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Mach80 10-08-2015 02:07 PM

540 engine vacuum question
 
I am wondering what others with a mild NA 540 see for vacuum while at idle. I'm seeing 10-11 inches of vacuum. This is low per stock standards but not sure about my engine. 540CI, 9.2-1 Compression, Dart single plane intake with Crane full roller setup. Thanks.

Jonesyfxr 10-08-2015 02:19 PM

I'm no pro, but IIRC your cam will dictate the amount of vacuum an engine will see. Lift, duration, LSA and valve overlap will all play a big part in how much vacuum an engine will produce.

bck 10-08-2015 03:12 PM

I'm pretty sure mine were similar to that. Then they blew up:)

GPM 10-08-2015 03:28 PM

It would help if you posed the cam specs,

SB 10-08-2015 04:34 PM

camshaft specs vs engine cid, ignition timing, intake manifold (dual vs single vs tunnel ram), and idle rpm are your largest contributors to intake vacuum.

Mach80 10-08-2015 07:44 PM


Originally Posted by GPM (Post 4363886)
It would help if you posed the cam specs,

I wish I had the cam specs. Bought the boat from someone that has no idea what they had.

GPM 10-08-2015 08:09 PM

That sucks,

Eliminated572 10-18-2015 07:24 PM

Both my 580 solid rollers fairly heavily cammed are 10" at idle. 260's-270's .700 plus lift.

sutphen 30 10-18-2015 07:28 PM


Originally Posted by SB (Post 4363908)
camshaft specs vs engine cid, ignition timing, intake manifold (dual vs single vs tunnel ram), and idle rpm are your largest contributors to intake vacuum.

and then if your carb/s are out of whack,remember adjusting idle while watching the vacuum gauge for the highest reading.

Mach80 10-18-2015 11:19 PM


Originally Posted by Eliminated572 (Post 4367615)
Both my 580 solid rollers fairly heavily cammed are 10" at idle. 260's-270's .700 plus lift.

Thanks, seems like mine is mostly normal.


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