Help with lifter/rocker noise

[Sandaro]

I've got a problem with my 308. At constant highway driving (3000rpm) I'm getting noisy rockers. It started about 6 months ago. The motors about 120K old. Oil pressure on my gauge shows good pressure. I have changed the oil and even the type of oil (new oil did help initially I thought)

I think that the lifters (hydraulic) aren't staying pumped up with oil and therefore the rockers are slapping. Am I right? What should I do? Not sure if its a pump issue or blockage.

Thanks for any help

Steve

[buck]

I know with the 5.0 litre vn onwards the oil pick up in the sump is very easily blocked, but i think this would show low oil pressure on the gauge.
The lifters would normally make more noise at idle if they where not holding pressure, not sure of the noise, but could be cracked or broken valve bridges?

[HK1837]

Did you fit a new oil pump when you rebuilt the engine? The most common failure on original 253 and 308 was the cam, and the problem was created by the oil pump. You should buy a new pump each time you fit a new cam to be certain. It sounds to me like you have a r00ted cam. Pull the valley off and pull a few lifrers, you'll know pretty quickly if the cam is shot. Fit a new cam, lifters, oil pump and get as much old oil out as you can. Put new oil in an run the cam in to manufacturers requirements and fit a magnetic sump plug.

[wbute]

Yeah cam is a good chance of being stuffed. Lots of slow town driving didn't help them either. It will be missing on one cylinder more than likely also.
The other main miss-diagnosis of lifter noise is often leaking extractors.

[Sandaro]

Thanks for the suggestions so far.

No I didn't change the oil pump when the motor was rebuilt (because was still showing good pressure), sounds like a good starting point

I should have said that on the highway (3000rpm) pressure is 50-60 psi and once I drop speed (and revs to 2000rpm) presure drops to about 40psi but the noise goes within 20 seconds. And I get no noise unless I'm hitting highway speed. Around town and 80 zones are fine, engine nice and quiet.

[buck]

yes i did forgot about flattening cams, but i noticed with my old 253 years ago, in the higher revs the lifter noise and it was 2 cracked aluminium valve bridges, took the tappet covers off and replaced all the valve bridges and problem was solved. must admit the old 253 used to get a flogging around melbourne, seeing the 5500 red line many times.