Quadra-bog

[Sensei]

Since I purchased my '81 in Jan '04, it has always had a serious bog down problem when the accelerator is suddenly floored. I mean it spits, sputters, coughs and almost dies for several seconds befor it catches up and goes. Otherwise the car runs great and will accelerate hard, just not suddenly from a stop or at low speeds. I got a carb kit last weekend and took the thing apart, gave it a thorough cleaning and put it back together with all the new goodies in the kit (sorenson). I checked all the adjustment screws as I took it apart and reset them back where they were. The car is still doing the same thing . Any ideas of what is causing this and how to correct it? Thanks and God bless

 

[gedmeyer]

I'm not sure what condition your carburetor is in, but getting mine rebuilt professionally was the best money spent. I can't remember the place (it was located in Jacksonville, FL), but it came back looking and running better then new. They replated ALL of the linkages and set everything back to factory specs. Apparently they test each one on a test engine before they ship it out.
There are WAY too many things that could be out of funk to cause carb problems.

-gedmeyer

 

[Mac]

Sensei (although you don't say which style :L) I wouldn't be so sure it's your carb. The same symptoms you've described can be caused by distributor, vacuum advance, fuel pump and a few other items including (of course) the carb.

It could be something as simple as your float adjustment (one of the first things I would check) or it could be as bizarre as a misplaced vacuum line or (this will sound weird) it could be a partial blockage in your exhaust system.

First things first... when this bog happens, after it clears up, do you see any smoke from the exhaust. If so, what colour (ie: light versus dark)? If not, do you smell anything (ie: rich condition, flooding carb) from the engine? Can you produce this condition parked (ie: by revving the engine) or is it only when your driving?

Basically, I guess what I'm saying is there isn't enough information in your post to make an accurate diagnosis. Perhaps you can check these few things and report back?

-Mac

 

[Vettehead Mikey]

There's very simple adjustment to eliminate the bogging you're experiencing. Any Qjet on any engine will bog as you describe unless the air door on the secondaries has the right amount of spring preload holding it shut. Yours has the classic symptoms of opening too soon due to inadequate spring tension to hold it shut. Too tight a spring will not allow the door to open at all, making the engine feel like it has no power.

There's technical paper either here or on the CF site describing the adjustment procedure. Takes about 5 minutes to do it.

 

[crause]

how would one find these "technical papers"? I would like to check mine to make sure it is working properly.

Andy

 

[wishuwerehere82]

Here's one!

http://www.corvettefever.com/howto/53360/

 

[Vettehead Mikey]

Here's another link:

http://www.corvettefaq.com/c3/myqjet.htm

 

[Bob Chadwick]

Mac makes a good point about the distributor. I had varying amounts of bog that I assumed was the Q'jet. Got a little better when I adjusted the spring on the secondaries only happening intermittently.

I just replaced the distributor and it is completely gone.

 

[wishuwerehere82]

Bobchad,

Where did you get your distributor? I tore mine apart today and think I may need a new one.

Pete.

 

[Bob Chadwick]

I got the MSD unit from Summitt. It was easy to set up to increase the rate at which the mechanical advance kicks in. I have 36 degrees by 3000 rpm where stock it was about 20. I have had a couple of runs with it. I like it so far. I have to admit it wasn't cheap.

Accel and Mallory appear to be about $100 cheaper. I have the MSD 6AL box as well and wanted everything to be the same manufacturer.

The only thing that it didn't have that it probably should have had was an adjustable vacuum advance. It turned out not to be a problem for me but in reading some of the material available, I was concerned that I might have too much combined mechanical and vacuum advance. I think the Accel unit has this feature but don't rely on me as I'm not 100% sure.

 

[wishuwerehere82]

Thanks, I will check it out.

 

[Sensei]

The secondary air door adjustment fixed it right up. thanks a million!

 

[Vettehead Mikey]

The secondary air door adjustment fixed it right up. thanks a million!

That's great news. The best fixes are the ones you do yourself, and cost 'zero' to accomplish.