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Joe... I love your story...glad to hear your vibration is history.

 

Ed, I have read before about the harmonic balancer slipping and I've looked at it and it seems fine but I'll do a through inspection just to be sure.

The fly wheel is another sore spot but this raises the question of it's location. When I had the engine rebuilt in 86 the guys helping me install the engine bolted the flywheel on wrong and the car shook like crazy. No one could figure this out until it went to a local performance shop and a thousand bucks later...ouch...so I'm wondering if the flywheel could be out slightly...one hole off center. You'd figure this guy was very well know in the local hot rod community and knows his stuff...but you never know...

 

Zimm63, I've done the low gear test and I still get vibration. 

 

Thanks, Joe Camisa

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40 minutes ago, joe c said:

Joe... I love your story...glad to hear your vibration is history.

 

Ed, I have read before about the harmonic balancer slipping and I've looked at it and it seems fine but I'll do a through inspection just to be sure.

The fly wheel is another sore spot but this raises the question of it's location. When I had the engine rebuilt in 86 the guys helping me install the engine bolted the flywheel on wrong and the car shook like crazy. No one could figure this out until it went to a local performance shop and a thousand bucks later...ouch...so I'm wondering if the flywheel could be out slightly...one hole off center. You'd figure this guy was very well know in the local hot rod community and knows his stuff...but you never know...

 

Zimm63, I've done the low gear test and I still get vibration. 

 

Thanks, Joe Camisa

Joe,

  If you have doubts as to whether the flexplate is installed properly you can barely get up into that area with an inspection mirror and confirm the extra hole in the flexplate is aligned with the drilling in the back of the crank. You may need to unbolt the converter and slide it back toward the trans to get a good look.

  If you suspect there may be an engine vibration run the engine from idle speed up through 4  thousand RPM and check for any vibration while the car is standing still. A glass of water on top of the dash may help with detecting vibration. If you do have any vibration it would be best to look into the engine before moving on to the driveline. Make sure you evaluate the health of the engine, as in each cylinder, by doing a compression/leak down test and/or cylinder balance test and then move on to any belt driven accessories that could be presenting the vibration.

Tom Mooney

 

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Thanks guys for your input, 

 

Tom I'm wondering again about looking forward at the engine rather than backward at the rear end, and I will inspect both the balancer and the flywheel as soon as I get it back to the shop, weather permitting. One thing that puzzles me is this vibration was present with my original driveshaft but not a real bad

vibration...that's why I left it for so long and focused on other things I wanted to do and needed. So why now the vibration is worse than before I rebuilt the original shaft and or replaced the shaft with a used one...

I've had the engine gradually rev up in RPM and there is a vibration while the car is sitting still...not a big vibration but it is there, and belt driven accessories are fairly new but I can remove the fan belts and run the engine.

 

Joe Camisa

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You might also jack up the engine, pull the pan and look for parts of a broken piston.  While you have it jacked up, put in some new motor mounts.  

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I’ve put in both new motor mounts just last month from reading all the forums and advice to try, I’ve never thought of broken piston and I’d be very surprised if it was something like that but you never know.

 

 Thanks Rivnut appreciate the help...

 

I’m going to inspect the flywheel position and harmonic balancer as it is original I really hope it’s one or the other and nothing internal to the engine. 

 

Thanks, Joe Camisa

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One more point Id like to add, like I mentioned earlier, I don’t get why the vibration is now worse than it was before I rebuilt and balanced and tried a different drive shaft. How could that come back to an engine issue. Right now I’m open to anything. 

 

thanks Joe

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I used the 64, 65 Carrier Bearing.  It's about 1 1/2 inches or so lower in height.  I purchased a new bearing and housing then cut it up so that it was the exact same height as the 64, 65.  I didn't want to have to redrill the frame so I reworked the housing.  It came out mint.

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20190329_142347.jpg

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Hi All, Here is my absolutely frustrating story of a very mild vibration my Riv had.

First off my 401 was rebuild to 425 by a Buick trained Canadian mechanic 30 years ago just before I bought it.

