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What's this metal in my oil pan?

13K views 31 replies 12 participants last post by  ericnova72 
#1 ·
I have a fresh built 406 SBC. I just pulled the pan because it is leaking and found these three pieces of metal in the pan. They are aluminum and look like they were sheared off of something. I have no idea where they came from and no idea what to check. It's a '79 block, with vortec heads and nothing is aluminum except the pistons and intake. I've been racking my brain trying to figure it out, but can't think of anything. The rear main bearing looks good and it doesn't appear to have sucked anything through the oil pump.

Any ideas?

 
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#6 ·
You know, I was thinking that could be it. Maybe the little tangs that keep the wear plate from rotating? I'll pull it out tomorrow and check for sure. That would be kind of an odd problem I would think.

They are not magnetic, and the pan was spotless when it was installed. I'll try taking a picture on a blue towel since that's all I have.
 
#10 ·
I would really try to find out what kind of metal it is first,since they are non magnetic as stated I would suspect either Al. or stainless.
Take a piece and anneal it,you can do this by heating with an oxy-acetyline torch,using only acetilyne just completely blacken the metal,let it cool then heat it again,use a carburasing flame and heat it just enough to make the previously blackened dissapear,do not heat it any more than this,if its aluminum it will now be annealead and easy to distort(crude method) put the metal on top of an anvil or vise and hit it with a ball peen hammer,if its Al. it will distort easy if its stainless it wont,this will narrow your detective work down a lot,what ever rings you used see if you can find out if they are stainless, I doubt if its a ring ,it would have to come in between piston and cyl.bore and the motor would have probably locked up by now.This ought to keep you busy for a while!
Besides maybe Im wrong but. Stainless oil rings?
 
#11 ·
Pre-Tuner said:
You know, I was thinking that could be it. Maybe the little tangs that keep the wear plate from rotating? I'll pull it out tomorrow and check for sure. That would be kind of an odd problem I would think.
Unless the distributor for some reason is sitting too low, and the tangs got sheared off (distributor bottomed out?)? But that plate/tangs should be magnetic, I would think...

Or maybe not the "steel" tangs, but the alloy tangs in the distributor housing that stop the steel wear-plate/tangs from rotating? (Is that the one you're talking about?)

At first I was thinking exactly what cobalt mentioned. But that means those pieces had to have either gone down between the piston skirt/cyl., or through the oil passages in the piston.
 
#13 · (Edited)
a1supersport said:
Hmmm...maybe?
Those thrust bearing/spacer tangs would have a difficult time getting to the oil pan unless there is some considerable damage to the distributor- so a casual glance will provide the news. I would expect there to be a LOT of aluminum debris from the radial pieces of the dist. body accompanying the steel pieces of the washer- besides the spacer/thrust bearing is carbon steel, i.e. magnetic. :(
 

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#14 ·
Pre-Tuner
Just a shot in the dark here, but by chance are you using cast aluminum valve covers with oil drippers. If so remove the valve covers and inspect to see if the rocker arms have made contact with the oil drippers.
No need to ask me why I thought of this scenario. ;)
Good luck
H D
 
#15 ·
I have to appologize for my ignorance. The pieces looked aluminum to me, so I said they are not magnetic. I just checked, and they ARE magnetic. So that shows you what I know.

I have fabricated aluminum valve covers, but they do not have oil drippers or even baffles.

The pieces look like they must have dropped straight through because they are not really chewed up; just broken off. The engine has 400 miles on it, and there was no metal in the pan except the usual new engine dust, along with these three pieces. No chunks.

I'm almost certain that they are from the distributor, especially after seeing a1supersport's picture, but I still haven't checked. As soon as the wife gets home, she can watch the babies and I can do something a little more manly.

If these end up being from the distributor, what do you think could have gone wrong. I mean it looks to me like it would be sitting too low, but the wear pattern on the teeth look like it is in the center. I actually had the distributor recurved about 150 miles ago, and the place that did it commented on how nice the wear pattern looked.

That leads me to another question I have. Is the wear plate sitting directly on top of the gear, or is there supposed to be a shim between them? I would think there would be a shim, but I don't know for sure.
 
#17 ·
Ok, I pulled the distributor. Those pieces are definitely from the wear plate. There appears to be a shim between the wear plate and the gear, so I am even more lost.

There is some wear from the thing spinning, which appears to have forced the whole shaft upwards, which in turn started to melt the cap and rotor. I always thought that the camshaft would pull the shaft down, but that doesn't seem to be the case.

My previously complemented wear pattern on my distributor gear doesn't look so good either.

I have no idea what went wrong here.
 
