what carburetor would you use?
 

I have a 67 convertible Firebird with a 65 389 and a 5 speed trans. As far as I know the engine is stock with the following add ons. Edlebrock Performer RPM intake, Edlebrock 1406 600cfm 4barrel carb, hooker competition headers and full flowmaster exhaust system.

When I bought the car the last owner had rejetted the carb with really big jets. I bought new jets to return the carb as close to stock as I could but it still runs really rich. I want to replace the carb but I'm nut sure what to put on it. Most guys say I should stick with vacuum secondary but from what I have read it sounds like mechanical secondary would be better.

What are you guys running?

i'm not an expert but i bet most pontiac guys are gonna say get a quadrajet, and cliff ruggles book on 'em.
thats what i use.

Get a Quadrajet. Cliff Ruggles wrote the book on them.

I'm a Holley carb kinda guy myself,,,which I know is an oddity on a pontiac forum...

I'd probably opt for a 650 CFM double pumper carb for a combo like that (0-4777C).

And yeah,IMO a manual trans car like this will absolutely love the throttle response of that Holley mechanical secondary carb.

Wont get the best gas mileage though.

Also,if the car is a regular driver,I'd for sure put one of the Holley electric choke kits on it too,as they work pretty sweet IME.

Also is a really easy carb to tune as well,and parts are available most everywhere too.

FWIW

Bret P.

If the engine is stock then your best performance will be with a factory intake. The Q-Jet is a great performing carburetor and will get decent mileage on the street compared with aftermarket offerings. The deal with the Q-Jet is they are 40 plus years old and usually need some work to make them function properly and be reliable. There are professional carb guys like Cliff Ruggles that can set you up with a nice q-jet all prepped and ready to go. Also if you want to work the carb your self Cliff Ruggles has a book that will guide you if you want to do it your self. I don't like the Edelbrock carbs, for racing I like the Holley and for the street I like the Q-jet. The Holley is a reliable carb and works well on the street too but mileage won't match the q-jet.

When I bought my car it came with a single plane aftermarket intake and an edelbrock carb; I'm not impressed with this combo for the street and will soon be installing a factory intake and Q-jet both of which I bought from members here.

From what I've seen, read and heard, the Edelbrock carbs work. That's about it. They will get your car from point A to point B. But they seem to be a nightmare to tune. Cliff said more than once that he won't allow any of those carbs in his shop. I would go with a Quadrajet and factory iron intake and never look back.

All aftermarket AFB's are jetted very rich as an insurance policy, not knowing whether or not the engine has been heavily modified kept the carbs from frying engines, just lean them out at your own pace.

There are tuning kits to deal with these problems, and get yourself a good running engine. There are a couple of good books over on Amazon that detail how to clean, rebuild and tune the Carter/Edelbrock, but the advice to get a proper Q-Jet and factory intake is pretty good.

Be aware: the Q-Jet took years to get over its "factory junk" reputation. It was far more sophisticated than many of its early tuners, who were used to the screwdriver simplicity of the Holley aftermarket carbs. It is a pretty finely calibrated instrument, but, start with a good core, and make all the proper allowances, you can make huge power with decent mileage.

BOB

My 2 cents. I agree with most, the Q-Jet and iron intake the way to go on a basic street car. I had a '70 Tempest with a 400 4speed years ago, tried a stock 650 DP, a tricked out 780 vacuum secondary and a tricked out Q-Jet. The Q-jet was the most responsive and fuel efficient of them all. I am not a fan of the edelbrock carbs. Although you don't here much about them, I did use a Carter AVS carb on a Chevy (decades ago) and I found it to be a great working and easy to set-up carburetor.

Thanks guys. I guess it's a good thing I kept the cast iron 4 barrel intake that was on the car when I first got it.
Anyone have any thoughts on Q-Jets from Jegs?
http://www.jegs.com/p/JEGS-Performan...52437/10002/-1

Do yourself a favor and don't buy a Chevy carb for a Pontiac.

Thanks
That's kind of what I was thinking but really didn't know if it would be a problem or not. I know nothing about Q-Jets.

Carbs.
 

I bought a really nice q jet on here.Q jet is the way to go. And there s a place around here that rebuilds them for around 175.Conn Speedometer in Hartford Conn.

