So, my father has a decently built 327 he shoved in a 82 C10 years ago and a few weeks ago I put a new clutch in it and drove it to break it in. A thousand miles later of mostly casual driving, I give him the keys back and he puts it through it's paces again. Normally, the engine runs at about 175 degrees warm and 30 psi of oil pressure. It's always been that way. After some burnouts on the new clutch, oil pressure has mysteriously permanently gone down by 10 psi. Now, this engine has been ran hard before, that's nothing new, and it's only got about 40,000 on it, so I've no idea what happened. Oil level is correct, I've been cautiously driving it since and it's never gone back up like it was before. It still goes up when revved and when cold, but it won't go over about 45 psi regardless of how hard you push it. I'm out of ideas and worrying over the worst possibilities, does anyone know what's going on here? Sorry it's not technically a 3rd gen question, but I'm not a member of any other forums and plus an sbc is an sbc. Thanks in advance.

 

Cut the oil filter and inspect for metal, etc.

Also need to verify the actual oil pressure with a shop gauge. Could be a faulty sending unit.

GD

 

did anything unusual happen during the 'burnouts'? like miss a shift and over rev it? does the pressure on the gauge hold steady with the rpm, or does it fluctuate with steady rpm,, are there any unusual sounds from the engine? Did you change to a lighter weight oil? Like GD says, check the filter, that's one of the things it's there for.

 

What brand of filter? I've seen Fram cut pressure like that.

 

So, I've gone and looked at the filter. There was nothing metallic to note. Y'know, there was the usually bits of dirt and grime but otherwise it looked fine. I've also noticed that the pressure "shifts" when driving it. One moment you're driving and come to a stop and at idle the pressure is down to 15 psi. Most times it's 20 psi and once in a blue moon it's back to normal at 30 psi. Also, when I did the filter, I figured I'd change the oil and when I first ran it, it had 35 psi cold and 30 psi once warmed up. Thinking it might be ok, I gave it a hard pull and once it idled again it went straight down to 20 again. Even during the pull it quit gaining psi after 40 or so. I really don't know what's going on. During the initial burnouts that seemingly started this, nothing strange happened and no over-revving occurred. It was just a few standard burnouts and then the oil pressure goes to hell. Last thing to note is that the engine does have an odd noise when listened to closely. It sounds like a subtle clunking if that makes sense. Not a tick or a knock at all, just a very subtle clunky-sounding noise that happens randomly at idle. The only other time I've noticed this noise was when the thing ran low on oil from blow-by pushing it out the valve covers. After I filled it up again, it quieted right up. Given everything I've said, I really don't think it's the gauge especially since it's a mechanical one and I check the line for leaks and there were none. Any ideas?

 

Put an extra quart of oil in it.

If the pressure comes up near normal, that tells you the pickup fell off the pump.

 

And that's exactly why mine is tack welded on in three places. I read that could happen and wanted no part of it.

GD

 

I like your style.