The Stovebolt Site Forums The Shop Area Engine Shop Shaking rod bearings

I'm getting the new 194 head for my 250 in tomorrow, and my only concern is the piston rod bearings. We originally took apart the engine to do a ring job (gas in the oil pan, i had to put a quart of oil in the tank every month and it was still going down) snd we've done that succesfully. However, when putting the pistons back in and tightening down the piston #1 rod bearing onto the journal, one of the bolts snapped at 10 newton meters. So, i got ARP's, and got them into the rod bearings, which was an extremely fit, done with a vice. We then torquad the rod onto the journals at 40 ft/lbs of torque. But when i was under the engine, i realised that i could grab the bottom of the rod, and it jiggles every so slightly, all 6 of them do that. The mechanic helping me assured that it would get seated after the engine ran a bit and oil got all over it, but i just wanted to see what yall think.

1965 Chevy C10,

They will move back and forth slightly, that's normal. They do have clearance, they aren't cinched down, and this allows them to 'slide' on the journal.

This movement is lateral, not up and down...that wouldn't be good. This is assuming everything measured properly or plasti-gauged (?) properly. This has been my experience.

Stuart

Yes to what atomarc says.

Harvester

If the plasti-gauged clearance was good. If it wasn't tested with palsti-gauge have it done. It is cheap and easy to use.

I have never heard of plasti gauge and neither has the mechanic helpin me. Everbody keeps talkin about it though. He's very confident that everything will be fine, but i just don't want to throw a rod or something. If im under the truck, looking up into the engine, I can hear and feel the rod shake left and right on the journal, although I can't actually see it move. So it's not going up and down but left and right.

Try this link:

http://www.ehow.com/how_2142943_use-plastigage-measure-clearances.html

Plastigage has been around at least 40 years- - - - -I've been using it that long, and it was not a new product when I discovered it. You need to find a more experienced mechanic to help you, as some of the procedures you've described on this job would shock a shadetree wrench jockey. Good luck!
Jerry

Gee whiz,Even my kids knew about plastigage at an early age!

Im with everyone else. Dont put it back together till you spend a few bucks(literally,3 0r 4 dollars) and plasti-gage the rods.
Did you have the mains apart too?

The link to the plasti-gauge pretty much says it all. It's different gauge fishing line basically that squishes at a known rate. It is a great way to measure tolerances. The rebuild manual on my 60 MGA calls for it and it was printed in the mid 60'. Available at all of the car parts places.

Plasti-gauge is NOT one size fits all. Be sure to get the kind for your specific clearance, which is my memory is right, is .0008 to .0016, but check the books.

best wishes,

Les

There are three colors, red, blue, and green. For a stovebolt engine, the red, which is the middle size, is probably the best choice. It's in the .001"-.003" range, IIRC. Green is smaller, and blue goes all the way to.006", I think.
Jerry

Not the mains, just connecting rod bearings delux. I wouldn't mind doing the plastigauge, it already have the oil pan back under the engine. The oil pan was a bad hassle for some reason because it won't come off or go on unless i undo the engine mounts and jack up the front of the engine, the oil pump and bellhousing get in the way from it sliding off. But if you guys really think i need to, i'll take it back off.

If the repairs were done correctly then you should be fine. From your explanations above of how this job went, it sounds like things might be questionable. Do you trust the abilities of your mechanic friend...do you think he assembled your engine using proper procedures.

The wiggle in the rod ends is common in a proper rebuild with proper clearances. To have them wiggle but not know the clearances are proper because they were never checked or may have been assembled incorrectly may be a sign.

If you didn't have the mechanical skill to do this job, can you recognize that your friend did have the mechanical skills.

If the engine was put back together with the same inserts on the same rods in the same hole you will probably be alright. If you have any doubt, the trouble of pulling the pan and checking the clearances will be much less than the pain of a scattered engine.

If you know and trust your friend, ask him what he really thinks.