Any q-jet you buy rebuilt from a mass rebuilder is going to have generic jetting and questionable parts. Buy a kit from cliff (and a book if you need it) and do it right.

So he's got the RPM manifold and it's on the car - why remove it? It takes some work on a stock manifold to equal the out-of-the-box performance of the RPM manifold.

The Holley is a little easier to tune than an AFB, but the AFB is still straight forward and much easier than a Quadrajet to set up properly. People bad mouth AFB's on here, but isn't it surprising how well AFB's all of a sudden work when placed on a 2-4 manifold? How many people bad mouth the AFB and have never owned one? I've had them on many of my cars from the mid 50's on up, and they have proven to be the most trouble free of all the carbs out there. I currently run Holley's, AFB's and Quadrajet's so I'm not predisposed to any single make of carb, and I work on all of them. AFB's just keep on running, Holley's have some trouble with dirt, and the hundreds of varieties of Quadrajets takes someone like Cliff to keep track of them all.

An engine is nothing more than an air pump, and the carburetor is blind to what it is sitting on. How many people set the spring on the secondary air flap to exactly one turn and never think another thing about it? That is no different than Carter selecting the weight on their secondary air flap. In either case, you better have a really sensitive butt to feel any slight difference in opening rate. There is a thin margin of opening rates on the air flaps that work satisfactory, and most people are better off not playing with the factory adjustments. :p

jwcfbd, is the rich condition at idle, part throttle, or full throttle?

In his original post he stated the engine is stock. Based on that I believe the RPM will slow the car down and will not be as responsive as the unmodified factory manifold.

My vote is for a mechanical secondary since you're running a manual trans. The one time you want to stab the gas pedal and the qjet takes it's sweets ass time is gonna make you pull it off and throw it down the hill. I could never get a qjet to open fast enough and equal what a good double pumper carb would do.

No amount of secondary rate adjustment is ever going to make up for an additional accelerator pump.

Manual trans = double pumper

Pretty much full time it's running rich. At idle it's horrible and after crusing on the highway for a while your cloths smell like exhaust when you get out. There is a lot of soot around the exhaust tips.

Without pulling the engine apart what would be the best way to find out if it has an other the stock cam in it? It does have a little lope at idle and I have had a bunch of people ask what it has for a cam.
http://youtu.be/XyMRq8ne_WQ

I did just find one thing on the Edelbrock website that may be one part of my problem.
While looking at my carb I found this in the write up "They are not recommended for use on RPM or Torker II intake manifolds."

I grew up on Holleys. you can buy them dirt cheap at swap meets. lots of technical support and literature.

I am sure your car would be happy with a correctly tuned Holley 650 or properly built Quadrajet. I would toss the Edelbrock carb in the trash or sell it to some sucker on ebay.

easy Tim.... thats where I'm lookin for carbs for my offy.

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I have a 65 389 also. Vacuum at 800 rpm is 12-13. Edlebrock rpm with 750 edel carb with one size rod leaner...runs great. also have run the edelbrock 2 X 4 package they sell with the two 600 cfm carbs. vacuum goes to 14 - 15 and from a dead stop I burns rubber forever........I have gone on a 5000 km round trip to the same place on both setups...amazingly both burned the same amount of gas.............

Thanks for the info guys. There are some ugly Qjets on ebay right now and I'm not sure which way I'll go. My first car was a 73 Firebird with a 350 and mechanical holly 4 barrel. I had to rebuild that carb countless amounts of times (kept blowing the power valve) but when it worked it worked great and I loved that you could always tell when the secondarys opened. One of these days I want to build a new engine with some kind of fuel injection on it but until then I'll keep it carbed.

Blown power valves are no longer a problem,all the new Holley carbs come with PV blow out protection,and it's super easy to retro-fit such to any older Holley carbs too,takes like 15 - 30 minutes to add that during a routine rebuild.

Plus back before that option was well known,that was why I always used the Holley electric chokes,no "sneezes" during cold start-ups,no blown power valves or such.

Anybody that's blowing their Holley power valves these days needs to brush up on their carb tech knowledge somewhat.

FWIW

Bret P.

You might find this article interesting:

http://www.thecarburetorshop.com/Car...eselection.htm

Jon.