Home » Public Forums » GMCnet » Holley 08670 Street Avenger Carb, Install report
| Holley 08670 Street Avenger Carb, Install report [message #61604] |
Sun, 25 October 2009 16:38  |
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Well yesterday I finally did it, I installed the Holley street avenger carb on the stock OEM manifold, this requires the addition of an adapter to fit the square bore holley to the spread bore mani.
A few things had to be adapted to the holley, cause a tang on the uni throttle lever intended for a trans kickdown had to be snipped off because it was catching on the exhaust crossover, the rest of the install was pretty straight forward, and I used a low profile 2" Air Cleaner, unfortunately the adapter raises the carb an inch which makes clearing the hatch tricky, I had to raise the hatch with inch spacers of 1x2 sourced from home depot for .79 cents. This is just a temp solution until I work out something more permanent.
The adapter can be sourced at just about any auto store for $25 bux. and the whole innstall took a couple hours due to a number of trips back to autozone to source more parts.
well after everything was buttoned up and I tuned the carb to a nice 21" vac at idle, I took the coach for a spin, and all I can say is "Woah"! what a difference a little bit of carb makes, the coach quite simply hauls ass! it can keep up with the GF's 01 Yukon under normal acceleration, and I can actually peel out just by stomping the gas to the floor! the old car would bog and the rig would have no power, now it feels like a new engine has been installed!
on a side note I will need a heaver spring in the vac secondary because they open with little effort and I can hear when they come on, as the rediculous amount of air being sucked in sounds like a mini tornado under the engine hatch.
over all im very pleased with this mod, though I have no idea how it will effect my fuel economy ... lol fuel economy.... hahaha
we shall see  I will try to get some pix of the setup later...
Shan
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
[Updated on: Sun, 25 October 2009 16:39] Report message to a moderator |
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| Re: Holley 08670 Street Avenger Carb, Install report [message #61729 is a reply to message #61605] |
Mon, 26 October 2009 10:11  |
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Well I see the jet assortment on Holley's website, a long with vac secondary spring kits, and so on. I will definately need a heavier spring in the vac secondary because of the ease which the secondaries open, I can hear it under med-light load at as little as 1/4 throttle. I wanna see if I can get an adjust-a-jet kit for it which allows you to tune the jets similar to idle mixture, makes it much easier because the metering plates do not have to be removed. the tunability options for the stret avenger carbs are many, so it should be possible to dial this baby in for both good mpg during cruise and solid performance climbing grades and for quick acceleration. dialing the primary jets and vac secondary timing will be the key to this I think. will try to get an mpg report as soon as I can...
| rgleas wrote on Sun, 25 October 2009 16:59 |
Holley as well as most carb manufactures tend to put larger jets than necessary in new carbs. This will cause it to get worse milage than it should. I have a 71 GMC pickup that I made the same change to. Since it was new the bast milage was 10.5. I changed to the holley and jeted it correctly and now it gets 14.5. The only problem is that jats are not available like they used to be.
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Holley 08670 Street Avenger Carb, Install report [message #61783 is a reply to message #61604] |
Mon, 26 October 2009 15:53 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I don't get how putting a square bore carb on a spread bore manifold is desireable or correct. Any basic understanding of fluid dynamics would steer you otherwise. Wouldn't you want at least a Holly spread bore on there if it has to be a Holley? I imagine that it would actually work correctly from a flow standpoint then. If nothing else, when tuning pay particular attention to the power valve choice as that will be the thing that makes or breaks the mileage at cruise. The Qjet must have had some real issues if it runs that much better now. Based on my previous experience in muscle cars there were no gains in power going from a Qjet to a Holly and just new quirks. I'm glad it's running good for you though and keep us posted.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Holley 08670 Street Avenger Carb, Install report [message #61852 is a reply to message #61783] |
Mon, 26 October 2009 20:57 |
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I swear, it was like a new motor was dropped in! even my GF said holy Sh!t this thing hauls now! I've had my coach for about a year and a half now, and have driven it almost 2k miles so far. So I was well used to how the old Q-jet performed. I can only assume the slightly larger then stock Holley at 670 cfm, and the adapter which seems to reduce the main bore to a Q-jet size might have something to do with the torque feeling, but this baby will now bark the tires when just mashing the gas. I got a very weird look from a BMW driver in the next lane. granted seeing a motorhome peel out off a stop is unusual muchless one that is FWD!
as for the tired old Q-jet I'm willing to bet its pretty gunked up inside, it had started hesitating and stammering, and once the float got stuck which started flooding the engine with alot of excess fuel whih is a dangerous condition to say the least.
