Hi all, I'm hoping to get some help diagnosing a problem with a friends LA360. It's a built motor with 10.5 to 1 compression, big solid camshaft (unsure of specs), extensively ported j heads etc and is regularly spun hard to 7500rpm. The motor was built about 8 years ago but it has not seen much use and is still very tight. After a recent pass, it has developed a knock that sounds like its coming from the centre of the engine (definitely not a big end or crankshaft bearing knock) which can only be heard over 3000 rpm. Its has 60 psi oil pressure when cold but it drops away to 10 psi when warmed up. It runs fine until the revs are brought up to 3000 and the noise can be heard then refuses to idle afterwards. I'm wondering if it is possible for the camshaft retaining plate to fail or come loose allowing the camshaft to float (move forwards) as I'm thinking this could explain the loss of oil pressure and poor idle as it could also cause the distributer to retard slightly. Has anybody experienced anything like this before? Is this even possible? Just not in a position to pull the motor at this stage and hoping it's something that can be fixed in car.
Thanks in advance,
Andy

Do NOT run this motor again till You find and fix.
You can't NOT be in a position to pull the motor if you find any metal in the filter. Check that first. Then check converter to flex plate bolts. At a minimum I would cut the filter open first, rock the motor back and forth and watch for slop in the timing chain by watching the rotor,then pull the valve covers and check for loose parts, broken springs, broken bolts, etc. Next pull the pan. If you haven'found the problem by the time you get to the pan then it is most likely in there. Gets expensive then.

Except for the idle it sounds an awful like like a worn down rod bearing to me. The camshaft could push forward if the thrust plate came loose, but I don't think it would cause an oil pressure drop until the cam was almost half the thickness of a cam journal out of place exposing the oil feed holes in the cam tunnel. And at that point you would probably hear the cam gear grinding into the timing cover and the oil pump lever. But there would be no way for it to slide back into place on its own when it cools down. Sorry to say there is no way I would run that engine again until its sorted out.

I've completely stripped a 360 in my challenger down to the crank without pulling the block from the bay. Wasn't easy, but when you don't have a shop or an engine hoist you do what you have to.

Start from the outside and work in until you find the issue. Could be as simple as a broken or backed off rocker allowing a tappet to travel up out of its bore, exposing an oil passage.

Some guys forget or don't notice the soft plugs behind the thrust plate. If the plate were to loosen up you would loose oil pressure that way and it wouldn't take much movement of the plate to lose pressure. As for the knocking maybe the camshaft is bouncing off the plate. Take the pushrods out, take the distributor out, remove the intermediate shaft, take a long pry bar or screw driver and see if the cam moves fore and aft.

Fix it before its run again... might be too late anyway.

I vote for valve train problems... bad lifter, bent pushrods or valves or a combination of these parts.

Gen 3 Hemi's have lifter issues... many times they act the same way just before the whole motor goes south.

Step one...... Cut open the oil filter see what's inside.

Although a bit more rare a cracked piston skirt can sound like a rod or wrist pin.

But as everyone has said, dont run it anymore.

Try a socket/breaker bar on the crank bolt and move back and forth gently just a bump, and see if you hear a thunking noise as well, you might here somthing is already loose.

7500? Oil system not "fixed"? Spun a rod bearing. #6 or 7. Lucky you didn't break the rod. Cut the oil filter open.

I will never understand why guys insist on reving these engines up to 7500 rpm with JUNK heads. How fast is this car.

I think it would be better to have a 340 based engine with the smaller main journals to start with if high rpm is the goal?

RPM may not be the cause of whatever issue it may have, but that just seems excessive for an LA 360 based build.

Thanks Transman, that is exactly what I was thinking but I've never seen or heard of this before. The motor only refuses to idle after it has been brought up to 3000rpm and my theory is that the camshaft is moving forwards just enough to slightly retard the ignition timing. I'm hoping to remove the intake and timing cover tonight, hopfully we can get a look at what's going on.