rod shim issue

B

Brian King

Member
Looking for some advice. I had a knock that appeared to be from the #1 rod bearing. I pulled the cap and plasti-gauged it and it read approx. .002-.0025. I pulled one shim from each side of the cap, put some assembly lube on the bearing and re-torqued to 35 lbs. and the plasti-gauge read .001-.0015. Perfect (or so I thought). With the plugs out of it I went to turn it over and it is so tight that there is no way mortal man could crank it to start. I loosened the #1 cap nuts a turn or so and it is back to turning over like normal.
Help!
 
Most Model T rod bearings are set a .002. Check the front main and the rest of the rod clearances.
 
if the crankshaft is worn out of round you can have clearance at one place----and be tight in another
 
The motor is relatively fresh - built in 2009 and maybe 100 miles on it. I can plasti-gauge the mains and the rods easy enough - but how can I check if the journal is "oval" without removing the rod/piston?
 
Also just remove one shim at a time. And you may have to scrape the bearing in.
Its amazing some times how much the bearing surface itself changes with just a little
shiming.
 
To check the journal remove the cap with the piston at the top. Then crank till the journal is at the bottom. Now you can mike the journal, then pull the rod down to reassemble.
 
Ah - my error. I was thinking about the rod diameter and not the crank journal. Thank you all for the help. Sounds like .001-.0015 is too tight either way. I will investigate further.....
 
.0015 to .002 is correct for rods and mains. The journals are all the same size +/- any grinding that has been done.
I do not use plasigauge to check I find it embeds in the babbitt and does not spread correctly most of the time and if you do use it, it needs to have oil on the journal and bearing not dry. I use the aluminum foil method and only taking one shim off one side at a time till the rod just does not want to turn. Depending on the thickness of your foil, I fold a 1" square about to 2 to 3 thickness's thick.
Ok the engine was built in '09, was that a full rebuild or just freshen up? If it was a full rebuild (new babbitt etc) I don't know that I would be worried about out of round journals at this point given the mileage.
 
Is there a chance that the cap was put back on backwards? The tiny offset caused could make things very tight.
 
An 'old time' model t man told me to use a layer of paper grocery bag soaked in oil to check T rods and mains. He said you should be able to turn the crank without the paper and not be able to turn the crank with the bag. I have tried it and it seems to work, though I have never 'miced' the layer of paper bag.
 
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