As for why not a spread bore carb, well I had the holley Street Avenger for another project, but I never used it, went fuel injection instead. So I decided to try it on the coach, it was a square bore so the need for an adapter to make it work with the stock manifold. with the low profile air cleaner it sticks above the hatch about 3/4 to 1" if I was able to run one of Jim K's aluminum manifolds, it would fit neatly under a stock hatch since the adapter is about an inch thick with the aluminum and phaelonic spacer, and that would not be needed with the RPM mani...
the real trick will be geting the secondaries dialed in, thankfully the street avenger comes with a quick change secondary actuator, just swap springs to control when it opens. though with a little feathering of the throttle you can control this but as I mentioned before i loves to come on, which is great for acceleration but bad for mpg! I dont need to really to burnouts at stoplights lol though I enjoy the bewildered looks it gets.
I will definately keep everyone posted, hopefully I can get some pix up soon...
| JohnL455 wrote on Mon, 26 October 2009 15:53 |
I don't get how putting a square bore carb on a spread bore manifold is desireable or correct. Any basic understanding of fluid dynamics would steer you otherwise. Wouldn't you want at least a Holly spread bore on there if it has to be a Holley? I imagine that it would actually work correctly from a flow standpoint then. If nothing else, when tuning pay particular attention to the power valve choice as that will be the thing that makes or breaks the mileage at cruise. The Qjet must have had some real issues if it runs that much better now. Based on my previous experience in muscle cars there were no gains in power going from a Qjet to a Holly and just new quirks. I'm glad it's running good for you though and keep us posted.
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
[Updated on: Mon, 26 October 2009 20:59] Report message to a moderator |
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| Re: Holley 08670 Street Avenger Carb, Install report [message #61904 is a reply to message #61852] |
Tue, 27 October 2009 08:04 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| Duce Apocalypse wrote on Mon, 26 October 2009 20:57 |
I swear, it was like a new motor was dropped in! even my GF said holy Sh!t this thing hauls now! I've had my coach for about a year and a half now, and have driven it almost 2k miles so far. So I was well used to how the old Q-jet performed. I can only assume the slightly larger then stock Holley at 670 cfm, and the adapter which seems to reduce the main bore to a Q-jet size might have something to do with the torque feeling, but this baby will now bark the tires when just mashing the gas. I got a very weird look from a BMW driver in the next lane. granted seeing a motorhome peel out off a stop is unusual muchless one that is FWD!
as for the tired old Q-jet I'm willing to bet its pretty gunked up inside, it had started hesitating and stammering, and once the float got stuck which started flooding the engine with alot of excess fuel whih is a dangerous condition to say the least.
As for why not a spread bore carb, well I had the holley Street Avenger for another project, but I never used it, went fuel injection instead. So I decided to try it on the coach, it was a square bore so the need for an adapter to make it work with the stock manifold. with the low profile air cleaner it sticks above the hatch about 3/4 to 1" if I was able to run one of Jim K's aluminum manifolds, it would fit neatly under a stock hatch since the adapter is about an inch thick with the aluminum and phaelonic spacer, and that would not be needed with the RPM mani...
the real trick will be geting the secondaries dialed in, thankfully the street avenger comes with a quick change secondary actuator, just swap springs to control when it opens. though with a little feathering of the throttle you can control this but as I mentioned before i loves to come on, which is great for acceleration but bad for mpg! I dont need to really to burnouts at stoplights lol though I enjoy the bewildered looks it gets.
I will definately keep everyone posted, hopefully I can get some pix up soon...
| JohnL455 wrote on Mon, 26 October 2009 15:53 |
I don't get how putting a square bore carb on a spread bore manifold is desireable or correct. Any basic understanding of fluid dynamics would steer you otherwise. Wouldn't you want at least a Holly spread bore on there if it has to be a Holley? I imagine that it would actually work correctly from a flow standpoint then. If nothing else, when tuning pay particular attention to the power valve choice as that will be the thing that makes or breaks the mileage at cruise. The Qjet must have had some real issues if it runs that much better now. Based on my previous experience in muscle cars there were no gains in power going from a Qjet to a Holly and just new quirks. I'm glad it's running good for you though and keep us posted.
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do you have any feel for gas mileage yet?
