Randalll

1963 Buick Riviera 401 Carburator vacuum port

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Hey Guy's

 

   I have a question that most may think is stupid but please help if you can and I apologize in advance. I have attached a picture of a carb thats just like the one on m y 63 Riv. What is the port that I have circled do? I have read a few post that say not to plug it but I wanted a second opinion and some understanding as to what it does and why or why not I should plug it. Again thank you in advance for all your help. 

 

 Randall5a9ccd0df3a66_InkedRivieraCarbvacuumport_LI.thumb.jpg.bace6b5623886f456c2ccd29e0c2ccc0.jpg 

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Hi Randall,

  That nipple is for a filtered air source for the hot air choke system. A rubber to metal line originates at the nipple and runs to the bottom of the exhaust manifold, thru the manifold and back up to the choke housing. Hope this helps,

  Tom Mooney

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Thanks Tom, I really appreciate the help. The reason I am asking is that after about 20 mins of driving my 63 Riv starts cutting out at low speeds like driving around town, almost or exactly like its vapor locking. I was wondering if that port NOT being hooked up to my exhaust manifold could be causing this. Thanks again!

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As Tom mentioned, this tube was to allow FILTERED air to be used for the heat to the choke.

 

The automatic choke housing is connected to an internal vacuum source (you can follow the passageways if the carb is apart), and if the tube is not attached, then unfiltered air would enter the carburetor through the automatic choke. This should not impact the way the engine is running, assuming that the choke is functioning normally.

 

To check, allow the engine to warm to full operating temperature, shut off the engine, remove the air cleaner, and observe the geometry of the choke butterfly (flapper). It should be completely vertical. If not, troubleshoot the choke. If so, you have other problems.

 

Cutting out at low speeds when hot COULD be fuel related; and it could just as easily be ignition related, especially if an electronics conversion had been done. Electronics don't like heat (well, neither do I, for that matter ;) )

 

Jon.

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Thank you Sir. I will keep you posted. There have been no electronic conversions on this car, however I am considering HEI Ignition. Any opinion's?

 

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OK Randall: Ya gotta diagnose your issue.  Fuel? Easy to Drop the tank and remove caca. On a 1963 car this would not be a "scientific diagnosis"  but a routine precaution. Then you can blow the lines out with air and isolate each part of the fuel system to make sure things are workin' and flowin'.  Next, the electrical.  Again, isolate each component and check for operation. 

 

I did have a 64 Riv that was cutting out going up a hill. I did the entire fuel system, which i figured I'd have to do anyway due to the fact that it was a 64 and in a long hibernation.  Everything functioned as it was supposed to.  After checking the electrical system I found everything was also operational.  Still cuttin' out. The problem?  The wire from the horn relay (the junction box where the battery cable connects) to the starter was arcing against the exhaust manifold. Sometimes it's easy.

Sometimes it ain't that easy.   Mitch

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Ok, so a family friend and mechanic told me that its a vacuum leak and its probably coming from under the intake manifold, that there is a "freeze plug" on the bottom of the intake that will rust out and cause a vacuum leak. Has anyone heard of this?

 

Edited by Randalll (see edit history)

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Very common problem. It will also make exhaust noise if rotted out as exhaust heats the intake. Also VERY COMMON is the steel gasket under the carb. is missing causing exhaust into the intake.

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Forgot to also mention. IF the heat riser valve on the right outlet of the exhaust manifold is stuck closed it will OVERHEAT the intake & cause the fuel to boil in the carb. which could also be a problem.

 

 

Tom T.

 

 

 

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3 hours ago, Randalll said:

Ok, so a family friend and mechanic told me that its a vacuum leak and its probably coming from under the intake manifold, that there is a "freeze plug" on the bottom of the intake that will rust out and cause a vacuum leak. Has anyone heard of this?

 

It is common for this freeze plug to rot. However, the plug is in the exhaust crossover passage and should not cause a vacuum leak, only exhaust leak/noise.

  Tom 

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Problem solved! I pulled the intake manifold and replaced the exhaust crossover plug and car is running great again.  Next issue: I seem to still have an issue with the power brake booster, I thought that replacing the crossover plug was causing the loss in vacuum to the booster, but as Tom said, it's not a vacuum problem its an exhaust leak. So why is my pedal still hard as a rock and hard to stop. These issue's seemed to have happened at the same time. Could my booster have failed coincidentally at the same time? And thank you all for your help!

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Ok so I thought it was problem solved, however it's not. It's doing the same thjing it did before replacing the exhaust crossover plug (which had completly blown out) on the bottom of the intake manifold. So you would think that would at least help but no it doesn't. It runs fine in park, revs nice, no sign of hesitation  whatsoever. Then the minute you put it in gear and drive away it falls on it's face, spudering.  If it is a long road I can feather my way through it and once I get up to 35 40mph its fine and runs good. Also this and loss of power brakes happened at the same time. Any help is very much appreciated. Thank you. 

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Just now, Randalll said:

There is no steel plate under carb.  Never has been. 

Then perhaps the absence of the steel plate has let the exhaust gasses, that are used to warm the carburetor, corrode the base of the carburetor to the point where the carb won't seal against the intake manifold. Exhaust gasses and cast aluminum are not compatible.

 

There WAS a stainless plate between the carburetor and the fiber gasket when the engine was installed at the factory. Why there is not one there now is anyone's guess.

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I see. Thank you for the information. Just had carb rebuilt. Used the fiber gasket. Do you know where a man could find such plate? Could the motor run fine in park but not in drive because of this plate? Would it also cause the power brakes to go out? Sorry I know its a lot of questions, I just don't want to keep throwing money at it to see what sticks. I have replaced the points, condenser, rotor, cap, and plugs. 

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The Carter part number for the stainless steel baffle plate that should be located between the carburetor and the intake manifold is 186-106. I don't have a Buick Master Parts Manual, so cannot cross this to a Buick part number.

 

Lets think about your issue:

 

You posted the issue occurs after maybe 20 minutes, so it sounds heat related.

 

If the only issue were a vacuum leak, it would occur as soon as the auto choke came off (vertical position).

 

So, start with acquiring the stainless steel plate (it keeps raw exhaust from contacting the carburetor).

 

If the plate does not solve the issue, next would be to test the automatic choke for function. (Remember, you may have multiple problems).

 

After either confirming that the choke is functioning correctly (or repairing if not functioning correctly), the next step would be a test of the ignition system.

 

DON'T JUST GUESS THE COIL IS BAD. Ignition systems can be tested! Replacing a good coil (or any other component) with a new component MAY put a worse component in the system (I am not in love with modern off-shore parts); and at best is going to lighten your wallet.

 

The power brake problem MAY be part of the running problem, or it MAY be a separate issue.

 

Jon.

Edited by carbking (see edit history)
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Quick question guy's,

 

   I have two ground straps coming off the firewall. The one on the passenger side goes to either  the exhaust manifold or engine head(Can't remember), and the one on the drivers side firewall is not connected to anything. Where does it attach? the engine or chassis? Would that cause a short? Also these are very thin/small ground straps, so my question is are there only two small ground straps for the entire car besides the battery cable (which is actually attached to the power steering bracket, not sure if that's right either)? And finally would it just be smarter to run a new ground strap from the negative battery post to the body so I know it's grounded?  I still can't get this car to run well, in fact the problem is getting worse and I can't tell if it's Fuel, Vacuum, or Electrical that's causing this. As always, thank you in advance. 

Edited by Randalll (see edit history)

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