I'm new to having a Blazer but help would be great. I have a 2004 Blazer 4x4 automatic and at stop lights/signs the oil pressure drops from 40 to about 20 until I accelerate again. Is something wrong or is this how Blazers do?? Thanks for the info

 

That is a little low but still well within safe range,you did not mention how many miles on your unit. Keep in mind the gauge clusters are not the most accurate either.

 

Actually the gauges are pretty accurate.
It all depends on where your gauge goes to at 1000 rpm cold start. ALL SBC's I've checked with a mech gauge went to just under 60lbs. If yours does that your dash gauge is accurate and the reading warm reflects the health of bearings and weight and quality of oil.

Otherwise it's relative.. ie; if it only goes to 40 cold, then you're in good shape.

 

Its got 134k on it. At first start up itll act a lil funny until it heats up and does mentioned problem. While its warming up, I think itd always be at about 40 at stop and then as i accelerate itll go to like 45-50. I cant remember for sure, Ill check later today.

 

yeah that all sounds about right.
i installed a mech gauge for giggles...stock cluster is actually pretty dead on to the mech system.

 

so warthog everything is peachy? or should i be worried im bout to throw a rod or kill a bearing

 

Everything is peachy. Mine will sit at 20 when its all warmed up as well. General rule is you want about 10 PSI for every 1000 RPM

 

no, that's misleading at least. It's not what I want. Perhaps it's what the bearings need?

OP.. if you are running 5w or 10w -30 oil and your cold start pressure is 50 or more @1000 and idle pressure warmed is 20 or more, you are ok. Within the 'expected' wear range.

Would be nice if you defined ' itll act a lil funny until it heats up'. The pressure should not exceed about 60 lbs. That's where the oil pump bypass opens.

 

I rechecked what it does when it was acting funny. Sorry been busy lately. But when it's warming up at idle it'll be about 45psi, and when I accelerate it'll go to about 55. Then when she heats up goes to 40 while driving and then 20 stopped.

 

Then you're okay. I think you have some bearing wear because mine never idles below 40 except when temp ga goes 210 or over. But I think wear within tolerances will allow that pressure.

I'm frustrated, though. I cannot find the nominal SBC pump bypass pressure to save my ***! I am sure it's vicinity of 57 lbs because I've seen several of the Stewart Warner 270 sweep gauges report that on higher revs, warm. Never over sixty unless high-revved cold, when the bypass exit port cant handle the flow.