Rod Frazier Posted August 29, 2016 Share Posted August 29, 2016 Forgive me for returning to well-trod ground, but I haven't been able to find the answer to my question in the archives. I have a '40 Century with a '50 320, that vibrates uncomfortably at around 2300 rpm, clutch in or out. 2300 translates to 50 mph, which is a speed I often want to use, but avoid because of the vibration. From a visual inspection, the motor mounts look O.K. and I have not removed the harmonic balancer to look at it, thinking the odds of that being the problem are pretty low in comparison to the hassle of getting it off. I understand that some folks have been able to cure or at least ameliorate a vibration of this sort by adding weights to the flywheel. My question is exactly what procedure to follow and what size and type of weights to begin with. Any help, especially including pictures, would be greatly appreciated. I'm putting about 5,000 miles per year on this car counting VMCCA tours. Thanks, Rod Frazier Link to comment Share on other sites More sharing options...
LAS VEGAS DAVE Posted August 29, 2016 Share Posted August 29, 2016 Has the car always done this? Was the engine ever rebuilt? Was it always a stick shift engine combo or did it once have an automatic? Engines just don't get out of balance. Link to comment Share on other sites More sharing options...
raydurr Posted August 29, 2016 Share Posted August 29, 2016 Is the vibration engine , driveline or chassis? The pulse rate or frequency can help determine this. Drive car at 50-55 mph then pop transmission in neutral. If the vibration persist even though engine is now at idle, then problem is driveline or tire related. Tire or wheel vibration seems to have a slower, steadier frequency. Driveshafts can almost have a buzz. Did vibration begin after some repair or modification was performed? Link to comment Share on other sites More sharing options...
Rod Frazier Posted August 29, 2016 Author Share Posted August 29, 2016 (edited) Unfortunately, I can't answer any of the questions. I bought the car 2 1/2 years ago from a friend who had it for 22 years and never rebuilt it, and he bought it from a friend who had owned it for several years himself. Nobody knows if or when it was ever rebuilt, but it runs very well, uses very little oil (though it has some blowby), and is smooth at every other rpm. Its two sweet spots are 45 and 60. Also, nobody knows when or why the '50 engine was installed nor what transmission it was originally bolted to. The clutch seems fine and the only other problem I need to deal with is that it jumps out of second on steep downgrades, of which we have plenty here in mountainous Utah. Edited August 29, 2016 by Rod Frazier (see edit history) Link to comment Share on other sites More sharing options...
Rod Frazier Posted August 29, 2016 Author Share Posted August 29, 2016 Raydurr, it appears to be engine. Clutch in and coasting at 50 equals no vibration. Standing still there's vibration at 2300 with the clutch engaged or not. Tires are perfectly balanced. There have been no repairs on the car since I've owned it, but, of course, it's had the vibration all this time. The previous owner has several cars so this one was used only occasionally, but he doesn't remember having to do anything major, not even a clutch. Link to comment Share on other sites More sharing options...
Thomas J. Bianculli Posted August 29, 2016 Share Posted August 29, 2016 Hello Rod, I have scanned for you the page in the 1940 Buick Shop Manual that addresses this problem. I hope this helps. Tom Link to comment Share on other sites More sharing options...
Rod Frazier Posted August 29, 2016 Author Share Posted August 29, 2016 Well, now, talk about feeling stupid! I actually own the manual and missed this section. I'll give it a try and see what happens. Thanks, all, for the help. Link to comment Share on other sites More sharing options...
Dynaflash8 Posted August 29, 2016 Share Posted August 29, 2016 If the engine has been rebuilt, and the crankshaft turned, you absolutely needed to have it balanced. It could also be an out of balance piston, especially if they were nos, or from different sources. I had that problem by not balancing the crankshaft on a total rebuild. The problem worked itself out, somehow, after some portion of the 51 years that have passed since 1965 when the engine was rebuilt. I don't feel the vibration now. That said, I've changed the clutch and pressure plate twice since 1965, so it could have been the clutch all along. Link to comment Share on other sites More sharing options...
Thomas J. Bianculli Posted August 29, 2016 Share Posted August 29, 2016 Don't feel stupid. It is not marked anywhere in the index. I just got the manual a couple of weeks ago. I just happened to see it thumbing through the manual looking for something else. My first impression of your problem reminded me of my 1973 Chevy half-ton with 2 piece driveshaft and center carrier bearing going bad. I thought it was tire until the bearing seized up and the rubber around it burned and stank. If you don't have the problem coasting it is not the driveshaft or universal. The first paragraph above describes your problem to a T The procedure looks simple at first glance but will probably be time consuming. Good luck!!! Tom Link to comment Share on other sites More sharing options...