#18 ·
Looks like either the intake manifold is machined too low where the distributor sits(or excessive block/head milling), or the distributor housing collar is machined too high(Chinese?) and the distributor shaft is jammed hard against the oil pump drive rod bottoming everything out. I'd want to inspect the pump now too, for scoring of the end plate and end of gears.

Oil pump drive rod could be too long also, there are three lengths that all look the same to the eye but with 1/8" or so difference - standard SBC, SBC w/BBC pump(slightly shorter), and BBC(longer), but I would be looking at distributor height first for manifold ot housing problems.

Moroso sells a distributor to manifold shim kit for this reason, did you check at assembly that the pump, drive rod, and distributor all had adequate end play??

Gear appears to show distributor sitting too deep in the block also.
 
#19 ·
You got off light- the damage will be limited to a distributor thrust washer, cap and rotor, probably an oil pump and a shim kit to set the distributor height/gear mesh.

The labor is another thing.

You might want to go ahead and get shims to set the distributor end play. Shims linked are for a 1/2" shaft diameter, check yours to see what it is before ordering.

The relationship of the dist. gear to the cam gear causes the dist. shaft to rise upwards- so when checking the pattern, be sure the shaft is fully up w/all clearance removed from the gear end- that is how the dist. shaft and gear is when the engine is running.

I do not believe you could have broken the tangs off an OEM thrust washer like that- the OEM piece is thick enough that I believe it would have taken out the aluminum housing first. But in any event, that dist. shaft had to have been really bound up to do what it did.
 
#20 ·
One thing I forgot... The 400 SBC block requires a necked down oil pump drive due to the larger main bearing bores in the block. If a pump drive shaft that is not reduced diameter is used, it will rub hard on the hole in the block and main cap that it passes through, and could well be related to your problem.
 
#21 ·
Pre-Tuner said:
I actually had the distributor recurved about 150 miles ago, and the place that did it commented on how nice the wear pattern looked.
If the distributor looked fine after 250 miles, and you put on another 150 since recurving (400 miles), makes me wonder what exactly was done when you had it recurved. If you didn't do anything else but pull the distributor, and put it back in...assuming with the same gasket between the dist. housing and intake...I would make a call to the guys who did your recurving. Does it look like they may have added a shim to take-up excessive play between the gear and housing?

I can honestly say I've never seen this happen. All the distributors, all these years...some were sloppy as hell...up-and-down and/or side-to-side...some were tight...and I've never seen this. But then...I've never had my distributor recurved. Hmmm. 0.o
 
#22 ·
I did put about 250 miles on when I first got it, and then decided it needed to be recurved because I needed more initial timing. Nothing was wrong with it when I took it out, but now there is. I'm not sure what they did to it, but I imagine they wouldn't admit to it. I will definitely be talking to them. I don't know if there is an extra shim or not because I don't know what it is supposed to look like.

The intake is untouched and the block was only decked enough to make a nice sealing surface for the heads, which ended up being .008".

I have the 400 oil pump rod which is necked down. The pump is a standard volume pump, so nothing special.

It's a Mallory HEI distributor, so I would think the machining would be accurate coming from a name brand company. Especially since it started off fine.

The gear teeth didn't look like that when I pulled it at 250 miles. The wear pattern was in the center just like it should be.
 
#23 ·
Pre-Tuner said:
I don't know if there is an extra shim or not because I don't know what it is supposed to look like.
On OEM HEI's, there is the thrust washer w/tangs against the distributor. Then a shim. Then the gear. If the end play was set, usually there will be several shims or possibly a thick shim to replace the ~0.015" shim that the dist. comes with.

As long as the dist. isn't bottomed out, there's a fairly wide leeway for where the mesh occurs on the gear itself, w/no adverse results. The pattern has to be all on the gear, not running off the top or bottom.
 
#24 ·
Well, my Dad got back in town from vacation and he thinks the distributor is still usable after the bottom is cleaned up (he's a mechanic). He has some thrust washers that will work, and some shims if needed. He isn't sure what happened either, but agreed that I should take it to the place that recurved it to see what they have to say, which I will try to do tomorrow. When I reinstall it, if the oil pump shaft isn't floating, then I can grind it a little for clearance since I already have the pan off.
 
#26 ·
The thing is, if there was a problem with the internal parts, it would have been damaged within the first 250 miles...but it wasn't. The damage occured after recurving...in the 150 miles after installation. Which means either:

1. Pre-Tuner did something "different" when reinstalling the distributor, OR
2. The people who did the recurving did something to change the position of the dist. gear.

I vote for #2. If the metal tangs weren't sheared off when the dist. was first removed, it's safe to assume all the internal engine parts are correct.
 
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