Vacuum Reading - Team Camaro Tech
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post #1 of 13 (permalink) Old Nov 4th, 09, 04:41 PM Thread Starter
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Vacuum Reading

What should be a normal vacuum reading for my 327? It has a 268 comp cam, Summit 2.02 heads, Edelbrock Performer Manifold & Q-Jet carb with headers. thanks guys.
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post #2 of 13 (permalink) Old Nov 4th, 09, 06:15 PM
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Re: Vacuum Reading

I would suggest anything between 14"-17", the more, the better.

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post #3 of 13 (permalink) Old Nov 4th, 09, 06:17 PM Thread Starter
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Re: Vacuum Reading

ok thanks
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post #4 of 13 (permalink) Old Nov 4th, 09, 07:48 PM
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Re: Vacuum Reading

I have a solid cam, "worked" 383, and can only seem t max out my vacuum bouncing between 4 and 7"

Keith
1967 Camaro
406, 10:1, comp xr282HR, Dart Iron Eagle 200cc, Holley Contender dual plane, Holley 750 DP
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post #5 of 13 (permalink) Old Nov 4th, 09, 10:29 PM
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Re: Vacuum Reading

Quote:
Originally Posted by keithl1967 View Post
I have a solid cam, "worked" 383, and can only seem t max out my vacuum bouncing between 4 and 7"
That is because he is running basically a little larger than stock cam in his 327, which probably have small port heads getting a lot of velocity and vacuum.
It's like comparing apples to oranges.
My .040" 327 with big heads and a cc286H-10 got about 3"-5" with a single plane and is now around 9" with a dual plane.

Good intake gaskets, and good rings, should see 15"+++ for the original ?

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post #6 of 13 (permalink) Old Nov 5th, 09, 05:31 AM
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Re: Vacuum Reading

I'd been thinking about a dual plane for a while now...try to give the car better "street manners"...

Keith
1967 Camaro
406, 10:1, comp xr282HR, Dart Iron Eagle 200cc, Holley Contender dual plane, Holley 750 DP
Muncie M-20
GM 8.5, 3.73 posi
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post #7 of 13 (permalink) Old Nov 5th, 09, 06:44 AM
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Re: Vacuum Reading

My 327 with 4bbl q-jet and 291 heads 194/150 ,stock cam and stock manifolds w/pwr brakes/rs vacuum stuff auto trans pulls 21" at idle

68 camaro RS 327/275 THM350 4 wheel disc brake 8.5 10 bolt 3.42 daily driver
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post #8 of 13 (permalink) Old Nov 5th, 09, 12:46 PM
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Re: Vacuum Reading

Every engine is different, even 2 identical engines built side by side with have slightly diff charactoristics....
Tuning timing idle to highest vac is no different to 'tuning by ear' and tuning idle timing by ear is BS....
Tuning idle mixture with vac.... yes

I have real bottom end low duration /overlap cam, dual plane...If I was running about 9 or 9.5 compression on 91 pump gas the idle vac with about 10 deg intial+VA advance I would have around 20 to 22"
With approx 10.8 compression on 105 octane 14 deg intial+VA I have a 14/15" vac
I can up the idle vac to around 18/20" putting more intial advance in, but my NOx and CO emissions climb, which indicates poor burn, over advanced at idle and long term slow death of the engine.
Higher the DCR (basically determined by the cam profiles) lower the advance
Higher the octane lower the advance.
So taking my engine for example, I need the upper curve to be almost a 45 degree graph under load (no VA)
ie 1500 rpms 15 deg 2000 rpms 20 degree upto 32 deg @ 3000 rpms with about another 8 deg of VA for cruise.
If I over advance the intial, I over advance the rest of the curve at cruise, and again high NoX CO slow engine death.

If you dont intend to keep the car for another 80 or 200,000 miles, dont worry, its the next guys problem....if thats the way you think.

My Spelling is not incorrect...it is creative

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post #9 of 13 (permalink) Old Nov 5th, 09, 04:34 PM
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Re: Vacuum Reading

was that in english??

Keith
1967 Camaro
406, 10:1, comp xr282HR, Dart Iron Eagle 200cc, Holley Contender dual plane, Holley 750 DP
Muncie M-20
GM 8.5, 3.73 posi
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post #10 of 13 (permalink) Old Nov 5th, 09, 05:46 PM
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Re: Vacuum Reading

I'm kind of lost now. The original post was a question about what range he can expect his vacuum to be in...

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
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post #11 of 13 (permalink) Old Nov 5th, 09, 05:59 PM
 
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Re: Vacuum Reading

A 9-1+ or so 327 should get 14-15 or so in. vac with just initial timing(About 16 or so)
it really depends on the real compression of the motor-it makes a BIG differance- and the timing-some vac advance at idle would add 2-4 more
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post #12 of 13 (permalink) Old Nov 5th, 09, 10:38 PM
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Re: Vacuum Reading

Quote:
was that in english??
That is english you guys speak American with a funny accent and wrong words like a trunk its a boot and fender thats a mud gaurd, and how can you lift a hood unless the car is a convertable... its a bonnet

My Spelling is not incorrect...it is creative

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post #13 of 13 (permalink) Old Nov 6th, 09, 09:05 PM
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Re: Vacuum Reading

With a 268 comp cam, I'm going to say vacuum will be around 12.
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