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carb help!! Fixed It!!!!

S

seslick77

1/2 ton status
Joined
Jan 27, 2002
Posts
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Location
Colorado Springs, Colorado
Hey fellas!! /forums/images/graemlins/1zhelp.gif Well I got her to pass emissions!! Problem now is driveability (sp). 79ish 400 with Q-jet. I rejetted it to high altitude jets and rods, retarded the timing to 14deg. before TDC, and went with ACDelco 45s plugs. When I gas it from a stop under any throttle, it stumbles for a second. And when I floor it, the secondaries just bogggg... Carb been rebuilt, new fuel lines, pump, filters, plugs, wires, cap, intake, and air cleaner. Now what do I need to replace or fix??? /forums/images/graemlins/angryfire.gif I'm runnin true duals, air injection, new cats, and original diesel mufflers. Really disapointed in the crappy performance of this thing. Was kinda hoping the chrome valve covers and air cleaner would make it faster... Guess I should find me some stickers! /forums/images/graemlins/thumb.gif

Thanks for the help!
Sam

Oh, if theres anybody close to me that wants to come over and tune this dang carb, I supply the refreshments!! /forums/images/graemlins/grin.gif Got some home-made wine thats 2 years old and smells like paint thinner!!




Adjusted the air valve and no more bogggg!! Oh and fixed the heater too! Think I might have to replace the blower motor cause she don't blow too hard.... Thanks for the help guys!!
 
Re: carb help!!

Homeade wine....If we drink enough you wont realize I have no clue what the heck I was doing, would ya... /forums/images/graemlins/grin.gif /forums/images/graemlins/k5.gif
 
Re: carb help!!

Sounds like the accelerator pump is done. Rebuild kit is about $15. Need a can of Carb cleaner (comes in a 1gallon can. Also need an empty antifrees jug. You can cut the top off the anti freez jug and the body of the carb will just fit. Also pick up a couple spray cans of carb cleaner of brake cleaner. While your at the store buying the parts pick up a book titled Rochester Carberator and it will have better information than I could post off the top of my head.
 
Re: carb help!!

Rebuilt the carb allready. Got the book too. I replaced the parts on the acc. pump that came with the kit. I rechecked my choke yesterday too.
 
Re: carb help!!

The big bog when the secondaries open sounds like the air door is opening too quickly. The book you have should tell you how to adjust it so that it only opens when the engine is ready for more air.
 
Re: carb help!!

Hmmm...that might be it!! Noticed the other day the secondaries air flapper was open at idle... That vacuum actuater thing sucked in and had it open when it was idling. Have to look at my book and see what I can do with it.

Harry when you comin over to fix this for me!! /forums/images/graemlins/grin.gif Oh ya, you got that fancy injection stuff... /forums/images/graemlins/rolleyes.gif

Thanks guys, Sam /forums/images/graemlins/usaflag.gif
 
Re: carb help!!

check the linkage from the choke pull off (vacuum thingy on the pass. side)that goes to the secondary.

the vacuum should lock it in the closed position(the secondary), and when the vacuum drops(when u have ur foot in it!!!)then (the vacuum thingny) the rod will let the secondary open .

check to see if the rod is not backward or way to bend or something like that.
btw reving the engine in neutral the secondary should JUST crack open, not open all the way (unless u rev it to 10,000)
anymore question just pm me
 
Re: carb help!!

Actually Doug Roe's Q-jet book doesn't tell you how to adjust your secondaries. (Or at least I couldn't find it, and read every page of it)

There's a screw in one end on the secondaries' shaft. As you turn it, a spring tighens or loosens inside. Adjust to make the secondaries open quicker or slower. There's an allen bolt that holds the first screw in place. You can barely feel it on the rear of the shaft much less see it. Loosen it before playing with the adjusting screw.

This should take care of your Quadrabog.

Good lock.
 
Re: carb help!!

Would have offered to help yesterday, but I was busy sandblasting and painting the 14-bolt that's going under my Suburban. I had to take advantage of the last 50-plus degree day that we're gonna see for a long while! /forums/images/graemlins/cool.gif The high today is supposed to be around 35 and only 26 tomorrow. /forums/images/graemlins/shocked.gif But I'm not too busy today! /forums/images/graemlins/cool.gif

The air door should definitely NOT be open at idle. /forums/images/graemlins/frown.gif A Q-Jet will open the secondary throttle plates immediately when you floor it. The air door is what regulates how much air is actually allowed to get through them and into the engine, based on engine demand. If it opens too quickly, you'll get a massive bog. Sounds like exactly what you're seeing. I haven't had a vehicle with a carb in at least 10 years, but I can give you a hand adjusting the air door. /forums/images/graemlins/wink.gif
 
Re: carb help!!

This sounds like the same problem im having I myself well have to check mine out also....Thanks for posting all the helpful info... /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
 
Re: carb help!!