Stuart

Well, he was a car mechanic until he joined the air force and became an F-15 Eagle mechanic. I know a jet engine is much different than an internal combustion, but as you probably realize there is NO room for error when working with that stuff. So after he left the military he has been pretty cautious with this stuff. He's not an obnoxious know it all, but every question i've asked him about the project i've gotten an instantaneous response, nothing has really baffled him at all. For the most part he's a do it yourself guy, for example, when i was told i needed an arbor press for the new ARP connecting rod bolts, he walked in the garage and came back with a picnic table, vice and 2 C-clamps and said "There's your arbor press." He's been right about everything so far and i don't doubt him at all, so i still don't know if i'll plastigage or not (not that i don't want to, but that oil pan is a PAIN IN THE @$$!!!)

Back when this saga began, I think a lot of us got concerned about how that rod bolt got broken. I've been at this business for over 50 years and the only broken rod bolts I've ever seen were seriously overtorqued. Then you decided to swap for ARP bolts without getting a machine shop to check the rods for diameter and out-of round, mistake #2. Your unorthodox pressing procedure is very likely to create a distorted rod bore. Now you're not sure if the bearings have the right clearance, and your mechanic buddy has never heard of a standard procedure that's been used for over half a century by engine builders all over the world.

If you're willing to gamble on things as important as connecting rod bearing clearance, come play poker with me. I'll bet you'll draw to an inside straight, too!

Good luck!
Jerry

Ouch!

I wish we could do a archive search about plasti-gage from about 8 years ago. The 'top hands' at the time were really rough on anyone using plastigage. They insisted that all bearing clearances should be measured with inside micrometers or snap-gages.

Dad always used plastigage and got along fine. I used snap gages and plastigage just as a comparison on my 261 and my readings were almost identical, so for the effort, plastigage wins. I am not building 10,000 rpm race engines, but I've built a lot of diesels and have had NO bearing clearance problems using plastigage.

I have always heard that if you change rod bolts that you should have the rods resized. I cannot personnally affirm or refute this on gas engines. I have not changed rod bolts on the ones I have overhauled, but again, I was not building a 10,000 rpm race motor. On John Deere diesel engines, rod bolts are tightened using a torque-turn method. Rod bolts are tightened to something like 90 ft/lbs and then the bolt is turned another 1/4 turn. There is no nut on a diesel, the threads for the bolt to mate with are cut into the connecting rod. This stretches the rod bolt which means the rod bolt cannot be reused. BTW the same torque-turn method is used on John Deere head bolts also.

On the gas engines I have built, I used the green plastigage.

Good points, Carl!
I've reconditioned a truckload of Cummins, Detroit, and John Deere rods, along with thousands of rods for gasoline engines. The average tolerance is less than .0005" in most cases. Unless the rod is round, and the right size, there's just no way the bearing will ever fit the crankshaft right. On the really high-HP engines, I've gone to the extreme of mixing and matching individual rod bearing halves to get the oil clearance I'm after, but that's really too nit-picking for street use, or a stovebolt restoration job. I did see one of my engines survive several laps of cycling between 9,500 and 10,000 RPM one night when the driver got the transmission in the wrong gear by mistake. No lower end damage whatsoever! We swapped rod bearings on that engine and ran it the rest of the season.
Jerry

65 chevy C10,,,
I think it all comes down to (after reading how this truck was your grandfathers and then your fathers) that we'd like to hear about it was a successful rebuild and youre still driving and enjoying it.
It may be a hassle removing the pan again to check what we've been talking about,but at least you wont be under there cussing while youre removing the blown-up motor.
"Why is there never enuf time to do it right,but always enuf time to do it over"?
Good luck,
Marty

I see your point Marty, thankyou. Hotrod i know you've been wanting me to do this, and you said stovebolts use red but i guess my 250 technically isn't stovebolt era, so what color, red, green or blue?

Not to hi-jack this thread but what is the opinion out there on using the new digital calipers for measuring journals etc. They are very reasonable to purchase and they claim to be accurate to .0005".

