The Stovebolt Site Forums The Shop Area Engine Shop Connecting rod knock ?

I have a 216 babbit bearing motor. The motor does not have many miles on it. The # 8 cylinder has a rod knock that is not bad. I pulled the pan to check clearances. I could move the rod journal back and forth on the cranck about a 1/16" back and fourth. I pulled the rod cap and the babbit had no burning or very visable wear. It had 2 shims on each side. I pulled the shims and still have too much clearance. My question is what are my options? Can I file the cap ends down to get proper clearance and run it for a while? I only drive the truck about 250 miles a yaer. Or do I need to pull the engine again?

Pull the head and fix the rod properly
Even if you don't drive it much you'll hear it everytime you do and you run the risk of more damage and more work

It's a lot more fun driving something that's right

Side to side movement is normal on a rod. The clearance between the rod & crank are whats important. Get some plasta- gauge & measure it. I believe 1-2 thousands is normal.If the crank is smooth you can replace the rod with a rebuilt one. On some cylinders & I think #1 is one of them you can remove the rod without pulling the head. Pullthe piton down till the wristpin is just below the bottom of the cyl. Loosen the clampbolt & slide the pin out far enough to remove the rod.

Now, that is a move that I have never heard about before! That is very intersting! I never dreamed of pulling a rod from the bottom!

Thanks for the ideas guys. I just measured it with plast-guage. It reads .003. There are no burn marks in the babbit and crank is clear and smooth with no ridges. That measurement is done after I have removed all shims.

How can this be?
Scott

If you have removed .002 from each side of the rod and you now have .003 clearance, it must have been quite loose. Usually a knocking bearing will leave some evidence. I would check all the rest. If you have .003 now, it may run that way without knocking. However, if you had the rod machined to take an insert, you could try a .001 under for a trial fit. Kanters sells standard, .001 .002 and some incremental undersize.

Now how many cylinders you got again? World's smallest straight-eight?

The 8 was a typing error. #6 is my problem.

i would be tempted to grind the cap till you get a tite fit and hope you never have to mess whith it again and keep the rpms down i had a 66 chev once i could here a knock i replaced two bearings with 2000. over size the crank was scared and didnt look good at all i drove it for two years then my friend drove it two more he sold it and it was still running fine it may hold up at the clearance you have now just keep the rpms. low

How did I miss that #8 & assume #1 ?