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Best way to check for vac leaks?
#1
FYI, I am a true novice in the mechanical arena.  My friend with the mechanical expertise helped me replace spark plugs and wires then we rebuilt the carburetor.  Didn't do anything but adjust idle after reinstalling carb.  Car started fine and idled although we didn't run it long. Next day, I took the car about 4 miles to get gas, engine stuttered on drive. Seemed to run better at higher speeds.  Started fine when leaving station then died at light.  I finally got it restarted as light turned green.  Managed to get it back home but it wanted to die at low speed/idle. My friend suggested checking for vacuum leak.  He's in the midst of a job search so I don't want to keep bothering him.  I checked hoses with my eyes and hands, seem tight. Of note, a number of the hoses are plugged/capped off (that's the way she came to me).  I saw on line to check for leaks by spraying carb cleaner while running.  How big of a concern is fire when doing this?  Makes me a little leery to try it.  Also, looking at the carb, it appears wet at the bowl cover gasket. Any thoughts/suggestions?
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#2
If you didn't have this problem before rebuilding the carby then it will most likely be either a vacuum leak in this area or carby related
Firstly you say a fuel leak at the bowl gasket, I would fix this first, either you have a loose screw or a bad or misaligned gasket
If all your vacuum hoses check out then it could be at the carby mounting gasket

You can spray some carby cleaner or aerostart around the carby base and listen for the idle, if no change should be okay, if not then your base gasket could be leaking so just check your nuts are tight but don't over tighten them but you may still have to replace the gasket
Best not to spray close to your distributor/spark plug wires in case of ignition leaks but should be fine - fire extinguisher nearby is handy!
I actually prefer propane gas, less messy

Probably others will chime in and may be best if you let us know what carby/engine you have
I had some idle issues I thought was vacuum leaks but it was more to do with the spacer I was using and needing to open the secondary butterflies up a little due to a long duration cam
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#3
The wet gasket may be a sign of an overfull fuel bowl, which could be flooding the engine, causing the stalling. Potential causes, bad needle valve, piece of debris keeping the float from closing the needle valve, saturated plastic float, or leaking brass float.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#4
Thanks for the advice.  I'll start looking at these possibilities tomorrow.  Need to find my fire extinguisher first!!  Big Grin   My car has a 351C 4 BBL engine (Q code) with a 4 speed manual transmission, Motorcraft D3ZF-LA carburetor. BTW, I was not having this problem before the carb rebuild. Replaced the base plate because the carb was dropped and the throttle shaft got bent and plate cracked.  It was replaced with same model carb base plate.  The carb rebuild kit was a Standard Hygrade #585A.  Also replaced mounting gasket (FelPro/#60179).
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#5
On the chance of fire. I like to keep a 5 gallon bucket of water handy. If you use fire extinguisher it makes a huge mess unless it is a Haylon or CO2.
The Ford carb has two needles and seats for the incoming fuel. Some say that the secondary smaller one should be soldered closed that can cause excess fuel. I am no expert saw it on one of the carburetor rebuild sites.
The gaskets are fragile on the Ford carbs for sure. They do have a special gauge for checking the float level on them but I do not have one. Can check with carb on the car.


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
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#6
I've never had carburetor cleaner catch fire while checking for vacuum leaks. You're not saturating the areas, just misting it onto the potential leakage spots. The cooling fan does a good job of blowing the vapors away.


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#7
(05-22-2019, 11:57 AM)Hemikiller Wrote: I've never had carburetor cleaner catch fire while checking for vacuum leaks. You're not saturating the areas, just misting it onto the potential leakage spots. The cooling fan does a good job of blowing the vapors away.

+1

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


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