m110 rod bearings as preventative maintenance?

[dave1980_300sd]

Hey everyone,

I'm getting ready to swap a used engine into my '73 280 (original threw a rod while PO was driving). It's a euro-spec m110 I got from a junkyard. I don't really know anything about its history, and I have a set of new rod bearings sitting around. I'm curious what the general consensus would be on whether or not I should go ahead and replace the rod bearings on principle while the engine's out of the car. My feeling is that I might as well, as it will never be easier. However, is there any downside to doing so? is it needlessly risky to replace them without replacing the rod bolts as well (as far as I can tell that would be impossible to do without tearing the engine down further)? Any opinions one way or the other would be appreciated.

thanks,
Dave

[t walgamuth]

I would plastiguage them. The bearings on the 110 are not known to have wear problems. If it has had good care they may be like new.

If they are why change them?

Tom W

[wbain5280]

Why did the original engine throw a rod? Overrevving, low oil, bad maintenance, poor gas and detonation?

If you can, take a rod cap off and check the crank for scoring. Then check the condition of the bearing. Clean the crank journal and the bearing and use plastiguage to check the clearance. Don't move the crank or the results will be wrong.

[dave1980_300sd]

I'm not sure why the old engine threw the rod... it was the #1 rod and it happened at about 70mph on the freeway according to the PO. I bought the car that way because the body and interior are perfect, and it was cheap, but the PO thought at the time that the timing chain had broken. When I got into the engine I realized it was actually a thrown rod. There seemed to be plenty of oil in it when I tore it down, so maybe someone had run it low previously.

I'll definitely be doing a visual inspection of the bottom end with the oil pan off, but if I'm going to take caps off to plastigauge, is there any reason not to just put the new bearings in? it seems like it couldn't hurt if I'll already be getting into some dissassembly.

thanks,
dave

[t walgamuth]

Originally Posted by wbain5280

Why did the original engine throw a rod? Overrevving, low oil, bad maintenance, poor gas and detonation?

If you can, take a rod cap off and check the crank for scoring. Then check the condition of the bearing. Clean the crank journal and the bearing and use plastiguage to check the clearance. Don't move the crank or the results will be wrong.

Why do you want him to plastiguage the junk engine?

Tom W

[wbain5280]

Good point Tom, I must have been either tired or dreaming when I wrote that one.

[t walgamuth]

Oh. I thought you had a good reason.

Tom W