I STARTED TO BOLT UP MY RODS TO THE CRANK AND THE CLEARANCE I HAVE IS .001 TO .015 ON THEM. THESE RODS HAVE INSERTS IN THEM. WE MACHINED THE OIL GROVES IN THE INSERTS TOP AND BOTTOM, AS THE 32 HAS A OIL HOLE IN THE TOP INSERT AS WELL AS THE BOTTOM ONES. YOU GUYS WHO HAVE WORKED ON THE EARLY CHEVY ENGINES, IS THAT CLEARANCE GOING TO BE OK. THANKS. DON

Don,It sounds like the ideal setting to me.

HI CHEV GENE, I WAS NOT SURE IF .001 MIGHT BE TO CLOSE OF A TOLLERANCE OR NOT. I WOULD HOPE THE INSERTS WOULD GET ENOUGH OIL AT THAT SETTING??

Don,The later manuals called for .001" to .003" but for new bearings your just right.They may loosen a bit as they break-in.

THANKS FOR THE INFORMATION CHEVGENE. I WILL KEEP YOU POSTED AS MY PROJECT PROGRESSES?

Hey Donald! I would say that your rod settings are okay, but maybe border line on a couple. The ideal setting on those early poured babbit engines is one half to one thousandth of an inch. At .015 (correction, that should be .0015.....thanks Raymondo!) the rod tends to be on the loose side and it may knock. On my new engine, two of my rods were set at .0015 and they both knocked. The rest were at .001 or under and they were fine. I adjusted the two rods down to .001 and the knocks were gone. Typically, this is true on other 1929-32 engines as well.

JunkYardDog,I hear what your saying.Thats why I like the babbited rods and you can just pull shims out to get the correct fit.I'm not sure just what the insert type should be set at but .001 should be safe.

You are totally correct! With inserted rods the clearances can be just a little more so old Donald should be just fine. I know on babbited rods though that the clearances have to be dead on or a knock will develop. Ya, pulling the shims will let you totally "fine tune" your clearances, and that is a cool thing for the old babbited engines.

Yes,I just adjusted #1 rod on my '34.Pulled just two silver shims and thats all it took.The pre '37 manual says to remove shims until you can tap it back & forth with the 8 oz. hammer and leave it at that.The 37 up says to add a shim at that point but I found on the early ones its best to do it as per 1934 manual,Also pulled the head and inspected #1 aluminum piston and found it to look as good as the day it was installed.Was getting paranoid after all the piston talk.They are Sterling brand pistons that I bought at a swap meet years go.

HEY CHEVGENE, ARE THOSE STERLING PISTONS ANYTHING LIKE THE BADGER PISTONS RAY IS GETTING FOR HIS ENGINE. I WONDER IF STERLING PISTONS ARE A LITTLE BETTER THAN BADGER PISTONS. ARE THEY STILL MADE AND IF SO DO YOU HAVE A CATALOG FOR THEM.

I need to adjust mine, so what would you guys suggest as the "best source of directions" to follow? I need "step by step" procedures, thanks!

Chev Nut: Sterling pistons are a great quality piston and they should last almost forever. If you were to compare the Sterling piston to the Egge piston you would see the difference in quality. Sounds like you are home free with the Sterling pistons!

THANKS FOR THE INFORMATION JOHNNY F. THATS REALLY A CLOSE TOLLERANCE FOR THE ROD INSERTS. I DID NOT REALIZE THAT IT WAS THAT CLOSE, .0010 T0 .0020????

The 1932 Chevrolet factory "Specifications Manual" states the following for POURED babbit bearings:

Diameter of standard connecting rod = 1.9980 / 1.9990 which is the same as what Federal Mogul specifications say.

Rod bearing clearance = .0005 to .0015

Crankshaft mains 1, 2 and 3 = .001 / .003

Donald: According to what you posted earlier, your inserted rod bearings are within the specs. that lil' johnny posted. Don't let the extra zeros after the number get you confused.

