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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Did this just start to happen? Or has it been like this for a long time? A (factory) SBC doesn't need a lot of oil pressure to run till it dies. at 50? PSI, you won't wear grooves in the bearings (assuming real OP), if the lifters don't clatter at idle, and don't pump up like solid lifters at RPMs, just run it as is. All factory gauges are indicators...so indicates you have oil pressure.
Thank you guys. It has been this way for a while. When the engine is cold or while driving, the oil pressure is in the high 70 psi range. At idle it is around 60 psi. The car runs beautifully and not really any valve noise that I can notice.
Well, sending unit might be the culprit, but when I had the opposite issue with my '89 (low reading), that's the first thing I did, and no change. Gauge was my issue.
You should have a hard to get to open port onthe back of the engine, if not loom at the front of the engine. Get some 1/8th in NPT fittings and a mechanical gauge and see what is really going on.
Also keep in mind your tach reading shows a little higher than what I suspect your base RPM is. Not sure what exactly base RPM is for your 305 manual (?) transmission, but your tach reading is over 1K RPM. It is normal for oil pressure to increase with RPM, to a point, due to oil pump spinning faster. That may not account for your entire reading but it has some factor.
Factory gages are only good enough to know if you have acceptable oil pressure, not so much what exactly is the oil pressure. All the gages will be skewed to one side if you have a less than ideal ground connection. Oil pressure reading will skew high as resistance to ground increases (gage will peg at the top if really high resistance to ground). I'd remove the gage panel and clean up the electrical connector with a pencil eraser and see if that helps all the gages to read more accurate. It's an old car, just kind of clean things up first before worrying too much about what's right or wrong.
My temp gage is nowhere near correct either, probably 30°F off from actual. I have data logs and know what the temp really is. I just mentally segment the gage into 3 zones. Somewhere in the middle is normal. Near the top is overheating. Near the bottom is cold. The numbers on the gage don't matter to me, I'm just looking for changes from what is "normal".
It's also normal for these tachs to read REAL high. That's almost certainly true of this one.
I don't think any factory 305 setup would produce over 50 psi at any RPM, let alone idle, even if the idle was a bit high.
These OP gauges don't go bad often; most likely, odd readings are the sending unit; but as 8Mike9's experience shows, it IS possible. I'd for sure just try a sending unit first before doing anything else though, if I was concerned about the reading.
Yes 305 manual transmission. I thought the rpms were high as well at idle. Should should be just under 1k rpm. My mechanic did the tune up and carb adjustment. Here is another gauge pic while driving.
Yes 305 manual transmission. I thought the rpms were high as well at idle. Should should be just under 1k rpm. My mechanic did the tune up and carb adjustment. Here is another gauge pic while driving.
