I have a 64 Deville Convertible, keep running into the same problem - vapor lock on hot days. So far I have rebuilt the carburetor , new gas tank , but when it sits in traffic on a hot day it will vapor lock .  It will take about 30 minutes for it to cool down, then starts up and runs again.  My Son said dont drive it on a hot day , think that is ridiculous.

Has anyone else run into this issue?  And does anyone know of any solutions or suggestions? 

Appreciate it 

Rick McBurney

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Not sure where the intake can and might crack myself 

When you tighten down the bolts work from the center bolts to both ends of the intake 

Make all bolts just  snug first then going around and around tightening them down a little at a time until you are ready to use a torque wrench for the last turns on the bolts to seat the manifold —evenly 

Not at all sure about using the brake cleaner spray —-as I always use water which I know is not a problem to be running thru an engine and does not stall the engine just changes its sound 

Water  will remove carbon deposits in an  engine so it is ok to be using 

Best I can do regarding installation advice 

As you have had a problem with one side of the manifold or the other not seating correctly - could you have the wrong intake manifold on your year engine ? 

There are two different 390 engines 

The 62 and 63 are different engine designs but not sure if the intake is the same one 

I only ask that - as these car engines have often gone thru  a number of parts changes thru the years in many cases with hobby mechanics who do the best they can to get the correct replacement part 

Just a long shot thought —that comes to mind under the circumstances you have described with one side not seating correctly —twice 


Found receipts and history what I did 8 years ago when I installed the 1406 to keep heat from carburetor and fuel.

Tried different spacers like Mr Gasket 6006, Edelbrock 8711. 
Either they didn't fit perfect or it was still hard to start the engine when it already ran hot before.

Best solution I found was insulator 8723 from Edelbrock. 
No stall anymore, only takes a little time (some seconds) to get it started when engine is hot.
But beside that no issues.

With the correct insulations for this spacer (I can't find the number anymore for the insulations) I did not need to fill the holes in the original intake manifold. 
And I didn't use original spacer at all, PCV directly into carburetor.

The small tube going into the original choke I just plugged with a carb grommet and used the 
electric choke from Edelbrock. 

And height is still ok with original air filter housing, too.
Just to keep it as original as possible.

Maybe this helps a little.

Thank you Sammy 

Your  spark plugs and  some cylinders ( closest to the air leak )  SB burning lean ( and hot ) if you have an air leak ( vacuum leak )  from outside air into  the intake manifold anyplace 

Plugs will have a whiteish color - S B  the color of brown paper bag when correct 

Use a spray bottle with water and spray all the intake seems  and the carb base 

You will hear the engine change its sound when you find the air leak spot for a moment


i don't know about an electric or manual choke conversion...

the car was running fine before i had this vacuum leak on the intake manifold.

is someone using the FelPro metal gasket with success?

Thats all I have been using,

just removed the intake manifold.

i can't see a crack from the undersite where it sucked air, but on all 4 intake ports on the passenger side you can see that the gasket is wet and did not stick on the lower part of the ports.

i was using the Best Gasket, will give the FelPro a try now.

would you use Gasket sealer around the ports?


Looks like you found your problem with the intake manifold vac air leak — wonderful !

The new gaskets SB just fine without additional sealant 

I only use it to be holding a gasket in place when needed as it makes for easy removal if needed in the future 

Russ’s expertise and advice on this site  is about as good it gets about our year Cadillacs 


Spray your intake manifold seams and the carb to intake seams with a spray bottle of water to find the location of your air leak 

The sound of the engine will change— when you spray water on the air leak location- at an idle  

Knowing the location of the intake air leak— should help to focus on that location to correct and seal it 




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