20 psi but when im driving down the road its 50 psi. its the idle oil pressure that has me a lil worried or is 20 psi normal? thanx
whats considered low oil pressure? I have a 390 with 10w40 oil and when the engine is hot and idleing the oil pressure is 20 psi but when im driving down the road its 50 psi. its the idle oil pressure that has me a lil worried or is 20 psi normal? thanx
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
20 PSI at idle is plenty. The rule is 10 PSI for every 1,000 RPM. The factory idiot lights don't usually come on until 5 to 7 PSI. I'd say yours is above average. Most people are happy with 10 to 15 PSI at idle.
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
Running restrictors in the heads? #80-90 won't show much change, #60-70 should show a 5-10psi bump in oil psi.
The top end gets plenty of oil even in a stock application, restrictors put the oil where you need it most.
The top end gets plenty of oil even in a stock application, restrictors put the oil where you need it most.
Tuned
Joined: Apr 2011
Posts: 298
Likes: 4
From: Highland CA
Dont mean to hijack Hey highboy I just rebuilt my 390 all stock and my oil pressure in idle is about 5psi wen hot with Holley # 90 jets on heads, no knocking or valve train noise,oil pressure goes up to 40psi wen driving on freeway, my question is how small can I restrict with jets with out starving the valve train or should I install a H/V oil pump,thanks in advance.
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
I wouldn't go below #60 otherwise you risk starving the valve train.
But the bigger question is why are you only seeing 5psi @hot idle? that's dangerously low, you should be seeing 25-30 psi on a fresh rebuild.
But the bigger question is why are you only seeing 5psi @hot idle? that's dangerously low, you should be seeing 25-30 psi on a fresh rebuild.
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
Pop your rocker covers one day and let the motor idle, you'll see way too much oil up top, increase the rpm's and you'll see the need for restrictors.
(Mike O has a great pic illustrating this point)
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Senior User
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do u have a pic of this? I have no idea where to put these things. are these like carb jets u mean? or something else. wont they block the the oil to much? u guys cookin out today? 
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Tuned
Joined: Apr 2011
Posts: 298
Likes: 4
From: Highland CA
mains.020 under,
rods.020 under,
cam is stock like everything else.
clearances with plastigage are as followed
mains .002
rods .0015
all galley plugs are in place,#90 restrictors.This is what my gage reads hot at idle in drive with foot on brake.
Do you think my gage is bad or is there something I need to check,engine sounds good no knocks no valve train rattle,just did my first oil change and everything looks good no shavings in oil please help this is driving me crazy, thanks in advance.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
It looks to be reading 7-8 psi, i'd be uncomfortable with that low of a reading, what weight oil are you running?
If I were you i'd get a second gauge to confirm the numbers you're seeing.
Did you install the oil galley plug behind the distributor? that's the one most often overlooked...
If I were you i'd get a second gauge to confirm the numbers you're seeing.
Did you install the oil galley plug behind the distributor? that's the one most often overlooked...
Tuned
Joined: Apr 2011
Posts: 298
Likes: 4
From: Highland CA
It looks to be reading 7-8 psi, i'd be uncomfortable with that low of a reading, what weight oil are you running?
If I were you i'd get a second gauge to confirm the numbers you're seeing.
Did you install the oil galley plug behind the distributor? that's the one most often overlooked...
If I were you i'd get a second gauge to confirm the numbers you're seeing.
Did you install the oil galley plug behind the distributor? that's the one most often overlooked...
Senior User
Joined: Jul 2011
Posts: 201
Likes: 0
I have same issue, rebuild with 6-700 miles. at idle in gear 3-5psi, no noise. .040 390, .010 rods and mains. no noise at all, using both fatory and aftermarket oil pressure guages, factory reads towards low end between both dashes. running a melling hv pump restrictors in the heads, 20w50 motor oil.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
A lot of guys get many years of service out of their FE's with hot idle oil pressure in the 5-10 psi range.
FE's measures oil pressure right at the filter, where pressure is the highest, so "actual" numbers are considerably lower, I've heard anywhere from 5-15 psi lower, that's why I like to see at least 20 psi at hot idle, for peace of mind more than anything.
I have 20K on my rebuild, .030 over 390, #70 restrictors, stock pump, running 6qts. of Rotella 15w40 and Wix filter, with coolant temps around 180 and oil temps around 210 I see the following numbers...
Cold idle 75-80 psi
Hot idle 20-25 psi (800 rpm)
Cruise 55-60 psi (2,500 rpm)
This topic gets discussed a lot over on the FE board, here's one thread among 100's...
332-428 Ford FE Engine Forum: Oil Pressure…one of the most asked about subjects in this forum?-
FE's measures oil pressure right at the filter, where pressure is the highest, so "actual" numbers are considerably lower, I've heard anywhere from 5-15 psi lower, that's why I like to see at least 20 psi at hot idle, for peace of mind more than anything.
I have 20K on my rebuild, .030 over 390, #70 restrictors, stock pump, running 6qts. of Rotella 15w40 and Wix filter, with coolant temps around 180 and oil temps around 210 I see the following numbers...
Cold idle 75-80 psi
Hot idle 20-25 psi (800 rpm)
Cruise 55-60 psi (2,500 rpm)
This topic gets discussed a lot over on the FE board, here's one thread among 100's...
332-428 Ford FE Engine Forum: Oil Pressure…one of the most asked about subjects in this forum?-
Postmaster
Joined: Nov 2011
Posts: 2,553
Likes: 10
clearances with plastigage are as followed
mains .002
rods .0015
all galley plugs are in place,#90 restrictors.This is what my gage reads hot at idle in drive with foot on brake.
Main clearances are just a bit on the big side for a moderate RPM engine. That may be part of what you are dealing with. .0015" or a bit less would probably help the hot idle oil pressure.
mains .002
rods .0015
all galley plugs are in place,#90 restrictors.This is what my gage reads hot at idle in drive with foot on brake.
Main clearances are just a bit on the big side for a moderate RPM engine. That may be part of what you are dealing with. .0015" or a bit less would probably help the hot idle oil pressure.
Thread Starter
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Senior User
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i found these on a google search are these the right ones? whats all involved in putting them in?
Oil Restrictors
Oil Restrictors