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can you adjust the pump shot ??? more initial fuel might help. Like i said i dont know q jets but Bogs can go one of 2 ways and most of them are lean.
The pump shot is as long as it's going to get, short of getting a shorter plunger. I really don't think that's it.
I actually found an idle screw tool I must have bought years ago. They were way outta whack. One was almost closed and the other was open close to four turns. I don't know if it will help but I turned them both out 2.5 turns. I'll test it tomorrow if the rain holds off.
Originally Posted by olds 307 and 403
Make sure it isn't timing related. Mine has a similar bog at times, I bumped the timing a couple of degrees and eliminated the secondary pull off which both helped.
I just put looser springs on the advance weights but the bog was there before. If memory serves, I'm running 14 initial and 36 all in. I also put a limiter on the vacuum advance because it was adding something like 20 degrees. But this all worked fine with the last carb.
What's the downside of eliminating the choke pull off? I've read that's a no no.
My carb had the unnecessary dual pull offs, I eliminated the rear one. Unless you have pinging, let the timing loose, your low compression Olds V8 will like it.
My old carb only had the front pull off and it ran just fine.
There's also a lever of some sort against the secondary butterfly shaft. Looks like it keeps them from opening under certain conditions but I don't see it actuated by anything. My old carb didn't have that either. Can it go as well?
Because GM was in the habbit of installing "unnecessary" parts on cars to increase production cost and reduce profit...
On most Qjets, the FRONT "pulloff" actually controls the seconday air valves. It has an internal restriction in the nipple that limits air valve opening speed. It is really a dashpot.
The REAR "pulloff" actually is the choke pulloff for the choke plate. It helps open the choke plate more quickly.
Originally Posted by olds 307 and 403
Yes, removed the rear pull off and linkage. That piece prevents the secondaries from opening with the choke on.
Sorry, but not correct. Qjets used one of two secondary lockout features. On most Oldsmobile Qjets, the secondary lockout is an "L"-shaped lever that is operated directly from a rod off the choke housing. It is labeled "Air Valve Lockout" in this drawing.
Note the little tab sticking out just above the leading edge of the secondary air valve in this photo. THAT is the secondary lockout on most Olds carbs. FYI, also note that the front vacuum diaphragm is connected to the secondary air valves, not the choke.
On most Chevy Qjets and on the 1980s Olds Qjets, the secondary lockout is actually on the secondary throttle shaft at the bottom of the carb, just rearward of the choke housing.
Oh DAMN this is TWICE now I busted Joe P being incorrect.
"note that the front vacuum diaphragm is connected to the secondary air valves, not the choke."
In the above photo, notice the zigzag bend in the secondary air valve link to dashpot. It bumps against a tang on the choke parts and does indeed serve as the choke pulloff. Bend tang to adjust.
The pulloff diaphragm/ dashpot serves both purposes on that carb.
Last edited by Octania; July 12th, 2016 at 09:33 AM.
Oh DAMN this is TWICE now I busted Joe P being incorrect.
"note that the front vacuum diaphragm is connected to the secondary air valves, not the choke."
In the above photo, notice the zigzag bend in the secondary air valve link to dashpot. It bumps against a tang on the choke parts and does indeed serve as the choke pulloff. Bend tang to adjust.
The pulloff diaphragm/ dashpot serves both purposes on that carb.
That is correct. On the single-pulloff carbs the link is bent to allow the diaphragm to serve double duty.
My front pull off does both, secondary was tied into the choke linkage. I thought he meant the lock out tab you had pictured. I went off what Cliff Ruggles suggested. He said, as long as the primary pull off can control both, eliminate the secondary pull off. GM did a lot of weird things, probably had a reason. I am pushing the performance of this Cutlass way beyond GM's smogger specs. Emissions was their main concern followed by good drivability and performance was barely thought of.
Last edited by olds 307 and 403; July 12th, 2016 at 11:52 AM.
So here's where I think I am now:
1. I advanced the initial timing until it was hard to start and then backed it off (I'm waiting on a dial-back timing light to come from HF). It helped immensely with the acceleration.
