Small Vibration after motor rebuild - Balancer issue?

[Chris McDade]

Just had my motor rebuild by Westside here in Houston. Always does a great job. Got the motor in late last week. Started up no issues. Good oil psi. Drive the car everything went good but, when I step off the gas like im making a turn or coming to a stop I get a very slight vibration at very low RPM that I have never had in this car before. It feels like it's coming from the motor but, not 100% sure. If, the engine was out of balance would it vibrate all the time or just at a certain RPM?

I wonder if, it could be a balancer issue. I have a spare im gonna throw on to see if it corrects it. Builder also said the disconnect converter then start motor to see if it goes away.

Thoughts?

 

[earlbrown]

Disconnecting the converter is a quick and easy test. No reason to brainstorm and guess until you do that and see if it's your problem.


Have you looked at the balancer/hub while running to make sure it's running true?

 

[Chris McDade]

Balancer looks like it's running true. Im gonna discount the converter this evening. I will report my findings. Thanks

 

[TurboBuRick]

If the new crank is internal balanced and you use a stock balancer or flywheel the motor will have a noticeable shake specially at lower rpm's.

Sounds like there is a wrong piece in the puzzle.

 

[MAK507]

Just had my motor rebuild by Westside here in Houston. Always does a great job. Got the motor in late last week. Started up no issues. Good oil psi. Drive the car everything went good but, when I step off the gas like im making a turn or coming to a stop I get a very slight vibration at very low RPM that I have never had in this car before. It feels like it's coming from the motor but, not 100% sure. If, the engine was out of balance would it vibrate all the time or just at a certain RPM?

I wonder if, it could be a balancer issue. I have a spare im gonna throw on to see if it corrects it. Builder also said the disconnect converter then start motor to see if it goes away.

Thoughts?

Can you record a video so we can hear the sound? Upload to YouTube and share the link



Sent from my iPhone using Tapatalk

 

[mikestertwo]

What kind of motor mounts are you using? Did you change them?

 

[Chris McDade]

I have HR mounts.

 

[Chris McDade]

If the new crank is internal balanced and you use a stock balancer or flywheel the motor will have a noticeable shake specially at lower rpm's.

Sounds like there is a wrong piece in the puzzle.

I reused my stock crank, rods, flywheel and balancer. So im not sure how this could be possible.

 

[mikestertwo]

I have HR mounts.

Did you have them before the rebuild? The HR mounts transmit a lot more vibration to the frame than stockers. I am using only the left HR mount and it still has noticeable vibration where there was none before.

 

[earlbrown]

I've never ran HR poly mounts but If I ratchet the hell out of a torque strap the car feels and sounds like a bad wheel bearing that I can 'see' in the rear view mirror.

If your vibration like that?

 

[Quick6'n'-K.C.]

Rods in backwards? Did he build it like a chevy? Had a few from DA SHOP and i LOL'd Do you have pictures of the rod dots in the block?

 

[Chris McDade]

I've been running HR mounts for years. Yes, they can certainly increase vibrations. I think I've narrowed it down some. When driving at the lower speeds I can feel the vibration but, I can put the car in neutral (while the car is still rolling) rev the motor and the vibration doesn't go away. This is telling me that it's not in the motor. I put the car on jack stands had my son put it in gear while I looked under the car and I can see allot of movement in my drive shaft by the rear end yoke. I could have something wrong with the drive shaft or rear end. Im gonna dig deeper this weekend. Thanks, for the input. I will let you know what I find.

 

[earlbrown]

Back when i used to drive my car 100 miles a day back and forth to work the pinion nut got slack. (no idea if it backed off or if the crush sleeve relaxed) and on a slight downhill my car would shake when I gave it just enough gas to not pull or engine brake.

Pure luck I found it that night, popped the drive shaft and snugged down the nut. That was about '98 or so. The vibration never came back.

 

[Chris McDade]

OK, here is the update......Drive shaft had .080" run out in the tube and couldn't be balanced. I had them make me a new one with new U-joints. Problem solved.....vibrations are gone

I think I hurt the drive shaft last time at track and didn't notice it until now.

Thanks for the help...

 

[HighMileage]

What u-joints did you use?

 

[Chris McDade]

I went with Moog grease type. I was told afterwards I should of went with the non greaseable type because the holes make them a little weaker. If, I ever upgrade this drive shaft I will change them out.

 

[HighMileage]

Thanks for the reply.

I was asking because a knowledgeable Turbo Buick racer (we all know his name,but I won't name-drop) once told me that the factory U-joints are the best you can have in there. When I was at his shop,I asked him to replace my stock ones. "If they are still good,keep them in there."

I still have my original ones in there,but am always open for input.

 

[earlbrown]

they are tough. Mine have 1/4 million hard miles on them and still tight.

I keep wanting to replace them in general principal, but if they aren't loose....


....then again ''If it ain't broke, break it!"