Hi, new member here. Picking up my 1976 4 spedd tomorrow.. 11-26-2011. Car is all stock, and after the test drive (which was good), the carb does stumble a tad. I do know the stock Q-Jets when older, doen't always perform the best. A mechanic has done a re-gasket and clean in the last month I was told. (he was there). Anyways, Holley has a replacement #4175 (vacume) and 4165 (mech. secondaries and emmissions). I don't need the emmisions with the antique plates.
Question... anyone have experience with this carb ? I've owned and tuned Holley's all my life and never had issues. Stock manifold doesn't bother me right now either, as it's not even sporting headers. Not sure if an adapter plate would fit under the hood etc. either (or do they even make em these days ?).
My 1st Corvette, and a great place to start.. never modded, so I know I can plan properly from here.
Thanks in advance folks, nice forum. Bet I'll be here often

 

A stock Quadrajet, correctly set up, will run just fine. Look at Doug Roe's book, and Cliff Ruggles' book as well. Between the two of them, you will be able to fix your problem.
But make sure all the basics are correct, first. Plugs, timing, filters, etc.
You will have to a bit of replumbing to get a Holley to fit where a Qjet was. Probably be easier to fix what you already have.

 

OH NO ... here we go again......welcome to the site . you can search the Qjet and you will find a ton of info....Problem with someone rebuilding the carb that dosent know what their doing is you just never know what they did..
Have your Qjet rebuilt... its better than any new carb you will find when built by the right person.....And there are only a few that can do it right ..

 

Wow..that didn't take 10 minutes. I barely got a fresh Pepsi and there ya have it !
Of course, soon as I posted, I thought dahh, do a search.. like you suggested. So, Off I go then.
Interesting, you guys like the Q-Jets. I read a long time ago about the company "JET Performance Products". Maybe it's gonna be one of those posted on the forum...

 

You can do your search, but read a few of these from lars....

http://www.corvette-restoration.com/...o_articles.htm

 

a stumble could be a few things...

Too much fuel is usually a studder under pedal to the floor accelleration

not enough fuel is like some one cut the key off for a second or two and then the engine recovers and continues to accellerate or this could be a combination of ignition timing as well as carburetor

check and make sure that the mechanical and vacuum advance in the distributor are working properly first.


if the advance is stuck it will run like a pig it will be real lazy at part throttle and will stumble also

( common) easy to diagnose

If the distributor is ok

Once you check the distributor..

Disconnect the accellerator pump linkage and see if it gets worse if it does it's lack of fuel

if it doesn't it's to much fuel or lack of ignition timing... doubtful it's too much fuel

simple troubleshooting will get you there

fix them in this order

Check the ignition timing first

easy to do with a light, most books will instruct you on this.
If all checks out with the timing

Carburetor works like this:

1. idle circuits (if it idles good the idle circuits are probably ok)

2. idle circuits to primary (Front two barrels) the transition from the idle is supplied by the off idle transitiion slots and the accellerator pump ( the function of the accellerator pump can be witnessed by looking down the throat of the primary side when actuating the throttle. and seeing the squirt of fuel.

3. primary to secondary enrichment (cover up the transition between the primary and seconday circuits" (these are holes directly above the air valve) you will se a light squirt of fuel lay on the air doors in their attempt to open ( remember only gas vapor burns)

4.Secondary circuits or wide open throttle: for an occasional driver don't bother as long as it does not stumble (max performance is another issue)


The other thing that will effect this is float level (a low float level can cause a stumble) if you get this far you might as well rebuild the carb because it will require checking the float level

check the easiest things first...

give a lazy man the hardest job and he will show you the easiest way to do it...


and Lars Papers are very good

Best regards, Jim

 

 

Nobody likes quadrajets were just tired of fighting about them.
And instead of wasting $40 on two books and waiting to get them in the mail just search here or other chevy sites to help with a rebuild or problem solving.
Those books do nothing but take a very easy process and turn it into a 4 year collage course and a chapter out of the New England medical journal of surgery.

