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Old 10-19-2003, 02:23 PM
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BBC Motor Mounts/69' Camaro/Vibration

Sorry for such a long post...I have a slight driveline vibration and a little clutch chatter in my 69' RS/SS 396 Camaro/Muncie m21. I put in a Moser 12-bolt rear-end in my Camaro a while back and found the spring perches on the Moser were for a racing setup. After a lot of research I was able to get the pinion angle correct using shims and the drive shaft balanced which solved most of my larger vibration woes. I have balanced wheels and new u-joints too.

My existing driveline vibration is small but still present up to 70 MPH. After 70 MPH, the vibration becomes worse as I accelerate past 70 MPH.

Here is an example of the problem: At 60 MPH when firmly accelerating or decelerating there is no vibration. The vibration occurs only when very slightly applying power to keep speed on a level surface. I can sligntly accelerate and decelerate and feel this small but truly annoying vibration "window".

I think I am past the pinion angle issues and now feel I have an issue with the motor/frame mounts that could be causing this problem. I have been reading about vibration issues if the wrong frame/motor mounts are installed. See this link: http://www.camaros.org/engine.shtml#EngineMounting.

Another reason I think I have a motor mount problem is the fact that my belt pully is about 1/8" away from touching the frame. There is no way that that the belt could be removed and replaced without removing the pully bolts. There is just no clearance. So the engine seems to be sitting low. I am wondering of the engine is sliding around on the mounts.

I got under the car and attempted to measure the frame mounts the best I could. As best as I could determine, the drivers side frame mount seems to be 2.5" high and the passenger side frame mount seems to be 2" high. This seems to be correct from what I have ben reading. The passenger motor mount rubber seems to have a crack in the rubber where it is bonded to the mount. I am not sure how serious this is. I can't tell if the mounts on the Camaro are the proper "thicker, narrower" mounts.

Does anyone have any advice? I am grasping for information that could help m solve this problem.

Joe

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Old 10-19-2003, 03:15 PM
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I Know that the BBC and SBC frame mounts are different,The big blocks are taller. Is your wiper motor right on top of the valve cover or do you have a lot of room under it? If you even have the wiper motor on it ?

Last edited by roys63; 10-19-2003 at 03:22 PM.
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Old 10-19-2003, 03:33 PM
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Thanks for the reply Roy. The crossmember is stock and and trans mount is correct and new. When I was working pinion angle changes a while back, I tried shimming up the muncie using the extra shim plate that came with the trans mount. It resulted in the pully rubbing the front of the front crossmember when the car was started. So the trans can't go up any higher. I would think if the trans was shimmed up the front of the engine would go down causing more of a problem though.

The rear had a worn out 10-bolt 308 gears in it when I bought the Camaro. I put the Moser in at the correct 3.73 ratio. So the whole drive line is spinning faster now and that is why I am seeing the vibration that may always have been there but not noticable with the low ratio. It makes me wonder if the shop that sold it to me put in the 3.08 gears to mask the original problem.

I measured the difference between the bottom of the wiper motor case and the valve cover and it is 2 1/4" of space.
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Old 10-19-2003, 03:50 PM
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From what i remember you very little room under the wiper motor with the Factory stock BB camaro and we had to remove the wiper motor to pull the valve cover. You very well may have the wrong frame mounts, is this a original BB camaro? some one could have changed the front frame and not changed the mounts? I am shore Troy - Curt will ring in on this he is the Camaro Dude!
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Old 10-19-2003, 09:19 PM
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The camaro (same one in my Avatar) is a true and correct numbered big block camaro, although not numbers matching. Nearly everything is correct, stock 396, rochester, muncie, paint, interior, etc. The only thing that was not correct was the rear end when I purchased it restored. However, I believe the card was originally restored from the frame up as it has new welded in floor and trunk pans.

2 1/2" of clearance seems to me that I could pull the valve covers without removing the washer motor. I sure am interested from hearing from others concerning this. Also note that the angle of the transmission output shaft with the car loaded on a level surface is 4* down. Attempting to raise the transmission up causes the nose of the engine down and the belt pully rubs on the frame.

I have attached a photo of the wiper motor to valve cover clearance.

I really appreciate your input Roy.

Joe
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Old 10-19-2003, 09:21 PM
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Here is a picture of the valve pully to frame clearance. I would say it is about 1/8" clearance here.
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Old 10-20-2003, 05:55 AM
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That pulley looks like it's rubbing now the edge looks like it polished a bit. They were a tight fit on the pulley and frame, you might try changing the rubber motor mounts if they look split and mushy, Send Troy -Curt a PM on this he may have more info on the frame mounts or stands .The car looks to be Very Nice!
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Old 10-20-2003, 08:04 AM
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Roy, I just ordered motor mounts from Ricks. One of them looks split where it is bonded to the metal mount. What is the best way to support the engine while I replace the mounts? I don't have a cherry picker.

I guess what I still need to know the exact height of the left and right side frame mounts so I can measure them when I am in there replacing the motor mounts. If they are the wrong size I can get Ricks to drop ship a new pair. I will try and contact Troy -Curt.

Here is a pic of the engine just for reference....
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Old 10-20-2003, 09:34 AM
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Dude,

Sounds like you have checked every thing that could be causing your problem. I will do some measuring on mine today, I have the front clip off so I should be able to get some good ones.The pulley is defiantly to close to the cross member.

Do a power stall with the hood up and watch the engine, do it it drive and reverse, if the mounts are bad you will see the engine lift up.

I had the same problem with one and traced it to a slightly warped wheel, just a thought.

I have a piece of 3/4 plywood that I put on my floor jack, and put the jack under the oil pan to change the mounts.

I'll get back with you latter today.

Troy
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Old 10-21-2003, 10:12 AM
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On my BB ss car the crank pulley has 1 inch clearance, and the wiper motor is 1 3/4 from the valve cover. I can remove it without taking the wiper motor off.

HTH
Troy
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Old 10-21-2003, 12:47 PM
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Thanks very much Troy for checking this. That brings me to the conclusion that I have the wrong frame mounts, possiblty for a small block engine. I have 1/8" clearance and 2 1/4" clearance from the wiper motor to the valve cover. I can't believe that the motor mounts would cause this although the motor mounts may be bad. I will be able to replace the motor mounts this weekend.

What I need to know is what the height is of the frame mounts for a true BB Camaro. I do know one side is higher than the other. I will try and find this on an internet search. If you know off hand, let me know.

Thanks again.... I will let you know what happens after this weekend.
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