The mechanic was a well respected (he died 10 years ago)

Yes, he once told me about the problems you can have going from 401 to 425 but after checking the block

and heads he proceeded. Nailhead worked fine until about 6 years ago I got a very mild vibration but progressively got worse.  

Vibration was almost non-existent when starting from cold. But after 60 to 90 secs it would appear.

 

Here is the story:

  • Rebalanced the drive shaft, new carrier bering and joints. No Change
  • Disconnected Trans from Motor. No Change
  • New Engine mounts: No Change
  • Replaced entire ignition system. No Change
  • Swapped over to a known good carburettor: No Change
  • Removed all belts. No change.
  • Pulled and inspected Harm Balancer. No Change.

 

Now we had to go inside the nailhead. (motor only did 40K miles from rebuild)

Full rebuild -New Pistons, Rings... but nothing seen to suggestion vibration issue.

Everything was double checked and balanced.

Motor back in Riv and still the vibration was there just like before !!!

 

The engine builder (old school) told me that there is nothing wrong with the engine but the owner of the firm

said that he stands by his customers and pulled the engine again and it was all good!

 

Now the engine builder remembered a job (many years ago) where the intake manifold was producing a rough idle and thorough the revs.

 

He pulled the intake manifold and blocked the holes for the exhaust cross-over passages that heat the carby.

Result - VIBRATION GONE.

Somehow exhaust gases where getting into the intake path.

 

Yes I know you all think I am crazy. I still can't believe this story myself, everything stated here is true.

Photos of the engine builder and the plates that block the exhaust gases.

Love to see any comments about my vibration nightmare.

 

Tom Kunek

 

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Hi Tom, 

thanks for the information, I’ve read your post earlier and i’m amazed like others are too, that you found this and corrected this vibration issue. My car is all stock 425 engine and transmission. I’m waiting for a dry day to get my car to my mechanics shop so I can inspect the flywheel and harmonic balancer. Your fix is going to be next one I try if these others check out fine. 

My vibration has become very frustrating to me and always on my mind trying to figure out something else to try. It really wasn’t that bad prior to that and it was just one of those things I’d get around to whenever I had time. 

 I hope to solve this mystery soon, 

any thoughts is appreciated. 

 

Thanks, Joe Camisa 

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Read a little about plugging those ports.  There are two ways of doing it.  In the head, as shown, or at the ports in the intake manifold right where the carb bolts to the manifold.  Research the advantages/disadvantages of each.

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Good point Ed, I’m not sure exactly where to look but I’ll search for it. Maybe I should block both of them?

 

Thanks Joe 

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   Let me make a note to EVERYONE, DO NOT BLOCK THE EXHAUST using block off plates, freeze plugs or ANYTHING else resulting in blocking the exhaust in the manifold.  Reason being is we need the heat in the manifold to help flash the cat pee we run for gasoline today.  It will leave the manifold TOO COLD & you will most likely have a hesitation problem you can't figure out.  You get your carb. rebuilt many times & have the same situation.  More $$$$ wasted & all the frustrations it manifests.

   The better, more proper way to do this is block the passages in the manifold where the exhaust circulates under the carb.  IF you have any cold running problems it will only last, at most, the 1st. couple minutes of running.

   Now you don't have to use the metal plate between the manifold or car.  ANOTHER MAJOR PROBLEM is the wrong carb. gasket.  Most repair shops or parts places don't have the proper numbers.

   Hope this helps some of you.

 

Tom T.

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One thing I forgot to mention is that when my nailhead was rebuilt 30 years ago the passage was blocked under the Carb.

Vibration stop when the inlet was blocked at the heads.

Again I know that my story is way out in left field but my nailhead stopped vibrating only after being blocked off at the heads.

So somewhere deep in the inlet there must be a passage letting small amount exhaust gases into the manifold.

Can't see any other explanation.

Now my nailhead runs nice and sweet.

Tom K

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So far (there is always tomorrow ;) ), absolutely the DUMBEST trick I have ever pulled in 59 years of working on my own cars was blocking the exhaust crossover on a Pontiac V-8!

 

The ONLY way to get it to run in city traffic without stalling at EVERY stop sign/stop light was to install a carburetor with a manual choke! And mine has a 4-speed stick transmission. I cannot imagine how bad it would be with an automatic. After 30 minutes or so, everything is fine, and it will idle perfectly without choke.