BuickBob49 Posted August 30, 2016 Share Posted August 30, 2016 I have similar problems with my 39 Roadmaster 320. I thought it was lumpy old tires. I took care of that with radials. Some change. Smooth when coasting from 50+. The engine was rebuilt before I got the car. So I don't know about the pistons, except that a mechanical engineer did the work. We rebuilt the trans with NOS gears last fall. And we had the clutch redone. But I still have vibrations. Were they new or old vibrations? We replaced motor mounts and trans mounts a few weeks ago. The vibrations are now only at 40-45 mph and at a certain rev. Beyond 45 the car sings. 60-70 is great--still have pedal. It all may come back to an unbalanced flywheel/clutch assembly. A chore to address it. Live with it? Your thoughts? Link to comment Share on other sites More sharing options...
Thomas J. Bianculli Posted August 30, 2016 Share Posted August 30, 2016 I am definitely not an expert and have not experienced this problem myself. It did strike me, however, that the first paragraph of the section in the Shop Manual is almost word for word with your description as well as Rod's above. If the clutch has been changed and the problem persists it would more likely be the flywheel. If it were my problem I would probably try the second method that does not require removing the clutch. Drilling holes in the back of the flywheel would, not be the first thing I would want to do, but it is sure easier than pulling the rear, transmission, clutch and flywheel and taking it to a machine shop to balance. Link to comment Share on other sites More sharing options...
Dave_B Posted August 30, 2016 Share Posted August 30, 2016 Rod, I'm going through the same thing with my '68 Volvo. It has an automatic trans and it vibrates at about 60 MPH. It actually vibrates at the same RPM in each gear, so as engine speed hits that particular RPM it vibrates till it shifts. It then stops vibrating till the RPM gets back to the same place. Because of that characteristic I don't think it is the driveshaft. It has done the same thing with two different engines so I don't think it's the engine. I think it must be the trans. The flex plate has a circle of bolt holes close to the ring gear and I have added bolts and washers and moved them around till it got better. Not completely gone, but better. It was a time consuming process but I had some success. I'm taking the trans out to have it rebuilt so I'm going to get the flex plate and torque converter balanced and see if that helps. Good luck with yours, Dave Link to comment Share on other sites More sharing options...
Rod Frazier Posted August 30, 2016 Author Share Posted August 30, 2016 Thanks, Dave. I'll let you know what success I have, if any. I've got another couple of projects more urgent at the moment, but I'll get to it pretty soon. Link to comment Share on other sites More sharing options...
Morgan Wright Posted August 31, 2016 Share Posted August 31, 2016 My engine ran a little rough as you described, but when I retorqued all the head bolts it stopped. Now it runs as smooth as the Mississippi. I wasn't expecting this to happen, I was very surprised. The only reason I retorqued them is it was 1000 miles after a valve job. If you had the engine rebuilt recently and it's running rough now, retorque the head bolts. Link to comment Share on other sites More sharing options...
jenz38 Posted August 31, 2016 Share Posted August 31, 2016 Hi Folks, At first I would check the firing order, second I would check for the timing mark on the flywheel ...here the problem could be a wrong mounted Flywheel on the crank flange, at Buick you can mount it in every (wrong) position , then you have that what you discribed. M2C Link to comment Share on other sites More sharing options...
Rod Frazier Posted August 31, 2016 Author Share Posted August 31, 2016 Thanks, jenz38, but those items seem to be in order. Up here at 7,000 feet and surrounded by 9,000 foot passes, I time everything with a vacuum gauge, but I can see that the timing mark is in the right place. Link to comment Share on other sites More sharing options...
Terry Stock Posted August 31, 2016 Share Posted August 31, 2016 Hesitate to suggest this, but the Buick might still run smooth on 7 (or 6?) cylinders if unstressed. Are all spark plugs firing when they should? Fuel not too rich? Link to comment Share on other sites More sharing options...
