At my wits end with this QuadraJet

[pontiacgp]

That is great news and nice job, now we can come to you with quadrajet issues...🙂

 

[Bonnewagon]

WOWSERS! Good job! I knew you could do it. And thanks for reporting back the results to us. Too many times we are left to guess what worked and what didn't. By all means get a decent vacuum gauge. It will allow you to really fine tune that carb. So the jets are #69 and the rods are #44? The jets are stamped with the number but I have seen some that are not. That is lean jetting for a 350 but the rods are relatively rich so you should get a nice crisp power curve. If and when you address the secondaries the trick is to NOT loosen them. If you can't tell when they open then leave them alone. But if you get a bog or stumble then tighten them by means of the spring loaded screw on the side of the flap. You want the primaries almost wide open before the secondaries kick in. Those "DP" rods are for economy on the 305. The tips are short and fat. Roe's book has a chart of all the rods in descending order and yours are towards the lean end. If you feel the engine isn't pulling strong enough at WOT them look to getting richer secondary rods. They would have long thin tips. Isn't this fun? And when you are done you can congratulate yourself for doing it by yourself and learning a new skill set!

 

[Longroof79]

I have noticed that it's extremely difficult to read the numbers on the jets and primary rods...even with a magnifying glass. The numbers seem to be almost worn away. The secondary rods, of course being fatter, are easier to read.
I'll probably have to refer back to this thread when fine tuning my freshly rebuilt Q-jet.
Thank you guys for putting all that great information out there.

D, I'm glad you were able to rectify the issue with your carb....thanks to our knowledgeable members. My hat's off to you guys.

 

[Rktpwrd]

Thanks gentlemen.
It feels great to finally have a properly running and idling car again. It never did seem to idle properly, even back when it was on the 305, so this is (literally) a breath of fresh air!

One thing of note, and a little unbelievable, was that the biggest restriction in the idle circuit was actually the idle tubes themselves. After a bit of a struggle to get them out, I found the restriction in the bottom of the tubes measured out at 0.026. Compare this to Cliff’s suggestion of at least 0.037 to start, and you can easily see why it wasn’t getting enough air and fuel at idle. The idle down channels weren’t much better either.

Mark, I do intend to further tweak and tune on this carb going forward, if only to continue to try and make it as efficient and powerful as possible. Thanks for the info and recommendations on the jets and needles, but I have no spare QuadraJet parts whatsoever available to me currently. The local speed shop MAY have a selection of parts for the Edelbrock QuadraJets, do you happen to know if parts for these are interchangeable with the standard QJ’s?
I would think they probably are, but I’m not certain...

In other related news, I struck out on locating a vacuum gauge for testing tonight and my own mixture screw adjusting tool. (The one I’m currently using is borrowed)
Two of the places I went were closed, and the other two didn’t exactly have an awe inspiring selection of mechanics tools.
I will continue the search tomorrow, hopefully with better luck.

D.

 

[olds307 and 403]

Yes, the Edelbrock parts are interchangeable. Primary metering rods need to match the series of carb, the secondary rods fit all years. The CV, found on most 70's carb or the CK rods which Edelbrock have discontinued should be ideal for your carb. Probably the CE rods and K hanger are your best bet for your current set-up from Edelbrock. I would also adjust the secondary air door opening, also in Cliff's book and make sure the secondary throttle bores are opening all the way as well.
Here is another source of parts.
https://quadrajetparts.com/quadrajet-secondary-rods-c-128_44_49.html

 

[denny]

Hey guys, what’s up.

I’ll get into more particulars of my issue with this QuadraJet later in this thread, but for right now, a simple question:

Is it possible to have a QuadraJet run on the primary circuit rather than the idle circuit?

My car WILL NOT idle on its own after starting it, even if it’s already up to operating temperature. It just stalls. If I very carefully feather the gas and hold the rpms around 800-1000 where it should idle, the engine sounds normal and you can hear the lope of the cam as you should.
But as soon as I take my foot off the gas it just stalls.

The only way I can get it to stay running on its own is if I rev it to 3500-4000 rpm, then it’ll stay running but it’s pig rich and doesn’t sound like it should. Revving it to anything less than these rpms won’t keep it running.

Once it does stay running this way, I can drive the car around for hours through start and stop traffic, and it pulls good throughout the rpm range but as soon as I shut it off and go to restart it the cycle starts all over again.
It’s almost as if when I rev it into this rpm range, it fools the carb into running on the primary circuit rather than the idle circuit. Is this possible?

I’ve gone through countless hours and trouble shooting only to find nothing out of the ordinary. It’s recently been rebuilt, no vacuum leaks, throttle shafts have been bushed, tinkering with the timing and vacuum advance pulloff locations has no effect on the problem. It seems to be an issue with the idle circuit, but unable to determine what. The idle mixture screws are turned out the recommended 3-3 1/2 turns.

The carb was thoroughly cleaned and air blown through all the passages when it was rebuilt, so dirt or contamination is highly unlikely. And yes, I have already bought the Doug Roe QuadraJet book. I see no mention of the problem I’m experiencing in it.

