I have a quadrajet off an 80 or 81 chevy 305 auto truck. Carb # is 1708213. Carb was rebuilt. It's on a stock '82 Olds 307 with headers and performer intake. Non roller engine with the bigger ports. No EGR, no AIR pump and tubes were removed from exhaust. I have a wideband A/F gauge and it's showing rich. I got the idle to run about 14.7 but part throttle to WOT is rich. A/F at part throttle is about 13.0. WOT it goes to 10.9 then back up to 11.8. I'm assuming the secondaries open and start to lean it out some. Changed the jets from 72 to 69. Rods are 50M. Secondary I went from DP .0686 with N hanger to CZ .0947 with P hanger. I'm thinking my primaries are too rich and need a smaller jet but not sure how small to go. I thought this carb would work pretty good on this engine. Should I try 66 jets?

 

Pop out the aluminum plug in the air horn and thread the hole and add a plug. Count the number of turns as you remove the APT. Notch it so you can adjust it with a flat screw driver. Go a 1/2 turn down at a time down till your put throttle runs where you want. You can also buy the spring assortment and experiment, someone may have put an aftermarket spring in there.

 

I've done the mods to the APT. I've been turning it in 1/4 at a time. That seems to help part throttle. Last night I locked out the secondaries and at WOT the A/F read 10.9 and stayed there. Accelorator pump is on the farthest hole which should make it leaner. Other than changing the jets is there anything I can do to lean out the carb?

 

Either smaller main jets or a thicker rod. You could try a stiffer apt spring possibly. How many turns from seated is your apt? I would keep going down on turns, 66 is an awfully small jet but may be necessary.

 

Bigger rods would only lean part throttle. I think it needs smaller jets but 66 does seem small. I guess I'll give it a shot. APT is 3/4 turn out.

 

Yeah, 3/4 of a turn isn't much to play with. True enough, a jet change is needed if you are leaning full throttle as well.

 

Starting to wonder if I have another problem other than rich jets. I checked my needle and seat and it seems to be sealing well. Float seems to be working fine and is set a tad lower than stock so it does not flood. I might take off the carb and fill the bowl and place it on a piece of paper to see if there are any leaks. I'd heard the older quads leaked out of the main well plugs.

 

They all can leak, your carb would be considered one of the better later castings. The early ones had awful cup plugs. Checking for leaking plugs won't hurt though.

 

69 jets are already really small and 50 rods are waay lean. yeah it must be something else going on causing the problem. but I would have it jetted around 70-72 and the rods for part throttle to be correct for a modified car with cooler air and go down to something between 40-45. For example 77-78 350 Pont low compr engines had 71 jet and 44 rod and the 400 had 72 jet and 45 rod and those were smog settings. 301 pont in 80 had 70 jet w 50 rod pretty lean and 305 trucks usually have a 72 jet in the early 80's 1/2 ton silverados.

 

I'd been looking at the jet/rod combos for other carbs and that's what made me think it should be pretty lean already. I'll check for leaks on the plugs tonight. Probably JB weld them anyway.

 

My factory 78 403 carb had 73 jets and 44 rods. Does the 50 rod have a different tip? I am sure the apt was set like 10+ turns from seated or it had a part throttle stumble. I know Cliff ruggles has a 44 rod available on his site, supposed to have a better tip design.

 

The 50M has the thicker .036 tip. Most others have a smaller .026 tip.
It appears I did have a leak. gas was in the intake and the gasket was wet when I took the bottom off. I cleaned the plugs and put epoxy on them.




The secondary plugs had a rubber seal over them. I left it. Hope they dont leak. I let the epoxy dry over night and I'll start the car tonight after work. Crossing my fingers.

 

How is your car coming along? This is Neeley.

 

Hey Neeley. Well my 455 blew up at the race track. Rod went through the block so that will have to wait. I put in an old 307 just to keep me driving. Progress is coming along slowly. Ive been working on my daughters 72 442 to get it on the road mostly. It was just a shell. You have any projects?

 

There is always the possibility of the early pre-75 Gen 1 style primary rods being in a later 75-later Gen 2 style Qjet or vise a versa since the have a different overall length. The power tip should all be the same diameter. Adjust the APT in more, but how many full turns out was it ?

 

The pre75 rods were longer and would lean out this carb. Also the power tips were smaller at .026 from the early carbs and the later carbs had the .036 tips. I've got the later .036 tips. APT is 3/4 turn out. I epoxied the well plugs and will see if it still runs rich tonight after work. There seemed to be gas all over the bottom of the carb.

