Fair warning to anyone looking to rebuild a quadrajet.

99716 Views 15 Replies 9 Participants Last post by N0DIH, Sep 2, 2007

Gwokable

Discussion Starter · May 19, 2007

I recently decided to rebuild an E4ME Rochester Quadrajet for my 88 brougham RWD. I found out a few things you guys should be doing prior to rebuilding one of these carburetors, as the cost of rebuilding it for me, had I decided to do it myself instead of buy a reamanned, would be over $400.

Basically, to estemate the cost, you look at a few tools and parts prior to disassembly. So first you list off what you need:

Minimally, here's what you're going to need:

NAPA Rebuild kit (sorrensons are crap): $45
Choke angle Gauge tool (no longer manufactured): $60
Special sockets set: $20
Carb cleaner: $40 (2 gallons for a 5 gallon bucket).
Float: $10
Epoxy: $10 (for sealing up the leaky lead joints).

General tools:
Dwell Meter w/ RPM reading: $30
Timing light: $30-$40
Distributor adjustment tool: $10
Vacuum tester: $30.

Before you even pull the carb apart, you do some basic tests:

*Test out the TPS. If you have to replace it, there's another $30-$40.

*Test out the MCS. If it's bad, then you get to spend another $60 on one, although for what you get it isn't too shabby.

*Test out the front and rear vacuum break assemblies on the passenger side of the carb. Get a vacuum tester and pump them up to 15PSI. If they move smoothly, they're ok. Otherwise, you're looking for parts that are difficult as all hell to find (I can't find em' anywhere).

*Test out the ILC; pump it upto 25PSI and make sure the screw moves freely. If it doesn't, then it's time for a new ILC. Most new carbs don't come with an ILC, BTW.

When it's all said and done, if you're looking a carb like mine where the ILC, front and rear vaccuum breaks, TPS and MCS are all shot, just get a new carb, have a mechanic install it, and be on your way. Autozone sells quadrajets for around $270 (remanned, core charge of $35) and to have a carb replaced and tuned up is fairly cheap.

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joe_padavano

· #2 · May 20, 2007

Here's my costs to rebuild an electronic Qjet:

Rebuild kit $45
Float $10
Carb cleaner $10 (two spray cans @ $5 ea - I use the spray cans because the little tube lets me spray into passageways)
Gas filter $5
Air filter $5

As for tools, if you plan on doing any work on your car at all, you should already have a dwell meter, timing light, and vac gauge. I wouldn't count these towards the cost of the rebuild. The special EQjet tools are nice, but not mandatory. I was able to adjust the M/C solenoid screw with a pair of long needlenose pliers. The factory service manual gives the gauge dimensions of the special gauges, so I made duplicates with bent wire and tubing. Since that rebuild, by the way, I've acquired a complete set of the special double D tools, the gauges, and the choke angle gauge all on ebay for cheap.

You are correct about testing the M/C solenoid and the TPS prior to disassembly. Mine were fortunately fine, but if necessary, wrecking yards around here (Northern VA) are full of B-body wagons with 307s and EQjets. You could grab a selection of TPS and M/C solenoids for just about nothing.

Note that I did spend $8 at NAPA to buy the terminals and necessary to fabricate a jumper harness to let me check the TPS voltage. Since then I've gotten a complete OTC Genysis electronic test tool (mainly for my 99 Chevy truck) that allows me to plug into the ALDL connector and read all the sensor outputs. You can find OBD I scan tools on ebay for cheap also.

Total cost to me: $75 (plus $8 for the terminals)
Knowing the carb is rebuilt correctly and satisfaction of a job well done: Priceless.

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Gwokable

Discussion Starter · #3 · May 20, 2007

I think my carb was one of the worst ones out there.

*The PCV intake passages were completely clogged with crap. I took a drill, and some shop towels, wetted the towels, wrapped them around the bit then drilled the sucker out real good. Repeated about 20 times to get it completly spotless. Similarily, I had to de-rustify the bolts so I used an old method that works great.

*I took a nut, got a new bolt and the proper wrench for it. Lubed the nut with an excessive amount of lithium grease (lithium grease is a dry grease and works itself in), then put the hex head on the drill and drilled it in and out of the nut. Then I washed it off with carb cleaner, then took a shop towel, sprayed it with some carb cleaner, then drilled the bolt in and out of the shop towel to remove the rest of the crap from the sides of the threads.

*I had build-up that was only removable with a toothbrush and a pick.

*Carb cleaner doesn't do shit for gasket that wants to leave residue on the carb. My gaskets were probably readily flammable from being soaked and hardened in fuel. Since the gasket was 3-ply, the third play decided to stick and the rest came apart on both of em'. The 2 hour soaking enabled me to remove the gasket with a toothbrush.

*Someone, at some point, had decided to spray the thing down with a rubberized coating to prevent rust.

*The carb had never been rebuilt, and still had the original plugs in it from 86. Same goes for the ones on my car.

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Motorboat

· #4 · May 20, 2007

Good discussion guys, thanks!

DevilleMN

· #5 · May 20, 2007

Here's one for ya.

In '91 I had a 25' Crestliner with a 350. Could not get it to idle. Rebuilt the Quadrajet more than twice, replaced the intake manifold -on and on.

