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!

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.

If they are the 0.0015, they should be ok.

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.

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...)

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.

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.

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?

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.

By the way, a 1934 engine is the old fashioned 207 engine and shares almost no parts with a 1937 and up 216 engine.

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?

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.

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.

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.

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

Yes, that is correct. It works better than what you think. Was common for all makes that did not use inserts.

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

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.

Chevgene, fantastic technical information!!!

Thanks, Dean

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

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.

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?

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.

I have taken down the oil pan and started checking / adjusting the rod bearings today.
I have not finished yet, but it looks like I will be removing 0,001" on each side (or 0,002" on one side) on most of the rod bearings.

But I ran into an issue on rod number 5..... I am not sure how serious this problem is:
When I rotate the crank, I have clearance on the rod bearing (the bearing is "loose") on part of the rotation, and no clearance (I have to tap the rod with a hammer to get movement) on part og the rotation. Something is not round...
I guess it has to be the rod journal that is a little "egg-shaped". Or can it also be the rod side that is "egg-shaped"?
I am not sure if I have to adress this issue, or if the engine can run ok as it is...?

The crankshaft is out of round. Fit bearing at the point when it is tight and keep it on the tight side - where tapping with little hammer is required to move it back and forth.

My name is Toms

you are only postponing the inhibitable..... The crankshaft must be round. Your engine will not be reliable, sorry very important.

Thats the advantage of the Chevrolet babbited rod bearings. If not too much out of round the rod will stay tight for a long time.

I measured the "egg shaped" rod bearing journal on the crankshaft (rod number 5) with a micrometer today.
I found out that this journal is worn about 0,02 millimeter (the smallest diameter is about 0,02 millimeter smaller than the biggest diameter), which means it is about 0,0008" out of round.
I understand this is far from ideal.. But in the repair manual it says that "if the journals exceed 0,001" out of round or taper, the crankshaft should be replaced".
Since I am just under 0,001", I hope I might get away with it for a while... At least I will give it a try.

We used to tighten them up with crankshaft .002" out of round and they lasted for many thousands of miles. Never to worry.
The worst thing that could happen is the bearing/rod loosen up a bit after 20,000 miles.

Thank you very much for your information and help!

Well good luck to you and the rebuilt engine. May it provide you with many miles of enjoyment. I hope you enjoy your 1934 Master as much as I enjoyed mine.

This may be your problem. Sounds like number 5 needs to be looked at very closely. If you can get it to a shop have then "mike" it to see.