How much Engine Vacuum should I have?
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,691
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From: Framingham MA
How much Engine Vacuum should I have?
I hooked up a vacuum guage to an intake port and found I have 17". (stock cam/rockers on 86 L98) I tried spraying carb cleaner to find it but I could not, I have already replace most of my vacuum lines.
I looked through my service manual and could not find any specs. My carroll SC manual claims, I should have 20". Is that correct?
I looked through my service manual and could not find any specs. My carroll SC manual claims, I should have 20". Is that correct?
Melting Slicks
Joined: Jan 2003
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From: What did the 5 fingers say to the face? SLAP!!
Re: How much Engine Vacuum should I have? (dgoodhue)
My stock '86 had 21 inches. I have cast iron heads. I don't know if your alum heads would make a difference
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Re: How much Engine Vacuum should I have? (dgoodhue)
Would it make that much of a difference that my idle is at ~675rpm? (aftermarkert 52mm throttlebody won't go any lower, because the plate binds with the bore)
Racer
Joined: Mar 2003
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From: Dover Oh
Re: How much Engine Vacuum should I have? (dgoodhue)
I measured my 92 ealier today due to a problem I'm having. The reading was about 20 inHg. If you take a reading, the needle should be pretty steady at idle and jump when you give it gas. If the neeldle is bouncing all over the place at idle, you got a leak.
Generally speaking for most cars, the vacuum should be about 16 to 22 inHg at idle.
Generally speaking for most cars, the vacuum should be about 16 to 22 inHg at idle.
Safety Car
Joined: Feb 2002
Posts: 4,212
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From: Sun City West Az
Re: How much Engine Vacuum should I have? (bheston)
You can probably get a few more inches of Hg by rotating the distributor. However, Your affecting your timing by doing so. 17" of Hg is ok for a stock motor.
[Modified by ittlfly, 6:46 PM 3/29/2003]
[Modified by ittlfly, 6:46 PM 3/29/2003]
Race Director
Joined: Oct 2002
Posts: 13,717
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From: RI
Re: How much Engine Vacuum should I have? (dgoodhue)
Guys on a side topic............where did you get your vacuum gauges from? I'm having trouble hunting one down locally and I'd like to measure mine just to see where its at. TIA.........back to our topic
Kitt
Kitt
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,691
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From: Framingham MA
Re: How much Engine Vacuum should I have? (kittmaster)
Guys on a side topic............where did you get your vacuum gauges from?
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Re: How much Engine Vacuum should I have? (ittlfly)
17" of Hg is ok for a stock motor.
If it is a vacuum leak, I suspect it is my intake manifold because that is when all my problems started happening.
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