rollingsculpture
Senior Member
hi i would like to hear from you all about your experiences with engine vibration caused by overtightened or undertightened rod or main bearings
thanks for your insights.
thanks for your insights.
engine vibration
- Thread starter rollingsculpture
- Start date
rollingsculpture
Senior Member
not worn out still runs well but i am asking about the experience of others not opinions about the motor
glenn in camino
Well-known member
Are the motor mounts stock and installed correctly?
Dave in MN
Well-known member
I have never experienced a vibration due to an over tightened rod or main bearing. I have never "felt" a rod knock in a running engine but have heard it many times. I have felt the result of a failing main...typically if the center main was in the process of breaking up due to excessive clearance. I have felt the shock (vibration) at the same time as hearing a knock when a main bearing is loose. The knock has to be pretty loud and the gap pretty excessive to actually feel a "vibration".
I suppose...
If a rod journal or main journal was out of round and the clearance was set at the "small" of the journal, it could bind at the "large" and cause a rotational pulse at idle. I have not experienced this though. The offending journal would need to be out of round in excess of your set clearance and that is pretty far out of round.
I have set up over 100 rebuilt engines with insert bearings and adjusted bearing clearances on about 25 in service engines over the past 5 years.
What experience information are you looking for?
www.durableperformance.net
Good Day!
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tbirdtbird
BANNED
This is an open-ended question. It would help to know your exact symptoms, at which speeds, which gears, at idle, on the road with clutch engaged, also on the road with clutch in (coasting), effect of shorting one plug at a time, etc. Also what work has been done on the motor/suspension in the last year or so. This could be anything from loose kingpins to bad center main
rollingsculpture
Senior Member
again i would like to have any persons who have experienced the type of engine vibration caused by rods or mains being too tight or loose give a run down on how they may have honed in on it and give their outcome , perhaps dreamworks or khonkee (sp) can weigh in here. Also i will let you in on my experience than , but would like to hear from those who have done their own bearing adjustments and the results they had.i am primarily interested in what happens to the crankshaft , and any binding or vibration that may happen. thanks to all so far .
tbirdtbird
BANNED
too open ended. too little info. is the pan down and side cover off? if so we can walk you thru checking caps. else we could type for weeks
I don't know if this is a quiz or not, but to markedly feel a "vibration" from a loose rod or main, it is probably the vibration of something breaking loose. Tight bearings don't vibrate. You will hear a loose rod or main before you feel it as a vibration in ordinary driving. Now maybe up around 4000 rpm I suspect you would get a pretty good vibration from a loose bearing but as said that would be a presage to failure.
To directly answer your question, I have never felt a vibration "caused" by too tight or too loose a rod or main bearing. I have had bearing failures, and do have vibrations, but never one "caused" by the other, so far as I know anyway.
As a teenager I had a '53 Chev with a knock in #2 that I had not gotten around to adjusting. Drove it for quite awhile actually, but the only vibration I felt was two large bam-bam vibrations. Turned out the crank broke behind #2. The front pulley was at about a 45* angle. That's how I "honed in on it." The "outcome" was that Pop was not happy about having to tow me home. ("I told you to fix that.....")
To directly answer your question, I have never felt a vibration "caused" by too tight or too loose a rod or main bearing. I have had bearing failures, and do have vibrations, but never one "caused" by the other, so far as I know anyway.
As a teenager I had a '53 Chev with a knock in #2 that I had not gotten around to adjusting. Drove it for quite awhile actually, but the only vibration I felt was two large bam-bam vibrations. Turned out the crank broke behind #2. The front pulley was at about a 45* angle. That's how I "honed in on it." The "outcome" was that Pop was not happy about having to tow me home. ("I told you to fix that.....")