The green stuff has a thickness range from about .0005" to .0025", which should span the clearance range you need. I really like to see oil clearance somewhere around .001" to .0015", but you can get by with .002" or more if you use a heavier than normal oil like 20W-50. Thew Federal-Mogul bearing specification manual lists oil clearance for a 250 rod bearing from .0005" to .0032", but I can tell you from long experience that anything over .002" is going to result in a noisy, short-life engine.
Jerry

Digital dial calipers are handy, but they're a little too dependent on feel to suit me for precision measurements. I prefer a dial bore gauge to check rod dimensions like out-of-round, etc. I've got a really nice Starret digital dial caliper I use in my gunsmithing work, but I double-check engine dimensions like cylinders or rod/main bores with an inside mike or a dial bore gage.
Jerry

So slide green plastigage on the connecting rod cap and tighten the cap to the journal, tightening to the specs given to me (40 ft./lbs)and if i get between .0005" and .002", im good?

Jerry,
thanks for the reply.

Fred

plastigageing every main and rod bearing makes it over twice the work/fun. romancing every part into place is the only way to know if it's right or not.i hate to do it sometimes, but it's part of the fun of a rebuild. i feel it's pretty accurate, but be aware if you got a small speck under the bearing even a human hair you clearence would be out. i have had a bearing that was slightly out and wiped the backside and it was in. good luck.

If you do the plasti-gauge at least you will know where you stand. It should give you an idea of the condition of the rest of the engine. How sure are you that the bearings went back in the same place they came from?

Yep, you've got the idea. One little precaution, when you torque up the rod with the Plastigauge in the bearing, don't turn the crankshaft, or it will smear the Plastigauge all over the place and ruin your measurement. Also, don't be terribly concerned with getting all the plastigauge off after you measure- - - - -it dissolves as soon as oil his it. I like to rub a little clean oil on the spread-out gauge material, and wipe it down with a clean, lint-free rag. That removes almost all of it.
Jerry

Keep us posted.............................................

I'm pretty sure the bearings ain't in the same place. We've must have done at least 10 full rotations on the fan trying to turn the crankshaft, the guys at the machine shop that we orderered the new head from called, the head came in this morning. The mechanic and my buddy will be pretty eager to put the head on and get the engine running, so i don't know if it's worth [censored] them off to go plastigage it. I trust yall and everything, and i keep worrying that i'll throw a rod or something. I'm pretty sure if i dont plastigage it, i'll be shaking too much to turn the ignition when we put it back together.

Some guys listen and learn from the mistakes of others, but there are always a few who just have to see what happens when they pee on the electric fence!

Good luck!
Jerry

Don't rush this thing. A little extra time spent on this project is time well spent. Use the plasti-gauge as others have advised. From what you describe, you are probably all right with the bearings, but both the risk and cost if things are 'not all right' is very high- don't rush just because someone else is in a hurry.

Harvester

Ok guys, I need to inject somthing here. Plasti-guage is great stuff. Most professional mechanics do not (DO NOT) use it. They work on flat rate time and unless they are building a race engine it is not used. The stuff was invented way early in the manufacturing of replacement parts and was mainly used to insure a good build when parts were not so high tech. You could get bearing shells that were mismatched or just plain wrong. In todays market that simply dosn't happen. So unless you have given your parts person the wrong info. or you failed to mic your crank to determin the cut. of the journal, your part will fit. Just my 2 cents.

NO, NO, NO! I'm with the plastigagers. Check everything, twice if you can! Part numbers dont care about your clearances! Plastigage is recommended by numerous OEMs to check bearing clearances, and it works well. Was'nt the original question regarding side play? I dont have a manual for 250s here, but I know most side by side rod configurations have tolerance specs for rod side play. I had a set of SBC rods resized once and two were replaced because of excessive side play. If the rods move too much from side to side they will knock and allow the piston to side load and wear right out. I may be wrong, but I would double check your manual for info regarding side play specs. It may be that the spec allows enough movement to detect, but it should be verified with a feeler gauge before calling it good!

