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07-28-2018, 02:46 PM | #1 |
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Engine Vibration
I have an engine that was recently rebuilt by a very good builder. It has a vibration in it that I cannot figure out. The flywheel and crankshaft were balanced together by a competent shop. The vibration feels like it is something caused by an out-of-balance component, but that could not be the case. The vibration is present when we ran the engine with only the flywheel attached, so adding the clutch pressure plate could not be causing the vibration.
I could tolerate the vibration of the engine, but the worst thing is that it results in a loud rumbling noise in the cab. That rumble is present even when the floor-board is removed. We changed the engine mounts to float-a-motors front and back which helped some, but not enough to want to drive for very long. The crankshaft has counterweights attached. The oil pan looked to be in excellent condition. There was no indication of any parts rubbing that we could see when we took the engine apart to try to find the problem. Could there still be some reaction between the counter-weights and something else, like oil splashing around. The shaking seems like it would take something stronger than that. Your ideas are appreciated. Richard Lorenz |
07-28-2018, 03:37 PM | #2 |
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Re: Engine Vibration
You might try shorting out each cylinder to determine if it from one of them. Hold a screwdriver from a head stud over to the top of the spark plug. Is the vibration at low idle or all through the range? Check the gap inside your distributor body from the contacts to the rotor.
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07-28-2018, 03:41 PM | #3 |
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Re: Engine Vibration
I know this seems very simplistic, but, stuff happens. Could the flywheel be mounted 180º out ?
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07-28-2018, 06:14 PM | #4 |
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Re: Engine Vibration
yep stuff happens. rebuilder and balancing shop didn't get it where it is supposed to be, if it vibrates with just crank and FW attached
Weights may not be properly centered to each other, either Or they didn't balance rods and pistons. Some piston sets are off by as much as 10-20 grams Also, if you used the old school stock type heavy pistons they are harder to get right |
07-28-2018, 07:50 PM | #5 |
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Re: Engine Vibration
Good Evening...It seems to me that you have a problem with the re-built engine that you are not going to be able to solve on your own. Before damage is done to the engine, talk to the engine re-builder and see if they would like you to put the car on a trailer and bring it to them as it is. Then they can hear and feel the problem and figure out what the issue is. Hopefully the re-builder is not too far away from you. The safest way to take delivery of a rebuilt engine is to have it completely assembled at the re-builder and run on their test stand as proof of a good rebuild. The flywheel, clutch and pressure plate should be in place. If all is well on the stand, then it will install well. If there is a problem, you have the correct folks assembled to figure it out before it is put in the car. Good Luck...Ernie in Arizona
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07-28-2018, 08:17 PM | #6 |
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Re: Engine Vibration
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07-28-2018, 08:31 PM | #7 | |
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Re: Engine Vibration
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07-28-2018, 09:12 PM | #8 |
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Re: Engine Vibration
we have 100 psi on a Snyder 5.5 on a brand new motor here....I would investigate.
65 is closer to stock 4.2 head. Sure it is a 5.5? stock and snyders are not marked..... |
07-29-2018, 07:59 AM | #9 |
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Re: Engine Vibration
Thanks for all of the suggestions. We will check compression tomorrow. The flywheel is not on upside-down. We carefully marked it with red paint.
My grandson, who is doing the heavy work(6 foot-eight inches tall), will have a new business work schedule which means that we will have to slow down on this project for awhile. |
07-29-2018, 10:00 AM | #10 |
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Re: Engine Vibration
I don't know how severe your vibration upon deceleration is, but don't overlook the fact that model A engines do vibrate considerably more on compression (when not applying power, or slowing down) than when accelerating. That's just the nature of the beast. I won't go into why, since that has been documented here in the past, several times.
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07-29-2018, 11:29 AM | #11 |
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Re: Engine Vibration
I built an engine several years ago, a BB crank in a B block. All was balanced professionally. It had 3 vibration points, none of which was in the RPM range I drive in, all of them turned out to be "normal" in some engines. It was more noise than anything, it was not noticeable unless out on the road with it. Yours doesn't seem to be anything near normal! Remove the fan belt to see if that helps. Good luck!
