Metal in the Oil

[carl hinkson]

Originally Posted by magnumv8

I am going to throw something out for you to check.....if you are running a timing chain and the block hasn't been align bored when you start your reassembly use a new timing gear and chain set....it almost looks like the timing set you had was "short" putting excess pressure on the bottom of your front cam bearing.....


D L Rambo.....

If a block is being line bored the operator should not be cutting the journals on the block side but only the caps, On performance engines the blocks should be finished with aling hone and not an align bore as most line boring machines can not cut all 5 journals with one set up.

As far as cam to crank center to center distance they are all over the place with GM OEM blocks we had pne a few years ago that was off .016.

When GM machine their blocks the cam tunnels can be off as they line bore with the cam bearings installed to correct to bad machining.

Try to by a GM OEM block with out cam bearings.

On the BBC we take and drill another hole appox. .3:30 grove the OD of the cam bearing between the 2 holes as we try to create another oil wedge before the load area. Make sure your using a performance cam bearings.

The edge loading on the main bearing maybe from tapered journal do to over polishing.

[Adger Smith]

Ben,
I second the thought that the wear on the outside of the mains is because of crank taper. Might have a lot polished off the center of the journals and the OS be tight. Check the size very carefully from one side of the journal to the other. Don't just let someone throw a Mic. in the middle of the journal to check the size. I also agree with the tight timing chain causing the front cam bearing wear. With .003 clearance it should have had a small oil wedge between the bearing and cam. When you re-assemble it put an indicator on the cam sprocket and see if it is running true. It might have had a load, un- load situation taking up the clearance. You can also put the indicator in a vertical (CL of cam to CL of crank) position and pry up on the cam gear and read the amount of strech the chain allows for bearing clearance. I've experienced tight chain sets before. I would also provide an oil path to the front of the block/cam gear/torrington bearing area. There are several ways to do it and they all work. Like: use a triangle file and slot the block under the cam bearing.... or use a very small round file and slot the bearing from the hole out to the back of the cam gear/bearing. (my preferred method) or drill a small .060 hole into the face of the block just below the bearing, intersecting the oil hole. From the picture the drain magnet isn't much of a problem to me. It looks like ring fuzzies from new engine break in.....
If the oil had that Golden metal look check the retainer/spring interface. New parts, either spring or retainer or both could have a fit problem and be wearing into one another. Spring dampers have a nasty habit of cutting up retainers and spring shims. You might have had some valve float to aggrivate a situation like that. Soft spring shims can make metal, too. I have found that dual interference springs generate a surprising amount of metalic (gold) on initial break in. You got some good input on this thread, most of the problem areas are covered.
I know it is human nature to look for or expect the worst first, but it might be something as small as dist. gear wear.....causing the concerns.
Good luck with your build and I hope you get comfortable with it.

[Ben Kallies]

All,

Thank you for your continued comments and suggestions.

Adger,

I have a question for you related to providing oil to the timing chain area: Wouldn't all of the methods described above ultimately rob oil from the front cam bearing? Why is this not a concern? I'll definitely pay attention to the timing chain upon reassembly based on your comments as well as others on this thread..

Thanks.

-Ben

[Adger Smith]

It is not a concern because the hole size in the front galley only feeds the front main and one rod journal. The same sized hole in the middle 3 feeds their respective main journal and 2 rod journals. The rear galley, like the front, feeds only one main and one rod journal. You would have to drill a Huge hole to draw away the same volume of oil from the front to match what is taken away from the middle 3. You are dealing with a passage (a branch of the oil system) that is the same size as the others, but is only required to flow 1/2 the volume of oil. Don't get oil volume and pressure confused. They are two different things, yet pressure is dependent on available and required volume. Required volume is dependent on width of journals, diameter and clearances in the engine (or simply oil system leakage). Availavble volume is determined by the pump type, size and rotation speed. In a system without a bypass, after the required system volume is reached, the more rpm you spin the pump it will just keep increasing pressure. (that is why we use a pump with a bypass) Simply stated all pressure is is resistance to flow.
Do it, the front cam bearing, rod and main will never know you modified the system. The timing chain, and front of the block and timing gear bearing will know you did it and they will be happy. :~)
Check that chain tension!!! It was probably so tight there was no clearance to build an oil wedge in that bearing. I liked that idea that was posted about drilling the bearing to provide a little oil on the leading side to build an oil wedge.