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: Holley 08670 Street Avenger Carb, Install report [message #61920 is a reply to message #61904] |
Tue, 27 October 2009 10:12 |
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not yet unfortunately, just had it on for 2 days now, and havent really gone anywhere... I sucked the main tank dry last night so I went and put $25 in it to keep it happy since I gotta move it every so often to keep the parking nazi's happy. I wanna get it prepped for a run up north for turkey day next month, and that would probably be the best way to get a feel for it, but I would guess at around town milage being probably about 6 mpg just due to the fact that the choke is just pulling off after a run down the street to a gas station.
being that I gotta fix the fuel senders in the tanks, I am trying to run them both out so I can drop them with little fuel as possible in them. I dropped my aux tank a week ago and found that despite reading empty, the tank was over half full! all I gotta say is all that time in the gym benching 200# barbels paid off when it came time to put the tank back in! I even managed to not spill any fuel! my next major priority is to fix those senders. I checked out the wiring, and that is not the issue, the sender it self is unfortunately. my tanks are newer aftermarket tanks installed a couple years abo by the PO, and they have baffels in them, im thinking the float arm might be binding on one ofthe baffels which is why its always reading empty, so that ma requite a little tweaking with a pliers...
| fred v wrote on Tue, 27 October 2009 08:04 |
| Duce Apocalypse wrote on Mon, 26 October 2009 20:57 |
I swear, it was like a new motor was dropped in! even my GF said holy Sh!t this thing hauls now! I've had my coach for about a year and a half now, and have driven it almost 2k miles so far. So I was well used to how the old Q-jet performed. I can only assume the slightly larger then stock Holley at 670 cfm, and the adapter which seems to reduce the main bore to a Q-jet size might have something to do with the torque feeling, but this baby will now bark the tires when just mashing the gas. I got a very weird look from a BMW driver in the next lane. granted seeing a motorhome peel out off a stop is unusual muchless one that is FWD!
as for the tired old Q-jet I'm willing to bet its pretty gunked up inside, it had started hesitating and stammering, and once the float got stuck which started flooding the engine with alot of excess fuel whih is a dangerous condition to say the least.
As for why not a spread bore carb, well I had the holley Street Avenger for another project, but I never used it, went fuel injection instead. So I decided to try it on the coach, it was a square bore so the need for an adapter to make it work with the stock manifold. with the low profile air cleaner it sticks above the hatch about 3/4 to 1" if I was able to run one of Jim K's aluminum manifolds, it would fit neatly under a stock hatch since the adapter is about an inch thick with the aluminum and phaelonic spacer, and that would not be needed with the RPM mani...
the real trick will be geting the secondaries dialed in, thankfully the street avenger comes with a quick change secondary actuator, just swap springs to control when it opens. though with a little feathering of the throttle you can control this but as I mentioned before i loves to come on, which is great for acceleration but bad for mpg! I dont need to really to burnouts at stoplights lol though I enjoy the bewildered looks it gets.
I will definately keep everyone posted, hopefully I can get some pix up soon...
| JohnL455 wrote on Mon, 26 October 2009 15:53 |
I don't get how putting a square bore carb on a spread bore manifold is desireable or correct. Any basic understanding of fluid dynamics would steer you otherwise. Wouldn't you want at least a Holly spread bore on there if it has to be a Holley? I imagine that it would actually work correctly from a flow standpoint then. If nothing else, when tuning pay particular attention to the power valve choice as that will be the thing that makes or breaks the mileage at cruise. The Qjet must have had some real issues if it runs that much better now. Based on my previous experience in muscle cars there were no gains in power going from a Qjet to a Holly and just new quirks. I'm glad it's running good for you though and keep us posted.
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do you have any feel for gas mileage yet?
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Holley 08670 Street Avenger Carb, Install report [message #63567 is a reply to message #61605] |
Mon, 09 November 2009 11:12 |
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| rgleas wrote on Sun, 25 October 2009 16:59 |
Holley as well as most carb manufactures tend to put larger jets than necessary in new carbs. This will cause it to get worse milage than it should. I have a 71 GMC pickup that I made the same change to. Since it was new the bast milage was 10.5. I changed to the holley and jeted it correctly and now it gets 14.5. The only problem is that jats are not available like they used to be.
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what jet sizes did you use? and holley jets can be had readily at summit racing. I ordered 2 additional jet sizes one about 5 numbers smaller, and the other a stock jet for a 570 cfm carb, since my motor will never turn more then 4k rpm Im not worried about leaning out with the smaller jets.
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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