2. I had the choke adjusted way too rich. It was different than my last carb (I think) and I didn't notice.
3. I adjusted the air door as best I can and the bog is much better.
4. It still has a slight bog and slower than ideal acceleration off idle (i'm sure the air door is too tight)
5. It also has a stumble at high RPM.
(a) I think, and my mechanic buddy agrees, it's running lean either from the float incorrectly adjusted or it needs jetting. I had my buddy drive it too.
(b) When I ordered the carb from an eBay builder I needed to specify my horsepower. So I guessed. I told him 250 hp. I may have underestimated. Or overestimated but it's not running rich.
6. The only simple thing I haven't tried, because I can be a doofus, is replacing the gas filter. I plumbed in a large, high-flow, clear filter before the fuel pump. It looks clean and full of gasoline so I haven't bothered yet.
Man, this thing wants to run strong. There's just a little something holding it back. I'll find it eventually.
Last edited by Macadoo; July 12th, 2016 at 01:25 PM.
Okay, you talked me into it, lol. I don't know why I haven't done it up to this point. Just don't feel like getting covered in gas maybe. Well, that and I just removed and cleaned my tank last summer before the trip to Niagara so I figure it's probably fine.
I can see it just fine. I will take a pic of mine on friday. I need to do an oil change, check plugs, adjust the air door looser and check slick's tire pressure for the 1/8 mile this weekend. Is this any better? https://www.google.ca/imgres?imgurl=...act=mrc&uact=8
Last edited by olds 307 and 403; July 12th, 2016 at 07:27 PM.
It looks like the carb I swapped out for this eighties-something unit.
The pictures look pretty small to me too, 307. I suppose it depends on the looker's screen resolution.
The second link you can see where the secondary pull off is missing. Mine was linked to the back of the choke linkage. I will show a close up, either way it runs better, probably because the rear pull off was leaking.
If no link rod at all is connected to your secondary air valve, then there is no dashpot to control the speed of its opening. If you counter that with more spring wrap, your top end will suffer though the bog in transition may improve [less bog].
So, just a thought, why not hook up all the carefully engineered links that control how things work and see how that goes? Adjust them per the CSM or carb kit instructions. Set the spring wrap correctly [tapping housing as you go, to allow the SAV to move little by little as the spring is adjusted].
If no link rod at all is connected to your secondary air valve, then there is no dashpot to control the speed of its opening. If you counter that with more spring wrap, your top end will suffer though the bog in transition may improve [less bog].
So, just a thought, why not hook up all the carefully engineered links that control how things work and see how that goes? Adjust them per the CSM or carb kit instructions. Set the spring wrap correctly [tapping housing as you go, to allow the SAV to move little by little as the spring is adjusted].
Could you please explain this further? I'm not sure I can hold the screwdriver and allen wrench AND tap on the housing.
I haven't removed anything. Both dashpots are there and hooked up. I was playing with the adjustment screw on the air valve dashpot. I think I see what it's supposed to do but I'm just guessing. I don't have a CSM for this carb, it's a mid-eighties. I've been looking online and youtube but some of these folks are..........well, they aren't as versed in Quadrajets as they think. "Wow, it must be really warm out. Did you see how the choke cracked right open when I started it?"
I replaced the fuel filter and low and behold it did help the high RPM/acceleration stuttering (I guess it was a little dirty, even after just 5k miles), but didn't help the off the line bog. Went back at that air door "spring wrap"? for most the afternoon. I thought I had it at one point but no, still bogging. Seems to get worse the warmer the engine gets.
I also discovered the fast idle screw was all the way out, which explains why I had no fast idle.
So I think I'm off the miss-adjusted float/under jetted idea. That was more about the high RPM stumble. It's got to be the relationship between the spring and the dashpot.
If no link rod at all is connected to your secondary air valve, then there is no dashpot to control the speed of its opening. If you counter that with more spring wrap, your top end will suffer though the bog in transition may improve [less bog].
So, just a thought, why not hook up all the carefully engineered links that control how things work and see how that goes? Adjust them per the CSM or carb kit instructions. Set the spring wrap correctly [tapping housing as you go, to allow the SAV to move little by little as the spring is adjusted].