Rod Frazier Posted September 1, 2016 Author Share Posted September 1, 2016 (edited) Terry, thanks for the ideas, but the car runs really well with lots of power. We use it for touring here in the West and just got back from a 4-day trip with mountain passes over 9,000 feet. Even at the rpm where the vibration lives, it still runs well and has plenty of oomph. I'm eager to try the flywheel weights, but have a '49 Ford with overheating problems and a '68 Electra that needs a new AC compressor, so it may be a few days before I can get to it. It seems strange to me that something as light as an extra washer or two could make much of a difference to the dynamic balance of the entire engine, clutch and flywheel assembly, but it's surely worth a try. Edited September 1, 2016 by Rod Frazier (see edit history) Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted September 1, 2016 Share Posted September 1, 2016 Just a couple of thoughts... Rod has clearly said that the problem exists at a certain RPM of the motor when the car is driving, stoped, in gear or out of gear. Also when the clutch is depressed or not. Now my point is that this CLEARLY eliminates the transmission, drive line (torque tube), rear end and all chassis parts except possibly the motor mounts. So with this in mind the next logical step is to eliminate engine accessories. IE: Water pump/fan and generator. With a cold engine remove the fan belt and start her up. Rev her up to the vibration speed and see if she still vibrates ( I suspect the vibration will still be there). If the vibration is still there then the most likely area is the flywheel/clutch/pressure plate as mentioned above. Keep the run time short without the water pump and you will be ok. If really concerned disconect the radiator hoses and feed a garden hose into the lower radiator hose and let the water flow freely. Keep us posted. Robin 1 Link to comment Share on other sites More sharing options...
BuickBob49 Posted September 2, 2016 Share Posted September 2, 2016 The engine vibration in my 39 Roadmaster is also at a certain rpm. And it is evident in first and second gears, but not as noticeable because of the upshifts. I will talk with my mechanic about the procedures outlined in the 1940 manual. Thanks for this very good discussion! Link to comment Share on other sites More sharing options...
Daves1940Buick56S Posted September 2, 2016 Share Posted September 2, 2016 I have a slight rumbling vibration around 1800 rpm in mine. Just slightly annoying. At some point I will get rebuilt motor mounts but that is way down the list. I think some of this is due to our cars having the mounts at the front. Cheers, Dave Link to comment Share on other sites More sharing options...
Rod Frazier Posted September 2, 2016 Author Share Posted September 2, 2016 Thanks, Robin. I'll give it a try. I suppose it's a long shot, but maybe the fact the previous owner converted to an alternator has thrown things a bit out of whack. When I bought the car I had to modify the generator bracket to get the alternator to really line up with the pullys. Link to comment Share on other sites More sharing options...
superbuick Posted September 2, 2016 Share Posted September 2, 2016 I agree with others that your vibration is a balance problem and not the way it runs. You have given a good description of it. I would take the belt off and is no change move to the flywheel. My 38 has the same vibration just a certain RPM spots. Just with engine running. I have not traced it down yet, but it came about when the last owner put in a later model rebuilt engine. Most likely from a dynoflow car. I have a 58 that had the same vibration and spent a little time (after eliminating other external items) balancing the engine with washer weights (on the flywheel/flex plate) as the shop manual describes. What an improvement and really dose not take the long. Let us know what you find. Steve F Link to comment Share on other sites More sharing options...
Rod Frazier Posted September 3, 2016 Author Share Posted September 3, 2016 Steve, it's interesting that mine is also a later model engine that might well have been mated to a dynaflow also....I'll never know. Even with the vibration, I love to tour in this car. The wife and I just got back from a 500 mile tour around northern Utah and she ran flawlessly. Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 25, 2017 Author Share Posted July 25, 2017 Been a long time since I had time to work on this situation, but yesterday and today I tried the flywheel balance with added washers solution, with some results. The vibration isn't gone, but it's a bit better. It took 2 extra washers on three adjoining bolts to do it. Just for interest I removed the opposing middle bolt completely but there was no additional benefit. This morning I loosened the fan belt as much as I could (an aftermarket radiator and alternator conversion makes removing it a real trial) but could perceive no change in the vibration level or rpm (which has migrated from 2300 to 1900 rpm, just about where maximum torque is). To my eye the motor mounts look good, and the transmission mount looks relatively new. The bad news is that the vibration still exists, but the good news is that it's no longer at 50-55 mph, my favorite touring speeds, and seems tolerable even at its peak around 44. Any ideas for further improvement would be greatly appreciated. Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted July 25, 2017 Share Posted July 25, 2017 Hi Rod, I did not see this thread last year, just found it today. The fact that the vibration is less with the changes made does point to the flywheel/clutch/pressure plate. It is my understanding that all 1950 Roadmasters , which was the only model to have the 320, came with an automatic. The crank in these automatic engines had no provision for a pilot bearing, so mods were/are necessary. In addition, I BELIEVE the bolt hole for the crank to flywheel is different. Over the years, folks have taken a couple ways to get around this when installing a standard transmission behind one. One was to use a crank from an older 320 that did not have a Dynaflow. The other is to make mods to the back of the crank. Since the speed at which it now vibrates is one you can avoid using, if twere me, I would let it be until engine rebuilding time. Which may be never, depending on your age. My first Buick, back in 1954, was a 1940 Special. Good choice. The Roadmaster is seldom seen. Ben Link to comment Share on other sites More sharing options...