CHEVY says: "THE CLEARANCE I HAVE IS .001 TO .015 ON THEM."

JunkYardDog says: "
Hey Donald! I would say that your rod settings are okay, but maybe border line on a couple. The ideal setting on those early poured babbit engines is one half to one thousandth of an inch. At .015 the rod tends to be on the loose side and it may knock. "

Would everyone please stand real still while we look around here on the shop floor for that other "0"

I couldn't find that other zero Raymondo because you were standing on it! Then you wouldn't give it back to me because you wanted to keep it for yourself to add to your "trade secrets". Anyway, Chev Nut gave me another zero so now I have one of my own.....so there! I have added my zero to the .015, so now it is like it should be, .0015". NOTE: I have made the correction in my earlier posting above. Thanks Raymondo!

Gator,I would follow the directions as in the 1932 shop manual.That is the best for the babbited rods>>>>>>as JunkYardDog also said.Never mind the plastigage get an 8 oz. hammer.

Chev Nut is that a 7.9990 oz. to 8.0001 ounces hammer, ball pein?
:rolleyes: :rolleyes:
or a 8 ounce ball peening hammer?

HEY EVERYBODY, I HAVE BEEN PLASTIC GAGING MY ROD INSERTS. IS USING A HAMMER SUPPOSED TO BE A BETTER WAY TO CHECK THE RODS OUT???WHAT STEPS DO YOU TAKE IN DOING THAT???? I HAVE BEEN TO DIFFERENT MACHINE SHOPS AND THEY ALL PLASTIC GAGE. ARE THEY ALL DOING IT WRONG?

Naw, Donald, plasticgage is ok for inserted bearings and and where the tolerances are less critical than for REAL rod bearings.

MACKIE WACKY, THEN I DONT NEED TO USE A TWELVE POUND SLEDGE HAMMER TO CHECK THE RODS OUT????????

No, Donald,because if you drop it on your face we won't be able to recognize you for a month or two.........

OH THANKS MACKIE WACKY FOR THE INFORMATION, NOW I WILL NOT HAVE TO GO OUT AND BUY A BIG SLEDGE HAMMER.

Are you guys being serious about the hammer method? I had seen that in the '32 shop manual, and I just assumed that was the only way to test for tolerance before plasticgage was ever invented.

I didn't perceive the hammer method as being precise.

Hey Donald! Don't use the 12 pound sledge hammer on your rods or mains. You actually need to use the sledge hammer to fine tune your carburetor!!!

YEP!, we surely are....On the babbit bearings with steel shims under the caps.

YES,it sounds rather antiquated but it works the best.What we are talking about is testing the side to side movement of the connecting rod on the crank shaft.In plain english you might say checking the drag of the bearing on the shaft.As it can't be felt by rotating the rod on the shaft it is the next best way.

And if you really want to do the job correctly you will also "blue" the bearings to check for high spots. If found scrape them down and "blue" again. Once no high spots than tap with the hammer to get the shims right.

That is correct Chip.Especially on new bearings.That is what bearing scrapers were used for.Does any one have one???Thats why the older bearings had such thick babbit.It gave you something to work with.

OK YOU GUYS, MY NEXT QUESTION???? WHEN I BOLT UP MY ROD INSERTS TO THE ROD, AND I PLASTIC GAGE THE CLEARANCE, IS THE CLEARANCE THE SAME ON THE BOTTOM INSERT AS THE TOP INSERT, OR WOULD THERE BE A DIFFERENCE BETWEEN THE TWO??

Johnny , all I have to say about the pictures on the "bearing scrapper link is : Right on! and either that is one huge bearing or one really tiny mechanic dude!

