Editing Finding vacuum leaks

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There are several methods for locating vacuum leaks. Occasionally, you may experience a vacuum leak into the intake ports from the crankcase of the motor due to the intake manifold / cylinder head interface not being machined parallel. No amount of propane or carburetor cleaner will find such a leak. The best way is to insure the elimination of such a problem while building the engine. See the wiki article: [[Manifold/Head vacuum leak, internal]].

=Propane method=

#Get a soldering propane tank and valve attachment.
#Unscrew the end of it so you have a threaded pipe without the nozzle.
#Attach a 2 foot piece of hose to the end.
#Start the engine and let it warm up a bit.
#Turn on the propane and run the hose all around the vacuum lines and the bottom of the carb.
#If the engine smooths out or revs up a bit, you have found your leak.

Hold bottle UPRIGHT during testing as liquid propane may run out of an inverted bottle.

PLEASE do this in a well ventilated area due to propane gas and exhaust fumes!!

Fixing a leak.  My old neighbor built circle track cars and after the ran the engine  he would shut it off...tape off every opening with duct tape then put a hose over the dip stick and hook up to a vacuum source.  He would then get his stethascope and listen in the area where the propane or carb fluid indicated a leak.  he used Rtv and calked into the area until the stethascope whistle stopped. too much vacuum will pull too much calk into the hole.

=Carburetor cleaner method=
#With the car running, using a can of carburetor cleaner spray down the hoses and vacuum connections.
#Notice a change in the running of the engine and you might have found your leak.

NOTE: I would use Engine Start-Up Fluid instead.  It is basically ether I believe and it is not caustic like Carb Cleaner is.  In other words the Carb Cleaner can strip painted parts.  I would not spray carb cleaner all over my engine, it is clean and painted just the way I like it and ether does not leave residue.

[[Category:Engine]]