What is the proper engine vacuum

PAUL KRAUSE2

MEMBER
1997 DODGE RAM
5.2L
V8
2WD
AUTOMATIC
2,000 MILES

Well since my cousin (mechanic) had ne replace lifters, push rod and rocker arms I did replace intake gaskets. Something else I would like to add is the vacuum. I capped all the outlets off and was only getting 16 inches of vacuum. On an old engine 17 is acceptable should be closer to 22 on a rebuilt engine. Is this correct or am I wrong. Thanks Thomas

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1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

That is generally correct. However, there is no set number that the engine must produce because each engine is going to be slightly different. Therefore, there is no published spec for vacuum reading.

We need to determine more based on what it is doing. If the engine does not have enough vacuum, then it will not run.

So, if the engine is running, then we need to know how it is running. If it is running lean, then you need to run through this check to find the leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

As the engine/intake valves wear, they will not seal as well and can cause lower vacuum readings, but this will result in lower power and unstable idle. You can hook a vacuum gauge to it and that will tell you if there is an intake valve issue if you find no other source of the leak.

Take a look at the chart below and that will help with determining if there is an issue with the vacuum on the engine.

Let me know what you find with this.

Thanks

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