97 250 5.4 LOUD KNOCK FRM CAM AREA
 

ran low on oil, drove ten miles with knocking on accel. needed three qts to top up. after let sit overnite, started it and it sounded like something in the right valve cover wanted bad to get out. as soon as oil pressure came up, it stopped. knocking is stll there. pulled off valve cover and several cam caps. rear shows some scoring, middle less, and front no scoring. pulled the k&n oil filter to check leak back valve. its ok. couldthe oil have leaked back from somewere else? would new bottom end bearings cure the cam noise? its loud enough you dont want to stand near it in case of shrapnel injury. bottom end knocking is constant, but not as loud.

May be too much clearance on the cam to followers if the head and cam retaining caps are worn. I had a 4.6L in my nieces 94 Cougar run low on oil and it galled a valve stem which in turn kept the valve from closing completely. This left a lot of valve clearance and a noisy engine.

good thought, but this one goes away after about 5 seconds, when the oil pressure pumps up. also, i went to look at the k&n oil filter the next day and it had drained out the oil i left in the top. the new purolater still had not leaked.
today i'm going to have somebody turn the crank while i watch what happens to the rockers and look for a collapsed lifter / lash adjusters as it turns over.
the noise is bad enough it sounds like it's got about a 1/4 inch clearance. i'll also put a dial indicator on the cam and see if it is movng up and down.

turned the crank while watching the lash adjusters and rockers. no excessive clearance. couldnt get a dial indicator on it, but everything looks as it is supposed to look. it must be oiling because the noise goes away when pressure builds. i will pull the pan next to see what the bottom end bearings and crank look like. will the pan come off a 98 (turns out i had the wrong year) f250 lite duty 2wd without lifting the engine?

be sure to check your timing chain tensioners, they are oil pressure controlled.

I always recommend a Motorcraft oil filter because they have the best anti-drainback valve in them .

Another thought, We had a 2000 F250 5.4L where I used to work that Had a couple of broken exhaust manifold studs and it sounded like a knock when first started due to the leak. Just another avenue to explore.