vacum

[Steves LX]

What kinda vacum readings at a warm idle should I be getting? MY motor is a 306, TFS stage 1 cam, TFS streetheat intake, GT40 Y heads.

[kennebellcobra]

I would think around 12

[Steves LX]

Just as my luck goes. I must have a vacum leak somewhere then. I am only getting around 7-8 in. Car is running very very rough at cruisind speed and very slow throttle response. The exhaust tone is real muffled stopped up sounding. At times it sounds like a huey chopper when at low RPMS. I have pretty much ruled out plugs and wires, cap and rotor, 6AL box, coil. If its vacum I would love to know where. I sprayed all around the intake and my vacum lines the best I could and the idle never changed, stayed the same.

[fst 5pto]

You have lines that run to the passenger side into your vacuum box, make sure all that is good. Also there are lines on the back of the intake as well.

[Steves LX]

Yeah I checked those as well last night. I talked to MSD and they were feeding me all kinds of BS saying that if I didn't have my 6AL hooked up directly to the battery it will do what the car is doing. I told the guy wrong answer Jack I pulled your box out of line and it still does it. I do know this though. It's not O2 sensors. I disconnected those and the problem actually was worse so I hooked them back up. It seems like I can't win for loseing.

[kennebellcobra]

If it's idling low it will show low vaccume also if you have leaking valves or rings that will also do it...it's not always a vaccume leak.

[nskaats]

If it's idling low it will show low vaccume also if you have leaking valves or rings that will also do it...it's not always a vaccume leak.

Yep, what he said. A compression or leak down test would help you out.

[fst 5pto]

I don't think that's his issue. I know for sure the block is fine and his heads/valves were fine before he took the engine out....

[PHAT69AMX]

Ignition timing and intial advance at idle can have a big effect on idle vacuum.
But my experience with F.I., ECU's, and Spark Advance Curve control maps is nill.

[Steves LX]

Leakdown and compression test are all excellent. What's going on really doesn't screw with my idol at all. It is sitting 900 RPM's and TPS voltage at
.98vdc. Man I hope its not a internal intake leak down at the lifter valley.

[nskaats]

Yeah, if leakdown and compression are ok and your vacuum hoses check out ok I'd start checking the manifold. These are always fun to track down when it's something hidden.