Ok. The non cc Qjet I rebuilt from teh junkyard isnt working right. First of all, it's got an off-idle bog.

When I rev it, or take off at a light, it bogs for a sec. If I watch the carb as I rev it, I can see that as I rev it it will not lose vacuum (the diaphram that holds the secondary airvalves closed doesnt release) and then as soon as it actually picks up RPM, the vacuum subsides.

When I blip the throttle with the engine off I see a good squirt of fuel come out. It's got all the stock jetting in it. The float is right. Guys, I'm out of ideas here. I am pretty sure it's lean, because when I disconnected the accelerator pump lever and revved it, the bogging got worse.

Brand new fuel filter, too. So could it be my fuel pump? Then why is it still fine at higher RPM? I had teh idle mixture screws turned out SIX turns, to no avail.

Anyone able to help at all?




(oh yeah, the second issue. cold starting. It bogs way worse when cold. Stalls when I put it in drive. The choke is set up pretty well, but the fast idle cam.. well I am no even sure what that is, so. Maybe I screwed up sommething in the choke linkage? Everything in that area SEEMS fine, it looks exactly like the old one, but still.)

 

Do you have the accelerator pump pushrod on the inner hole of the arm (closest to the fulcrum)? Does it begin to squirt fuel the instant the throttle arm moves- no delay?

QJet accelerator pumps are usually plenty good for all but the most bizarre of applications if they're working correctly.

Another thing you can try as a test is to slowly bring the RPMs up in 300 RPM steps (idle up to maybe 3000 or so) and then MANUALLY close the choke plate at each step. If it's lean anywhere in the range- idle, off idle, mains- you'll notice that as you close the choke plate the engine will pick up RPMs and run smoother. I just recently found a jet in my "good" QJet that was actually drilled 6 (SIX!!!) jet sizes smaller than what it was stamped and this is the test I used to begin diagnosis. Once I figured out it was running wicked lean on the primaries (this test had meaningful results from about 2500 on up) it was just a matter of going through the carb with a fine tooth comb before I nailed it dead-bang. I didn't have a bog since the problem was in the mains, but it had a slight flat-spot as I got beyond about 10% throttle.

BTW- was this old carb originally from a V8 application? Ones used on V6s are often set up too lean for even a mild V8.

 

One other thing..... how's your ignition timing? Overly advanced or retarded timing can give you a bog you'll never tune out at the carb.

 

The ignition timing is about 4 degrees advanced past stock. I will check how it squirts tomorrow, as well as bring up the rpms. Maybe I should put the jets/rods in from the old one and see what happens.. It was off a v8 though...

 

Ok, so I have replaced teh fuel pump. I did nothing to help. There is a really good squirt when I flick the throttle when the engine is off. No delay. Manually closing the choke plate doesnt seem to have any effect on it..

Yet it still bogs.. If anything, with this new fuel pump it seems to be running WORSE, though it isnt showing any symptoms at all of it running rich. When I disconnect the accelerator pump (lever is connected to the linkage via the inner hole, btw), it bogs even more.

I also have noticed that once in a while, while I am tuning the thing, it will drip a bit of gas externally. It drips from the area right under the choke, from those springs and things that are connected to the shaft that the throttle blades (primary) are attached to.


I am so terribly stumped here. I am tempted to just go buy another carb from the jy and transfer all teh new components form the rebuild to it...

Thnaks for the help Damon, btw.

 

But how is she after the bog? Does she pull strong?

You're watching the carb from the driver's seat with both the hood up, and with a load behind it, right?

Did you try tightening the secondary flap continuously, until the bog goes away (the only way to tune it, is with a load behind it)....

How do you're plugs look, and are you tuning the engine with a vacuum gauge?

Three turns out on both sides should be a good starting point. Again though, let us know if you're measuring vacuum with a gauge... otherwise you're playing a guessing game.

