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Rod bearing clearance... Should I re-adjust my bearings? #403528
02/15/18 12:15 AM
02/15/18 12:15 AM
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Hi.
I know rod bearing clearance has been discussed earlier, and I would like your advice...

I finished the restoration of my 1934 Master in 2017.
I got help to rebuild the engine, it was done by a local shop. The rod bearings were all adjusted with shims to be "loose", you could move them front-back by hand (about 0.0015-0,002" bearing clearance), because the shop thought this was the correct clearance.

I have driven the car about 200 miles since it was finished, and everything seems to be ok (no "bad" sounds that I can hear).

I have later found out that the rod bearings were not adjusted correctly, the rod bearings should be adjusted so tight that you need "the light tap of an 8-oz hammer" to move them front-back.

So, my question is:
Should I drop the oil pan and try to adjust the rod bearings tighter, even if the engine seems ok...?

What is the idea with the very tight rod bearing clearances? Will the bearings "wear to fit" (more clearance) after a while?

Thanks!

The Filling Station 1933-36
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403531
02/15/18 12:58 AM
02/15/18 12:58 AM
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Chev Nut Offline

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If it were mine I would drive it for a few hundred miles and then see if you can hear any rod noise after the oil is good and hot. (oil thined out).
If no noise just be mindful of rod noise. It is not unusual for the rods to loosen up a little in the first few thousand miles due to high spots and babbitt compressing.
If the rods are adjusted the "correct" way the engine usually turns over slow when hot in the first 1000 miles.
The loose adjustment used would be more correct for 216-235 engines as they had larger rod journals according to Chevrolet.


Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403533
02/15/18 01:37 AM
02/15/18 01:37 AM
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If they are the 0.0015, they should be ok.

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403539
02/15/18 02:04 AM
02/15/18 02:04 AM
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Eagle Point, Oregon
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My rods were set up by a local engine shop at .0015" (one was set at .002") on my rebuilt engine and the rods started knocking almost immediately. Adjusted the rods to the correct clearance like they should have been done the first time and that stopped the rod knock. Learned never to take a vintage engine to a local machine shop if it was to be done correctly.

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Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403544
02/15/18 04:28 AM
02/15/18 04:28 AM
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If the engine was rebuilt using aluminum pistons the rods may not make noise due to the less load of the light pistons ?


Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chev Nut] #403550
02/15/18 09:24 AM
02/15/18 09:24 AM
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Originally Posted by Chev Nut
If the engine was rebuilt using aluminum pistons the rods may not make noise due to the less load of the light pistons ?

Thanks for the replys!
Yes, aluminium pistons.
To be safe, it might be a good idea to drop the oil pan and re-adjust the bearings then, right?
Then I will not be worried and listening for "bad noises" all the time when I drive the car (I am not exactly sure what rod knock sounds like either - other than I guess it is a knocking sound...)

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403553
02/15/18 01:57 PM
02/15/18 01:57 PM
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If you re-adjust them for peace of mind I wouuld put a few more easy miles on it and do it at about 400 total miles. That is a good time to change the oil for the first time also. This will allow time for the high spots to wear in and get a good adjustment.


Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403556
02/15/18 03:15 PM
02/15/18 03:15 PM
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Quote
To be safe, it might be a good idea to drop the oil pan and re-adjust the bearings then, right?


Yes! That way you will have peace of mind. Also, you can do as Gene suggests....wait about 400 or 500 miles to allow everything to "wear in" and then readjust the rod bearings. It wouldn't hurt to re-torque the cylinder head at that time as well.

laugh wink beer2


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Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Junkyard Dog] #403561
02/15/18 04:37 PM
02/15/18 04:37 PM
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since the oil pan is off I may as well adjust the rods, I guess.

in a previous life I have worked on many Model A Fords.

we have an ingenious method of setting the Ford rod bearings using a double layer of heavy-duty aluminum foil to create a go-no-go process and get the right amount of shims in the rods. gives more accurate results than Plastigauge.

will this work on my '35 216 engine?

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chris_in_WNC] #403562
02/15/18 05:53 PM
02/15/18 05:53 PM
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Should work just fine. Don't know the thickness of aluminum foil but as long as it can be combined to result in 0.0005"-0.001" it definitely will be better than Plastigauge. I have found Plastigauge to be very inaccurate with thicker babbitt bearings such is Chevrolet 6 cylinder engines 1929-1953.


How Sweet the roar of a Chevy four!
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403570
02/15/18 07:56 PM
02/15/18 07:56 PM
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By the way, a 1934 engine is the old fashioned 207 engine and shares almost no parts with a 1937 and up 216 engine.

Last edited by Chev Nut; 02/15/18 07:57 PM.

Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chev Nut] #403574
02/15/18 10:37 PM
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Originally Posted by Chev Nut
If you re-adjust them for peace of mind I wouuld put a few more easy miles on it and do it at about 400 total miles. That is a good time to change the oil for the first time also. This will allow time for the high spots to wear in and get a good adjustment.

The old, original rods/bearings (and crank) was reused when my engine was rebuilt (they were only re-shimmed).
Will there still be "high spots to wear in" and should I still put more miles on the engine before adjusting the rod bearings, or is this relevant only if you have new bearings/rods?

Last edited by AMS; 02/15/18 10:38 PM.
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403577
02/15/18 10:52 PM
02/15/18 10:52 PM
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If the original rods were used (in the same location) with the original crank there will be no igh spots to wear in and the babbitt is already compressed. Just do not make them too tight. IF THERE IS A QUESTION/DOUBT KEEP THEM ON THE LOOSE SIDE. yOU MAY BE ABLE TO REMOVE TWO SILVER SHIMS OR ONE COPPER COLORED.


Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chev Nut] #403583
02/16/18 12:27 AM
02/16/18 12:27 AM
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The way I was taught to do these when a young boy by my father and grandfather was:
On number one, Then on number two when finished with number one, and onto three, etc. Pull shim, tighten cap in place snugly but not enough to damage the lead, use hand crank to turn the engine over. If it does not turn over (locked up) place shim, turn over with shim in place and that is good enough. When you do not get it to lock up by removing shims then you must carefully hand file across the cap where the bolts go through the lead and where the shims are located. When it hangs up then place shims until it is free. This is the "old time" way of doing it. Your so called "clearance" is indicated by the "shim size".00001; .00005 and up. Also, when starting do not "race" the engine as you do not have oil pressure to cushion the caps. Remember these are soft lead and tend to self adjust themselves to the main depending on oil pressure. That is why in the above running some couple or few hundred miles is advised provided no "bad" noises. If it was my engine I would not re-adjust after the break in miles if there were no "bad" noises. Your so called clearances being unimportant by the adjustments made by the oil, soft lead and shims on the main.

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403737
02/19/18 03:17 PM
02/19/18 03:17 PM
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I agree with some of the others on running it for a few hundred miles first

The Old Timer VCCA member who adjusted my 1933 Master rod bearings back in 1975 used the 8 oz ball peen hammer method and the car has been running with no issues since that time.

One at a time he would tap on the rod caps to find a loose bearing and then remove one shim from each side on the loose connecting rod. After reassembling each bearing he would lightly tap the rod back and fourth with the hammer again and if it would not move with a light tap he would add a single shim to one side and test it again after reassembly. So on and so forth until he had all bearing adjusted.


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Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Vila] #403749
02/19/18 06:02 PM
02/19/18 06:02 PM
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I have never been into a babbit bearing engine like this.

Are y'all telling me there are shims on each side of the rod cap, where it bolts to the rod, to adjust bearing to crank journal clearance?

Doug

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403750
02/19/18 06:04 PM
02/19/18 06:04 PM
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Yes, that is correct. It works better than what you think. Was common for all makes that did not use inserts.


Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403765
02/19/18 08:40 PM
02/19/18 08:40 PM
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Looking around to educate myself, i find shims for sale from one outfit that are .009" thick, and some other place has .002" shims, with nothing in between.

Where are you getting shims in various in between thicknesses? or are you making them out of shim stock?

Doug

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403769
02/19/18 09:48 PM
02/19/18 09:48 PM
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Chevrolet installed 4 .001" silver shims and two .002" copper shims on each side if I remember correctly.
Rebuilt (rebabbitted) rods had various amounts and some ad a spacer abiut n.020" thick spacer along with the shims.
When no shims were left the caps were filed if the babbitt still looked good.
Up to 1o and including 1932 the babbitt was .047" thick on new Chevrolet rods, From 1933 and up .024", In 1948 it was reduced down to .003" -.007" for longer life between rod adjustments. The thinner babbitt did not compress as much. This was the trend for engines with rod inserts also.
Chevrolet did not sell under sized rods for use when the journal was turned down to a smaller size. The aftermarket sold under sized rods down to .030" by increasing the thickness of the babbitt. They did not stand up well and either the babbitt melted or compress excessively and the rods would keep lossening up.

Last edited by Chev Nut; 02/19/18 10:33 PM.

Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chev Nut] #403773
02/20/18 12:20 AM
02/20/18 12:20 AM
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Chevgene, fantastic technical information!!!

Thanks, Dean

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chev Nut] #403775
02/20/18 12:39 AM
02/20/18 12:39 AM
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Originally Posted by Chev Nut
Yes, that is correct. It works better than what you think. .


On a non pressure rod oil lube system at low RPM, I can see why it would work. At 7000 RPM, eh, not so much.

Thanks for the info!

Doug

Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: DMelton] #403784
02/20/18 02:12 AM
02/20/18 02:12 AM
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The dipper system works fairly well up to abut 3000 RPM. Chevrolet in the 1933 -34 engine and Hudson used the dipper system and babbitted rods on most engines til 1953.The later Chevrolet with dippers and oil jets directly to the dippers was good up to about at steady 3500 RPM.
Most cars had rod inserts by 1933 or so. Chevrolet, Hudson not til 1948 (for Hudsom 6) an the 8 til lits end in 1953. Buick changed to inserts in mid 1948 but has full pressure oilng in the '20's.


Chevgene
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: Chev Nut] #403816
02/20/18 10:20 PM
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Thanks for all replys and information!
The rod nuts on my 34 master should be torqued to 40 foot pounds (or more - if the nut does not line up with the pin), is that correct?
If I will not be able to have the same shims on each side, does it matter which side have most / least shims?

Last edited by AMS; 02/20/18 10:21 PM.
Re: Rod bearing clearance... Should I re-adjust my bearings? [Re: AMS] #403817
02/20/18 10:57 PM
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If they don't line-up at 40 go a little tighter. They didn't even have a torque spec in 1934.It dosen't matter which side odd number of shims are but Chevrolet suggested the camshaft side and was more of a way to remember what side had what.

Please let us know how many shims you removed.

Last edited by Chev Nut; 02/21/18 12:50 AM.

Chevgene

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