Thread: 3.9 V8 engine knock

Originally Posted by chazza

. Mindful that a new cam needs to be run-in I took it for a 10km drive and nothing seemed bad but when I got home a knock, which sounded like a big-end or two, had started

Did you run the cam in? If not you could well have wiped a lobe or two or more off it.

Well I lubed it with Penrite grease and took it for a 10km run at 90 to 100km/h and I avoided any excessive idling before doing that; so I don't know what more I could have done.

I forgot to mention that the particles in the sump are non-magnetic and melted quickly under a soft LPG flame, which must mean either white-metal or aluminium. There is no sign of any magnetic metal at all.

Thanks for your thoughts,

Cheers Charlie

Charlie,
have you opened the engine oil filter to see if theres any metal in there?
if there were no signs of damage to the big end bearings its unlikley that the metal came from the oil pump. it may be that the cam has milled some metal off the block or you have damaged a cam bearing during the change out.

Roger

To run a cam in you hold the engine revs up around 2000 for about 20 minutes. This work hardens the lobes.

I have eliminated the big-ends and four of the main-bearings from the enquiry; very slight wear mainly on the big-ends and after 253 000km less than I expected.

Roger, I haven't opened the filter yet but there was a fair bit of metal in the sump oil. Good suggestion; I will do that next. I didn't damage the bearings putting the cam in - I was extremely careful not to. The lifters were primed; the camshaft end-float checked; the key clearance on the cam checked; the chain and wheels oiled; and the motor was rotated four times by hand to make sure nothing was binding. I made sure the thrust plate was in place as well.

Your suggestion about the cam milling the block may well be the case, but I can't think what I can have done wrong to cause that. Any ideas?

BigJon, I ran it up at 2000rpm for about 3 or 4 minutes and then got it out of the shed and took it for the gallop out to my farm, all of which would have been in the 2000/2200rpm range, so I don't think I have done anything wrong there.

Thanks for your comments chaps,

Cheers Charlie

I would take the timing cover off and check for evidence of the timing gear fouling the inside of the cover due to incorrect fitment or wrong parts.

I think my next steps will be:
1. Replace big-end bearing shells - mainly because I might as well while the sump is off.
2. Fit oil pressure gauge and check that there actually is decent pressure.
3. Play it from there with an investigation of the cam and followers, followed by or preceded by, an investigation of the pump and timing mechanism.

Did you use a single row cam chain .... or a double row?