| Trip report with the Holley carb... [message #69730] |
Tue, 05 January 2010 21:12  |
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Well my new years trip was 1150 Miles and though I dont have my total milage (havent filled the rig back up yet) but for 858 of those miles I was averaging 10.5 miles a gallon with the olds 455 and stock final drive.
only mishap was on the way back when a new autozone alt belt broke, fortunately I broke down near a kragen and was able to obtain a new belt and was back on my way in 30 minutes.
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Trip report with the Holley carb... [message #69734 is a reply to message #69730] |
Tue, 05 January 2010 21:23  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Well my new years trip was 1150 Miles and though I dont have my total milage (havent filled the rig back up yet) but for 858 of those miles I was averaging 10.5 miles a gallon with the olds 455 and stock final drive. ""
It's good to hear there are alternatives that work. Some of us with the wrong Q-Jet part number have been worried that we may be banished from GMC'dom
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Trip report with the Holley carb... [message #69739 is a reply to message #69734] |
Tue, 05 January 2010 21:51 |
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| Bob de Kruyff wrote on Tue, 05 January 2010 21:23 |
""Well my new years trip was 1150 Miles and though I dont have my total milage (havent filled the rig back up yet) but for 858 of those miles I was averaging 10.5 miles a gallon with the olds 455 and stock final drive. ""
It's good to hear there are alternatives that work. Some of us with the wrong Q-Jet part number have been worried that we may be banished from GMC'dom
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im actually also using an adapter to mount it to the spread bore manifold. its a 670 CFM street avenger carb. single pump, I bought some jets, secondary springs and accelerator pump cams, and found that going with the next to heaviest secondary spring, next to largest accel pump cam, trick fuel "4 door"
7.5 in Hg power valve, and number 64 (one size smaller then stock at sea level) jets on the main block as well as an adjustable vac advance dialed in for max timing without detonation really semed to work.
The thing is, with the holley you need a vacuum gauge, which is not a bad idea anyway. you can use it to watch your vac at cruse, the Holley Throttle is more responsive then the old Q-jet in my opinion, but with the vac gauge you can keep a 12 to 16 in Hg cruise on flat lands easily.
Also with the holley and the vac secondaries, its important to tune this, if you leave the stock light spring in which is calibrated to a 3500# car, you will have secondaries which come on at part throttle, and on a big motor like the 455, the extra fuel isnt going to bother it, but it will drop your milage. 2 minutes and a stiffer spring is all thats needed to make sure the secondaries come on only under heavy load acceleration when they are needed.
just thought I'd share my result its not bad to "dare to be different"
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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