James Rogers
Well-known member
If you have a rod vibrating, you will soon not have any vibrations of any kind. A rod that is loose enough to vibrate that much, ie: to feel it, it is soon to be removed from the crank, ie: catastrophic failure.
tbirdtbird
BANNED
"If you have a rod vibrating, you will soon not have any vibrations of any kind. A rod that is loose enough to vibrate that much, ie: to feel it, it is soon to be removed from the crank, ie: catastrophic failure."
well said. by the time you get to vibration you are in big trouble. Audible comes first. His issue may not be bearings at all, but he is set on his diagnosis.
well said. by the time you get to vibration you are in big trouble. Audible comes first. His issue may not be bearings at all, but he is set on his diagnosis.
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rollingsculpture
Senior Member
ok thanks guys heres what is going on motor is old as you know i have had to replace main and center bearings and also checked clearances using both plastigauge and foil method motor in truck could hear rod knock so went through all of those did foil resist and took out 1 shim each side when retightened the motor would be hard to turn at first but after first revolution turned easily but stiff put together and ran engine seemed fine but would vibrate at 30 mph ran for a week dropped pan went through all bearings to check for wear main cap showed signs of wear in so i replaced a shim on one side, rods seemed ok , as you know when tightening the castle nuts you can only go so far than have to back off to get the cotter pins in , did that , put back together engine still felt tight at first crank but turned ok as the revolution continued ran for a month , engine vibration now at 40 mph , snow and bad weather came so no driving all winter , good weather came a few days back so i decided to drop the pan and see whats up went through all bearings have had no rod knock but checked anyway , main bearing still showing wear so added another shim to other side ( yes this bearing was a doner and was not made for this motor BUT it seems to have worn in ok not pits or melts just abrasive streaking seen on rear of main no wear at front , what the heck its keeping the motor running until i can save for a real babbit job ) checked the rods very light polishing on caps as a streak about 1/8 wide hard to see but there so i added back a shim put all back together tightened down as much as can to put cotters in , not too tight as you know trying to put a torque on them is moot as you have to loosen to put in the cotters . closed it up took the old boy out for a ride , no knocking also much reduced vibration still a small amount at 45mph but definitely not there at at 30 or 40 so i know from this experience that doing this work has changed the vibration , my thought is that the rod caps were tightened down too much previously so when i reassembled
i made sure to really check ease of rotation of the crank. i know by now some of you may be shaking your head and say well i get what i get by doing the work this way and you are right i also get a bit of experience that i can now relate to that helps me understand my truck and its engine . risk taken risk paid off in my opinion otherwise no running motor anyway so why not try ! best to everyone !
i made sure to really check ease of rotation of the crank. i know by now some of you may be shaking your head and say well i get what i get by doing the work this way and you are right i also get a bit of experience that i can now relate to that helps me understand my truck and its engine . risk taken risk paid off in my opinion otherwise no running motor anyway so why not try ! best to everyone !
tbirdtbird
BANNED
1. "yes this bearing was a donor and was not made for this motor BUT it seems to have worn in ok." Did you use prussian blue or other disclosing dye (even magic marker) to see if this cap really fit the crank journal?
2. If the motor is in the truck then use the foil method, plastigage can mislead you. You are looking for .0015-.002 clearance. Never take more shims from the center main than anywhere else, even if you end up with more than .002 at the center
3. If the windows on the castle nut do not line up with the bolt hole when at specified torque the proper procedure is to remove the nut entirely and lightly grind off (face off) some of the nut on the SIDE of a grinding wheel while constantly rotating the nut to maintain even grinding. This must be done with a light touch and is trial and error and may have to be done more than once. Mains set at 50# will NOT clamp as well as mains set at 70 and you will have misleading readings. Ask me how I know. This is partially because you are trying to hold up the weight of the crank and a 64# flywheel if you are doing this in the truck. This is also why plastigage may not be accurate done this way.
