Got my engine back from the machine shop and noticed this carbon looking stuff on the number 3 piston. It is very hard and does not flack off or scrape off. When I returned it to the machine shop he told me he did not know what is was. He said it could be from the original casting of the rod and recommended I leave it alone. I do not know if I should try to wire brush it off or take his advice and leave it alone. Has anyone see this before or Know what it is.

 

Pure-D Guess here:

The bottom saddle of the rod looks like it had too much material removed at some point in the past. Note the digits on the side are cut off. Then, after that PO made it too light, perhaps they JB Welded a weight of some sort. The weight went bye-bye some where along the way, leaving the "JB Weld." The outer edges look like they've been hitting the inner wall of the block, thus the "JB Weld" starting coming off. That material sure looks like worn/damaged JB Weld to me.

As I said, Pure-D Guess. But it looks plausible...

I'm surprised the mechanic said to leave it alone. I think I'd want to get to the bottom (get it! ) of the situation.

 

You need a better machine shop! They should have noticed that and pointed it out. Jmo

 

Thanks for the replies. I agree finding a good machine shop that knows what they are doing is getting hard to find. I think I may need to find another rod and replace this one.

 

And then have them re-balanced as they won't be the same.

 

Doc,
Have you tried to scrape it off ?? I have seen some pretty crappy OEM castings that look very similar. Not necessarily Oldsmobile but it really does not matter. If it scrapes off easily then you need to remove it so it wont come off in operation. Could be baked on oil if that bearing got real hot. As far as re-balancing, I doubt that taking it off would make more than a gram of difference. Was your assembly balanced ? Does not look like it so there is probably more difference than that in the rods anyway.

 

cutlassefi and BillK thank you very much for your help. Bill this doesn't scrape off easily it is very hard. I think I will weigh it and then try to remove it with a wire brush on the bench grinder, If it is baked on oil it should comes off without much effort. If it is JB weld as backinthegame mentioned it will not come off easily. Thank you all for your time and advice it is greatly appreciated.

 

Well I tried to remove it with a wire wheel today and all it did was polish it!!!!!! I hit it on the grinding wheel and it did grind some off. I think that backinthegame is correct and this is JB Weld. I think new rods are in my future.

 

Doesn't look like JB, looks more metallic. Could possibly be flame sprayed metal from the looks of the discoloration on the side of the cap. Possibly to add weight to the rod for a previous balance.

 

I think you are worrying way to much about it. Whatever it is has probably been there since the engine was new and isnt going anywhere.

By the way, was the engine supposedly balanced this time ? Does not look like it.

 

I have used a bernzomatic propane torch to remove JB Weld. If you don't mind putting some heat to it you will know weather or not it is JB. It doesn't take much. A few moments with the tip of the flame on a corner will tell. If it is JB it will crumble off easy after heating. I think JB is good to about 6 or 7 hundred degrees. Anything over that will cause it to deteriorate. If you want you can use a vise or other heat sink to keep the heat from heating the rest of the rod.

 

No the engine was not balanced this time. I am probably worrying about nothing. The engine was running with this rod in it and seems to have no problems . Maybe I should just put it back together and let it ride. Thanks for all your replies

 

HEY THERE
All the best

IF
you are going to run that engine leave that material on the rod end. Chances are it (the material) was added to balance the engine.
Button it up and enjoy the ride