CyberCholo

Hey guys

My car currently has a Quadrajet carb on the car, p/o said it was rebuilt recently and the carb seems ok, but I'm waiting until I get the brake booster with its vacuum leak replaced before I can really judge. I have no idea how to turn a quadrajet. this is only my second car but I've messed withit a little bit and it seems ok for the meantime. I know a fair bit about cars, but when it comes to working I am usually doing things for the first or maybe if I'm lucky second or third time.

I want to put a rebuilt carb on there, maybe professionally just for peace of mind. The carb is the heart of the engine on these old cars and I want to make sure its working right.

My Monte Carlo came with a Holley 650CFM the model number I can't remember but can get if you guys want it, p/o said it has been rebuilt but it leaked gas and seemed out of tune heavily. It also had an edelbrock intake manifold, I replaced the carb with an Edelbrock Performer 500CFM that worked great on the 305, and wasnt bad on the 350 afterwards. I still have the Holley in my shed and am considering rebuilding it or getting my trusty indie mechanic up the street my family has been going to for years to do it.

The primary thing I'm concerned about is replacing the carb and intake manifold to make sure there is no problems with either, but I see no reason why I can't gain a nice chunk of power while I'm at it...

So what is my best option, should I rebuild the Holley and find an intake manifold and go for it? Should I buy another new/re-manufactured Edelbrock Performer this time a 600 cfm or 650 cfm which should be fine for a street car, pair good with the intake (does this matter?), and get me some more power. Or should I get Q-Jet looked at/rebuilt and find an aftermarket intake manifold for it, is this possible? Can I get higher performance our of a Q-Jet? Will it pair well with a high performance intake manfold?

DoubleV

A new carb will get you nothing for power. You need your Qjet carb rebuilt and tuned. An aftermarket intake won't get you much if anything either but would be lighter. If you want a light factory style intake manifold consider getting an aluminum A4 intake from the early year 307's.

CyberCholo

Hmm is that just how the Rocket 350s are? The q-jet and the stock intake are good enough already? I'm pretty surprised to be honest thats pretty impressive.

455man

The qjets are good carbs. Some people wont run anything else. get your vacuum leak fixed and let us know how it's running. Without a cam upgrade or other upgrades an aftermarket intake wont get you much more power than a stock intake. I like to run aluminum intakes for the weight advantage.

oldcutlass

If it's working well, plus you said the PO had it rebuilt, why change it? Spend money on other things. Just because the parts are stock to the engine does not mean they are not good.

Professur

For what little it's worth ... the Q-jet isn't all that hard to rebuild. I think that pros spread the rumour that they are just to scare people into giving them the work. And it's a decent all around carb, well designed for daily driving. If you want to rip up pavement and someone else is paying for the gas, there are better in the after market ... but I love the knowledge that if I keep my foot light and keep those two big rear throats closed, the two drinking straws up front save me enough gas that I can afford to scare the juice out of that fart can Civic at the lights .... even if I can't really chase him down.

Octania

Many of ANY carb's functions operate on vacuum.
If the vacuum signal isn't proper [there is a massive leak or poorly tuned timing] then how can the vacuum operated carb features work correctly?

76olds

Awesome post professor, really that's all you need after you hit a certain age.
I personally like the edelbrock 600 with the performer for street use. The new run out of the box carbs are darn close, not too much tuning on for stock engines and I didn't notice any difference from the original quad . The intake is a huge weight savings and pop when you open the hood.

captjim

Huge weight savings? If you go by the old 100 lbs = .08 off in the quarter, the weight savings on the intake makes your car .02 quicker. I defy anyone to notice that.

captjim

I'm going to disagree with that. Q-jets are very sophisticated compared to other carbs. They are great street carbs, but not particularly easy to rebuild or really tune, IMO, and if he has a worn out one with a worn throttle shaft (which many have), even more so.

CyberCholo

Ill have to get the carb looked at by my mechanic and see what he says, thanks guys. The P/O says its been rebuilt but I've heard that so many times haha.

