Have a 1986 318 engine in a camper van, just installed new timing chain and gears, rv camshaft, new lifters, did not replace cam bearings. Engine runs super great but has a knock at low rpm idle seems to be getting a little worse after 1000 miles, but not majorly worse. Sounds just like a diesel engine at idle. Noise goes away with acceleration and is quiet at speeds above say 15MPH Oil pressure is 20lbs at idle with a new high volume oil pump i also just installed. My question is could a bad front cam bearing cause this noise it seems like it is coming from that area of the engine and i think the bearing might have been bad when i inspected it. I did not change the cam bearings because i did not know how, never done that before. I am thinking about trying to replace just the front bearing without pulling the engine is this possible?

 

It could also be a rod bearing. 20 lbs of oil pressure is kinda low for idle. You might have a high mileage worn out motor.

 

On my 360 that I had with a HV oil pump It had around 60 psi at Idle. When it blew up After running the pan dry (7500 RPM with stock pan) It only had 20 psi at idle. Sounds like your motor has very high mileage

 

I don't believe there's any possibility that this is a cam bearing problem

 

You change to a RV cam? And have a non adjustable valve train? Correct?

So what was your new PR length?

I have a feeling you are hearing the noisy valve train from improper lash.

 

Did it knock at all before all this work? I'd fill it with some thick oil and maybe a bottle of Lucas. My work van developed a knock at 60k miles, I'm at 130k and it runs great but still knocks. BTW, with a steady hand and some disassembly you can change cam bearings in vehicle, but I doubt it's cam bearings causing the knock.

 

i would check to see if your push rod length is correct call the cam manufacturer and find the recommended length for your cam- engine head combo also make sure your valve springs can handle the lift
i just rebuilt my 318 we know the bearing clearances are correct and when the engine gets hot this is florida heat the oil pressure will drop to 24-25 pis at 450-500 rpm, at off idle 1000- 2500 cruise, 45-60psi and 60-80 psi at3000- 6500 rpm also did you use the correct break in oil containing zinc
if it is a engine knock u can replace the bearings + seals by dropping the oil pan i've done a few over the years