Engine Vacuum Ports

[Aar1064]

I'm wanting to check for vacuum leaks on my 340 six pack engine using a smoke machine. What ports need to be plugged other than:
1-manifold port
2-vacuum advance port on center carb
3-PCV port on center carb?

Thanks for the help.

[71-440]

I'm no mechanic but why plug the ports? Wouldn't that defeat the purpose? My thought would be to run your smoke with the engine running and all your vac lines working. Any leaks
would pull the smoke in.
I may be wrong here but I am sure someone will correct me if so.

[Cuda Cody]

What is making you think you have a vacuum leak?  What is the vacuum pressure at idle and does it move at all?  What cam are you using?

[Chryco Psycho]

  plugging ports defeats the purpose , you want it running as is .

[Topcat]

A vacuum gauge can tell you alot.

[JonH]

Not a mechanic either but, when you do a smoke test, don't you introduce smoke into a system under slight pressure and watch where it escapes from? Had it done on my Ram fuel system to find a vapor leak. Option to original poster is to use an unlit propane torch around suspected vacuum leaks, with engine running. If engine speeds up, (sucking in propane) you have found your leak.

[Aar1064]

I needed to check for leaks and it turns out it was center carb base. It was slightly warped. I fixed it by disassembling, then sanding it down using a 1/4 inch thick piece of glass with 80 grit finishing with 320. All is good now.

Smoke machine really is a great tool for checking for vacuum leaks.

[RUNCHARGER]

Glad to hear you found it.

[Aar1064]

I used propane but wasn't sure if engine fan was blowing the gas away so I went to carb cleaner and found leak around intake ports.

After this was resolved I wanted to try to use smoke to check for others and this is when I saw issue with base plate.

[Topcat]

I used propane before.

The Benzomatic 2 can system with a pencil tip torch worked great on finding vacuum leaks.

https://www.bernzomatic.com/Products/Hand-Torches/Manual-Ignition/WK5500OX

The smoke method is a new one to me.

I haven't seen that done before. Thanks.

[Aar1064]

It was -5  . Now it's a solid -15.

[fc7cuda]

It was -5  . Now it's a solid -15.

Yeah, that would be a problem leak, nice feeling to find and fix it. 

[Timbbuc2]

I used propane but wasn't sure if engine fan was blowing the gas away so I went to carb cleaner and found leak around intake ports.

After this was resolved I wanted to try to use smoke to check for others and this is when I saw issue with base plate.

Carb cleaner works very good.

[GoodysGotaCuda]

I'm a fan of smoke. I'll keep any harsh chemicals I can away from my engine paint. Some brake clean can really fade and/or lift even the heartiest of paints.

I made a smoke machine out of a paint can, baby oil, a glow plug and some fittings. Works very well.

https://photos.app.goo.gl/CRCgqDkZj9XEm90N2


Sent from my iPhone using Tapatalk

[Aar1064]

Thanks for posting the gauge video. In the beginning of this issue I didn't realize vacuum gauges could help with issues like this.