The rear pull off was only attached to inner choke silver link, that's it. Not to mention, I am running NO CHOKE PLATE! I was going to buy one but saw that Cliff Ruggles thought it was unnecessary when the front pull off controls both. As long as both aren't leaking, sure leave them on.
That's it I'm saying it. Invest in a holley lol. I haven't messed with a q jet ever lol. Edelbrock and holleys over that last 10 years have worked reliably. Not saying the q jet is bad but the holley is simpler.
Holley float adjustment: loosen lock nut, turn screw, tighten lock nut. Pffft, you call that wrenching? Haha.
Although it's not as bad as the guy in the internet that wrote an article about how to adjust the secondary air valve on the QJ. It's easy, just start by removing the air horn! Aye carrumba!
You will see those letters on the metering rods near the top, they SHOULD read CV but who knows what might be in there. The CV or aftermarket Edelbrock CK rods, both .527" are a good starting point along with a G hanger. Most carbs I have owned had CV rods with I through M hangers. The lower the letter, the more it pulls the metering rods out, makes it richer.
The metering rods are CV but the hanger is "U". From what you've said, that sounds pretty rich. I have a "J" hanger on the old carb but's a 70s model. Can I swap it?
I do all the wrenching at work. Messing with Can bus systems , air bags systems and fixing mangled steel. That takes all my thinking at home i go by the K.I.S.S rule lol. Hope you get it figures out mac. get that thing out on the track.
Lol, I get it. And as much as I love a good Q-jet, I'm leaning the Holley way for adjustability. The trouble is that I would need a $150 linkage kit for the AOD trans plus the price of the carb.
I'm going to call the guy that built this carb and see if he has a build sheet. I want to know what primary jets and metering rods he put in there.
Okay, I talked to the builder and he said it's got #72 main jets but I've forgotten what he said about the rod size. He's going to send me an assortment of jets and rods to try. He offered to do it for me if I send it back but I'm not waiting for shipping from illinois to Cali and back! Lol.
He also thought that maybe the dashpot is pulling too soon and that a reducer on the vac line could help (which is what I thought that spring adjustment on the dashpot was for but what do I know?
U hanger is very lean, try the J hanger. Higher letter equals leaner, less the rods pull out of the secondary jets. Secondary rods and hangers interchange between all years.
Well on my last carb that ran very well, it has the J hanger and CV rods. This carb has the u hanger with CV rods. I'll just swap the hanger and see what that does. I'll take it from my original original carb. It's also a J hanger just really really dirty.
I guess I misunderstood what you meant by the letters. U being very lean I'm taking as good news
U hanger is very lean, try the J hanger. Higher letter equals leaner, less the rods pull out of the secondary jets. Secondary rods and hangers interchange between all years.
You, sir, are a steely-eyed rocket man! The "J" hanger did the trick. Geez, I've been at this for almost two weeks. Such a simple fix had I known about the hanger ratings.
I laid a nice, black, long, two-wheel patch from a decent roll. I knew there was power there somewhere. Now, to deal with that torque converter.....
Thanks dude!
Last edited by Macadoo; July 16th, 2016 at 11:12 AM.
You, sir, are a steely-eyed rocket man! The "J" hanger did the trick. Geez, I've been at this for almost two weeks. Such a simple fix had I known about the hanger ratings.
I laid a nice, black, long, two-wheel patch from a decent roll. I knew there was power there somewhere. Now, to deal with that torque converter.....
Thanks dude!
Hmmm, I didn't see the updated pics of the two wheeled patch, its been a while here Mac.
Dam I miss this awesome thread !!!
Hope your doing Ok and your Olds is rumblin' along just fine.
Hey Eric. How are you my Canadian friend?
The work continues on the Olds, for sure. Now I'm teaching myself bodywork. I'm doing okay at it but I don't think I'll be quitting my day job, lol. I started picking at the small rust spots behind both rear wheels and uncovered a real mess. I ended up cutting out a lot more steel than in the pictures and a bunch from the outer wheelhouses. It's been a hard, but fun, learning experience.
July 11th, 2016, 09:01 PM