Professur

There's an easy way to tell. There will be two v shaped notches cut into the base directly below two recessed screw heads. Glaringly not original. If you don't see that, it's highly unlikely it's been rebuilt ... either right or at all.

billmerbach

That could be the difference between winning and losing tho not saying he gonna race it but any bit of time is critical

coppercutlass

.02 aint much. I had to shave off over 150 lbs to gain .13 . I gain .1 by opening up the exhaust. You can over come the .02 by driving or tuning. If its a nice running engine and you want a bump in performance tune it well curve the dist. advance initial timing free up the exhaust etc. have the q jet rebuilt by a reputable rebuilder and you will be happy.

MDchanic

QuadraJets are good carbs. I've never found them hard to rebuild and I rebuilt my first one at about 15 or 16 years old.

- Eric

DoubleV

I'm betting he says something like 'I don't know anything about Qjets'. You would be miles ahead IMO to just take it to or at least talk to a Qjet pro like Dean at Deano's Carbs, Cliff Ruggles, or someone at Sparky's. The 'average' mechanic today who doesn't deal with carbs much if at all is just going to screw it up more since they don't have a clue what they're doing.

Professur

If he doesn't know carbs, he doesn't know Olds blocks either. But any wrench with enough grey hair shouldn't flinch at either.

tru-blue 442

Plus one.
I think I was 17.

captjim

You old farts (I resemble that remark myself) gotta remember, we grew up with that "technology". The last production car with a carb rolled out of Detroit almost 25 years agao. The younger guys grew up on fuel injection. Again, Q-jets are great, but IMO not the easiest carb to rebuild if you have never done one, especially if the throttle plates are worn out.

olds 307 and 403

They are not that bad to build or tune, if you know carbs
. Where you run into trouble is wear and everything way out of adjustment. The newer carbs are very limited in idle fuel and air and don't like big cams.

CyberCholo

I just found out that there is adapter plates for the stock manifold? Are these hard to find and do they work ok? I'd like to just throw a basic edelbrock performer on there or something in the meantime while I get the rest of the car sorted out and worry about this stuff later when I drop a cam and stuff in it? Or it would probably be cheaper to just get the Q-jet professionally rebuilt? I normally wouldn't mind but this car needs lots of little things and while I'm getting it all setup I'd like to know the carb is 100% so I can forget about it.

billmerbach

Easy to come by and yes they will work make sure u get one for a spread bore tho I'm about to run the exact same setup as you let me know how it runs

pmathews

I'm running an Edelbrock 1406 with an adaptor plate, and I'm not happy. I'm currently building a Q-jet. If you do decide to run an Edelbrock, get the 1405, the 1406 is designed for mileage and runs lean. A 1405 runs a bit richer. Also, if you're going with an Edelbrock, I would get the matching intake. The adaptor plate between my 1406 and my Q-jet manifold is clumsy at best. Maybe others have had better luck, but matching the square bore with the spread bore is not optimal, even with an adaptor. That's my 2-cents.

billmerbach

He can get a calibration kit and jet it himself I seen a few on eBay for 36 bucks free shipping brand new seal not broken I'd ****** one up

coppercutlass

1405 maybe too rich with manfiolds. I put one of my 350's that I ran a 1405 on with headers and an x pipe and free flowing mufflers into my dads car with manifolds , smaller full length exhaust and restrictive mufflers and it seems too rich.

pmathews

True, worst case, you could re-jet a 1406 to add some richness, it's cheap and easy

CyberCholo

The other thing I'm worried about with the adapter plate/bigger carb is hood clearance, its a shame no-one makes nice cowl hoods for this car, one thing I liked about my 83 Monte Carlo was there was toooooons of repro and aftermarket body panels for that car.

Once I get everything working 100% I'll see what I can with the q-jet and see if it needs a rebuild, my brake booster is leaking vacuum bad so right now I have the carb idle set a bit too high and its running too rich, bogs when you floor it, but no point messing with it while I've got vacuum problems, if the booster is leaking when I'm on the brakes and causing the idle to drop and the car to run rougher, I imagine its leaking the rest of the time too? Haha I'll probably get more power gain out of fixing that than I would an aftermarket carb

oldcutlass

You can get a bolt or bond on cowl hood scoop through Harwood.

CyberCholo

Cool those look nice, I might get one just for looks, I imagine cutting the hood to do it functional is a pretty hairy and expensive job. Do the bolt on ones just involve you drilling the hood and then securing it with nuts on the other side?

oldcutlass

They are pretty easy to install.

CyberCholo

Cool, thanks for the link! Another thing I'll add to the growing wish list which is on its way to being a textbook