 

Stock, or high pressure pump (is there a return line on it)? I know you stated that the float was set properly, but you'll probably need to set it again (if you're running a stronger pump)...

By the way, how is she on turns? Does she hesitate, and 'want' to stall at anytime during a turn?

What do you mean? With the engine idling, and with you're hand fully covering the choke plate.... the engine doesn't stall out?

Which symptoms are you looking for, I'm just curious?

Because the mixture is too lean this way, same difference with an early opening secondary flap. I still think it needs to be tightened continuously until the bogging stops...

Did you have the carburetor completely apart? You need to replace that gasket on the shaft. If she's idling fine, and there's no loss in vacuum (via gauge reading), then I'd still be looking at you're secondary flap (opening too soon).

 

Not really. Well sort of, but I know there i smore there..

Ok, I'll give it a shot

Dont know yet, and I wasnt, no. But I just got one today, finally.

Yeah, that's what I thought lol. 6 turns seemed like a little much. It was FOUR on my old one, too...

No, it doesnt. I try to close it all the way, but obviously I dont cover it ALL up..

Well I disconnedted the accelerator pump lever and revved it, and it bogged worse..

Ok. Is this the flap tightening thing on teh top passenger side or lower drivers?

Yeah, but I didnt take teh shaft out. And when it's cold it stalls when in drive if I give it ANY gas at all. But I will try to adjust the secondary flap.




Thanks for all the help. I really appreciate it. I would've gotten back to this thread sooner, but I have been working a LOT.. I'll try all your suggestions and see what happens.

 

Ok, so this is what happened when I connected the vacuum guage. All numbers are in in-hg.

At idle it would range from about 16-18. Idle in drive it would measure about 19-20. From a crawl, in gear, engine idling, when I hit the gas, it would drop to like three, and then slowly climb a bit. When I revved it in neutral it would also drop to like three, and then it would climb, and THEN the engine would pick up rpms. When I held it in second geaar at 50 mph and let off the gas, it would go to about 23 or 24..

And the temperature was around 180 degrees f. That's what it normally runs at.. It's FAR worse when it is cold.

 

....Isn't it hard to hold on to the hood while the car is going that fast?



Before you get too into checking the difficult stuff, remember, a stock carb from a very similar engine (you took this carb off an LG4 right??), after being rebuilt RIGHT, should work perfect.
Now you're on to rebuild #2. I imagine you just missed something little, like a tiny spring or clip or something... Did you blow out the passages with compressed air? I noticed a difference when I did that, one of my idle air bleeds was plugged....
If you have some spare time, re-rebuild it, and make sure everything is blown out, and put back together exactly as it's supposed to be (you still have your original stock carb as a template if you forget how something goes...)
-J

 

lol I ran a hose out between the hood and the cowl, and pinched the gauge under a windshield wiper..

I blew out the passages, yeah. There were a few things in the old one that werent in the new one. Like that clip that held the float needle to the lever, and some plastic thing that went in the hole in the float bowl to the left of the inlet.. Other than that.. hmm. I didnt take out the shafts, maybe I should have. But first I need time to figure out the secondary issue. After that, if the bog is gone, all I need to do is find out why the hell it is so messed up when it's cold.

 

yea, I wouldn't bother with the shafts, espescially the choke/primary one, so many tabs and "thingies" on the choke side, it's hard to remember which tang goes inwards/outwards and up/down (such as the fast idle cam, etc...)


You didn't fix that clip?

I'd say it'd be worth fixing...
You left the primary rods/jets as were in the old carb, you didn't use the ones from your original carb? hmm....

oh, did you adjust the phillips screw on the choke pulloff and your t-stat? That should cover the cold start...

One last thing, do you know what your base ignition timing is?

 

nono, I did fix it.

Phillips screw where? I adjusted the choke though.

Uh, I advanced it like.. four degrees above stock, which was ..six?

