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Discussion Starter · #1 · (Edited)
12 years ago I installed a factory new engine composed of several brand new parts from different suppliers in the UK. I did so because cilinder liners in nr 6 and 8 were letting water in. At the time I had a new 4.6 LC short engine and converted it to HC by changing the pistons and conrods. These were also brand new. I took the bearing shells from the LC big end bearings and put them in the HC conrods.
Right from the beginning there was a ticking noise on acceleration that you could describe as a diesel engine noise. At first I was convinced it was a small leak in the exhaust manifold or its gaskets. Since the headers were also brand new I put the old ones back in place but no difference there. The catalytic converters were renewed, as were the mid end end muffler. No difference.
Than I checked the preload of the lifters and they were very off at the back of the engine so I installed adjustable pushrods and corrected the preload to specification. To no avail.
On youtube some people uploaded clips that dealt with ‘pistonslap’.

The ticking noise is only there on acceleration but when driving with a constant speed of 25/30 mls it is silent. When I play just very slightly with the accelerator pedal I can make the ticking appear and disappear. As the speed gets higher the pressure in the combustion chambers gets higher for it to overcome all kinds of resistance from tires and aerodynamics and from there on the noise is constantly there. Unless I let go of the accelerator of course.
It has done so for the past 25k kms/15k mls and the engine runs otherwise beautifully smooth, has excellent pressure in all cilinders, no cooling issues or coolant loss, no leaks anywhere.

I did 8 testruns with each time a different individual injector disconnected. The ticking noise was always there.
When I have the car stationary with brakes applied and I give it some revs, I can hear the noise too but slightly different. Somewhat softened instead of the metal-to-metal sound.

From the pictures I took 12 years ago I could see that the arrows on the pistons were pointing in the correct direction but I couldn’t recall if I had the dimples on the conrods in the right place ( front of engine left bank, rear of engine right bank) so I took the oilpan off. All dimples ( or bosses) on the correct side. While I had the oilpan off I might as well check the clearance of the big end bearings by means of Plastigauge. I have done cilinders 1,2,5,6,7 and 8 so far and they are all in spec. I have no reason to assume cilinders 3 and 4 are any different.

That is where I am now and it seems that either I have been tracing a ghost or that I am thinking in the wrong direction.
Anyway, when taking the bearing shells out to put the plastigauge in place some scoring of the bearings revealed itself. The journals were very smooth except for cilinders 1 and 2. With my fingernail I could feel some wearpatterns on the journal. But the others were smooth as silk. But still the bearingshells looked like below in the pictures. Should I be worried?



 

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That looks like contaminated oil or dirt in the oilways to me (see Types of Engine Bearing Damage | KnowYourParts). The front journal will be closest to the oil pump so if there was any dirt in the oilways, that one would have got it first. What oil have you been using?
 
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