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Old 01-31-2006, 06:38 AM
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Vacuum at idle

I have a 454 gen iv which was stock I had 19 in vacuum at idle , I then took it apart and put on a set of 049 heads and the cam with the below specs I now have 13in vacuum it runs well with no problems I can see what vacuum should you get with this cam?

Part# SUM-1301
Intake @ cam 2942 500 Rocker Arm Ratio
Exhaust @ cam 2942 500
Intake 276
Exhaust 286
Opens Closes Max Lift Duration
Intake 0 ATDC 38 ABDC 109 ATDC 218
@ .050 Exhaust 53 BBDC -5 BTDC 119 BTDC 228
Exhaust @ Valve 1.7
Adv. Duration
Cam Timing
Engine Identification: 1967-up Cheverolet V-8 396 thru 454 cu in
Lift: Intake @ Valve

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Old 01-31-2006, 08:06 AM
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Pas55-I read your post a few times and still not really sure what you are asking. If the new cam is larger with more lift and duration you may have a drop in vacuum. 13" is still good/decent vacuum. If you have power brakes and they still feel good and it runs good, then you should have no issues. It is impossible to say what the vacuum should be. There are alot of varibles that are at play. Just adjusting the carb ot timing could change the vacuum on any given cam. Hope this helped.
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Old 01-31-2006, 10:08 AM
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13 is probably about average for your cam choice.
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Old 01-31-2006, 10:18 AM
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EA3.2 estimates about 16"hg with this cam.
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Old 01-31-2006, 10:27 AM
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I'm getting 16 on my 454 with an almost identical cam. If you're using a stock ignition curve setup, don't expect more than about 13. Recurve that puppy, bump up your initial to whatever your compression allows, then you can back the idle adjustment screws way back. You'll get a smoother idle, more vacuum, and better MPG.
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Old 01-31-2006, 11:53 AM
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vacuum

Thanks I thought it would drop with the new cam, I was just wondering if 13 was ok.
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Old 01-31-2006, 11:58 AM
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13 is okay, but you could have more.
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