I posted this over at the Corr@l as well, but I'm just looking for some fresh eyes to see this and maybe have some ideas. I got my car (85 Ford LTD with 94 Mustang 5.0) all back together last weekend after swapping the stock heads for some AFR 165s and Crane Cobra 1.7s RRs with new pushrods and it fired up first try. I had a little lifter tick for a few minutes, but it went away and the car ran perfectly. No leaks, noises, nothing. I thought it was too good to be true, and I was right. After I let the car idle for about 15 mins, I hopped in and started to drive it around and there was nothing wrong until I looked at the oil pressure gauge at idle. It was showing about 7 psi. I pulled over and checked the oil and it was all there. So I started it back up and drove it a bit more and noticed that oil pressure seems to be fine off idle. The only other weird thing I noticed was that when accelerating from a stop, the oil pressure would go up rapidly to maybe 60 psi, then drop down to steady 40-50. After that, the pressure stayed steady at about the same levels I can recall it being before the head swap. I don't remember exactly what the idle oil pressure was before the head swap, but it was higher than 7! I thought my gauge (a mechanical Autometer) might be wrong, so I went down to Autozone and picked up a cheapy Sunpro unit and it showed the same pressure. I also noticed that the oil wouldn't make it all the way up the plastic gauge tubing unless I revved it over 2 grand. Is this normal? I didn't do anything to the car that should affect oil pressure. The only thing I can think of is debris/junk caught up in the oil pump pickup. I was as as careful as possible to get all the old gasket debris off the engine and rotated the engine by hand 3 times to wipe the junk out of the cylinders after the rings pushed them to the top. The only other things to note are that I used an oil pump primer attachment on my drill to get the oil in the top end, and that I had to get a new PCV valve grommet for the lower intake because I guess tmoss forgot to reinstall it after porting the intake. The grommet is not exactly the right one, but it fit and is snug, plus I used RTV to make sure. I changed the oil/filter as well. --- Since then, I put in straight 40 weight oil to see if the pressure pumped up but it didn't. After a longer drive, (engine got to normal temps) pressure at idle dropped to 5 psi, and at cruise it was 30-35 psi. I also cut open the oil filter and found no metal shavings, so I think the bearings are ok. So it seems the problem is not the filter (changed twice), the gauge (installed new gauge/tubing/fitting), or the oil viscosity. The best consensus so far has been that gasket crap from the engine has accumulated in the oil pump pickup. Any other ideas? Thanks.
Here: I tried to scrape as much off the engine as possible (I had a ton sitting on my headers as proof) using a razor blade. The rest I tried to scrape into the cylinders, so I could then spray the cylinders with brake cleaner and rotate the engines by hand to wipe the gunk out after the rings pushed it to the top.
It doesn't look like the 5.0 has oil drain holes through the block... the heads drain to the lifter valley? If so I don't think you could have got anything into the oilpan, though that is a lot of gasket material and would have been an issue on a motor with holes in the deck to the crankcase... My other thought was that there was an internal oil leak, and at low RPM the pump couldn't flow enough to overcome the escaping pressure. But I don't know how a head swap would do that unless something was really fubared with the seal of the oil feed to the heads (leaking to lifter valley if it is adjacent to there?) or the installation of the rocker shaft. I got no idea how the lube system on this motor is set up though.
