I finally finished my complete rebuild. For most of the cam break-in procedure, (20 minutes at 1500 to 2000 rpm) oil pressure was great, right around 55 psi. After about 15 minutes the pressure gradually dropped to about 28 psi. Now while idling at 750 rpm, it sits at around 10 psi. I dropped the oil and there is no metal on the magnetic plug. This seems very low to me, as before my rebuild, idle pressure was 18 - 20 psi and 60 psi at 2500 rpm. Any ideas as to what could be going wrong?? I have replaced everything including the oil pump.

 

What, exactly, did this "complete rebuild" include?

 

Complete rebuild; bored 30 over, new pistons, rings, crank machined, bearings, oil pump, head including new valves, new Clifford 264 cam, high lift springs, lifters, hardened push rods, intake, Weber carb and headers. You name it, it's new. The only thing I can think of that was not replaced, was the fuel pump. I am worried I used too much assembly lube, if that's even possible? I have read that the pressure I am getting is sufficient, but pre-rebuild pressure on the tired motor was far better.

 

I wouldn't think so but I'll ask an engine-builder friend what he thinks.

When I rebuilt my engine I used a special red paste on anything that touched the
camshaft, something different everywhere else, and a very expensive, high-zddp break-in
oil for the first 30 minutes (or so) of operation.

 

Were the cam journals polished? I don't want to alarm you, b/c its most likely not the case for yours, but I read on another site that some of the Clifford cams had by-passed the polishing process, and so became very good at destroying/sanding down c.bearings.

Did you plasti-gauge the mains, the rods? If the crank was 'machined', did you use the proper bearings to compensate? Did you pump oil through the system b/f start up?

When you got the block back from the machinist, did you wash it, and the crank, running bottle brushes through ALL the oil journals, and blowing them out with air?


DO NOT throw out the original filter. Put it in a container and keep it. If the psi continues to drop, you will need to slice open the start up filter and carefully search for contaminets. If you toss it you will never know.

Good luck.

 

Thanks for the input F-250 restorer, Yes all was done to spec. I did check the cam before I installed it, and compared it to another new cam I have. When the truck is cold and first started, the psi is around 50, but once it is good and warm, it drops to 10 - 12 psi per 1000 rpm. This is sufficient but not ideal. I may disconnect my oil pressure line and clean it out. I may also install another gauge to see what it reads as well. The gauge I have was installed new a few months before the rebuild, and pressure was much higher. I did check the break-in filter; It had some fine metallic dust particles throughout. nothing large, I was told this was normal. I did another oil change after about 200 K, checked that filter, and still a few speckles of metallic, but not much.
You had a simular issue a while back. Did you solve the problem, if so, what did you find was the problem?

 

On my first engine I never found what the problem was. Something went through the oil and wiped all but the rear main, and all the rod bearings, but didn't affect the cam bearings! I know that sounds crazy. Even after I changed to new bearings, and a new h.volume oil pump, Psi continued to drop. When it got to about 5 psi at idle I pulled it and went with another engine.

#2 engine is like yours: 50 psi at start up, 10 psi at fully hot idle. I just don't think machine shops have the quality they used to.

Btw, I too tried different gauges, but got the same result, yep, even after 'bleeding' the gauge line. If you are using a mechanical gauge, there are two places on the main cam/lifter galley you can connect it. Interestingly enough, I found that the front location (oem is at the rear) gave a 7 psi higher reading than the rear!

Good luck.

 

Thanks! I'll just have to keep an eye on this issue. Have a look at a thread I created today called (Fuel filter empties and purculates). Maybe you'll have some advise on the issue.
Thanks!

 

What was the break in procedure for this engine, and what oil was used? I wouldn't break a flat tappet cam engine in on anything less than an HDEO or racing oil. I'd want 1200ppm+ zinc to break a flat tappet engine in on. And ideally always use an oil with that much, or no less than 1000ppm.

 

Ok, so I found my low oil pressure problem after the complete rebuild. I pulled the pan to have a look, and can see that a few of the cam bearings walked. I am going to pull the motor too see if the bearing bores were ruined, meaning the block is no good, as it won't except new cam bearings. In the meantime, I am putting in another stock low Km 300 to get me buy for now. I was wondering if I put my Clifford intake, 2v carb and headers on to the other stock 300 with a stock cam, would I be reducing my HP because of less back pressure by running this setup with 2 1/4 dual exhaust, or should I replace the dual exhaust with single exhaust. I just hate to pull the dual exhaust. Any thoughts?

 

I might suspect the Cliff. cam. Another guy on Fordsix had one that kept eating bearings. He r&r'ed it twice, with the same result. Then he found that someone had not polished the cam journals!! Were your cam journals polished and looked like chrome, or like dark metal???

 

The cam journals looked like they were somewhere in between that. I actually compared them to another new RV cam I happen to have, and they were similar in polished appearance. I don't know who the manufacturer is, or specs of the other RV cam I have, as I removed it from a freshly un-started rebuilt 300 block, but they were similar in journal appearance. I too suspect the Clifford cam, but won't be sure until I remove it and have it checked by a machine shop. I am just hoping the block bearing bores are ok, but I suspect the bearings turned in the bores rendering it un-usable. Any advice on my question about my exhaust question?

 

From what I have read over at Fordsix, it has pretty well been decided that back pressure is a myth. Again, by what I have read, a single 2.5" pipe, or dual 2.25" ones is great for the 300.

One question: Clifford requires 110 psi @ valve spring recommended installed height. Did you check the height and psi?

 

I didn't check it myself, I had a machine shop rebuild the head with new valves, guids etc. They installed the new dual high lift springs that came with the cam, according to the specs on the cam card. 110 lbs at the seat, with a height of 1.700. I can only assume the shop did all this to spec.

 

"...would I be reducing my HP because of less back pressure..." The "needs back pressure" mythology was debunked by David Vizard and others way back in the last century.