>PROBLEM: It developed this weekend while driving. When driving the TR6
>(approx 70K miles), there is a noticeable knocking (rat tat tat tat tat
>....) that begins almost exactly at 2500 rpm
>POSSIBILITIES: I have thought about bad engine bearings, extreme valve
>noise, timing chain, oil pump, and just plain new rattles.
>SOME OTHER INFO THAT MAY BE PERTINENT:
>2) In 90 degree weather, oil pressure tends to idle around the mid-point
>between 25 lbs and 0 lbs on the gauge, and at driving rpms, oil pressure
>tends to hover around 25 lbs. I use 20W-50.
My initial reaction, with the oil pressure as low as 25 psig and 70k miles
on the engine, is that your connecting rod bearings are knocking (the
dreaded "big end knock" that I spent my teen years losing sleep over, having
had several cars that exhibited this!). Its probably time for a rebuild.
Does the knocking get worse under load, ie acceleration in high gear? Does
it get less or disappear on the overrun? Is it a slow thumping noise or a
fast woodpecker-like noise?
Now, having said all this, I once replaced the connecting rod bearings in my
Morris Minor because of a knock like this, only to discover after the fact
that the rattle was coming from the brake pedal rattling against the floor
from which I had recently removed the carpet because I had stepped in dog
poop which became transferred to the carpet etc etc. So, make sure that
obvious sources of rattles and bangs have been eliminated before going
further. For example, under heavy acceleration the gear shift ratlles
alarmingly in my TR3A, sounding for all the world like major disintegration
taking place inside the engine....
In applying the "Frye Factor" to this note, I estimate a 63% technical
content and 37% extraneous bulls---, or dog poop as the case may be (just