THANKS JOHNNY F FOR YOUR EXPERTISE ON ENGINES, IM SURE ALOT OF GUYS APPRECIATE YOUR COMMENTS AND HELP YOU GIVE US ALL. AS YOU KNOW, I CONSIDER MYSELF A REAL GREENHORN AND NO MECHANIC AT ALL. SO MY NEXT QUESTION IS, WHEN THE PISTON IS ON THE DOWNWARD MOVEMENT, IS THERE A CLOSER TOLLERANCE BEING PUT ON THE TOP INSERT THEN THE BOTTOM INSERT OR ARE THE TOP AND BOTTOM INSERTS STAYING THE SAME CLEARANCE ALL THE TIME.????? THANKS

Hi Guys
In relation to where the oil clearance is the greatest my theory is "the clearance varies depending whether the crank or piston is causing the movement".
When the piston is going down because of ignition there is less clearance on top but when going down because of crank on induction the clearance is greater on top. As piston on up stroke either exhaust or compression though less clearance on top.
This is why the top bearing wears the most as it is doing 3/4 of the work. For this reason most pressure fed big ends have the oil hole under the rod at top of stroke to add the oil supply where the most load occurs. Of course this can not happen on splash or dipper oiled bearings.
If any of you have another theory I will not be offended to read it, as I said "my theory" and I am not right more than 1/2 the time.

The last two posts tell it all.Just want to add that if its too loose and is knocking the noise is caused when the excessive clearence changes from bottom to top as the piston forces the rod against the crank shaft.That is why if the spark plug is shorted out there is no force from the piston,the clearence stays almost equal (on all sides of the bearing) and the noise stops.

WOW YOU THREE GUYS REALLY HAVE EVERYTHING DOWN PAT. CHEVGENE, ARE YOU SAYING THAT THE KNOCK IS MORE LIKELY ON THE TOP OR THE BOTTOM ROD BEARING OR IS IT THE AMOUNT OF CLEARANCE EACH ONE HAS WHICH GIVES THE KNOCK? AS I UNDERSTAND IT, ONE OF THE TWO INSERTS WORKS HARDER THEN THE OTHER OR COULD WEAR MORE THEN THE OTHER???? EITHER THE TOP OR THE BOTTOM ONE. ALSO IF I PLASTIC GAGE ONLY THE BOTTOM INSERT AND SAY IM AT .001 CLEARANCE, THEN THE TOP INSERT THAT I DID NOT PLASTIC GAGE COULD BE TO TIGHT FROM THE DOWNWARD THRUST OF THE PISTON?? THANKS

Ha!Ha! , this question about where the most clearance is simular to removing the top from a new can of nightcrawlers!
Did anyone also think about clearance when the starter is cranking and when the oil is cold and thick or hot and thin.
How about when you are decelerating and the engine is used as a brake?
Or when you are at cruising speed and let off the accelerator?

What it boils down to is it don't make any difference, clearance should be considered as a 360* factor.

...or you can use a technique that my 'ol buddy Fred used to do... use your ball-peen hammer to flatten the plastigage until you have the clearance that you want, then use that to eyeball your rods until the gap in them matches the width of your plastigage!!

I won't go with MrMacks theory be cause it is the sudden force of the combustion as the rod changes direction causing the clearence to move from one side of the rod to the other causing the noise (as rod pounds against the shaft)The forces he mentions,although there, is not great enough.That is why the noise stops when the plug is disconnected and there is no combustion.Even a burned out bearing will stop making noise when there is no combustion (unless the piston is coming up to far and hitting the head).Then you will hear that noise.>>>>In short the clearence stays more constant when there is no combustion.

I have that position because, the only babbit rod I have personally seen thrown was in a 47 Chev 1/2 ton pickup. I was a teenager and was chiding my Dad about his old hotwater six, that it wouldn't run as fast as my old (34 stripped down 1/2 ton Pickup) hotrod. He ran it up to 80 mph for a mile or two and then abruptly let off the accelerator, we slowed down to about 50 when BAMB! numbner 2 rod shucked all its babbit and sounded like it was comeing out. Dad said that if he had of slowly let off it would not have thown. Luckly it didn't do too much damage, just the rod, he stuck a spare rod in and drove it for another 3 years.

