Oil passageways?

[ESPREE]

Just an update... Replacing the main cap didn't resolve the issue (noise is still there). As indicated in the other thread, I will talk to him today and ask that my original main cap go back since having the other one in there can potentially cause alignment issues. If the end float is so loose that the cap does need to get replaced then I will see about a line bore since the engine will soon be out of the car.

He removed the left valve cover and there is indeed some significant wear on the cam seats and caps. In particular the rearmost seat on the head itself. I am not sure if it is enough wear to cause a rattle, but there is definitely some wear. Looks like grooves from debris.

I was also thinking to suggest that while everything is out we check out the wrist pins, since I've heard that they can cause a noise that is very similar to a rod bearing (and this rattle does sound almost identical to the rod bearing sounds I had previously).

So two questions if anyone cares to comment...

1. Can the heads be repaired if there is some wear on the cam seats, or do they have to be replaced?

2. Can the wrist pins be checked easily by trying to wiggle the connecting rod, or does each piston have to be removed?

Thanks,

[Günter]

ohh dear ..this story is way beyond

Are you sure that you'r spanner man knows how to inspect & rebuild an engine ?

The cams also run in a line bored way, that's why there are numbers/orientation sighns all the way down. Maybe you can go to a machine shop, and fit a alloy sleeve into the faulty cam-bearing points ..but that is not the typical way to do it (it is more my 'field service' way of doing it to use less money) -an line boring would still be needed for this sleve after all.

If you only have a wear sign around where the oil channel is, on one bearing and not on the full width it should still run centered -so why not check the play with the typical 'plastigage' stripes ..as this is also the way on many other 'clamped' bearing points on the engine rebuild ..every good mechanic would do it so !

Have you used the workshop-manual at least ? -the data for cam, main bearing and big ends is all there ..so what is the problem with your workshop that does all this .. hmmm -strange

gudgeon pins can be measured with the part in your hands on the wiorkbench ..the exact numbers are also there in the manuals.

I really hope your mechanic knows what this is -and how to use ..

http://www.mw-import...us-0-25-mm.html

http://www.mw-import...sschrauben.html

http://www.mw-import...ale-DIN874.html

http://www.mw-import...-messuhren.html

http://www.mw-import...essgeraete.html

http://www.stahlgrub...astigage&page=1

Edited August 15, 2012 by Günter

[ESPREE]

ohh dear ..this story is way beyond

Yes, this about sums it up!

The guy from the machine shop is coming out to measure everything. I have not met him personally but I would hope that he would be an expert with plastiguage and measuring tools. He should be checking out the heads, caps, and cams. They definitely have the shop manual right there. I'll post back with the results.

[sailorbob]

If there is wear to the cam bearing faces of the cam caps and cylinder head then they can be repaired by building up with white metal and machining back to specification size. You'll also need to check the cam bearings themselves for wear.

[ESPREE]

If there is wear to the cam bearing faces of the cam caps and cylinder head then they can be repaired by building up with white metal and machining back to specification size. You'll also need to check the cam bearings themselves for wear.

Thanks. I don't think there are bearings per se on the V8 (just the caps and the head). I'm thinking that the caps can just be replaced but that the head might need some metal as you say. Then a line bore.

Is adding some metal in this way a lasting solution?

[sailorbob]

Even thought there are no balls, rollers or shells, they are still bearings. White metal repairs are almost as old as engines and can provide a superior bearing surface than some stock engines have.

[ESPREE]

Thanks, Derek.

[Günter]

what Derek calls 'white metal' repairs on bearings is meant as the 'white metal' bearing layers used in old cars, like say 1920 ish or so ..as the separate 'multy layer' steel, aluminium, copper system was not invented in fabrication processes those old days.

the possitive effect of those old engines is in fact that you can 'reuse' those bearing cabs by simply adding (melting) new soft alluminium on the steel, and reshape (line bore) it for use. The positve on the modern system is that you simply discard the worn bearing shells, and fit new shels into the caps/seats.

The camshafts on the 918 (and nearly all modern engines) run directly in the alloy from the head, this is the same material as the cabs there ..and this alloy is specified for certain characteristics, for example to have an specific resistance/rigidity on the surface. If you use a TIG/WIG welder to add material you heat up the old surface area there, and this surface will lose its specified characteristics (even knowing that Aluminium can not be hardened in the same way as steel by adding other substances, it is there more a way of controled cooling processes within fabrication) ..so you have to be sure that the new formed alloy there on the bearing zone can hold up with the specified characteristics on wear resistance. Therefore I mentioned to fit an separate sleeve/ separate shells of the right size (for example fabricated from the same alloy that was used for the head, and with the specific surface characteristic) into the re-machined bearing area there for the related camshaft

Edited August 17, 2012 by Günter

[ESPREE]

Just an update... heads and cams are done. Didn't have to add any material - the machine shop just machined down the cam caps a bit to smooth them out (taking material from the bottom surfaces and then reboring I imagine). I guess there wasn't that much material gone from the heads after all.

Now onto the block and main caps again. Turns out the sound was from one of the main bearings being spun (the one with the thrust washers). So this makes 2 different rod bearings and one main bearing failing. A few thrust washers too.

But they are all in the same general area, so I'm really thinking there has got to be a lubrication issue somewhere (like a blocked passage).

So the lower end is finally getting align honed and the block cleaned again. I'm insisting this time that all of the oil passages get thoroughly brushed out in addition to the hot tank. It looks like there is a plug at the end of the oil gallery that has to get drilled or something. Has anyone done that before?

And another set of bearings of course with the machine shop measuring everything in every possible way. Hope to finally resolve this soon!