 

Would not consider doing this again on a street engine.

 

But the above is my opinion, others may differ.

 

Jon.

Edited by carbking (see edit history)

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Thanks for your input Tom T, Tom K, Jon 

 

I did change the carb last year with a matching carb and no difference was felt either way, I had no idea then about exhaust ports and vibrations going hand in hand sort of...

 

I’ll mention this to my mechanic friend helping me with this issue that we’re both looking for advice which is very much appreciated. 

 

Thanks guys!

Joe Camisa 

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You could probably give your engine a trial run by putting the stainless "gasket" directly on the manifold, and put an square bore gasket that does not have the horseshoe cutout in it under the carb.  That would temporarily block the exhaust gasses and you could check the driveability.   No change?  Go back to the correct gaskets and stacking and look elsewhere for your problem. 

 

Maybe the base of your carb is corroded and you have internal gas an/or vacuum leaks. 

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Thanks for your input Tom T, Tom K, Jon 

 

I did change the carb last year with a matching carb and no difference was felt either way, I had no idea then about exhaust ports and vibrations going hand in hand sort of...

 

I’ll mention this to my mechanic friend helping me with this issue that we’re both looking for advice which is very much appreciated. 

 

Thanks guys!

Joe Camisa 

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Sorry I sent the last post again 

 

Thanks a good idea Ed, I’ll try that. The carb was brand new last year so it wouldn’t be corroded. 

 

Thanks Joe

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    In that case I would almost guarantee one intake manifold gasket, OR both, were put on incorrectly causing a vacuum leak.  I've seen this MANY times.   

    IF you or someone was not aware that the gasket could be put on wrong then it's a very good possibility they were installed incorrectly & the reason it took care of the vibration because it had a vacuum leak...

 

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Ummmm.  I'm a little foggy on this right/wrong thing, but end up wrong a lot of the time.

 

Tom- can you be more descriptive of how the gaskets can be installed incorrectly?   Knowing that, I assume the correct way is simply not the wrong way as there are only two choices.

 

 

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21 minutes ago, Zimm63 said:

Ummmm.  I'm a little foggy on this right/wrong thing, but end up wrong a lot of the time.

 

Tom- can you be more descriptive of how the gaskets can be installed incorrectly?   Knowing that, I assume the correct way is simply not the wrong way as there are only two choices.

 

 

  When the intake gaskets are installed correctly the gasket completely surrounds the ports into the head . If you flip the gasket the voids/holes in the gasket will not align correctly with the ports. This can be inspected without removing the manifold, it can be seen by overhead inspection. I have seen this quite a few times also but when done it is pretty obvious in the way the engine responds.

Tom M

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Hey guys 

I’ll look at the intake gaskets too. I’m just heading out with my car to my mechanics shop now and taking tomorrow off work to try to get to the bottom of this BS

 

thanks, Joe Camisa 

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Hey guys 

I just checked the flywheel and it looks to be in the correct location. I can see the alignment hole with the help of a small mirror and a light after pushing back the torque converter, thanks Tom for your instructions on that. The harmonic balancer looks ok too but I’m going to remove the fan belts tomorrow for a closer look.

 

Exhaust passages??? 

 

I was was hoping it would be one or the other so I can put this problem to rest.

 

Thanks, Joe Camisa 

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Hi guys, 

I took the day off to do more investigating on my car for this vibration problem. I confirmed the flywheel is in the correct position and the harmonic balancer is in good shape too. I ran the engine at various rpm’s to feel for vibration. Nothing really was present other than the running of a big V8. So I removed the rear axles and differential and took them to a rear end shop who “said these are fine, nothing wrong with them”. I put everything back together but was not able to road test because of weather. I’m going to try the plate under the carb to block off exhaust gases that was suggested earlier. This weekend I’ll take my drive shaft to another shop out of town for another opinion as this vibration was not as prominent prior to removing and rebuilding my driveshaft. 

 

Any thoughts or comments are appreciated. 

 

Thanks Joe Camisa 

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