73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: 85MudMonster on January 27, 2009, 06:23:32 pm
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Okay, I'm having trouble figuring out what carb I need or want. I don't understand the differences between the holleys and the edelbrocks, I mean one has vacuum secondaries one has air valve, what's the difference between those, or should I get mechanical and avoid vacuum/air valve secondaries altogether? Also, I've done the calculations and for what I'm building I need a carb that is between 600-675 cfm, cause much more than that and it would just be overkill I think. As you can see I've got no idea what I need really...
I know that this truck WILL go off road, it WILL have a bigger cam in it, and it WILL be driven down the highway's as well. I guess I need a good balance between power and economy, but I'm willing to sacrifice economy for power. So please tell me what you think and why.
Thanks,
Dan
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I have had two of the Edlebrock carbs and both worked great right out of the box. For the money, I thought they were hard to beat. Holley is a good carb as well, but I know more about q-jets than Holleys. Holleys are supposed to be real easy to work on, I just never had one.
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For Offroad you didn't put it in the list but Q-jet if I was going with a Carb.
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I second the Q-Jet
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we had a q-jet on one of our race cars for dirt and WOW did it perform. if you find a good one you better keep it or sell it me. I have a carter on my truck.
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The Edelbrock/Carter AFB carb is the easiest performance carb to tune and they work nice. I use Holley also and Q-jets. I tell everyone for simplicity it doesn't get much easier than the Edelbrock Carters.
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If you know enough about q-jets to tune the properly and get more performance out of them, then I'd stick with a q-jet. The main thing against q-jets is that nobody knows how to tune them and retune them for what they want.
2nd choice for me is edelbrock 1406. It's electric choke, where the q-jets divorced choke can be a pain if swapping intake manifolds. Also it has vacuum secondaries like the q-jet which means the secondaries will only open as much as the engine needs. They are extremely easy to learn and simple as legos. They have less gaskets and no gaskets below the top of the fuel bowl (less to go wrong). I bought q-jets for my stuff because at the time it was the cheapest option and they are good carbs.
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I've run em all. Q-jet's tend to give a little bit more mileage due to the small primaries. Holley's and Edelbrocks are both easy to work on, and I've also used the Proform series of carbs with good luck too. They all work on the same principles, sometimes you just have to work a little bit to get them right for your combination. Make sure you pick a vaccuum secondary.
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we had a q-jet on one of our race cars for dirt and WOW did it perform. if you find a good one you better keep it or sell it me. I have a carter on my truck.
I have a couple of spaires that I will never part with, they are Carter Q-Jets!
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I am confused ;D
I thought (that might be my problem... Thinking :) ) for a SBC not too built up you didnt want/need more than 650 CFM arent the Q-jets at least 750 CFM?
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Yup gm put them on almost every model for years
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q-jets are 750CFM and a few of them are 800CFM. but that's where vacuum secondaries come in. When you floor it, all 4 LOWER butterfly valves open fully, however the valves at the top of the secondaries only open up far enough to give the engine what it ACTUALLY needs to operate in those conditions. that's why q-jets are on such an array of different engine sizes. The engine will only suck the top secondary valves open as far as is required, intead of being on a throttle controlled linkage to where all four open all the way and bog the engine down.
If you really wanna make a q-jet go, you need this book by Doug Roe and Bill Fisher. This is an old book so it's likely not $6.95 anymore...lol
(http://i160.photobucket.com/albums/t195/wes2880/Parts%20n%20Pieces/GEDC0001-1.jpg)
q-jets came on gm stuff and on a few dodge trucks in the late 70's
holley's mainly came on fords but came on other cars too.
carter AFBs came on quite a few different cars but as a rule were for mopars; the new edelbrocks are slightly modified carters and are actually made by weber. Most of the stuff from carters goes right on an edelbrock. But I'd get the edelbrock just because it's the same design, but with improvement over time.
All these carbs are the same in one respect though, if you don't learn them pretty well, they will NEVER do what you want them to as well as possible.
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okay, well, I went and picked up an Edelbrock 1406 carb. I saw this air valve thing in person, and it's so simple it's genius!! Now I see why edelbrocks are so amazing, they are so simple and easy to use and tune. When it warms up tomorrow I'm going to go put it on.
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Personally I thought the Edelbrock would be a better carb as well. I bought a brand new one that was manual choke and bought the electric choke conversion since they didn't have an electric choke version in stock. I went to undo one of the screws and it broke off with hardly any force. It would have been no problem except that the electric choke needed this screw. So I returned it and bought me a Holley street avenger carb which cost a bit more but I have had no problems and it runs good right out of the box too. I only had to change the secondary spring to the stiffer one which was included in the box and its set. So I guess holley would get my vote and then q-jet.
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I said a Q-jet for offroad use because of its central location of the float and when you get a holley off camber on a hill, it will flood. Not to mention they are really sensative to atmosphere changes.
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Well, where I live there aren't many hills, maybe small mounds of dirt that's about it. But I've got the edelbrock on and it runs out amazingly, I think this is the first time that truck has ever had a carb where the secondaries actually opened up under full throttle cause it hauled when I got on it. Haven't had a chance to get it off road yet though, I'll let you know how it does on the off-road venue.
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I prefer Holley personally, Id like to try a Barry Grant sometime, just havent yet. Q-jets are awesome , but if you run into trouble with em, & you dont think like them they can be a total pain in the rear. I had one on my 396 Chevelle years ago set up by the Carb Shop, I loved it.
I like the old Carter AFBs, but it seems to me that everysince Edelbrock started selling em in the 1980s the quality isnt there, I normally like Edelbrock products, but I never met an Edelbrock carb I liked.
I put the 770 Holley on my truck in 2003 & I never have to touch it. I tinker with it every now & than, but not because it needs it.
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Haven't had a chance to get it off road yet though, I'll let you know how it does on the off-road venue.
Just to let you know, Edelbrock recommends using their spring loaded needles and seats for off-road use. So if you experience bog or surge while hitting rough terrain, I'd suggest trying them.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D1465&N=700+115&autoview=sku
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Haven't had a chance to get it off road yet though, I'll let you know how it does on the off-road venue.
Just to let you know, Edelbrock recommends using their spring loaded needles and seats for off-road use. So if you experience bog or surge while hitting rough terrain, I'd suggest trying them.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D1465&N=700+115&autoview=sku
Holley also recommends the spring loaded needle and seat for aff road use.
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I said a Q-jet for offroad use because of its central location of the float and when you get a holley off camber on a hill, it will flood. Not to mention they are really sensative to atmosphere changes.
Right on cap... in my own experience of living in the Sierra Nevada mountains at around 6000 ft altitude, it was easier to tune a good ole q-jet than a Holley carb to run in the leaner air. All of my off-road rigs ran q-jet carbs.
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I've had it off-road. Even found a steep slope, probably about a 30° angle or more, not really sure It was steep. It did just fine, not even a sputter or anything.
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Cool, glad to hear it.
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I have a q-jet on my truck and I have had very little trouble with it. Also I don't have to adjust very often