 

k, timing should be ok...
The phillips screw thats on the vacuum can... The one that you asked about in the other thread that has "no purpose"......
Anyway, good luck.

 

Ah, right. I am thinking of simply copying all of the adjustment specs from the old one to the new one...?

I also got a job at a dealership. The parts guy there said he might be able to get me a deal on a carb somewhere, so I am also pursuing that front. But I'd honestly rather get this carb working and spend the money on a y-pipe for the headers I have in my basement.

 

amen!

Which dealership? I'll have to come by and heckle you
Ask you for a price on piston return springs, or a powerband, then get livid when you tell me they're not in stock, or on back order

 

There are two screws that need to be adjusted when setting you're secondaries. Find the smallest, and thinnest, screwdriver.... than find yourself an even smaller allen-wrench.

With the engine off, underneath the air-horn... on the rear, passenger side of the carb, there is a very very small screw that is screwed 'upward' into the airhorn (it's best if you have a spare carb, and flip it upside down to see. You'll be able to see both the screw and spring, and you'll better understand how it works)....

Once found, look for the screw that is going 'into' the airhorn from it's side (you'll see it, as it is on the outside going into the hidden screw... just move the linkage around a bit to find it). These two screws work hand in hand, as the hidden screw is used to hold the outer (or visually seen) screw in place.

Loosen the hidden screw a tad with the allen-wench... and while it is loose a bit, tighten the other one with the screwdriver. Be careful though, as when you go to re-tighten the hidden one, you need to hold the outer one in place with the screwdriver (otherwise the tension will cause the outer screw to back out on it's own if you don't, causing an even worse bog).

Keep doing this until the bog goes away. If you find that the bog goes away, but perfomance is being held back... you simply tightened it too much. Back it out again, then repeat until desired perfomance is reached....

Good Luck!

 

if this isn't crystal clear, check the main TGO page for instructions, there's a tech article, with pictures
-J

 

It's more fun asking for a 62 Corvair water pump.

 

It was in that article, too..

 

That's a new one on me... Which one didn't exist, the corvair or the water pump?
Kinda like a '75 Camaro Z-28 or..... There was a corvette year that didn't exist too I thought....

 

Hahahaha I will have to try that on them, see what happens..

I tightened that screw btw. Didnt do anything. Loosened it, too. Nothing.

 

There was no 83 Corvette, but this one is even better. The car existed, but the water pump didn't.

 

You'll honestly need to explain what you did a little bit better. Which screw (singular) are we talking about here?

Keep tightening the outer screw until the secondaries don't open up at all under a load (the car will drive, but will obviously lack power under full throttle). Get to this point (if possible), then come back and follow up with this thread...

Note that if you cannot get to that point above (and you honestly tightened it all the way, and the secondaries do not open... and you still have a bog), then it's probably you're accelerator pump.

 

Sorry, I was replying to what Sonix said. The one on the secondary.. the one that seems to do nothing at all, but actually controls how much the secondary flaps on teh top open when it's cold..

About the secondary thing though, when it's cold, they dont open, but it still bogs. Worse, even. Considerably worse.

 

How do you know that the secondaries (rear flap) won't open when the engine is cold? Is the choke's flap (front flap) opened slightly when the engine is cold, or is it opened all the way (all the way would cause a bog when cold)?

 

Well I thought it was pretty much a moot point for the secondaries, because the butterflies dont open when it's cold because of the lockout. But I decided to mess with the screw anyway.

The choke flap is almost completely closed. Like, open enough for the engine to run.. I have spent a long time on this, too.

 

Wanna drop by and we can oogle it? I'm bored as SIN this week, waiting to get paid to buy parts... Lots of time + no cash = me reading TGO posts......

 

lol ok that might actually work well. What time would work well for you? My only solid commitment is that I'm working mon-friday, but I'm off at five every day..