Desperate, as the family wanted a boat ride and I had run out of ideas, started on the phone trying to find a used carb thinking that would be easy, not at that time. One junk yard asked what was wrong with the old one-told him-he said give this guy a call "Scoobers Carb Shop".

The guy took my call, seemed to be quite old, said he could not hear me. So loudly said three words-Qudrajet won't idle. Reply was, boil it. --Boil it in what?--White vinager. and he hung up. Not how long, or the consentration, or why.

Thinking it through, vinager will dissolve salt and other crystals that water contamination leaves behind, carb cleaner won't do. Looking at a diagram of the Quadrjet the idle circuit has a blind bend that goes down from the float chamber and up to the exit below the throttle plate as I remember.

Anyway I boiled it, took the paint off and a whole lot of other crud, even started to pit the aluminum. Bottom line --it worked.

Ah, the good old days before StaBil. Right!

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Motorboat

· #6 · May 20, 2007

^ Funny but OHSO true. Had the same problem with a Chriscraft I had with a 350 in it. Learned my lesson the hard way, Sta-bil in everything that is going to sit for more than 3 months.

3141592654

· #7 · Jul 4, 2007

At some point in situations like this, I back up rethink my options. If the Qudra-JUNK is giving you so much headache...pitch it in the weeds! I gotta' believe that there are some good used Edelbrocks or Hollies out there that will fit your GM 350. Try E-Bay.

Get the good used one and rebuild that. If special tools are a problem, I believe the Hollies are less dependent than the Quadra's. BUT, be very careful putting sharp objects into orifices and the like. (No, I am not talking about sexual things!) Misshaping these orifies, seats, and so on can have a very bad influence in the overall performance.

I seen that Summit Racing Equipment was offering a chrome-plated Edelbrock for a couple hundred bucks. I almost went for it.

Good luck!
pi-

z06bigbird

· #8 · Jul 4, 2007

I drove my older cars about 100k miles. Never had a real problem with a QJet. Had to tighten screws on top. May have changed float. Did change choke pull off and temp spring (??) I forget what you call that coil spring on side.

Tons of other cars with carbs. There really aren't any moving parts in a carb. Keep butterfly free. Tighten down screws. Replace choke, etc.

Maybe I was just lucky.

the APEMAN

· #9 · Jul 5, 2007

I have clodrajets here that have lots of use. One was a Cadillac carb which was fitted with a later and fatter (idle circuit) baseplate. They are great carbonators for everyday use. Holleys are better for all out power but can really **** up intake valve stems on a Cad engine. Heck they are all toilet bowls filled with gasoline and it's 2007. Fuel injection............

z06bigbird

· #10 · Jul 5, 2007

Sounds like you write instruction manuals.

the APEMAN

· #11 · Jul 7, 2007

z06bigbird said:
Sounds like you write instruction manuals.

You are very perceptive sir.

N0DIH

· #12 · Jul 7, 2007

Speaking of toilet bowl fuel injection...

http://www.killerrons.com/toilets.cfm

The Ape Man said:
...Heck they are all toilet bowls filled with gasoline and it's 2007. Fuel injection............

cadillacmike68

· #13 · Aug 21, 2007

3141592654 said:
At some point in situations like this, I back up rethink my options. If the Qudra-JUNK is giving you so much headache...pitch it in the weeds! I gotta' believe that there are some good used Edelbrocks or Hollies out there that will fit your GM 350. Try E-Bay.

If you go this route you can kiss your climate control goodbye, so i don't recommend it. The QuadraJet had an enormous air flow rating 650-700 CFM for the really big ones - like as in my 1968. You don't need these aftermaket items unless you are racing down cliffs.:tisk:

N0DIH

· #14 · Aug 21, 2007

In 77 or so, all Q-Jets went to 800 CFM. But some in smaller applications restricted the secondaries. But the primaries were opened up to full size at least.

It is pretty easy to spot what a 750 vs 800 looks like (look down the primaries). The uber rare SD455 840 CFM is not something you would want to drive on the street with a small engine.

cadillacmike68

· #15 · Sep 2, 2007

I need to duh myself here. my Q-jet is rated for 750 or 800 CFM not the smaller numbers I posted earlier.

N0DIH

· #16 · Sep 2, 2007

Fairly easy to tell which too, look down the primaries, and look for the venturii ring, if you see a bulge in it, then it is a 800, if you see the ring with no bulge, then it is a 750. IIRC it is a screw boss.

Jim Hand has some good Q-Jet tweaks too on his that shows improvement on the flow bench (yeah, he has his own!), http://www.pontiacstreetperformance.com/psp/rebuild455jh2006.html, and easy ones for anyone to make it they really want to see improvements in airflow on the Q-Jet. Smoother airflow coming into the carb and aircleaner is always welcome and highly recommended. Even a 307 will respond to these type mods. Considering he runs 11.5's on 3.31 gears with a 474 CID engine with a mild 224/234 duration cam is QUITE respectable. And shifts around 5500-5600 too, so he isn't spinning the snot out of the engine doing it. This is a very streetable engine too. Wouldn't it be great to go spanking with a wagon on the street with this???

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