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Old 03-11-2009, 09:36 AM
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Pick up truck Q-jets

I was looking to get a Quadra-jet to play around with. As I understand it the '77 and later ones are the best as long as they're not electronic. They are newer and have better build quality then the early models, APT, a divorced choke, and I heard bigger primaries with idle bypass and flow 800 cfm but I'm not sure about that. If anyone knows the facts about later model Q-jets that'd be great.

Anyway, it seems the most common and affordable ones are off of early to mid 80's pickups. It makes sense since so many of the pick ups were sold. My question is are these a good performance choice? I suspect that most of them came off a 305. Most of them are non-electronic. But I wonder if they have the smaller primaries or other issues for performance applications?

It would be nice to get a Q-jet that has APT, bigger primaries and idle bypass. Without an advance book, all you can really tell from the the part number is the year, whether it's federal emissions and what make it was on. You can't really tell what engine model and car model it's from.

Anyway, does anyone know if the truck ones are good? I figure this is the place where someone would know.

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Old 03-11-2009, 10:45 AM
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Hi Cruiser and welcome to the HR forums!

Qjets come in thousands of combos on rods and jets and just grabbing one and hoping for the best is pretty much a crap shoot.

Personally, I like the Qjet. Have 3 on all of my vehicles.

I like the 80's versions that have the electric choke. For me, just way easier to get and keep the choke working properly. What i've found too is most, if not ALL qjets will need to have the primary throttle shafts drilled and bushings installed. They wear all the time and need attention.

As far as bigger primaries, that is hard to address. Needing 800cfm from a carb is usually un-necessary, unless you are running a very healthy engine and finding the 800 version is not easy. There are conflicting opinions on which one's flow that number, but mainly, the older Pontiac qjets on big blocks will get you there, but again, usually not needed.

the Qjet will flow a minimum of 750 in stock form PROVIDING the upper secondary flap opens all the way. That was the cool thing about the qjet, it can be set to flow a lot or less or anywhere in the middle.

There is a great book out by Doug Roe on Qjets that addresses all the tips and tricks on rebuilding and tuning a qjet. You can find it on eBay or Amazon too. Every qjet owner/builder should have it!

The earlier qjets are usually more friendly for engines that need more fuel as the idle circuit is not restricted like the new ones are. Qjets with a number starting with "70*****" numbers will be plenty rich on the idle circuit BUT, most are worn out.

The newer ones start with "170*****" and those are the ones I like, providing they have the electric choke. Granted, the idle will be lean but you can drill out or remove the idle restrictors to richen it up. Again, the book mentioned above will explain it all.

One other thing is the primary rod length. Those rods are NOT interchangable between the "70****" and the "170****" carbs. Again, that is why I like the newer ones, lots more to choose from in the scrap yards.

Anyway, get the book and have fun!

Just checked on eBay and found one going really cheap. clicky here for the auction

Mark
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Old 03-11-2009, 03:57 PM
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Hey JMark, thanks for the welcome and the informative reply. So I take it provided the 80's truck Q-jet is properly rebuilt and moded, it would make a good choice. I don't really need an 800 cfm or an 850 either, but I figured having the bigger primaries would give it more potential with larger engines and more radical cams. I assume all '79 up Qjets have the APT and idle air bypass?


I have read Roe's book before from the local library, but that was awhile back and I don't remember any details. The library doesn't carry it anymore. I need to get a copy to keep. It's cheap. Funny, you should link to that item on Ebay. I've been watching it but haven't bidded yet lol. I like to get Ruggls book too. Seems like the Q-jets are getting a little pricer and harder to find. They use to be basically free but now they seem to usually run $20+ for an old core. It's kind of like the older GM radios. they use to get thrown away or practically given away, but now they're going for around $100.
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Old 03-11-2009, 04:57 PM
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Quote:
Originally Posted by Jmark
Personally, I like the Qjet. Have 3 on all of my vehicles.

Mark
Never saw a car with 3 Q-jets on it before

Thanx for the writeup --- really!

Bryan
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Old 03-11-2009, 06:16 PM
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howdy there,

the E4ME carbs and EST systems did not come out on the chevies until 1980 and even then only on GVRW lower than 6200 or 8200 depending on the model and year

most 1 tons and some 3/4 tons were non-E4ME and non-EST controlled
all 79 and older chevies were non E4ME carb


you can find the good electric auto choke non computer q jets on the heavier 3/4 and 1 tons 1980-86

very common

all q jets are 750 or 800cfm BTW

the difference between 750 and 800 is in the primary venturi

the 750 ones have a raised casting ring around the primary venturii that the 800 dont have


truck and car ones same deal ones not better than the other, they are all lean runners and smog equipment years ones.,

car truck van doesnt matter

good luck
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Old 03-11-2009, 06:21 PM
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Quote:
Originally Posted by Bryan59EC
Never saw a car with 3 Q-jets on it before

Bryan

Being a woodworker, making a custom Oak "three quad" intake was a piece-o-cake!! LOL
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Old 03-18-2009, 01:35 PM
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I may be a little late on this thread but the book you want is by Cliff Ruggles.
http://www.cliffshighperformance.com/
As far as a high performance carb is concerned look for a 1977 up to about 1980 or 81 when they went with partial electronic control. All Qjets during that time were capable of 800 cfm or up to about 850cfm if the choke flap was removed. I run a 1979 Oldsmobile unit on my 1969 GTO. The biggest issue with the later carbs is the idle circuit, which is generally sized to work with anemic lean engines from the period. That is fairly easily changed. Working on the carbs is really not that difficult and the results are amazing.
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