Well, I made it over to Sam's place yesterday and we got started working on his carb. It was rebuilt at some point in the past by someone that was a total hacker. /forums/images/graemlins/shocked.gif The linkage that is supposed to control the air door had been bent completely out of shape and made to fit into a hole on the wrong vacuum pot! This was causing the air door to be held slightly open even at idle. /forums/images/graemlins/frown.gif After looking at lots of pictures in the manuals we figured out where the linkage was supposed to be hooked up and bent the link back into shape. The truck also didn't like to run when cold, so we adjusted the choke while we were in there.

The truck starts much better now, but Sam had a 160 degree thermostat in the engine so the choke never turned all the way off, even after we drove around for about an hour. His rig still has the MASSIVE diesel radiator in it and the temps by this time had dropped to 19 degrees F, so the heater wouldn't even blow warm air. /forums/images/graemlins/eek.gif The hesitation is gone now, but the air door still isn't opening all the way. By this time the roads had all iced over and traffic was horrible as all the all-season-tire-equipped front drivers were just spinning the tires on even the slightest grade. So we decided to continue at a warmer time. /forums/images/graemlins/thumb.gif

Sam is going to install a 195 degree thermostat, then the next step is to check the tension on the air door return spring and check all the linkages to see if any of the others are blocking the air door linkage when the engine is running. I think that the air door spring may have been set too tight in an attempt to get it to close when the engine is running.
 
Re: carb help!!

Hey Harry, really appreciate the help!! Got the thermostat swapped out. Damn heater still blows ice cold air!! Don't know whats wrong with it now...

I flipped through my books to see how to adjust the return spring, but cant find anything. I looked around on the carb and couldn't find anything that looked like it would adjust the air doors. Anybody got a good description of where its at?

Thanks, Sam /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
 
Re: carb help!!

The temp is supposed to get up to a sweltering 40 today. /forums/images/graemlins/wink.gif Give me a call and we'll get together and mess with it some more if you're off this afternoon. /forums/images/graemlins/cool.gif
 
Re: carb help!!

Hope you guys have fun down there haha If your going to be working outside you just mite freaze your onions off. /forums/images/graemlins/blush.gif Anyway I found a link that mite help you out some Q-Jet
Have fun

Eric
 
Re: carb help!!

Hey thanks for the link!! Thats what I was lookin for. I'll probly head out this afternoon and play with it. Was messing with the heater last night, went for a drive and the windshield iced over... Damn defroster is like an air conditioner!! Oh, dont stick your hand into a running engine compartment in the dark... Especially when you don't have a fan shroud.. /forums/images/graemlins/rolleyes.gif Luckily I still got my fingers, they just a little sore!!

Sam /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
 
Re: carb help!!

It helped me whan I was thinking of changing out my 600 cfm Edelbrock carb for the 750 Q-Jet that whole site has some neat info.
I've got a one piece shroud if you want it All I know about is it came off a Chevy truck not sure about the year.
Have you made sure your getting coolant to heater core? What I mean is the heater core pluged up? Mine at one time would not defrost the winsheild and I had to put a vauume hose one a little ball by the heater core thing this is one the right side close to the eng. the vacuum would open the flaper in the dash. this mite not be whats happening with yours I take it your getting air to the winsheild right? mine didn't.
Well you have Harrys help you couldn't of asked for better.

Eric
 
Re: carb help!!

195 Thermostat should get you decent heat. Might be something else wrong. The way GM set these trucks up is the coolant is alsways circulating through the heater core. A "Blend door" is how it turns the heat on and off. If you remove the screws at the bottom of the dash that hold the glove box door on and remove it the lever for the blend door is right on top of the heater box. Make sure it's opening all the way. You can see it working when your sliding the heat lever back and forth. Lots of times they are misadjusted after replacing a heater core.
The heater hose routing is from the intake there should be a 5/8s hose going to the bottom conection for the heater core on the fire wall. The top 3/4 line will return the coolant to either a fitting on the radiator or to the water pump depending on the year. A lot of folks make the mistake of changing the intake and trying to use the water pump connection and the radiator connection and it just doesn't work very well when your using two returns /forums/images/graemlins/smile.gif
 
Re: carb help!!

I think you found my problem!! I did exactly what you said, running a line to the pump and one to the radiator. /forums/images/graemlins/rolleyes.gif I put on a new intake and those thermal switches took up both holes on the front of the intake. I'll have to look and see which one I can lose. As for the heater box, I did a A/C to heater conversion and got 3 different years of control cables. It will blow air, just not hot air. I did replace the heater core and all lines during the swap. Will fix it all tomorrow, found a small crack in the radiator at the upper hose connection. Patched it up with some JB Weld...hopefully it will hold!!

Thanks fellas!! Sam
 
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