How much vacuum is normal?
Thread Starter
Advanced
Joined: Jul 2004
Posts: 98
Likes: 1
From: Maple Grove Minnesota
How much vacuum is normal?
I've never had a forced induction car before this one, and I'm surprised how much vacuum it pulls just driving around town. My ATI Procharger is only set up for 8 lbs., but I'm curious how much vacuum you guys are pulling just driving around - and how much more vacuum do you pull on sudden deceleration?
Thread Starter
Advanced
Joined: Jul 2004
Posts: 98
Likes: 1
From: Maple Grove Minnesota
yeah, ok, mine stays around 15 (I think it's actually in mm of mercury) when I'm just cruising, and dips down to 20 when I suddenly let off the gas. Seemed like a lot to me, but sounds normal compared to you. Thanks.
Safety Car
Joined: Apr 2001
Posts: 3,525
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From: Houston TX
I see 17-19" Hg when cruising and will dip to the 24-25" Hg when quickly decelerating. I am running a 246/254 SR Comp Cam. It will actually get good mileage if you keep your foot out of it.
Aaron
Aaron
Burning Brakes
Joined: Jul 2003
Posts: 904
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From: Santa Cruz CA
Hmm, low vacuum.
Interesting, my cam is only around 214/218 if I recall correctly and I am only getting 3 to 4 psi of vacuum. The car idles badly. Guess it's time to try checking for vacuum leaks on the SuperRam. I wish there was a way that wasn't hugely messy or expensive. Love the smoke machine one that blows smoke in to show leaks while the engine is off, very cool. Except the cheap one is 1400 bucks. Ouch. The idle jumps around enough as it is that spraying starting fluid would have to cause a huge rpm jump to be noticeable. Not going to use carb cleaner, seen too many fires. Not sure what else would cause really low vacuum. Timing maybe.
EDIT: Ok, went and double checked the engine specs and I have a EM380R cam. Says it's 224/230 at .050. That would still pull a lot more than 3 or 4 pounds of vacuum at idle I am assuming. I had a old 440 mopar that had a 256 at .050 Megacam and it still pulled more than that. Anyone with any experience have an idea? Thanks.
EDIT: Ok, went and double checked the engine specs and I have a EM380R cam. Says it's 224/230 at .050. That would still pull a lot more than 3 or 4 pounds of vacuum at idle I am assuming. I had a old 440 mopar that had a 256 at .050 Megacam and it still pulled more than that. Anyone with any experience have an idea? Thanks.
Last edited by Jaxian; Jun 2, 2006 at 11:03 PM.
