Best Carb for the 345?

NewcScout

NewcScout

Member
Hi guys,

I'm new to the board cause I've just bought my first Scout. I've been a blazer guy my whole life, but wanted a change. I picked up a 73 II in pieces from a buddy that got tired of working on it.:out: one thing he did do is he rebuilt the motor and changed it from a 2 bbl to a 4bbl intake.

So I need a spreadbore 4bbl. I've done some searching and found that a fair number of people prefer the q-jet. I'd like to hear from you guys what you think. Here's what I need:

1. Reliable
2. Easy to tune
3. Rebuildable

also, if I'm going to pick on one used, are there any gotchas as far as what I see when I get it? This would be gotchas that I couldn't remedy with a rebuild kit.

Thanks for the help!!!
 
If you don't have to deal with emissions (a '73 shouldn't no matter where you live) and you're not concerned with an authentic restoration, then yeah, a q-jet is a great choice. IH built many 4bbl v-8s w/square bore intakes too, so I assume you know what you've got.
Q-jets are great because they can be rebuilt anywhere, and they only meter the amount of fuel/air the engine is capable of using. So if you keep your foot out of it, you'll knock down mpg numbers that rival any 2bbl, and have the extra juice when you need it. If you're going to scrounge one from the junk yard, well, that May or May not work out. You should definitely rebuild whatever you find because chances are it'll be crudded up inside and you'll have bad performance and tuneability. And then it'll be my fault for recommending a q-jet, and on and on....!
Seriously, if you go that route, find an early to mid 1970s Chevy to pick from. The other versions have fuel inlets in the front, and that's a dealbreaker because of the IH water neck. The chevys fuel from the passenger side so clearance is ok. Then have it rebuilt by someone you trust (might even be you). Now you at least have a good starting point when you start tuning it. Also, make sure you have the correct base gasket. There are several variations, so make sure you end up with the one that matches your carb, or you'll chase your tail solving vacuum leaks.
And it goes without saying you'll want to make sure the tank is free of old crud, the lines are new, the fuel pump is new (or new-ish) and fuel filter is new. The fuel we burn nowdays will contribute to corrosion much faster, so anything that has been sitting around with fuel in it is junk. You'd be foolish to think otherwise.
Good luck and post some pics!
 
I am also a fan of the q-jet (run one on my 69 Bronco). I pulled mine off a 79 buick for $8. Rebuild kits run around the $20 range and are plentiful. The late 60s/ early 70s chebby pickups are the best source but you can find them in all kinds of GM cars, trucks, vans. Stay away from the electronically controlled ones that started in 1980! You'll see them with hot air chokes and electric chokes. Mine had a hot air choke but I swapped it out in the junkyard with an electric choke from a dualjet (2bbl version) & capped the hot air line fitting on the choke housing. Mine came with dual choke pulloffs but the earlier versions only had one (either is fine). You'll want to check these as a bad one runs in the $30+ range to replace! Detach the vacuum hose, push the plunger in then cover the vacuum hole. If the plunger moves back out with orofice covered it's bad. Mine also has the front fuel inlet that I bought a 90deg fitting for and essentially made a side inlet out of it (necessary due to the distributor placement on a sbf). I run mine on a squarebore intake with a 3/4" adapter to the spreadbore carb. Runs awesome, good mileage and rivals efi offroad and off camber.
 
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Cool. Thanks guys. Great tips

no I'm not fully interested in an authentic restoration. I just want a once a year tune in stead of a once a month tune.

And yeah, even here in California I don't need to smog a 73. Woohoo. I wish all my vehicles were pre 75.

Do you guys know of any better rebuild kits than others?

Thanks again...
 
Can't recommend any kit over the other personally. I'd say whatever your local house has/ can get once you get a carb. Warning: not all q-jets are created equal/ the same! Once you get one (assuming it's a junkyard version or one in need of a rebuild), clean the part # off on the side of the carb main body. You'll need that # to make sure you get the right rebuild kit.
 
Here are a couple articles to get you going. This should get you 95% there.
 

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It would likely be a metering rod/jet difference. Check the pdfs. One lists all of the possible combos for nearly every q-jet made. Pick a mild 350 application and have it jetted that way as a start. You can still buy metering rods and jets from edelbrock. Check their website.
 
In the carburetor world, there are huge differences in the quadrajet spread over the many years of production and each oem/engine family. I keep four completely different kits on hand for those mixers in an attempt to cover the spread I see regularly in this boneyard crap folks drag up.

Big differences in gaskets especially, as well as choke pulloffs and choke actuation. There were about as many variations done for divorced choke as there was for electric or hot air choke.

The magic part would be the choke pulloff assemblies, many variations of those and how they actuate. They are all vacuum operated with many calibrations, without a correct pulloff for the carb number, the secondaries cannot actuate in any fashion. And I've never seen a pulloff on a q-jet that has been in service that actually works, that is why we rebuild 'em.

But we can still obtain most all choke pulloffs under the standard brand, the actual delco fuel systems components for those carbs was discontinued some time ago. Same for float systems, the float must be replaced with a fresh one on every carb build.

And...if the carb core selected for an attempt at freshening has the "apt" system, then do not change anything regarding the adjustment, without an exhaust gas analyzer, that system cannot be corrected.

All factory-plugged passages on these carbs will leak raw fuel after all these years, a "special" epoxy is used to repair those faults, jbweld will not hold up to this application.

Before anyone attempts to even open up a q-jet, I'd highly recommend they obtain and study..."how to rebuild and modify rochester quadrajet carburetors", by cliff ruggles (isbn-13 1-932494-18-9).

Since only one potential source for the quadrajet still messes with 'em as far as remanufactured (that would be jet and I'd personally never pay the price for those items), I'd highly recommend that if you are set onna q-jet, you contact "bruce" in peoria, az (phoenix metro) as linked in this thread:

http://www.forums.IHPartsAmerica.com/carb-tech/4632-quadrajet-tquad-questions-Mike-m.html
 
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