73 eldorado 501...should i or not hook this up?

[Terry Cox #26379]

hi men, on going over my 73 eldorado some time ago sorting things out for future "when i get around to it's"....one thing on my list to conquer / determine is whether or not to re-hook up the "therm-vacuum switch" (that's what i think it's called without going to look it up)..that is on front of the intake manifold on my car.
currently there are no vacuum lines hooked to it and there are no vacuum caps plugging the ports on it either.
i think this switch has markings on it as follows; carb. / manifold / and on other thing.
what is the reason for this and is it needed today for the car to run properly? i am a stickler for correctness and this being unhooked is bothersome.
can anyone shedd some light on this subject ? i see plenty of cars with it unhooked !  thanks alot, terry   

[Dave Shepherd]

Controlled timing ( vacuum adv. ) till the engine warmed.  No vacuum comes thru the switch till about 120-140, you could run the vacuum right to the dist, you may have to bump the timing back some if you do this.  Strictly an emissions issue.

["Cadillac Kid" Greg Surfas 15364]

Terry,
On your car the thermal switch has vacuum lines to the timed vacuum port and the manifold vacuum port on the carburetor, as well as one line to the distributor.  When the engine is below 220 degrees (approx), the vacuum to the distributor is via the timed vacuum port of the carb.  When the car experiences an overheating situation, such as hot day, heavy traffic and the water temperature warms up 220 (+) the vacuum to the distributor is from the manifold connection on the carb, allowing full vacuum advance which is intended to help the motor run cooler under these conditions.
I for one, have never been able to see any difference in either performance or fuel consumption between running the vacuum lines as designed or running directly from the manifold vacuum port, so on my stock engines where this feature is involved, the thermal valve and the stock vacuum line routing remain as designed.
Greg Surfas

[TJ Hopland]

I have never seen one that worked properly.   If they are not bypassed when I get them I usually end up bypassing them.

I have always liked running distributors direct off manifold vac.

[Terry Cox #26379]

thanks men for the imput. i think i will leave it alone for the time being, if it bothers me next time i'm under the air clnr. i will reconsider then. but for now it runs like a scalded - - - ape since i tuned it up in the fall.
but, as one knows with older automobile's ...sometime's they require work on them. (which i look at as a "i get to" instead of have to..i'm just slower now. )
i guess the ethonal in the fuel has worked it's terror on my accelerator pump. it's seeping out on top of my once was...spotless carburetor. but...oh well. i guess i knew it was coming. 59k and 38 years...& original. not too bad i guess. while i'm at it i will replace all the tank to frame and frame to  fuel pump hoses with the new type of fuel injection hose. BOY.i..t that stuff expensive !
any recommendations on where / what brand of carb. kit and fuel injection hose to buy? thanks, men,,,terry

[TJ Hopland]

I have not had issues with Gates hoses.  Dont see any need to go with the FI hose, the standard stuff is just as 'resistant' to ethanol as the FI stuff is.    Luckily you can get the rear lines without having to drop the tank.   IIRC its a 1/4, 5/16, and 3/8.

I have also not had any issues with the carb kit line that Napa sells, Echlin?   The float is not part of the kits so if you need one you have to order it.

[Terry Cox #26379]

thanks...i will go with the kit from napa...and probably a new float while at it.   i'll go for the gates hose and skip the f.i. type...that stuff is outrageously expensive ! ouch ! terry

[TJ Hopland]

I believe the standard gates hose is rated for 30psi which is well above the 4psi a carb system runs at.   Im even using the regular stuff on my TBI system that runs at 13 psi.  On that system I am using what they call EFI clamps that are supposed to hold better than the typical screw type.   IF you want stuff that seems to last forever get marine rated hose.  The wall thickness is at least 2x what auto stuff is and usually the price is much higher also.   I use the marine stuff when I need to do a tight bend, it tends to resist kinking.

You should have the option of either a brass or one of the plastic floats.  The newer plastic ones are fine with ethanol.    When you install and check the level of the new float be sure to also have that black retainer thing installed and hold it in its proper position.  On some floats the arms of the float hit that black plug thing before the needle seats.  You can first test and set the float level without the plug then install the plug and verify that its not hitting the plug.    I use a file or dremel type tool to add a little clearance on the plug if needed.