Slightly lower oil pressure, worn bearings or kooky sensor? (After cam swap) C1500 5.7 1988

[Slade88]

Hi everyone I did a cam swap this spring, went from my stock cam to a comp CL122494. Just slightly larger then my stock cam. Everything has been behaving after driving about 1500 miles. I have noticed, and did notice a slight decrease in oil pressure many months ago and the “problem” still persists. Now when everything was stock I had 60 psi all the time, or just a. Couple clicks under. After the cam swap, (and I’m also using VR1 oil instead of penzoil both 10w30)

My oil pressure is just under 60 on a cold start and stays at the same spot when idling, however when the engine gets good and warm and I’ve been driving a real long time when I pull up to a light it will go down to 50-55 and the ribbon gauge will fluctuate a bit. Then when I step on it, it returns to 60 even when the car is in motion and I’m not on the gas. This seems to occur intermittently though

I cut open my oil filter from the cam break in and had a little bit of metal but no copper or gold shavings. I also cut open my oil filter after the 700 mile break in tonight and saw pretty much no metal or gold sheen.

My question is what could be causing this? Is it a bearing or something insignificant that I shouldn’t worry about? Would bearing material always end up in the oil filter? I don’t have metal in the oil pan either. I plan on taking my truck on the longest voyage it’s ever been on, from Charlotte to myrtle beach if anyone is familiar with that drive, a couple hours on the high way and I don’t want my engine to explode!

Thanks everyone

 

[Schurkey]

The FIRST thing to check is the oil pressure sending unit for the dash gauge. They're a high-failure item.

They can fail by indicating too high, too low, random too high or too low, or by leaking. Best practice is to connect a known-accurate mechanical gauge to that pressure port, and compare to the reading on the dash gauge.

Wild Guess: Your dash gauge is reading way too high. "True" hot idle in gear is probably around 15--20 rather than 55.

As best I can tell, there is ONE manufacturer of that sending unit, but it's reboxed and sold under multiple brand names.

BEWARE, many parts stores have the WRONG sending unit listed for '88--'89 engines. At some point--'90 (?) perhaps, they switched to a different sending unit.

If the sending unit they give you doesn't have some green paint on the end, it's not the right one. It'll be too damn big so that it won't fit properly.

Photo of correct-size sensor with a touch of green paint, compared to what was listed for my truck at the local NAPA, which is too big and doesn't fit. The box shows the incorrect part number.

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Oil Pressure Sending Unit--TBI V-8 dash gauge - Automotive Forums .com Car Chat

Oil Pressure Sending Unit--TBI V-8 dash gauge C/K

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[RichLo]

Also, send in an oil sample to get it analyzed next oil change. There are a few around the web, I use Blackstone and like them. They give a detailed explanation of what is going on with high readings and they answer emails promptly with any further questions. Be sure to include how much mileage is on your new cam so they know.

 

[Jeepwalker]

Yeah, try a new gauge. It wouldn't much of a tolerance difference to lose 5 or 10 psi. When you see it drop on idle it's likely bearings of some sort (assuming your oil pump hasn't worn in a few months and filter isn't clogged). But 50 psi all or most of the time is well within the good range for normal street driving. If it really bugged you, you could pull out the cam and inspect or reinstall new cam bearings that were a better match. Course you're talking a bit of work there.

One of my DD GM vehicles (not my GMT400), the oil pressure switch pops off on hot days. I measured it with a certified gauge (which goes 0-60psi), and the pressure drops to 6psi when it's warmed up. Down the road it goes up to like 26-28 ..if I remember correctly. I'm making plans to do a rebuild. It has an Atlas DOHC engine which was discontinued (unavailable) years ago.