Posted by Matt Wilson [172.69.69.37] on Tuesday, February 12, 2019 at 17:06:41 :
In Reply to: Re: Connecting Rod Bushings posted by Matt Wilson [108.162.221.77] on Monday, February 11, 2019 at 19:09:56 :
I stopped by a different machine shop this morning and talked to them about all this. Their lead guy, who's been doing machine work on all manmer of engines up to and including big truck diesels for 40 years, said he agreed with the amount of press fit that Sealed Power had told me, which was 0.004 - 0.0045". He said it needs to be this tight for bronze bushings, which is what these are, as it turns out (not steel-backed bronze - so NAPA needs to update their website). I was flabbergasted. I thought that sounded like way too much, but he said if you only put them in with 0.0015" of interference/press, then the bushings would come out. For steel bushings, he said the fit should be less, like on the order of two thousandths. I asked him if he is capable of installing oversize bushings properly and burnishing them, and he said he able to, and told me that burnishing is really the best way to do bronze bushings (he said it's not needed for steel, though). He really sounded like he knows what he's talking about. So I went to the other shop and picked up my rods and I'll be taking them to this new guy, who is more expensive but probably worth it.
Further confirmation of this press fit: I got a hold of a bushing having standard OD, one having the next oversize OD and one having the largest oversize OD, and they are all about 0.004 - 0.005" larger than advertised. I now realize when the ads (NAPA and others) state the bushing OD, they are actually referring to the inner diameter of the rod that it's going into, or maybe the final installed OD of the bushing, which is about the same as the rod ID. These uninstalled ODs are all about 0.004 - 0.005" larger than the advertised ODs. So it seems even clearer to me that the press fit is around 0.0004 - 0.0045, as Sealed Power had indicated.
Anyway, I thought I would provide an update for anyone else's benefit.
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