When my 350 is cold it's running at about 40psi at idle. once it warms up it runs about 20psi and when under a load goes to 40. What I'm wondering is, is this normal?
CK5
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Oil pressure
- Thread starter Babaganoosh
- Start date
lectric80
3/4 ton status
When the oil is cold, the pressure is going to be higher at idle. Once warmed up it should drop some, then when under load should come up. A good rule of thumb is 10 PSI for every 1000 RPM's minimum. It sounds like your engine is doing alright, if a little tired.
it's got ruffly 60k on it, not real sure because 1 engine swap 1 odometer swap and now the 2nd one is going 2-3 miles for ever mile the tires turn.
Thank you for the info. I guess it's right in the ballpark for the mileage on the motor.
Thank you for the info. I guess it's right in the ballpark for the mileage on the motor.
lectric80
3/4 ton status
It is also going to vary from place to place. I can say that I don't have any clue how many miles are on the engine in my Blazer, but it idles cold at 50 then drops to about 35 once warmed up. It runs around 50 -55 when cruising, and I have really high gears resulting in really low RPM's.
I have 3.08's and 31 inch tires. I can do 50mph and only turning 1200
Sounds pretty normal to me, althouth the pressure at idle when warm is a tad low. 30 psi when warmed up and idling is good, 35-45 psi on the highway is also good. Cold pressure is almost irrelevant.
Pressure is created by the volume of oil being pushed through the bearings and stuff. The tighter the bearing clearances are the more resistance there is to the volume of oil being pumped. Thicker oil, more resistance to flow, higher pressure. More rpm's, more volume through the same resistance, more pressure.
A friend of mine did head gaskets on a really high mile 4.3 V-6 a few years back. He also replaced the oil pump with a new stock oil pump. Bearings were left untouched, but after the new oil pump he gained oil pressure across the range and even being high mile and tired it made an honest 30 psi at idle still when warm. Before and after readings were with Autometer mechanical guages.
Rene
Pressure is created by the volume of oil being pushed through the bearings and stuff. The tighter the bearing clearances are the more resistance there is to the volume of oil being pumped. Thicker oil, more resistance to flow, higher pressure. More rpm's, more volume through the same resistance, more pressure.
A friend of mine did head gaskets on a really high mile 4.3 V-6 a few years back. He also replaced the oil pump with a new stock oil pump. Bearings were left untouched, but after the new oil pump he gained oil pressure across the range and even being high mile and tired it made an honest 30 psi at idle still when warm. Before and after readings were with Autometer mechanical guages.
Rene
I'm running 10w30 in the winter and 10w40 in the summer. Dad said this is about right but he wasn't to sure, so I figured I'd get more opinions.
Thank you guys for the help.
Thank you guys for the help.
blazin_blazer
1/2 ton status
all that is said is about right, about where my truck was running...then k&n oil filter...start up @ 60 .....warm ideling 40-45..from just a quality filter
Chrisblazzer89
1/2 ton status
MY truck runs at 55-60psi cold then warm idle 45psi on throttle 60+ psi
Cowboy_80
1/2 ton status
my '79 would idle at about 10-15, but cruising it would be between 30-45, depending on speed. I never worried about idle pressure as long as it read something. I've seen some rigs idle in the single digits, but once the skinny peddle started moving everything was good. IMHO it should be anything above 30 while cruising. Anything lower and something needs replaced.
I recently replaced the heads on my K5. The oil pressure has always been a concern with this truck due to how low it is. Just Sunday retorqued the heads and and adjusted the valves and gained a few lbs of pressure, now it idles hot (180') with around 15 psi.
With Hyd lifters if your not just right and too sloppy you can have low oil pressure. That's not to say go crank your valves open, just keep the valves from rattling and the rule of thumb someone early on quoted about 10 psi per 1000 RPM is what I've always heard and used.
With Hyd lifters if your not just right and too sloppy you can have low oil pressure. That's not to say go crank your valves open, just keep the valves from rattling and the rule of thumb someone early on quoted about 10 psi per 1000 RPM is what I've always heard and used.
Are you going off the factory guage? If so I wouldn't trust the numbers... the factory guage in my '85 is so far off I never even look at it anymore... it says something like 20lbs idling cold then it drops to around 10lbs when its all warmed up and only goes up 5-10lbs under heavy throttle.
This is on my SB350 that runs like a top.
This is on my SB350 that runs like a top.
I should have quoted it for clarity but I was asking Ben (the starter of the thread)...
vortec
1/2 ton status
i wouldn't worry about those numbers as long as temp is staying reasonable (don't put too much faith in that, though) and the oil looks decent when you change it. if the pressure is really too low, the engine will be slowly (if you're lucky) chewing itself up, so the oil can get pretty nasty.
i know the feeling. i have a bad ground or something in mine, so it's just pegged out to the high end of the gauge. i'm feeling too lazy to fix it, so an aftermarket may be going in. mechanical or electrical? oil line run to cab or throw down tons of money for a gauge?
i know the feeling. i have a bad ground or something in mine, so it's just pegged out to the high end of the gauge. i'm feeling too lazy to fix it, so an aftermarket may be going in. mechanical or electrical? oil line run to cab or throw down tons of money for a gauge?
"tons" of money for a guage 
vortec
1/2 ton status
"tons" of money for a guage
yeah, i guess i've been looking in the wrong places, because right after
making that post, i found some decent deals. previously, it seemed like most didn't include the sender and by the time everything was purchased, it was $100 or something...which is more than i feel like spending on one gauge for my non-dd truck.
Understandable but what a handy guage to have 
I'm running castrol oil and fram oil filters and I'm going off a sunpro gauge.
IMO you have double digit oil pressure and its not a drag race motor. Call it good.
As said before (I think) cold oil will be thicker and give higher oil pressure. As it heats up it will drop a little. The faster the motor spins the higher the pressure will get.
As said before (I think) cold oil will be thicker and give higher oil pressure. As it heats up it will drop a little. The faster the motor spins the higher the pressure will get.
