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By RV3 - 13 Years Ago
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Engine in question is newly rebuilt 368 Y-block (56 Lincoln). I just built up the engine and it overall it runs great, with the exception of nearly zero oil pressure at idle after it gets to operating temperature. Running 30w oil, at cold start-up oil pressure will go to 50-60 psi. Upon reaching operating temperature I will get 0-5 psi at idle 750 RPM. (At 1250 RPM it will go up to 10 PSI). General info and other things I have tried:
1 - I confirmed the pressure reading with 2 different direct read oil pressure gauges (not electric).
2 - Changed the oil pump, but no difference in behavior
3 - Verified crankshaft bearing clearances. I re-checked a rod and main and both came in at around .0026 . Service manual calls for acceptable tolerances of .0007 to .0036 so it appears bearing clearances are with range.
HELP I need:
1 - Could Cam bearing clearance be suspect? Would that potentially cause this?
2 - Only other major machine work that I had to be done was 2 cylinders needed to be sleeved. Could that have breeched an oil gallery? If so, I would assume that it would be sealed back up with the new sleeve.
3 - I do not believe the oil pump is sucking air, due to no oil pressure fluctuations or air in bubbles in the oil.
ANY help with ideas or past experiences would be greatly appreciated. This one has me stumped.
Rob
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By The Master Cylinder - 13 Years Ago
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Rob, The very first thing that came to mind before I even finished reading your post was "Did you replace the can bearings?"
Obviously that's also the hardest to check. I would check everything else you can think of or others suggest first.
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By charliemccraney - 13 Years Ago
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How was the oil pressure before it was rebuilt?
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By RV3 - 13 Years Ago
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charliemccraney (10/5/2012)
How was the oil pressure before it was rebuilt?
The block was a certified Ford rebuilt short block still in the original crate when I got it from an old Lincoln friend last year. I think it was built back in the late 60's so it had been sitting in the crate for many many years. I tore it back down and built it up with heads I already had. I had the crank polished and 2 cylinder sleeves were required. The pistons, rods, and cam were all reused but I did have the cam bearings replaced. Unfortunately I did not get the exact specs noted on cam bearing clearances from the machine shop. My thinking is that if it was common to have cam bearing journals machined back when the short block was assembled, and the new cam bearings the machine shop put in were standard then there is a chance the clearance is far beyond limits. However, I am told that there is only one set of cam bearings available for that engine.
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By Grumpy1 - 13 Years Ago
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It sounds like you have a clooged oil passage. Maybe the cam bearing were installed improperly. Try this. Pull the valve covers and the dizzy. Use a drill to spin the oil pump and see if your getting oil at the top of the engine. Spin the hell out of it and see if you can get the oil pressure up and the oil to flow. Let us know what happens and we can go from there. Greg
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By John Mummert - 13 Years Ago
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It was common for the Ford rebuilders to grind the bearing journals down around .015" and use undersize cam bearings. This could easily be your problem.
You might be able to remove the fuel pump and check for vertical movement on the cam. .015" clearance should be obvious.
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By MoonShadow - 13 Years Ago
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Oddly enough I'm having the identical problem with a 292. Complete rebuild and balanced. Oil pressure at initial startup was 60+. Now it starts cold at 40 but idles at 3-5 lbs when warm. Comes up nicely with rpm but just isn't right. I havn't had a chance to troubleshoot it as yet. Other than possible improperly installed cam bearings it was also suggested to check the rubber seal where the pickup tube goes into the oil pump. Seems they can suck air if the seal is bad. If I run across any other ideas I'll post them. Chuck
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By gekko13 - 13 Years Ago
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Yet another WAG: side clearance on the rods. At least it is easily verifiable. Also, I hope you are not using a Fram PH 8 A. As of late, they are junk IMO. Motorcraft, Wix, or Hastings are all preferable.
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By MoonShadow - 13 Years Ago
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I was wondering (read hoping) that the problem could be in the oil filter pressure relief. Another thing to check. Chuck
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By RV3 - 13 Years Ago
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All - *PROGRESS*! Many many thanks for all of the posts and ideas. You guys are great. I spent the evening in the garage and the possible good news is I think I found the root cause. The bad news is that if I am right, then the root cause is my own stupid fault  . As a test I decided to drive the oil pump with oil pan off and the engine inverted so I could see anything out of the ordinary. I rigged up a feed pipe to the oil pump from a jug of oil and had someone else drive the oil pump with the electric drill. **And yes ... I made an enormous mess** But, I found a large gush of oil coming through the hole in the block where the oil pump drive shaft connects to the oil pump. Definitely not correct! I removed the oil pump and found that I put the d@$? gasket on 180 degrees off. Stupid, I know. With it incorrectly installed 180 degrees off, it fits, but then there is no gasket material between the pressure port and hole in the block where the oil pump drive shaft connects with the oil pump. Hence, I lose most of the pressure right at the pressure port of the oil pump! I reversed the gasket, bolted the pump back on and I could tell a difference as soon as I tried to drive the oil pump with the drill. The drill labored much much more and no more oil coming from places it shouldn't. I am kicking myself, for being that stupid ... but I never stop learning from my mistakes.
I need to reassemble everything, put it back on my engine run stand and then crank it up again, but I am convinced that was the problem. The gap at the oil pump was not big enough to drop the oil pressure when cold, but when hot at idle it just dropped to nothing. *MoonShadow - Check your oil pump gasket.
I am unable to run it this weekend, but I will post back next weekend with the final results. Thanks again for all of the help and hopefully this post can be referenced by others and save them some time.
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By MoonShadow - 13 Years Ago
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I'm sure you are not the first to do this. Thats another hope for a "simple" fix. I would be happy if I find thats my problem too. Chuck
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By Grumpy1 - 13 Years Ago
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Rob, i like the creative problem solving. I was going so suggest you do something very similar but didnt think you would be crazy enough to try it. Please give more details about your build. Did you convert to a spin on oil filter? I thought that could have been a source of your problem. Chuck, did you loose oil pressure all of a sudden or over time? Greg
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By DryLakesRacer - 13 Years Ago
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Glad you found your problem...I was going to ask if you were using Valvoline oil. It always went to 5 psi on anything I used it in. Went to Castol then and the problem went away............Good luck
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By RV3 - 13 Years Ago
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I have things back together filled it with oil and ran the oil pump manually with my dummy distributor and the oil pressure went to 70 lbs. Never had that much before. True test will be at crank-up and running temp but that problem is looking to be solved.
However, I do have another current problem, which is likely much more common to everyone. While testing my previous oil pressure issue I noticed that the right bank rocker is not getting oil. I pulled the rocker arm and nothing comes up through the head, via driving the oil pump with a drill. Air pressure down the hole yields the slightest bit of air that I can hear flowing, but it is most definitely obstructed. I do not believe that the galley is plugged with gunk as the block and heads were hot tanked. I am concerned that it is an issue at the cam bearings. I am not certain if I have the cross drilled or grooved cam, but I get oil on the left side no matter the position I turn the crankshaft, so I believe it is grooved. Per the manual, on the 368 the No. 2 cam journal flows oil to the left bank rocker and the No. 4 cam journal runs oil to the right bank rocker. Can anyone confirm? I believe the Ford Y-blocks oil both sides from the No. 3, but the 368 uses both 2 and 4. Any ideas on other steps I can take to check for the easy things before I have to pull the head or the cam to validate? I have also heard that the cam groove needs to be deep enough, but I can't find a spec for how deep it needs to be. Anybody have a spec that I can reference?
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