4. I have yet to be able to get a torque wrench on the rear main bolts if the engine is in the car. As it is, I had to make a special socket by welding a 3/4 inch nut onto a spare correct-sized socket after I had shortened it by 1/4 inch with a cutoff wheel. Then I use a box wrench with a short length of pipe to get the leverage needed for 70-80 # of torque. Now I am ready for a 'ha-ha there is a special tool for this' from the crowd but I haven't found it yet. How do I know I have 70-80 # on those rear nuts? Easy, set an equiv. nut and bolt up in your vise, get the torque wrench out and crank it to 70 # and see what it feels like. It takes a fair bit of force and your arms will remember if you are good.
5. Unfortunately for some owners whose cars I have worked on, some previous mechanics either loosened to the closest window giving precious little clamping force (such as 30-40 #) or tightened the living daylights out of them to catch the next window to where it took a 6' cheater pipe to get the nuts off. Of course these fasteners were stretched beyond usage
6. The crank should turn with little effort right at the start (assuming the plugs are out); it should not be tight and then loosen up. Be sure to keep oil in the bearings while testing.
7. Make a logbook of what you have done to the shims and all in case you have to go back in; at least you will know exactly what has transpired. Be sure your shims are removed evenly from each side of the caps. At most, be one shim off; ie 3 on one side and 4 on the other. If I have to remove an odd number of shims from more than one bearing, I like the extra one to be on the same side on both caps. Prolly more OCD than needed. If removing shims to adjust, be sure to remove only one at a time, do not remove in pairs. Be sure the caps go back on with the same orientation they came out, do not flip them around. Do One cap at a time only. Start at the rear and work forward.
This is tedious but so important. With some patience you will be doing your engine a tremendous favor. this is what was routinely done in the old days until there were no more shims left. Clearly doing this with the engine out is easier, but we have this down pretty slick here in the car over a pit. I have also seen nuts with no cotters at all, makes me cringe.
Maybe think of trying it again with good torquing, I use a minimum of 70, that way I can go to 80 if the window doesn't quite line up; but you will still end up grinding some nuts.
Be sure to dump a qt of oil down the dizzy hole to get some oil to the main oilers in the valve chamber. The rest goes down the oil filler thus filling the dipper tray. Good luck
2. If the motor is in the truck then use the foil method, plastigage can mislead you. You are looking for .0015-.002 clearance. Never take more shims from the center main than anywhere else, even if you end up with more than .002 at the center
3. If the windows on the castle nut do not line up with the bolt hole when at specified torque the proper procedure is to remove the nut entirely and lightly grind off (face off) some of the nut on the SIDE of a grinding wheel while constantly rotating the nut to maintain even grinding. This must be done with a light touch and is trial and error and may have to be done more than once. Mains set at 50# will NOT clamp as well as mains set at 70 and you will have misleading readings. Ask me how I know. This is partially because you are trying to hold up the weight of the crank and a 64# flywheel if you are doing this in the truck. This is also why plastigage may not be accurate done this way.
4. I have yet to be able to get a torque wrench on the rear main bolts if the engine is in the car. As it is, I had to make a special socket by welding a 3/4 inch nut onto a spare correct-sized socket after I had shortened it by 1/4 inch with a cutoff wheel. Then I use a box wrench with a short length of pipe to get the leverage needed for 70-80 # of torque. Now I am ready for a 'ha-ha there is a special tool for this' from the crowd but I haven't found it yet. How do I know I have 70-80 # on those rear nuts? Easy, set an equiv. nut and bolt up in your vise, get the torque wrench out and crank it to 70 # and see what it feels like. It takes a fair bit of force and your arms will remember if you are good.
5. Unfortunately for some owners whose cars I have worked on, some previous mechanics either loosened to the closest window giving precious little clamping force (such as 30-40 #) or tightened the living daylights out of them to catch the next window to where it took a 6' cheater pipe to get the nuts off. Of course these fasteners were stretched beyond usage
6. The crank should turn with little effort right at the start (assuming the plugs are out); it should not be tight and then loosen up. Be sure to keep oil in the bearings while testing.