BuickBob49 Posted July 26, 2017 Share Posted July 26, 2017 Can we rule out a faulty harmonic balancer as the source for the vibrations? Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 26, 2017 Author Share Posted July 26, 2017 No, Bob. It looks like a truly tedious job to get at it. (Unless you know a way to check it without removing everything that's in the way). Link to comment Share on other sites More sharing options...
FLYER15015 Posted July 26, 2017 Share Posted July 26, 2017 Rod, It sounds like you are on the right track. I would try 2 MORE washers in the same place. Then I would try moving them around to the next bolt or so, one at a time. Short drives in between will tell you what the effect is. Mike in Colorado Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 27, 2017 Author Share Posted July 27, 2017 Mike, it was interesting that completely removing a bolt opposite of the added washers didn't make any additional difference. But maybe I'll buy some longer bolts and try it. Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 28, 2017 Author Share Posted July 28, 2017 Anyone ever try using a small strong magnet as a test weight? At what rpm do you think it would launch itself, ricochet off the garage floor, and exit through the broken window? 1 Link to comment Share on other sites More sharing options...
Daves1940Buick56S Posted July 28, 2017 Share Posted July 28, 2017 1 hour ago, Rod Frazier said: Anyone ever try using a small strong magnet as a test weight? At what rpm do you think it would launch itself, ricochet off the garage floor, and exit through the broken window? The rpm at which that will happen will always be exactly the speed at which you decide to throttle back. - Corollary to Stovall's law Cheers, Dave Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 28, 2017 Author Share Posted July 28, 2017 Yeah, that sounds about right. And Stovall's law is.....? Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 29, 2017 Author Share Posted July 29, 2017 Mike: I've found that short drives aren't necessary. I just hook up a tach to the coil and lean against the fender. I can feel the vibration peak perfectly well as I increase the rpms by opening the carb manually. I did drive the car again today about 40 miles and the vibration was never enough to be discerned above the road service and high tire pressure. I deliberately didn't look at the speedometer until I reached the speed that was most comfortable (including wind noise, etc.), which turned out to be about 52...quite comfortable. Link to comment Share on other sites More sharing options...
Daves1940Buick56S Posted July 29, 2017 Share Posted July 29, 2017 5 hours ago, Rod Frazier said: Yeah, that sounds about right. And Stovall's law is.....? When performing a test that carries any risk such that test deviation or failure will damage either the device under test or something in the immediate surroundings, said failure is likely to occur and will do so in such a manner as to inflict maximum damage, and further, as the possibility of repair or replacement of either the device or objects in the immediate surroundings decreases, the likelihood of test failure or deviation increases. 1 Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 29, 2017 Author Share Posted July 29, 2017 Truly immutable. Link to comment Share on other sites More sharing options...
Guest Posted July 29, 2017 Share Posted July 29, 2017 The statement about the crankshaft being different between the 1950 Dynaflow and the older stick version is true fact. The center hole of the stick flywheel has to be made larger in diameter to accept the larger diameter shoulder sticking out at the back of the crankshft. One potential issue with that is the small or no space left between the attachment bolt holes and the crank flange shoulder(flywheel weaker?). I also seem to recall something about smaller diameter bolt holes in the crank flange needing spacer sleeves around bolts to accommodate the difference. Don't know if these things impact your scenario or not, but food for thought if naught else! Link to comment Share on other sites More sharing options...
Rod Frazier Posted July 29, 2017 Author Share Posted July 29, 2017 Interesting information, 2carb40. Something to look for at rebuild time. For the nonce, I'm going to drive her as she is, but always alert to possible bandaid fixes/improvements. Ideally, I'd like to replace the engine with a year-correct one someday. And go back to 6-volt and the generator. But for now she's a good runner and we're putting on at least 5,000 miles a year with tours and weekend drives. Most comfortable old car I've ever had. Link to comment Share on other sites More sharing options...
FLYER15015 Posted July 29, 2017 Share Posted July 29, 2017 10 hours ago, Daves1940Buick56S said: When performing a test that carries any risk such that test deviation or failure will damage either the device under test or something in the immediate surroundings, said failure is likely to occur and will do so in such a manner as to inflict maximum damage, and further, as the possibility of repair or replacement of either the device or objects in the immediate surroundings decreases, the likelihood of test failure or deviation increases. HUH ? 1 Link to comment Share on other sites More sharing options...
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