Engine Idle And Vacuum

[RangerJoe]

I posted a thread earlier concerning the lack of vacuum with my new FTI cam. Here is a little video with the vacuum gauge attached. Looks like I have abut 7 inches of vacuum at idle, but the needle does jump around some.

Does the needle look like it is suffering from a vacuum leak, or is that normal with hard hitting cam? BTW, idle is about 800 rpm.

Joe


View: http://m.youtube.com/watch?v=HjnKehVm7_k

 

[7991LXnSHO]

What is the loud whistle? The IAB and an aftermarket throttle body?

The sound and needle look about the same for a nasty cam to me. I bet your power brakes are weak.

 

[RangerJoe]

The loud whistle is a combination of the bbk TB, but I believe mostly the electric fans. I realized they were running after I took the video and they are a little more pronounced sounding in the video. The engine doesn't seem that loud in person.

Yes, power brakes are hit or miss depending on what the engine is doing. Do you think the needle jumping around is normal for a big cam.

Joe

 

[Micheal Nadeau]

How much lift @ .050? My F303 is 226 and pulls about 11 or 12 inches of vacuum. The bigger the cam, the lower the vacuum. Some big cams require you to run a vacuum pump. I also have that same whistle sound.

 

[RangerJoe]

I don't know what the loft is at 0.05, but max lift is .613/.588. I understand the n lack of vacuum and why, I am just more or n leas concerned with fhe needle jumping around. Is that normal with a big cam? I know on a normal car, the needle jumping can signify a vacuum leak.

Joe

 

[RangerJoe]

Well, low and behold....the mysterious vacuum leak was found. It now idles with 12" of vacuum, has power brakes again, and the needle is much more stable.

Joe

 

[mikestang63]

where was the leak?

 

[RangerJoe]

The pcv valve was popped out. My wiring harness is dropped down behind the engine and it makes it difficult to see behind the intake. I had run my hand along the vaccum line and felt it connected to the pcv, but didn't realize it wasn't seated. It took an experienced mechanic 2 seconds to recognize that little sound over everything else going on under the hood. Someone else pointed out a whistling noise in my video, but i attributed it to the TB and electric fans. Simple fix, I was just a little blind to it.

Joe

 

[jrichker]

The pcv valve was popped out. My wiring harness is dropped down behind the engine and it makes it difficult to see behind the intake. I had run my hand along the vaccum line and felt it connected to the pcv, but didn't realize it wasn't seated. It took an experienced mechanic 2 seconds to recognize that little sound over everything else going on under the hood. Someone else pointed out a whistling noise in my video, but i attributed it to the TB and electric fans. Simple fix, I was just a little blind to it.

Joe

That little bugger is hard to see and easy to dislodge just enough to cause problems. Glad you got it fixed.