 

Which butterflies? What lockout? The choke's, right? Again, you'll have to be a little bit more elaborate. Just to briefly go over (and I'm sure you know this already), the choke's flap should be opened slightly when cold.... and open gradually as it warms. The secondaries are vacuum controlled, and only open when a certain amount of vacuum is achieved (regardless if the engine is cold or warm).

If you've observed you're choke during the warm up process, and it's doing exactly what it's supposed to be doing, then move on to next possibility....

With the engine idling, lightly press down on the secondary flap and see if it opens up too easily. If the secondary flap seems firm, and doesn't open too easily... then while you're under the hood, pull the throttle lever all the way back, and at least verify that the secondaries are in fact opening at a certain point in vacuum.

Move onto the next possibility, the float. How did you adjust the float level (by bending the metal tang), how many thousandths?

It honestly sounds as if the carb has had a bad rebuild, especially if she's leaking fuel. I would honestly consider getting myself a new rebuild kit, torx screwdriver, and rebuild the damn thing myself...

 

haha, he did rebuild it himself.
His first time, hence why all the weird problems. Mine had all sorts of goofy problems, it took a while of adjusting tangs and whatnot, then it ran pefectly, save for a somewhat difficult hot start...
We'll see what it looks like this evening.

 

IT WORKS!! IT WORKS!

Sonix is a freaking ***. I just spent a bunch of time with him, tuning, and we made a LOT of progress. My bog is completely gone, when I brake stand it I can spin all through first and a bit into second.. it's freaking amazing. Runs better than my old one ever did. I just did the best donut of my life in front of the grocery store that I used to work at, that I hate....

Thanks a million, man.

And thank all of you for your help.

 

damn it...
I wrote a nice long post, my attachment was like 1kb too long, and so it deleted it on me.

i'm too tired to rewrite this w/ good grammar and such->

glad it worked for you. you have a nice car, runs so much smoother than mine....

long story short
he has 41 rods
73 jets
dr rods
some hanger...
anyone else's opinion, that primary system ok? seems rich for a bone stock LG4

also, FYI, his problem was:
lean stop bottomed out
float slightly low

choke t-stat a bit off, adjusted
choke pulloff screw bottomed out, adjusted to my car's spec

We'll see about the cold start eh?...

 

finally... anyway, saw this in doug roes book, since you asked about this:

 

lol the ONLY way I DIDNT have that tang on there.. Oh well. Next time I'm in there..

Tomorrow, cold start.

 

That primary system is fine. You can tune around it to compensate (I do it every weekend at the track)...

I could have sworn I mentioned the float setting above.... j/k

There is really only one out of those four reasons that are mentioned above that would cause the engine to bog like that.... and that's the bad float setting.

With the float set properly, you can honestly set his choke back the way it already was... and the bog will still be eliminated.

Either way, I'm glad it's resolved!

 

Now that explains it all! j/k

 

Well I think the fact that the power piston was seating WAY too low had a huge effect on it too...

And as for the primary system, it's now 43 rods and 73 jets. When I get the headers installed, we will see what it needs...

 

Yea, the choke didn't affect his bog I wouldn't think....

but his other main problem was a terrible cold start, bog getting worse during cold starting, therby making the choke system.... wrong.

And yea, the choke pulloff screw was, well, tightened, like completely bottomed out.... It needed adjustment...

The float was pretty close, I think the power piston being way too low was the main problem, but that's just guesswork now, either way, it's better so.... however, he swapped a fuel pump 'cuz he said it was running out of fuel.... Then the float was too low so....


Lethal, what do you mean tune around the primary system as is? Like adjusting idle mixture? I figured tuning would result in changing the primary rods/jets...
Anywhoo, how is the cold start? you have slept since, right?

 

Mhmm. It was far worse with the ld fuel pump. I meant to repace that like.. three months ago.

Now, yeah, I think I still need to mess with the choke a bit to take care of the high idle. because of it running at a lower tmp.... Meh, that'll be easy to fix. But first, I will mark it's current osition.