| [GMCnet] 403 Engine Vacuum [message #287870] |
Fri, 25 September 2015 20:17  |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Senior Member |
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Quick question on the 403 engine vacuum. What should engine vacuum be
at Idle and at various RPM's. I haven't been able to find the info on
this.
Thanks.
--
Ray Erspamer
78 Royale - "The Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMCRoyale@gmail.com
414-484-9431
Web Site: http://ray-lisa.page.tl/
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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| Re: [GMCnet] 403 Engine Vacuum [message #287876 is a reply to message #287870] |
Fri, 25 September 2015 23:35  |
Bullitthead
Messages: 1411
Registered: November 2013
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Manifold vacuum (under the throttle plate) depends on load, not RPM. No-load manifold vacuum should be 18-20 inches with factory parts (cam, manifold, pistons, correct cam timing, etc.) Idle is a no-load condition. Aftermarket and performance parts can change that value. Manifold vacuum can drop to almost zero when you stuff your right foot into the carb and have enough load on the engine. When cruising, you want to keep the vacuum as high as you can for fuel economy. get a long enough hose and hook it directly to the manifold vac port and put the gauge where you can see it while driving. Do not have anything else hooked to the vac line for best response and accuracy. Soon you will learn how to get the best fuel economy and still maintain highway speed.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] 403 Engine Vacuum [message #287886 is a reply to message #287876] |
Sat, 26 September 2015 08:44 |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Senior Member |
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Thanks for the info Terry, I'll check it out.
On Fri, Sep 25, 2015 at 11:35 PM, Terry wrote:
> Manifold vacuum (under the throttle plate) depends on load, not RPM. No-load manifold vacuum should be 18-20 inches with factory parts (cam, manifold,
> pistons, correct cam timing, etc.) Idle is a no-load condition. Aftermarket and performance parts can change that value. Manifold vacuum can drop to
> almost zero when you stuff your right foot into the carb and have enough load on the engine. When cruising, you want to keep the vacuum as high as you
> can for fuel economy. get a long enough hose and hook it directly to the manifold vac port and put the gauge where you can see it while driving. Do
> not have anything else hooked to the vac line for best response and accuracy. Soon you will learn how to get the best fuel economy and still maintain
> highway speed.
> --
> Terry Kelpien
> ASE Master Technician
> 73 Glacier 260
> Smithfield, Va.
>
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> GMCnet mailing list
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--
Ray Erspamer
78 Royale - "The Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMCRoyale@gmail.com
414-484-9431
Web Site: http://ray-lisa.page.tl/
_______________________________________________
GMCnet mailing list
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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| Re: [GMCnet] 403 Engine Vacuum [message #287905 is a reply to message #287890] |
Sat, 26 September 2015 15:12 |
Norisan
Messages: 18
Registered: April 2015
Location: Calgary
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Junior Member |
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I think we should add that those readings would be at sea level and for each 1000 feet above sea level we need to subtract about one inch from those typical readings.
Norm.
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| Re: [GMCnet] 403 Engine Vacuum [message #287906 is a reply to message #287905] |
Sat, 26 September 2015 15:29 |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Senior Member |
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This is GREAT Tony! Exactly what I was looking for. I ran out and
tested the coach right away, I got a perfect #1 reading. When I
quickly opened the throttle it performed ecactly like #2.
Happy guy here!
Thank you !
Ray
On Sat, Sep 26, 2015 at 3:12 PM, Norman Allinson wrote:
> I think we should add that those readings would be at sea level and for each 1000 feet above sea level we need to subtract about one inch from those
> typical readings.
>
>
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--
Ray Erspamer
78 Royale - "The Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMCRoyale@gmail.com
414-484-9431
Web Site: http://ray-lisa.page.tl/
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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