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Discussion Starter #1
well the new straight heat choke rod solved the problem car starts cold now and idles without dying when cold, I believe I had a 2 barrel vhoke rod on there..oops.. now the other major problem I have warm or cold when im at WOT at around 50 or so ill bog right down if I let off itll accelerate again to say 60-65 then bog i let off it comes back if I stay at wot it stays bogged down...I dont think its a fuel delivery problem, (aftermarket 130 gph fuel pump) and I dont think its too much fuel it fine if I accelerate normally... its not plugs or wires all new a few different times same results and I have a pertronix unit I know works well.....so im left with distributor weights? or is it possible my secondaries arent opening up so maybe I need ot do a little rod bending?
 

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Discussion Starter #2
update

I am thinking now something with the secondary the car was arm when I did this not at operating temp but when I put the carb linkage at full throttle I couldnt open the secondaries but when I hold the primary all the way open by hand then I can also if I push in the plunger on the carb I cant open it is sometyhing wrong with the lockout or travel?
 

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my1971gto4spd,

Yikes! Does that ever sound familiar to me. I had the exact same thing happening to my car(1970 RamAirIII 455 +.030). I found that if I stood on the throttle it would scream through first and then I'd shift into second and it was as though I shut off the ignition. It would just die if I didn't let off wait a second and then stand on it again. What I discovered was that at some point in it's life the QJet was rebuilt with a standard inlet needle and seat .110" This is simply too small. I went to the .130 and the trouble vanished. No more problems at all. You can even go up to the mondo .147" unit from right here:

http://www.carburetion.com/Quads/r4needle.asp

But just remember to readjust your float level. After I made the jump to the giant inlet needle and seat I saw raw fuel dripping from everywhere inside the Carb. Not good!! The larger inlet causes the float level to rise way too much so keep that in mind if you change the inlet and the engine won't idle right.
Drop the float level and it will clear right up.

Just my cents... :)


Turbo
 

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Discussion Starter #4
thanks

im going to go throught the adjustment basics first, but I will definitely chck nto the needle size and having that site for the parts is super thank you
 

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With the engine off, first make sure the choke is fully open and cycle the throttle linkage to be sure that the both secondary butterflies (in the carb base) open and the secondary air valve (in the top of the carb) can be opened as well. The choke mechanism can lock them out if the choke is partially applied. The secondary airvalve opens from air flow, not linkage, so once the carb is wide open you should be able to push down lightly on the air valve and make it open.
 

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Also, check your secondary airvalve spring windup. If it's too loose, you'll get the fall-on-your-face problem. Spring windup on your car should be about 3/4 turn for good secondary operation.
 

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Discussion Starter #7
getting closer

Well, cold everything seems fine but at operating temp, the choke is wide open no problems, but when I press on the secondaries they go down about 1/4 inch and then still open all the way but after the 1/4" they push harder and when i crack the throttle they only go down about 1/4" so either sticky shaft or the spring adjustment (as mentioned) I am guessing. Sound right?
 

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We need some more definition here. The secondary air valve should get slightly stiffer as it opens and you should feel some spring tension on it at all times. As Lars pointed out, if the spring that controls the opening is backed off too far or broken and the air valve opens with no resistance, you're well on your way to bog city.
and when i crack the throttle they only go down about 1/4" so either sticky shaft or the spring adjustment (as mentioned)
Exactly what do you mean? Is this with the engine running or off? And, are the secondary butterflys open or closed at the time that the air valve only opens part way?
One more test. Take it out for a drive and once it is warmed up and you're at about 20 mph, depress the throttle slowly, so that it takes about 5 seconds to go from your 20 mph throttle position to full throttle and report back how the car behaved.
 

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Discussion Starter #9
update

when I cracked the throttle this was at idle with the engine at operating temp and as far as I could tell the secondary butterflies didnt open, the pressure on the air valves was also when it was running when its not running theres no pressure of course because there is no vacuum. I know the basics of the quadrajet but not all the specific names of components so I may need a little hand holding here. I have a great book from 1973 called rochester carburetors by doug roe and bill fisher that has helped me learn quite a bit. I will try the 20 mph test after work this evening thanks again for your help Chad
 

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You can't operate the secondaries on a Q-Jet in neutral by "winging" the throttle. The secondary airvalve will stay closed until the engine is under load and there is airflow demand for the secondaries. Depending on secondary airvalve spring windup, you can sometimes slam the throttle to the wide open position momentarily while in neutral and see the airvalve just barely crack open. But to better check it, with the engine off, you can verify that your throttle cable is pulling the secondary throttle shaft fully open (have someone push the pedal to the floor and verify that the throttle lever goes to the full open position). If this is happening, the secondaries are working. Don't understand the "secondaries going down 1/4"" comment... the secondaries don't go down...
 

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Discussion Starter #12
test complete

I did the 20-80 test accelerating smoothly (not wot) it was real smooth from 20 to 50 at 50 it stuttered slightly but kept climbing and kept bogging all the way to 80, not going from 20 to 80 wot, it climbed to 50 great and cut out badly after that had to let off and accelerate less to gain speed
 

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Sounds like it could be a fuel supply problem. Here's the question. If the car was ok before the carb was torn down or gone through, it can be a float level problem or a needle and seat problem. If the carb has not been touched (other than the choke rod problem) and the problem has come on gradually, it can be a clogged fuel filter. How and when did the bogging problem begin? Oh. one more random thought, but I don't think it is the problem. There is a rod that runs from the secopndary air valve to a dashpot which is a round plastic diaphram at the top front of the carb that has a vacuum hose running to it. The job of that dashpot is to keep the secondary airvalve from floppping open too quickly. So at idle and low throttle opening, the dashpot shout keep the secondary air valve closed. That's why you cannot open it by hand at idle, so it sounds like it is working. If it is disconnected or defective, it will cause a bog. But since you've said the secondary air valve won't open at idle, it is probably ok.
 

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Discussion Starter #14
cont.

the problem existed before the rebuild, which is the main reason I had it rebuilt, but it didnt solve the problem so then ive been going through all the adjustments. I have thought about putting a new fuel pump on it I just didnt think it was the problem as the fuel pump is fairly new and is an edelbrock 130 gph pump, I was considering trying a 80 gph or even a stock fuel pump as I think it would be sufficient. The motor is a 400 30 over 9.2:1 ram air cam balanced with exhaust manifolds. Barring anything else I guess blowing 60-100 bucks on a new fuel pump cant hurt
 

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Where's your secondary airvalve spring windup set? If it's loose, it will cause the problem you describe.

A lot of these Q-Jets have been rebuilt and creatively re-jetted by previous owners. Make sure you have the right secondary rods in it so you're not getting a lean condition on the secondary side. Have you checked the rod code against spec?

Also, the secondary rod hanger height is critical to proper secondary performance. Check and verify your hanger height at .640" (41/64").

If fuel supply/pressure is a problem, you may have to add an electric boost pump back by the tank. These cars are pretty long, and under acceleration, the fuel in the line wants to go back to the tank. A mechanical diaphragm-type pump has a hard time dealing with sucking the fuel against a resistance...
 
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