squrlathon

I have two mechanics in agreement that the lifters are making the noise -- although the injectors are making some noise, it seems that they can't be responsible for the particular noise in question, and this makes sense as that noise is loud enough to be heard inside the car at idle and at speed. I am now running Motul 15/50 synthetic oil. The car is now noisy when cold, when warm and particularly after pushing it a bit.

The lifters have been replaced twice, so they are not likely defective per se. I requested some info from europec regarding my 268 cams, no word yet, but I think that the base circle of the new cams should be the same as the stock cams since only the cam lobes need to change to achieve the desired effect, so one person's theory probably will not come into play here.

It seems reasonable at this point to check oil pressure. It's really the only thing left to blame, right? As it turns out, my mechanic didn't actually check the pressure but assumed that it was okay because the oil pressure lights are not indicating anything -- however, the sensor could be out, and I'm sure that there is a margin where oil pressure is not at optimum but still doesn't fall below the threshold to trigger the sensors, right?

So low oil pressure could be caused by the oil pump (we've ruled out the possibility of leaks, such as crank shaft bearing...). Is there anything else that might be causing low oil pressure? Or anything that might cause low oil pressure in a particular region of the engine, i.e. not enough oil getting to the lifters?

I would appreciate further input.
Thanks

MikTip

Do you allow the engine to "fully warm up to operating temps" before pushing it?

15w50's a bit "thick" to be running in that particular motor, unless your racing, and live in Arizona. ;o)

The V6 heads have whats called a "pressure limiting valve" or what some call an "anti-drain-back" valve. If they are weak, or partially clogged, they can effect oil pressure inside the head, by not allowing full pressure to reach the lifters. ;o)

squrlathon

Of course I do let it warm up before I push it at all. The mechanics kept telling me that it's not hurting the car to drive it in the condition it's currently in, and after the recent oil change he said open it up a bit and see if it makes any difference. I've neared the redline a couple of times accelerating hard, and I hit the speed-limiter on the highway at 205 and was still accelerating pretty well when that happened. That's about as hard as I've pushed the car. Didn't seem to change anytning from what we could tell.

Eurospec responded to my email today suggesting that the mechanic measure the base circle of the cams -- they said if the cams are undercut then certainly that could cause the noise I described to them. I guess we'll compare them to the stock cams which I still have of course.