 

right, look forward to the results. It was acting like leaky wells

 

So are you in need of a block? If so i got one!Projects Yes a 1967 442 running and driving it will be for sale very soon.I will send you my cell number.

 

Well that was a failure. Car would not idle below 1100 rpms. I notice that the secondaries were not opening and the linkage was binding up so I took it apart again. Fuel was all over the bottom of the carb again. Put it back together. This time i had it idling better. Took it for a drive and seemed to still run rich. Opened it up and it got real rich. Stayed about 9.9 and barely made it home. So it's coming off again. I have a spare quad I might mess with or an edelbrock but it's a 750 and probably need rejetting. I'm frustrated at this point.

 

I would call you but i can't my phone quit screen shattered and lost all my numbers. I do have a new cell phone now.

 

It appears to be leaking fuel out of this little hole in front of the primary. Any idea what that hole is and why fuel is leaking out of it?

 

Neeley I'll call you in a few hours. Gotta run some errands.

 

Did some more reading and took a break from the garage. My top airhorn is warped and I think that is causing the leaking fuel. Possibly from the accelerator pump leaking between the bowl and the top airhorn. I'll report back.

 

Makes sense, Qjets are great when they work but I have had a few with issues not so easy to find.

 

Aaaaaah..... maybe. Does the Acc Pump fuel go thru the air horn?

Air horn gasket is above the fuel level, and should not be an issue.

I have worked on a QJet that was absurdly warped, like 1/4" across the air horn, but the body matched, and the carb performed flawlessly. It was astonishing.

 

Yes the acc pump pushes fuel through the gasket to the airhorn.

 

as long as the air horn and float bowl are warped together, there should not be an issue, other than appearance. the calibration of that carb. is wrong. jets/rods/power piston spring/etc. check to see that your needle/seat are sealing by inverting the float bowl, holding the float hinge pin in place, and sucking on the inlet. if you can't hold a vacuum, there's a leak. also, chwck your fuel pump pressure... no more than 6 psi.


bill

 

" check to see that your needle/seat are sealing by inverting the float bowl, holding the float hinge pin in place, and sucking on the inlet."

And take a picture of that and post it, please.

:-)

 

I need to check the gasket to see if there is an impression in the middle of it. I checked the needle and seat with pressure and vacuum and it seems good. You forgot to tell me to make sure there is no gas in the line first. No pics Octania. I set the float a little lower just in case it was causing it to flood. I need to check the fuel pressure.

 

are those really enough to be considered rich? your idle is like right on the money and cruise seems good too, wot is richer but seems fine to me since thats a full load on the engine. what kind of numbers are you looking for? i skimmed through the thread after the first few post

 

Remember he is running a low 8 to 1 307 with the tiny stock cam. The stock non CCC 307 carbs were quite lean from the factory up here.

 

Young olds, with the secondaries locked out it stumbles at WOT and dies from a dead stop. I'm looking for 12's at WOT.

Checked the fuel pressure and it was at 5 psi. The bowl was warped too but not much. There was not an impression in the middle of the gasket so the top horn is not touching. I'm still working on flattening the top plate. I have a little more to go. I'll leave a small arch in it to fit the bowl.

 

Idk if it is but this could simply mean you need to adjust the secondary air door

 

It actually leans out when the secondaries open up. Its just very rich on the primary side. I was busy and didnt do anything in the garage last night. I'll see what I can get done tonight.

 

bummed you didn't think of it first?


bill

 

If it goes lean they could be opening to fast, going lean and killing the engine or trying to and creating a stumble

 

It gets leaner all the way through the RPM. There is not a lean transition then gets rich again. It's a smooth transition to secondaries. And when i say lean it goes from 10.9 on the primaries to 11.8 which I still consider too rich for WOT.
Busy last night so no updates. This weekend I'll get some work done. Hopefully start it up and take it for a drive.

 

What kind of air filter arrangement are you running when doing this WOT A/F testing ?

 

Stock Air cleaner.

 

Well that would be the problem then if your are running a closed single snorkel air cleaner. It cannot flow what the carb wants to flow at WOT and therefore you keep leaning secondary out with an already small primary jet and still have a rich WOT (No air) , if you flip the lid or go to an open element 14" you will likely find it now way too lean at WOT with that set of lean .09" tip rods. you will need to richen that a bunch to get 12:1 later at WOT I bet it goes 15-16:1 with an open air cleaner as it is. You will want to go to a .04-.05 or smaller tip after the unrestricted open air access to the carb to get it just right.