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Vacuum Leak Tools

DC67

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Just posting these vacuum testing tools (no affiliation) and photos in the case anyone is chasing down a vacuum leak.

To plug the intake manifold I used these silicone plugs intended for masking parts being powder coated. The ones I bought were too small, so I had to use them upside-down and be carefull they didn't drop into the manifold. They created a very good seal but I would recommend the larger size:
The photo below shows how to use the plugs on a 4-port intake to create a seal for smoke testing and how the adapter is used to test both sides of a dual plane intake manifold. I'm sure any such machine or rubber plugs (even a bathtub stoppers) would work.

In the case you have a different manifold setup, you could de-grease and use duct tape over the carburetor opening or use an 'Intake Manifold' plate like this sold on ebay: MOPAR DODGE PLYMOUTH 340/383/440/426 HEMI INTAKE MANIFOLD COVER BLACK | eBay

I realize there are other ways of checking for leaks, using soapy water or spraying carb cleaner while running the engine etc., but those methods are limited in scope. Using the smoke machine, I was able to detect a very small leak from my oil pressure sending unit and rule out leaks from hard to get to areas; like below the intake manifold, the crank shaft seals, oil pan etc.

There are other areas one needs to plug on an old engine, like the valve cover breather cap or oil dipstick, etc. can also be done with silicone plugs of various sizes. When I tried to use duct tape, it was never a perfect seal and smoke always got out.

In any case, just posting this as an idea generator for anyone doing vacuum leak diagnostics since my searching didn't yield too much. One can test virtually any system that could leak with this tool but below is my setup testing the intake manifold since it seems to be common part checked on this forum.

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Best way to run the test is with valve covers off and the rocker shaft bolts loosened so all valves are closed (sealed) - I did this while running my leak-down test.

Not loosening rocker shafts should also buildup enough pressure and worth a quick try just check for anything that does show up.
 
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Sorry to tell you this but that test will not work. All the intake valves would have to be closed.
 
Never seen anything quite like that before. I take it your exhaust must be in perfect shape and you plug up the tailpipe (s), as well?? How is there not always a giant loss thru one valve or other since there are always some open, correct??

TIA, Lefty71
 
Well this post was just intended to showcase the tools and alternative application of those silicone plugs to seal a 4 port manifold - not the full procedure involving sealing the intake valves by loosening the rocker shafts - i’ve edited for clarification.

However, conversationally: any leakage through open intake valves would stop in the cylinder chambers, and any leaks from there would be very minimal past the rings or any exhaust valve slightly open at ‘valve overlap’ and still allow for sufficient pressure buildup in the intake manifold chambers to test for leaks
 
Well this post was just intended to showcase the tools and alternative application of those silicone plugs to seal a 4 port manifold - not the full procedure involving sealing the intake valves by loosening the rocker shafts - i’ve edited for clarification.

However, conversationally: any leakage through open intake valves would stop in the cylinder chambers, and any leaks from there would be very minimal past the rings or any exhaust valve slightly open at ‘valve overlap’ and still allow for sufficient pressure buildup in the intake manifold chambers to test for leaks
You get an A for effort. However there is no way this test will work on a rotating engine. The smoke will take the least path of resistance. With the intake being an open plenum there are two many valves open. The smoke is going to take the easiest way out the exhaust. No matter where the engine is rotated to there will be to many easy paths for the smoke to take. For the test to even remotely work ALL INTAKE valves need to be closed.
 
So did it work for you?
what did it help you find?
 
You get an A for effort. However there is no way this test will work on a rotating engine. The smoke will take the least path of resistance. With the intake being an open plenum there are two many valves open. The smoke is going to take the easiest way out the exhaust. No matter where the engine is rotated to there will be to many easy paths for the smoke to take. For the test to even remotely work ALL INTAKE valves need to be closed.
Correct, I ran the test with all valves closed (see edit)

But pressure loss from valve overlap here and there must have minimal impact (since the tool keeps building pressure). When done with valves open it worked on my dual plane stock manifold. It built enough pressure to almost pop out the silicone plugs.

However, I agree this ‘intake leak’ test is best run (without short-cuts) buy loosening the valve shafts and closing all the intake valves.

Going back to original intent: this the ‘ Garage, Shop and Tools’ section, i’m endorsing a set of tools I like - not going over all the procedures on how to use them.
 
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