All i am saying is that if you go to any shop and ask if they use plasitguage they will 90% of the time tell you that it is not worth the effort. The stuff works great but in almost every case no changes were needed to the bearing surface to change the clearance. I have been in the busness for 35 years as a technition, service advisor, parts man, and service manager. and after witnessing literily hundreds of complete overhauls I have seen 1 tech. use plastiguage he did not need to change one thing after he used it. And after seeing him use it 3 or 4 times he also quit using it. I guess if you are the avarage joe and dont have a feel for tolerances then for peace of mind use the stuff.
Dont get me wrong there is nothing wrong with using plastiguage.

Toyvo, since you're a relative newcomer to this thread, let me bring you up to speed on what's happening.

This situation began with a broken rod bolt on reassembly, and has steadily gone downhill from there. The side play issue is only the latest problem in a comedy of errors that would have any professional machinist climbing the walls. A set of ARP high strength rod bolts were forced into place with some sort of Rube Goldberg rig involving a bench vise and C-clamps, and then the rods were not checked for size and out-of-round like several of us reccomended. Then the engine was assembled with mismatched bearing shells from several rods, using old parts. So many basic common-sense engine building rules have been violated during the job that most of us will be surprised if the thing runs for more than 10 minutes without burning out a bunch of bearings. Anyone who's not trying to fudge the flat rate system for a few more hours a week does not cut corners on engine assembly, and he will double-check everything about a rotating assembly, including all the clearances. Plastigage is a minimum check for people who are more interested in saving time than doing the job right. To do it properly, the rods and bearings need to be assembled and measured off the crankshaft, then the diameters are compared to get actual clearances. Ditto on main bearings. If I've got less than 50 hours involved in setting up a customer's rotating assembly, I'm shortchanging him, but then the average engine I build costs at least $15,000.00. It's guaranteed to start- - - - -once it's running, it's all yours!
Jerry

Actually Hotrod, we got new Sealed Power Bearing shells. I talked to the mechanic (we call him Mr. Paul) yesterday about plastigage once i got an understanding of what he is. I told him it measures bearing clearances. He said he's used plastic pieces that look like noodles and come in a paper package that looks like a ruler. I guessed he was talking about plastigage, just didn't know the name of it. Anyways, i also talked to my buddy Ralf, the 18 year old that's been helping me with the job so far. He said the rods shook like that before we ever started unbolting them. I was kinda [censored] that he had not said anything about it yet, as i've been freakin out about the whole plastigage thing for a whole week. So, we relayed this info to Mr. Paul, he said that over time, the journals have worn down, and there's nothing we can do about it short of getting a new crankshaft. In funnier news, the new head came in yesterday (I can see my reflection in the valve heads!) and we put on the head gasket and the head, then put all the bolts in their correct holes, then realized our torque wrench stops at 80 ft/lbs and we needed 95.....AHHHH!!!!!

Geeze Jerry $15000.00, I would not only plastiguage but also wipe the guys sweat from his brow while he puts it in. I just had a local machinshop do a complete o/h including machining the babbet rods to use shell inserts and adjusting the squirt nozzles in the block on a 216 for 1500.00 His warranty is for 12 mo, or 12000 miles fron date of installation. He dosn't use plastiguage.
He did paint it the wrong color thow.

WOW !!!(deer in the headlights look) I'm going to stay on the sidelines with this one.

Machinists make mistakes every day and some are downright hacks so any part has potential to be out of tolerance. A micrometer will change size simply by the warmth of the hand of the person holding it and most are completly unaware this is happening. Plastigauge is a direct reading result of the actual clearance and not a calculated value base on the difference between what an I.D. and O.D. tool read. On top of that 50% of people (including machinists) use measuring tools incorrectly polluting results. When engines seize after a "professional" rebuild it is nearly always caused by incorrect use of measuring tools. When the clearance really matters all the old fart millwrights will confirm readings with plastigauge.