Welcome Guest [Log In] [Register]
Posted ImageWelcome to the all new Geo Metro Forum. We hope you enjoy your visit.

You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are features you can't use and images you can't see. Registration is simple, fast, and completely free. If you're already a member please log in to your account to access all of our features:

Join our community!




Username:   Password:
Add Reply
Have question about rod bearings
Topic Started: Mar 13 2013, 08:22 AM (525 Views)
rydholm11211
Big sky

I just bought a set of rod bearings from King, and I meausered one with a micrometer, the one Geo Glen sugested to buy on ebay, so I bought that one, The rod bearing that I measured was .0785 ? What should the rod bearing thinkness be? thanks.
Offline Profile Quote Post Goto Top
 
rydholm11211
Big sky

I have three geo metro engines, and im going to be rebuilding one, and should I measure the rod bearings on it now? and reuse them?
Offline Profile Quote Post Goto Top
 
Memphis metro


When rebuilding a engine, I never recommend using old rod bearings myself. :die Heres why. A rod bearing with 200000 miles on it has got to have considerable amount of babbit worn off the bearing as well as slight imperfections in the bearing surface and crankshaft. I recommend a polished crankshaft and if the crankshaft is still within standard tolerance go with new standard bearings of your choice. Its unheard of for professional engine rebuilders to put used rod bearings back into a rebuilt engine. They do just what I described and if the crankshaft is out of specs, grind it and go to the next size bearings. Most engine builders purchase their rebuild kits from engine suppliers as well like federal mogul and the parts are aftermarket parts. Of course this is just MHO.
Offline Profile Quote Post Goto Top
 
Deleted User
Deleted User

rydholm11211
Mar 13 2013, 08:22 AM
I just bought a set of rod bearings from King, and I meausered one with a micrometer, the one Geo Glen sugested to buy on ebay, so I bought that one, The rod bearing that I measured was .0785 ? What should the rod bearing thinkness be? thanks.
:hmm

You must certainly be measuring the main bearings. The minimum thickness for rod bearings in the Factory Service Manual is 0.0786". If those are main bearings, they're fairly inadequate.

*****

Now, about rod bearings.

The sizes that I have seen from engines, as removed, are 0.0583" - 0.0587". Many of these are quite serviceable.

Here's your issue: Crankshaft to bearing clearance.

The standard size crankshaft rod journals on engines range from 1.6529" - 1.6535".

The big end of the connecting rod diameters range from 1.7716" - 1.7722".

Worst Case:

Rod = 1.7722"
Crank = 1.6529"
Bearings = 0.0583"

1.7722"-1.6529"-0.0583"-0.0583" = 0.0027"

New limits connecting rod to bearing clearance = 0.0008" - 0.0019". Service Limit = 0.0031"

Even worse: Polish the crankshaft. Now it measures 1.6527". Your clearance is now 0.0025"

Best Case:

Rod = 1.7716"
Crank = 1.6535" (not going to happen, but, anyway)
Bearings = 0.0587"

1.7716"-1.6535"-0.0587"-0.0587" = 0.0007"

What you're likely to end up with, polishing the crankshaft and resizing the connecting rods.

Rod = 1.7716"
Crank = 1.6527"
Bearings = 0.0585"

1.7716"-1.6527"-0.0585"-0.0585" = 0.0019"

Quote Post Goto Top
 
1 user reading this topic (1 Guest and 0 Anonymous)
« Previous Topic · Engine Tech & Diagnostics · Next Topic »
Add Reply