What would be your first adjustment? - Team Camaro Tech
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post #1 of 29 (permalink) Old Oct 16th, 02, 04:50 AM Thread Starter
 
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Ok here goes. When I am stopped at a stop sign or for that matter just cruising along and I try to romp on the accelerator, I get a hesitation. Sputtering is more like it. Then car takes off like a bat outta you know where. Sputtering lasts maybe 4-5 seconds. Yesterday I sputtered through an intersection and then when it engaged I broke loose the tires between each shift. Where would you start to correct this. Ok here are the specs and recent replacements. 73 350 in a 74 body turbo 350 tranny with a shift kit. I know it was bored 30 over. Cam was added but 10 years ago I never considered asking the guy I bought it from what the specs were so I cant tell you any details on the cam. Recently(within 300-400 miles), put a rebuilt Roch Q-jet on. New plugs, points, condensor, rotor, fuel filter, timing chain, plug wires, starter, coil, fan clutch, hoses belts etc. I do have good vaccuum at dist. Dont know what the compression is. Set timing right now at 8 BTC. We did initial tuning of carb so far but havent rechecked anything yet. Car runs good when you dont ask a lot out of it. Nice steady acceleration and cruising. So where would you start and what would be your first move?

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Scott
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post #2 of 29 (permalink) Old Oct 16th, 02, 05:09 AM
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Steve
 
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Gee, where to start? It could be either and ignition or fuel problem. I chased the same problem for several weeks before I got it worked out. Could be that your accelerator pump shot in not large enough. This is adjusted by increasing the shooter size and/or the cam that operates the pump. I am not that familiar with Qjet,s; have a Holley myself. The other problem I had was that my vacuum advance canister on the distrubutor had too soft a pull rate and did not back off under heavy acceleration. You can check this by removing and pluging the vacuum line from the advance canister and do a hard acceleration run. If the hesitation is gone, it's the canister, or where you have it hooked up, either ported or manifold vacuum. It could be a number of things, but that's where I would start. Good luck!
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post #3 of 29 (permalink) Old Oct 16th, 02, 05:22 AM
 
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I just had the same problem last weekend. I put the intial timing at 10 BTDC and shot for 32-36 total advance. No more hesitation. Does it "pop" out of the carb? Backfires?

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1969, X-44, Export Model, Hugger Orange, Std. Int., BC Rear(soon to be a BT 12 bolt), PDB, GMPP 350HO, M22 Supercase, SSM Lift Bars, AirGap, Holley 750, FlowMaster American Thunder Exhaust, FlowTech Headers
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post #4 of 29 (permalink) Old Oct 16th, 02, 05:51 AM Thread Starter
 
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Nope, no backfires. Just sputters then takes off. Seems weird cause it runs ok after that. Would runnig to rich or lean create something like this. I dont know yet. Havent had a day to just tinker with adjustments. I always get good advice form this board so I like to get alot of opinions. Think I might try playing with the timing first and see what happens. Please keep the suggestions coming thouhg.

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Scott
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post #5 of 29 (permalink) Old Oct 16th, 02, 08:49 AM
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Not sure about rochesters but I seen holleys where the choke opened too far and got right in front of the squirts. The gas just hit the plate and ran down causing it to stall

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69 convertible
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post #6 of 29 (permalink) Old Oct 16th, 02, 09:12 AM
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Check the secondary air valve adjustment.



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post #7 of 29 (permalink) Old Oct 16th, 02, 09:15 AM
 
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The problem is most likely associated with the carb.....the venerable "Quadra-bog" strikes again! I would say start with re checking the carb and making subtle adjustments. You will most likely find one adjustment, and then it will run like never before......its just finding out which one it will be.
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post #8 of 29 (permalink) Old Oct 16th, 02, 09:26 AM
 
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"Quadra-bog," I like that. How 'bout "Quadra-junk?" To help Gateruner out, my car was running way too rich as well. This was due to the vacuum leak that I had at the spacer (carb). Corrected the vacuum leak with a Mr. Gasket heat dissapator, re-timed it (10 btdc), adjusted the fuel mixture, checked the vacuum and advance. Now she runs great. Is the car loading up at idle?

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1969, X-44, Export Model, Hugger Orange, Std. Int., BC Rear(soon to be a BT 12 bolt), PDB, GMPP 350HO, M22 Supercase, SSM Lift Bars, AirGap, Holley 750, FlowMaster American Thunder Exhaust, FlowTech Headers
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post #9 of 29 (permalink) Old Oct 16th, 02, 01:09 PM
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Matt Jones
 
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Anybody who can tune a Q-jet will tell you that they can run right up with any Holley or Carter...most (but not all!) people who call them Quadra-junk, bog, crap, whatever, usually just don't know how to cure the problem.
Those things can be ported to flow 1100CFM and run on just about any engine. It's nice to run as fast as a Holley could, and get much better fuel miliage, for a heck of a lot cheaper!!

Make sure your accel. pump rod is on the inside hole on the lever.

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post #10 of 29 (permalink) Old Oct 17th, 02, 02:47 AM Thread Starter
 
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Well, money is an object for me and I really dont know alot about carbs so I felt it would be best to replace the carb with what was already on the engine. It doesnt run badly except on really heavy accel. Fine tuning is new to me so I am learning as I go. Just hoping to get some good ideas on where to start. Right now I think I am going to advance the timing just a bit and see what happens. Someone else told me to check the secondary adjustment. It might be opening to soon and creating a lean issue. Also, How do you achieve 34-36 degrees total advance? I just dont see how that happens unless you advance plug wires around the dist. Hmmm

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post #11 of 29 (permalink) Old Oct 17th, 02, 04:15 AM
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Is it a bog or a stumble? To fix a stumble, make sure the acc. pump squirts gas as soon as the throttle starts to open. Bend the lever to remove ALL slack to get a better pump shot.

Mark
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post #12 of 29 (permalink) Old Oct 17th, 02, 04:59 AM
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I've had a few Q-jets that leak fuel into the intake, causing the engine to load up at idle, and at shut down. Do you see any black smoke in your rear view when you jump on it? Does it sometimes flood out for no reason when you restart after shut down?
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post #13 of 29 (permalink) Old Oct 17th, 02, 06:36 AM Thread Starter
 
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I dont see any smoke out the back and I have been looking just because it sat for so long. No flooding either. Cranks right up and runs right into fast idle. As for the bog or stumble, it acts like it is trying to fire,(blublbubbllbilbulbulbblub then zoom). It will basically limp 10-15 yards spitting at you then here we go. Little like a roller coaster huh.

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Scott
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post #14 of 29 (permalink) Old Oct 17th, 02, 07:14 AM
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Don
 
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Scott, those are the classic symptoms of the secondary air valve flopping open.

There is an adjustment.

On passenger side of carb, on the secondary air valve (those flat plates that cover opening) shaft you will see a small screw that a pocket screwdriver will fit into. It is spring loaded.

Below that you will see a small allen head capscrew that is used to lock it. You may need a small mirror to see it at first.

Loosen the capscrew.

Insert small screwdriver, turn clockwise until valve plates just seat. You may have to go back and forth a couple of times...

Continue turning 1 turn, and lockdown allen head.

Test drive.....and please let us know the results.



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post #15 of 29 (permalink) Old Oct 17th, 02, 07:18 AM Thread Starter
 
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I will try that tonight and will definitly post results in the morning. Sounds simple enough. It always seems like the simple things are what bug you the most. Thanks.

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Scott
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