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The owner wisely decided to abandon this carb and go on a search for a good, solid, original, rebuildable Q-Jet.
Several options, good and bad, popped up on eBay. We screened every one of them, rejecting most for various reasons, including all the ones that were obviously Commercially Rebuilt carbs. But after a few days of searching, this little gem popped up:
You may ask why in the world this horrible-looking, dirty, crummy carb is a “gem.” In fact, this is a wonderful, original, unmolested carb that is a perfect candidate for rebuild. It’s a real 1969 Vette carb, and it’s being sold for $75.
Here’s why it’s a fantastic buy:
It has not been commercially rebuilt, so it has only been messed with by amateurs
Look at the screws in the airhorn: They are the correct slotted-head screws, and they still have their original black phosphate coating without corrosion.
Look at the secondary airvalves and the choke plate: No rust, and original silver cad plating still in place.
All the parts are there for the bowl vent system (aka, “doghouse”).
All the choke pulloff parts and linkages are intact and correct for a ’69.
There is no corrosion on the carb – it has lots of dirt and grime on it, which has protected the factory plating – I’m betting the original plating is under all that crap somewhere…
Once the carb was paid for and received, I did a quick teardown and inspection. All the jetting parts and metering rods were original and correct, attesting to the unmolested nature of the carb. But it has been sitting around for a while, and the jets were seized into the bottom of the float bowl:
When parts are seized, don’t ever try to force them out. You’ll either break the parts/screws/fasteners, or you’ll round out/tear up the screwdriver slot. Just heat the parts up a little with a small torch and they’ll come right out:
Typical issue with old Q-Jet airhorns: One of the secondary fuel feed tubes had fallen out and was laying in the float bowl. Most Q-Jets I receive have both of these tubes missing. These tubes provide the secondary fuel tip-in shot, like a secondary accel pump, and when they fall out, the carb develops a massive stumble when going into the secondaries:
All disassembled and ready for the hot tank:
Nice clean parts ready for assembly. A little work with a toothbrush gets everything nice and clean:
Carb was given a precision assembly with some new primary jets to match the owner’s engine application with headers and intake system. A few “tweaks” to the setup and the carb is ready for test:
Note the correct plating on the various components: Q-Jets were not built with gold cad secondary airvalves and gold choke plates. These parts were plain silver cad. The screws were not gold cad plated - they were black phosphate coated:
Q-Jets up through 1969 did not have a provision in the rear of the throttle plate for a power brake vacuum fitting - the casting is not drilled. They can be drilled and tapped if you want to use a '69 carb on a later-model car:
Correctly-configured and set up 1969 choke and choke pulloff system. Same system was used on 1970. Compare this photo to the photos of the altered/mangled '69 choke system on the commercially rebuilt carb in the previous thread:
It's not possible to rebuild a carb and assure that it's "right" without running it. Here is the carb up and running on the test engine. Carb fired up and ran immediately:
Running cold with the choke closed and cracked upon by the correctly-working choke pulloff. Most Q-Jets run best cold with the pulloff cracking the choke open about 1/4" as measured from the forward lower edge of the choke plate to the casting wall:
Fast idle speed was initially just a tad low, so it was bumped up to a nice, stable 1340 rpm:
A quick check of the wideband shows the cold idle mixture to be right at the desired point in the mid-12’s. This can be adjusted by changing the choke pulloff from the 1/4" spec noted above:
Once the engine warmed up, choke was set wide open, and the secondary lockout lever retracted as it should:
A little tweak of the hot idle speed screw produced rock-steady, smooth idle at about 850 rpm:
I had taken a wild guess that this ’69 carb would idle well with the mixture screws at 3 turns out, and this produced idle air/fuel mixture dead on the numbers at 14.7: 1 and 1.00 lambda. A perfect running carb. Idle mixture screw settings vary greatly from one carb to another and from one year to another. Correctly set, Q-Jet idle mixture screws can be anywhere from 1-1/2 turns to 9 turns out from seated:
This carb will be a huge improvement over the hacked-up Commercial carb that the owner was running before. It should be reliable with a very nice level of performance. Total cost for a well-running Q-Jet, including the initial purchase price, ended up at about $300. Not all carbs can be set up and repaired at this price level, but this is a good example of a well-bought carb by someone willing to spend the time doing a little searching. You '69 Vette guys looking for a correct carb are going to cry, but this carb is going to be mounted on a Porsche 914...
Thanks Lars, now I have something to compare with mine from the 69. T
If you need detailed photos of correct '69 Q-Jets, just drop me a note - I keep photo files on a lot of Q-Jet configurations. Send me your carb number and I'll send you a photo package.
This is a very similar situation to when years ago I used to scarf up used Holley's at the swap meets. Actually when I lived in Denver it was great pickings because so many folks ruined them by 'tuning" and getting them so far out of whack they'd never run right. I just started from scratch and would put them back to how they came and THEN made whatever MINOR tweaks were needed to make them run well at altitude. Sold quite a few re-furbed ones!!
They were partially stripped, but still serviceable for most applications. I machined them and fixed them to assure long life reliability for the owner. I didn't include that operation in the photo sequence since most people do not have the specialty tooling or machine capability to do the operation.
This is a very similar situation to when years ago I used to scarf up used Holley's at the swap meets. Actually when I lived in Denver it was great pickings because so many folks ruined them by 'tuning" and getting them so far out of whack they'd never run right. I just started from scratch and would put them back to how they came and THEN made whatever MINOR tweaks were needed to make them run well at altitude. Sold quite a few re-furbed ones!!
JIM
I have and still do the exact same thing!
I have a chem dip and an Ultrasonic cleaner which really brings finishes back from the dead and brightens aluminum......I do a lot of vintage bike carbs too......here is the set from my own bike, a 1979 CBX......it has over 400 parts on each set
The other two photos are a Holley 450 that I brought back from the dead as well as a Carter WCFB from a 1955 Caddy
Can you elaborate on the “doghouse” adjustment setup procedure?
It's a simple matter of slightly bending the wire tang so that the bowl vent reed cracks open when the throttle is at idle, and closes upon throttle opening:
Originally Posted by RickDett
Carb rebuild kits recommend rpms set to 2400 which I though seemed very high.
Rev'ing a cold engine up to 2400 rpm immediately upon start would not be a good idea... GM spec fast idle is 1500, and I find even that to be uncomfortably high, especially when dropping an automatic into gear at that rpm. I prefer setting fast idle at 1250 - 1350 rpm. This produces a nice, stable idle on most engines, and avoids excessively high rpm on a cold engine.
02-21-2018, 04:15 PM
Rebuilding a $75 '69 Vette Q-Jet Found on eBay
