TheSamba.com :: View topic - engine rebuilding theory

Sun Apr 17, 2011 6:17 pm

do the bushings on the small end of the connecting rods need to be just reamed or reamed and honed. I reamed them to a great fit with the wrist pin but there are slight "ridges" on the inside of the bushing from the reaming. I could hone them perfectly round but i heard doing that leaves microscopic grit embeded in the bushings that would cause premature wear. What do you guys think? I would have to start all over because if i hone now, the wrist pin fit would be too sloppy.

Sun Apr 17, 2011 9:37 pm

Play it safe have them Pressed out and replaced with either aftermarket or Nos. Sure you can do as you had mentioned, but to have several thousandths of differance can give you un- even where spots in the bushing and lubrication is comprimised if this happens and a host of unwanted outcomes may result. Again In my opinion PLay it safe and Replace them out right. 8)

Sun Apr 17, 2011 10:20 pm

They are bran new bushings. i can press them in and out, but they have to be reamed and or honed to fit the wrist pin perfectly, but which one? Both? I know the big end of the connecting rod is resized by honing only for concentricity by a sunnen honing machine, mine are in good enough condition to not need that but how is the small end done? see question above.

Sun Apr 17, 2011 10:36 pm

In my 30 + years of rebuilding/Restoration=I have only Lightly emery clothed the inside of a Rod bushing (If at all) to aid in a smother fit. I have read your post. Something is Truly wrong on your bushing deminsions. If you have to force a piston Pin thru your rod, or hammer it thru???? Good Luck!

Sun Apr 17, 2011 11:58 pm

Did you measure end to end length after replacing the bushings? this is normally set when the bushing is cut to size and is done on a special fixture or in a milling machine that is set to bore it to the correct measurement. If you just pressed them in and reamed then out without a fixture to hold your end to end size true then you will have problems.

Mon Apr 18, 2011 8:17 pm

OK, sound advice from you all. I already got new bushings ready to be re pressed in (i can do it with a c-clamp and sockets). Your right about the center to center. How close does it have to be? I got it with in .005" ctc. It doesn't say in the mechanics handbook for VW it just says weighing within 5 grams (that's alot) and concentric within .001" which it is. How much woulf it cost for a mcahine shop to do this?

Mon Apr 18, 2011 8:57 pm

Clearance between the wrist pin and connecting rod (bushing) is .0004-.001". Allowable wear is .002".

Mon Apr 18, 2011 9:25 pm

Thanks. I got that close but it was only reamed, i have to start over and hone too because reaming is not a perfect circle on the inside there are highs and lows but luckily bushings are cheap, i will look for a pro.