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07-29-2018, 05:55 PM | #12 | |
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Re: Engine Vibration
Quote:
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"There are some that can destroy an anvil with a teaspoon and shouldn't be allowed to touch anything resembling a tool." |
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07-29-2018, 06:11 PM | #13 |
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Re: Engine Vibration
Universal joint. It got better because it got re-lubed (deep down inside the surfaces, but it will only get marginally better. Put it up on jack stands and star it up. Jar of water on the head, and watch the water. Kick it in gear and watch again. Pull the drive shaft / rear end, and I bet the vibration goes away. If you suspect the fan, slack the belt and drive it abt 1/8 of a mile. It's either a fan, U-joint, flywheel position, or in the worst case a bad rod.
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08-04-2018, 02:42 PM | #14 |
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Re: Engine Vibration
I have looked at all of the above suggestions and checked them on my engine.
They are good ideas, but they are not what is causing my vibration. The good news is that we installed float-a-motors front and back and that took stopped most of the vibration from being transmitted to the frame and from there to the cab. The noise level in the cab is way down, so we can drive it and be comfortable. Not perfect by any means. Our latest compression test, is 56, 55, 58, and 62 psi. We plan to drive the car 100 miles or so and check the compression again. We did a bleed-down test by blowing air into the cylinders using a gadget that I built. There was a lot of air bypassing the piston rings and coming out the oil filler tube. This might be normal for a room-temperature engine, or it might mean that the piston ring end gaps are unusually large. After a 10-mile drive, there was only a very small amount of oil that came out of the filler tube and got on the engine. We ran a timing check to see if the dimple on the fiber cam gear might have been put in the wrong place. It checked out to be O.K. With the #1 cylinder at the top, the timing pin detent was felt, and the old timing mark on the pulley was also in the correct place. As mentioned above, we hope that driving will improve things. Thanks again for your help. Richard Lorenz |
08-04-2018, 06:04 PM | #15 |
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Re: Engine Vibration
In my experience, NEVER Balance a Model A, or any 4 cylinder crank with the flywheel!
Balance a rebuilt Flywheel, always with the new pressure Plate, and Mark the position. Pressure Plates are always way out ! A crank with chunks of weight bolted, or welded, or both, on one side of the crank, will never be in as good of balance as the Ford weights, that encircle the crank, not by a long ways. I can also tell you, there are Guys that Balance, and Guys that know how to balance. There are always a difference in Doctors.! Herm. |
08-04-2018, 06:45 PM | #16 |
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Re: Engine Vibration
Question Herm, What then is your opinion of Burlington or Scat cranks as far as balance?
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08-04-2018, 07:18 PM | #17 |
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Re: Engine Vibration
Hmmmm.My motor is modified and was scrupulously balanced by a highly respected balancer.
It had vibration periods exaggerated by camshaft gear rattle. After changing to bronze timing gear and matched crankshaft gear also from a highly respected source, nothing changed. Finally I fitted a harmonic balancer pulley which simply transformed the motor. Is your vibration continuous or are there vibration periods? A harmonic balancer pulley could solve your problem? |
08-05-2018, 10:43 AM | #18 | |
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Re: Engine Vibration
Quote:
They have balanced out good, as they have more weight between where the weight would be welded on, and smoothed out and filled in to the Rod Pin. Picture of a scat Model T crank. Herm. |
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08-05-2018, 03:13 PM | #19 | |
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Re: Engine Vibration
Quote:
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08-05-2018, 07:07 PM | #20 |
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Re: Engine Vibration
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08-05-2018, 07:38 PM | #21 | |
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Re: Engine Vibration
Quote:
THERE IS ONLY ONE PROPER WAY TO BALANCE CRANK ASSEMBLIES. If it is an inline 4 cylinder, you balance the rods and pistons first. Plus or minus 1/2 gram on that stuff. Then you balance the crank both statically and dynamically with no front pulley, damper or flywheel. Then you put whatever goes on the front of the crank and balance that statically, making any adjustment on that attachment. Then you attach the flywheel and balance that statically, making any adjustment on that only. Then you attach the clutch cover and balance that statically, making any adjustment by drilling the spring towers. Never weld on a clutch cover. Then, recheck the whole assembly for dynamic balance. All of this assumes the rebuilder checked the runout of the crank, front pulley and flywheel/clutch assemblies at assembly time. The clutch disc can be balanced on a separate arbor. All model A/B engines have natural resonant frequencies/rpm's that they vibrate at. These are minor and you can not get rid of them without redesigning the engine. They had these right from the factory. |
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08-05-2018, 08:05 PM | #22 |
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Re: Engine Vibration
Where did you get a harmonic balancer pulley from?