I will agree that often when a rod goes out it is on deaccelleration.But I believe the damage was already done before that.The original question was about the bearing clearance changing and I still say the clearance is next to nill as the piston forces the rod down.That is why the top half of the rod bearing gets the most wear and pounding and when a crankshaft is out of round the "low spot" will be the top of its travel.Now if you take an 8 oz. ham.......Oh..thats another story I have always refered to throwing a rod is the rod breaking and coming thru the side of the block.The babbit melting is burning out a bearing.This was usually caused by a oiling problem, The most common was for the pipe to the burnt out bearing being plugged up,starving the rod of oil.80 mph for a few miles never hurt a 216 if everything was as it should be.

Now to complicate things a bit. The clearance does not change much at all if an oil with the proper viscosity is used. Yes it is true that some of the oil film is transferred around the space between the rod bearing and the crank journal. But because of the relative rotational speed of the parts the film thickness is quickly restored.

If you ever get metal to metal contact, then bad things are soon to occur. That is when you gaul, burn or destroy the bearings and blue the crank. Or do the same to the piston pin. Right Ray? The initial knock is caused by creating air gaps in the oil film and then collapsing them, not metal to metal contact.
It is similar to the hammering you get in water pipes. Why do you think that STP sold so much of their oil treatment? Yes, students because it increased the viscosity of the oil. Made it harder to pound out of the bearing gaps and go past the rings. But also increased internal resistance.

I will not go into any details of the cause of wear but it basically deals with erosion from the oil film or abrasion from contaminants. Just think about the rock at the bottom of the waterfall or on the one on the stream bottom. They both will eventually get worn away but one much faster. Which one depends on how much other stuff is in the water!

ChevyChip,I will agree to that ,especially on a bearing with proper clearance.It is amazing only .001" leaves room for adquate lubrication.

My point about clearance being 360* problem must have been missed in some of the discussions, The thing is that when there is too much clearance it moves around the bearing and journal as the forces acting upon the rod rotate and also change directions, and a properly timed engine does not often put the most force toward the centerline of the rod thru the crankshaft in fact most of the force is angular or acts as a moment, or a rotational force. Can you agree that excess clearance acts in a 360* area?

A QUESTION I HAVE IS, WHAT IS THE VERY LEAST AMOUNT OF CLEARANCE YOU CAN HAVE AND STILL HAVE A ADEQUATE AMOUNT OF OIL AS NOT TO DO DAMAGE??????

DON,According to Chevrolet in 1932 it would be .0005" (thats one-half of a thousands) with the original poured bearings.With you inserts I would say .001" to be the minimum.

CHEVGENE WOULD YOU SAY THAT THE INSERTS WOULD STAY MORE CONSTANT OR WEAR BETTER THEN POURED BEARINGS AND ALSO WHY WOULD YOU WANT A GREATER CLEARANCE ON THE INSERTS THEN THE POURED BEARINGS?

THANKS JOHNNY F. YOUR INFORMATION AND KNOWLEDGE IS SO OUTSTANDING THAT NOT ONLY ME BUT I HOPE OTHERS PICKUP ON WHAT YOU KNOW AND SAY. THANKS AGAIN.

Donald, If we keep asking questions do you reckon we can squeeze a couple more pages out of this rod thang?........

What was the name of a good book to read about oil film and rod bearing clearances?

I do have a library card now, I got it at the Senior Citizens Center!

YEP MR MACK, I CANT STOP NOW, I HAVE TO FIND OUT EVERYTHING I CAN BECAUSE THE JUNKYARD DOG WANTS ALL HIS PUPPIES TO BE MECHANICS SOME DAY. THIS MAY LEAVE ME OUT BUT I WILL KEEP LEARNING AND TRYING. THERE IS ALOT OF GOOD INFORMATION COMING OUT OF THESE QUESTIONS AND IM NOT SURE I UNDERSTAND THEM, BUT I WILL DO MY BEST? THE LAST THING IS, I DO NOT WANT RAYMONDO TO THINK IM SLEEPING WHILE CLASS IS IN SESSION.