Please help before another QuadraJet finds its way onto the scrap heap. I’m at my wits end with it.

i installed a blue print bp3503ct1 engine in my 81 malibu last summer. it has vortec heads and a hyd. roller cam,.495 int .502 ex and dur at .050 .221i .226x. i run a edelbrock model 1904 (t think thats the right number). idle at 16 in. vac. and at 2100 rpm cruise 21 in. vac. idles at 800 rpm very good. i went up one jet size,opened the idle tubes a couple thou and opened up the idle mix. holes per Cliffs book. this q-jet runs great. i run an edelbrock performer intake. most q-jets were never intended to be used with big street cams and do not perform well. also i run a locked out dist. with 34 fixed. 3:73 rear. i have had hot rods since the late 50's and this set up is very responsive and hits very hard. i had thought about f.i. but this set up is on it and you know the saying about if it's not broke. try to get a few spares (they are still cheap if you look hard) and study Cliff's book and you will be rewarded. these are outstanding carbs. and can be made to work on any engine. hope you work things out. Denny

 

[Bonnewagon]

As stated, grab as many as you can to cannibalize for parts. This is a situation where the interweb is your friend. There are quite a few Q-jet parts vendors out there and parts are actually more available now then back in the day. I got this assortment on Ebay and it covers a large range of jets. But get Roe's book first so you know what to look for. A general rule of thumb is that you need to go at least 3 jet sizes to feel any difference in the seat of your pants. 1 size change may register on sophisticated equipment but you'll never feel anything. That is why I suggested #73 jets but if the #69s work then that's fine. Also look for a vacuum gauge on any car parts vendor site or Ebay as they are cheap and plentiful. https://www.ebay.com/itm/ROCHESTER-QUADRAJET-CARBURETOR-HIGH-PERFORMANCE-TUNING-KIT-JETS-9-PRS-SPRINGS/320931072732?hash=item4ab8fb8adc:g:ZcsAAOxydlFS0a~8

 

[Rktpwrd]

Yes, the Edelbrock parts are interchangeable. Primary metering rods need to match the series of carb, the secondary rods fit all years. The CV, found on most 70's carb or the CK rods which Edelbrock have discontinued should be ideal for your carb. Probably the CE rods and K hanger are your best bet for your current set-up from Edelbrock. I would also adjust the secondary air door opening, also in Cliff's book and make sure the secondary throttle bores are opening all the way as well.
Here is another source of parts.
https://quadrajetparts.com/quadrajet-secondary-rods-c-128_44_49.html

i installed a blue print bp3503ct1 engine in my 81 malibu last summer. it has vortec heads and a hyd. roller cam,.495 int .502 ex and dur at .050 .221i .226x. i run a edelbrock model 1904 (t think thats the right number). idle at 16 in. vac. and at 2100 rpm cruise 21 in. vac. idles at 800 rpm very good. i went up one jet size,opened the idle tubes a couple thou and opened up the idle mix. holes per Cliffs book. this q-jet runs great. i run an edelbrock performer intake. most q-jets were never intended to be used with big street cams and do not perform well. also i run a locked out dist. with 34 fixed. 3:73 rear. i have had hot rods since the late 50's and this set up is very responsive and hits very hard. i had thought about f.i. but this set up is on it and you know the saying about if it's not broke. try to get a few spares (they are still cheap if you look hard) and study Cliff's book and you will be rewarded. these are outstanding carbs. and can be made to work on any engine. hope you work things out. Denny

As stated, grab as many as you can to cannibalize for parts. This is a situation where the interweb is your friend. There are quite a few Q-jet parts vendors out there and parts are actually more available now then back in the day. I got this assortment on Ebay and it covers a large range of jets. But get Roe's book first so you know what to look for. A general rule of thumb is that you need to go at least 3 jet sizes to feel any difference in the seat of your pants. 1 size change may register on sophisticated equipment but you'll never feel anything. That is why I suggested #73 jets but if the #69s work then that's fine. Also look for a vacuum gauge on any car parts vendor site or Ebay as they are cheap and plentiful. https://www.ebay.com/itm/ROCHESTER-QUADRAJET-CARBURETOR-HIGH-PERFORMANCE-TUNING-KIT-JETS-9-PRS-SPRINGS/320931072732?hash=item4ab8fb8adc:g:ZcsAAOxydlFS0a~8

Thanks for the additional info and links guys, much appreciated!

I did have a modicum of success today, I picked up this really nice OTC vacuum tester gauge kit:

It was very reasonably priced and comes with all the attachments for different size lines. It should more than do the job.
While I was at it, I also grabbed a Lisle mixture screw adjusting tool.
No more borrowing other peoples sh*t!!
🙂

I’m planning on a trip to the speed shop tomorrow, gonna try and find me a decently priced Hi-Torque mini starter (the who-knows-how-old-stock-style one struggles to start against the initial timing sometimes) so I’ll see what they’ve got on the shelf in the way of bigger rods and jets for QJ’s.

 

[pontiacgp]

Donovan, not wanting to sound like a survey but on a scale of 1 to 10 how hard was it to disassemble, modify and reassemble your quadrajet. I think guys like you give more incentive to others to work on their quadrajets than some of the experts on the forum ,

 

[Rktpwrd]

Donovan, not wanting to sound like a survey but on a scale of 1 to 10 how hard was it to disassemble, modify and reassemble your quadrajet. I think guys like you give more incentive to others to work on their quadrajets than some of the experts on the forum ,

Steve, I suppose that would depend on one’s mechanical ability. I personally am very mechanically inclined, always have been, so for me it wasn’t that bad.
Information is the key as far as I’m concerned tho. If I had no books, illustrations, exploded diagrams etc to go by when I started, then I suppose I would rate it at probably a 8 or 9.

However, with the right resources available (including the awesome guys here on the forum) it was no harder than maybe a 3.
It also depends on how in depth one wants to get into it. If all someone wants to do is change needles and jets, then it’s relative gravy.
Pulling idle tubes out of their bores however, was a real b!tch. It took some real patience and perseverance to make that happen.

Overall tho, I’m gonna say if you can pull a wrench or turn a screwdriver and are willing to learn, it ain’t that bad. Most people shouldn’t have a problem.