Main and rod bearing adjustment ?

B

bill boz

Junior Member
I’ve read all of the posts that I can find on the topic. I’m wondering when it’s time to drop the pan and do it. I had my engine rebuilt using Babbitt in 2014 since then I’ve put about 13000 miles on the engine. I feel as though the engine is making more noise, especially when it’s cold. I don’t want to fix something that ain’t broken, but don’t want to put off any necessary maintenance. We have several trips planned for later this spring and summer and would like to be sure I’m not going to cause any damage to my bearings. I do have an overdrive transmission and a 354 rear end, (thinking about going back to 378) but that’s another story.
My question, is there an interval or mileage that anyone follows for the inspection and adjustment of the bearings, or just play it by ear?
Thanks
Bill
 
I don't think you'd be out of line dropping the pan and checking the bearing clearances. Worst that can happen is that you find out they are all still within spec, 13000 isn't all that many miles. Are you sure it's the mains or rods making noise and not something else?
 
I can't give a mileage to check not knowing how the engine was setup in the first place, babbitt used, clearances etc, but if you are going to check the mains and rods I would suggest pulling the engine. The No.3 main is a bugger to do under the car, can be done. No. 1 and 2 you need to reach up and turn/hold the wrench while holding/turning the main bolt or have a helper. Still a bugger to do multiple times while checking.

The mains could be ok and the rods need attention, which would be doable under the car.

With that 65+LB weight hanging off the end of the crankshaft, there will be some bowing, down for the 3rd and up for the center.

Have you brought the engine up to temperature and used a stethoscope to listen for noises yet? Could be lifters/valves timing gear etc.
 
I did set my valve clearance a little wide, so they are a bit noisy. I will get a stethoscope and probe around. Noise isn’t all that bad, not like before I had the engine rebuilt, there was a definite clunk from the center main then. I guess thinking more along the lines of preventative maintenance, just don’t want to cause more problems by doing so
 
The nice thing with Babbitt, is it can rattle or even knock a while without doing any damage. I’ve had a small rattle for a thousand miles or so. #1 rod was a little loose after 38,000 miles. And I agree, pull the engine and do it on a stand. So much less aggravation ect.
 
An overdrive with a 3.54 rear axle ratio can be a strain on the engine if used in high range in hilly country driving. I am a long time Model A owner, not a mechanic, but an engine overhaul should be good for around 80,000 miles with one check on the bearings somewhere in the middle of those miles. If you hear suspicious knocks at any time check right away but the norm is for a longer time span.
 
I just finished mine, take the engine out by itself, then on a stand.
This is a trial & error thing, I lay the crank in, fit each main cap (grind the cap down on side of a new chop saw blade, works fine) until there is a good drag to it, then put in .001 shims, you want these bearing at about .001, babbitt will fit itself, you end up with snug bearings that last. Use modern OIL, forget the old 'book' junk.
I'm using 5W-20, same as my modern cars, this thinner oil passes down those oil tubes better, especially when cold, this is what ruined engines in the old days of heavy oil, picks up better with the rod dippers also.
I also put in a 'pressure' line to the center main, probably a good idea, I had the parts on hand.
Word to wise: Use modern 80-90 in ****** & rear, forget the 'book', modern lube is by far best.
Fit rod caps with crank on the bench, same drag & shims.

warrene
 
Thank you all for the great advice. I will hold off on doing anything for now but will keep an eye (ear) on the engine. I am convinced that when I decide to go over the bearings that I will pull the engine to do the job.
Hanks for the input
Bill
 
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