In all respect to liljohnny what he says is correct but years ago no mechanics went thru all of these steps.Most were lucky to have the wrenches.Due to the thinner babbit on your inserts they should live OK with the clearence you have.You are in kind of an expermental mode and if or when they do make noise all you can do is add a shim under the insert.

I've also followed this thread along from the beginning, and it's been a great learning experience to understand not only what clearances to achieve, but why they are supposed to be that way.

I've had knocking problems on the number six cylinder on my '32 over the summer, and the first pass at removing shims made minor improvements. I've always been deathly afraid of making my bearings too tight, but I've built up courage from the discussion (plus some past direction by the Junkyard Dog) to finally take the day off today, pull the oil pan off, and reset the offending rod to a half a thousandth. It was some tense moments getting the engine started, but eventually she coughed into life and steadily putt-putted. I can't sense the knock any longer.

Getting the background story behind these tolerances in this thread was a nice boost to me.

THANKS FOR THE INFORMATION CHEVGENE. FROM WHAT YOU GUYS SAY PUTTING SHIMS BEHIND THE INSERTS IS A NO NO, BUT I HAVE NO OTHER CHOICE UNLESS I REALLY TEAR INTO THE ENGINE. IM NO MECHANIC AS YOU KNOW, BUT I DO NOT SEE WHY I SHOULD HAVE A PROBLEM DOING IT SINCE IM NOT GOING TO TAKE THE ENGINE APART TO REDUE THINGS. WHAT HARM WILL I DO BY SHIMMING BEHIND THE INSERTS. THANKS

Don,In my opinion it will do no harm as all you may need is .001' or so.This is not a modern highspeed engine that you are going to put another 100,000 miles on. Thats the nice thing about being my age.....I know that I won't be driving my old cars for another 20 years

THANKS CHEVGENE. IF I PUT 500 MILES A YEAR ON THE CAR AND DRIVE IT TILL IM 100 YEARS OLD, THEN I WILL HAVE ONLY 18000 MILES ON THE CAR??HOPEFULLY IT WILL HOLD UP THAT LONG AND ALSO I DO NOT PLAN ON DRAG RACEING IT TO OFTEN. THANKS

Yeah, but Donald when you go to that big Bowtie parking garage in the sky, you don't want to leave a knocking banging engined car to your heirs,..... Now,......... Do you?

HEY MACKIE WACKIE, YOU MEAN I CANT TAKE IT WITH ME??? THE DOG PLANS ON TAKING ELVIRA WITH HIM??? OFF WE GO IN THE WILD BLUE YONDER.

Yes,Yes, It finally happened. Today Jim Farris came over to my house and we fired up the 32, After having the pan off for a couple of months and shimming the rod inserts to a clearance of .001. this Is a closer tollerance then what was before. I have to say that the engine purred like a cat eating tuna. The engine sounded, oh so good and there was no knocking noise at all. We run the engine for quite a while, Two or three times and hopefully I will have no more problems. Also I got the cork end gaskets on better this time when I bolted the oil pan back on the engine. No oil dripping at all. For being a real crude, greenhorn backyard mechanic, This day was a happy one for me. I have my fingers crossed, hoping I have fixed my engine problem. HAPPY HOLIDAYS TO EVERYONE.

Don,Congratulations on your sucess....I have been wondering as to what the outcome was but was afraid to ask.

Ain't Chevy life good Donald, three months ago you couldn't even spell shade-tree and now you is one!

Should Don check the bolts after driving a while and re-tighten them????????

Don,..I'm sure Gator means the pan bolts and not the rod bolts

Good going Donald! Isn't it amazing how the knocking noise goes away when the rods have the right tolerance? By the way, taking that Budwesier beer can out of the oil pan probably helped a great deal too!

Who is Jim Farris? Is he one of those Model T dudes?? ha ha!

You are right, the pan bolts.

Thanks to all of you guys who responded about my engine. also thanks Johnny F for the good information, Now if I can find some oil to put into the engine?????