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08-06-2018, 04:19 PM | #23 |
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Re: Engine Vibration
These dampers are made by Murray Horn in Levin N.Z. His Company is Engine Restorations Ltd. His email is [email protected]
Murray says this is the best way to contact him. The dampers are a straight fit to replace the standard Model A pulley. An added benefit is a shallow reverse scroll in the rope seal area to help contain oil. |
08-06-2018, 04:54 PM | #24 |
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Re: Engine Vibration
Wensum, could you tell me where you got your harmonic balancer pulley ?
Thanks, Bill |
08-06-2018, 06:01 PM | #25 |
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Re: Engine Vibration
Why would you balance the rods and pistons first?
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08-06-2018, 07:38 PM | #26 |
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Re: Engine Vibration
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08-06-2018, 09:59 PM | #27 |
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Re: Engine Vibration
It is not essential for an inline 4 cylinder, but, when you balance a V8 you need to do them first because you need to record the weights to make up the required bob weights. No bob weights are required for an inline 4 cylinder street engine.
So it comes down to using the same sequence of events for all engines. Less procedures to remember and get confused. |
08-07-2018, 02:14 AM | #28 |
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Re: Engine Vibration
Peter, when you say to balance the parts statically,how do you do that,
I,m very interested. I have the scales and fixtures to do the rod and pistons and stuff but not the crankshaft I could save a lot of $$ at the reconditioners If I can get the static close first. Lawrie |
08-07-2018, 01:25 PM | #29 | |
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Re: Engine Vibration
Quote:
The heavy side will always seek "down". Static balance is balance in one plane. Dynamic balance is balance in overall length. It is possible for a crank to be in balance on one end but not on the other end or in the middle. A balancing machine is required to detect this. You will not save much if anything by knife edge balancing before you have it balanced on a machine. |
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08-07-2018, 04:05 PM | #30 |
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Re: Engine Vibration
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08-21-2018, 04:28 PM | #31 |
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Re: Engine Vibration
Thanks again for everyone's suggestion. We checked camshaft timing by watching piston #1 top out. It agreed with the NUREX timing scale and our old mark on the pulley when the timing pin dropped into the detent on the fibre timing gear.
We also checked the compression with the engine warm , probably about 160 F. Results front to back were 58, 63, 62, 60, and 58 psi. These are slightly higher than previous room-temperature measurements, but nowhere near the 100 psi that could be expected with our 5.5 Snyder's head. As soon as it quits raining in East Tennessee, we will put some driving time on the car to finish the break-in. Richard Lorenz |
08-27-2018, 09:08 PM | #32 |
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Re: Engine Vibration
Richard:
I had the exact problem you have, my professionally rebuilt engine vibration was between 0 and 30 MPH, noisy above 30 MPH. I was ready to give up from frustration as I refused to drive it anymore. I believe my problem started after I installed my rebuilt engine and tightened the stock front mount too tight and thus not lining up the crank hole properly. I then decided to install both front and rear float-a-motor mounts which didnt help much. I removed the front float-a-motor and reinstalled the stock front mount, kept only the rear float-a-motor mounts making sure the rubber was not too tight. The problem went away completely, no vibration at all and very quiet - no harmonics sound. Make sure the front stock mount is lined up properly with the crank hole. let me know if that makes a difference for yours Tom |
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