 

just cause you dont like them doesnt give you the right to speak for everyone else
I for one love my qjet and glad i returned all those crap polly carbs they sent me when i was looking for another carb..
best thing i did was have it built by a pro

but tim is always right, hes had 82 cars,,,
now i now why you had 82 cars,...they all fell apart from all the crap parts you put on them,,,,,, jk

 

Congrats.
The Holley replacement carbs don't need an adapter nor is there room. Many run them & are happy w/them.

 

your very lucky to have the original carb. I would send it off to one of the three or four true QJet experts left in country and let them restore it rather than a rebuild. They will fix all the issues.

 

If your able to drive this car I would run a can or 2 of seafoam thru it if it has been sitting, this is amazing stuff and will get you an honest baseline on your carb!

 

Some good advice above about the Q-Jet and it is a good carb if it can be setup correctly, but in my opinion is way too complicated for what it needs to do. With that said, I have run a Holley 4175 on my L-82 since 1985 and just last December finally rebuilt it myself-very easy if you have any carb experience.

If it was me, I would check out all possible causes for the stumble and only then would I think of touching the carb. If the carb does need a rebuild I would buy a 4175 and run that while you or someone else rebuilds the Q-jet. A little expensive but you could reinstall the Q-jet after the rebuild and if all is well keep it on the car. Otherwise reinstall the Holley 4175 and drive on. At least you could make a back to back comparison of the 2 carbs if all goes well with the Q-jet.

I have had 26 years of experience with the 4175 and really like it but just my 2 cents.

 

That says a lot about you.
My Holley works perfect and I rebuilt it myself.
I rest my case.

 

And owning 83 cars tells me alot about you .. you cant stick to one car...
Or they just keep falling apart..

After 83 cars I hope you can work on them...

My carb was way to screwed up for a green horn like myself to rebuil it..

So I sent it to the best..Henry Olsen ... he taught Holly how to make carbs..and still does research and development for them all the time.. So rather just have it done right ...

 

ptroxx,

People have historically ridiculed that which they do not understand...
Your carburetor choice was a good one, Performance per dollar there is more Horsepower to be had in a professionally built carburetor than any other bolt on piece that can be installed in under an hour.
Besides a Q-Jet makes more horsepower and has a better idle circuit design than the Holley does.

Best Regards, Jim

 

Once you get a carb dialed in to provide optimum air/fuel mixture ratio for the engine....and enough of it so that it doesn't bog down...any brand of carb will provide equal performance. You can dial a Q-Jet in; you can dial a Holley in. It doesn't really matter at that point.

But, the OP stated that the car was totally (or, nearly) original, which means that he/she would prefer to keep it like the factory shipped it. That would be a Q-Jet...unless the OP has a different preference.

 

Thats just a out right lie, do you think people would buy a $500 Holley if they could take a $30 quad and run faster?
Its just not going to happen.
And ptroxx your on my ignore list so I can't see what your writing anymore because you waste my time reading your nonsense about basically not knowing close to nothing about a car. Your what they call a buffoon.

 

I bought a Jet 35001 for my '76, mainly because mine was missing a few parts. It works great right out of the box. Two concerns: 1. It uses an electric choke, so you need to remove and block off the hot air choke tubes from the manifold. Most places sell a block off plate. 2. You need to provide a switched power source for the choke. This means that power is on only when the ignition is on. Best place seems to be the power to the wipers. One downside is that they sell you a generic GM Q-Jet. Mine is from a '78 Olds. But the engine runs great, idles good, and no choke problems. Good Luck!

 

Lol. Finally now I won't have to hear all you stupid remarks about slowmasters. And Polly carbs.
You just know you have been proven wrong I gave my pleanty of examples of hot rods with magnaflows and now your just scared I'll show you up on the holley/qjet fight. If anyone's the buffoon it's you. So good luck with that ignore list. Like I could care. Lol.

And after reading some of your threads, your nothing but a hack..