7. Make a logbook of what you have done to the shims and all in case you have to go back in; at least you will know exactly what has transpired. Be sure your shims are removed evenly from each side of the caps. At most, be one shim off; ie 3 on one side and 4 on the other. If I have to remove an odd number of shims from more than one bearing, I like the extra one to be on the same side on both caps. Prolly more OCD than needed. If removing shims to adjust, be sure to remove only one at a time, do not remove in pairs. Be sure the caps go back on with the same orientation they came out, do not flip them around. Do One cap at a time only. Start at the rear and work forward.
This is tedious but so important. With some patience you will be doing your engine a tremendous favor. this is what was routinely done in the old days until there were no more shims left. Clearly doing this with the engine out is easier, but we have this down pretty slick here in the car over a pit. I have also seen nuts with no cotters at all, makes me cringe.
Maybe think of trying it again with good torquing, I use a minimum of 70, that way I can go to 80 if the window doesn't quite line up; but you will still end up grinding some nuts.
Be sure to dump a qt of oil down the dizzy hole to get some oil to the main oilers in the valve chamber. The rest goes down the oil filler thus filling the dipper tray. Good luck
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Tom Wesenberg
Well-known member
Is this your first A, or are you familure with the typical vibration that the 4 cylinder Model A engine has? Mine seems to vibrate most about 45 MPH.
tbirdtbird
BANNED
Tom, you are the wizard of special tools and jigs; what is your solution to my para. # 4 above? dave
....and I too never met an A that didn't vibrate between 45-50....but (and no one believes me haha) that harmonic went away when I installed elctronic ignition (FSI)....go figure....
....and I too never met an A that didn't vibrate between 45-50....but (and no one believes me haha) that harmonic went away when I installed elctronic ignition (FSI)....go figure....
rollingsculpture
Senior Member
tom while i have heard from many that the model A has vibration it seemed to me that since i had this problem and the vibration was reduced by going back in and checking the bearings that it may be the case for others thus the reason i posted so others may be informed , i get that the crank is not balanced but i also doubt henry would have sold many cars if this was the case since new ,so i suspect that many an A has bearings that are too tight and may be causing binding or harmonic vibration to happen ALSO tbird that is the best paragraph on the procedure i have ever read thank you , i do keep a log book on the things i do to keep track of it and only work on one bearing at a time , the whole procedure takes me about 5 1/2 hours to complete . i have a question about removing shims , if you have an equal number of shims and need to remove one do you choose the cam side shim or the other side ? im interested to know if there is any relationship to rotation of crank and force or walking that could happen and how to counter act it. thanks again for your expertise i will keep you all posted when i get back into it again as you know we just got another dump of snow here !
best mike
best mike
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Tom Wesenberg
Well-known member
Motor's Manual has a recommended side for the shims with the least number for my 49 Chevy truck, but I've never seen such a recommendation for the Model A.
tbirdtbird
BANNED
Set the bearings the best you can, that is all you can do. Then see what happens with vibration. Do the mains then the rods.
Typical household foil is .001, but mic it to be sure (the heavy duty is thicker). The foil method has all been written up here, do a search. In an ideal world when you fold the .001 foil once you get .002 and that SHOULD lock up the crank, and next step is to use just one layer of foil at .001 and that should NOT lock the crank. You never want less than .001. Vibration is prolly coming from caps that are too loose, not too tight. Just set it the best you can that is all you can do. good luck
Typical household foil is .001, but mic it to be sure (the heavy duty is thicker). The foil method has all been written up here, do a search. In an ideal world when you fold the .001 foil once you get .002 and that SHOULD lock up the crank, and next step is to use just one layer of foil at .001 and that should NOT lock the crank. You never want less than .001. Vibration is prolly coming from caps that are too loose, not too tight. Just set it the best you can that is all you can do. good luck
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