Any Tips for Tuning the Rochester Quadrajet

[Draginwagon]

Any Tips for proper tuning of the Rochester Quadrajet on my LS-5 454???
Under Normal use, average pedal pressure, it goes fine. Stomp on it and it bogs, then goes.
It seems to Bog under heavy acceleration, then gets up and goes.
Any sugestions??? Any thoughts? Help is greatly appreciated.

[VintageMusclecar]

Have you tried adjusting the tension on the secondary air door spring?

Eric

[Draginwagon]

I will have to ask, but I don't think so.
with my handicap, I can't do the work anymore, so my wife does it all. She learned to be a mechanic long ago.
Carbs though, are an art. needing a little finese.
I will check, Thanks for the Idea.

[68 Vert]

I agree with Eric, additionally, I would also check the choke pulloff to make sure it's working properly. The pulloff and the secondary air valve spring control the opening rate of the secondary's...to quick = bog.

Nothing like trying to find the cause of a bog in an LS5 wagon

Mike

[Draginwagon]

Thanks Mike,
We put a new choke on it last year, the old spring was Caggatz. So between that and the secondary air valve spring, this all makes sense.
In a couple weeks I will be "waking up" the Wagon, as soon as the weather breaks a bit here and give these suggestions a try.
There is a Great knowledge base here. Love this group.
Thanks again
RICH. . .

[67 GTO]

If the carb has sat dry for quite some time it's also possible that the accelerator pump isn't 100% anymore. If it used to take one stab at the pedal to cold start and now it takes, say 5 shots... With the car not running it's pretty easy to get a visual confirmation. Hope this helps?

[SmallHurst]

I would agree with the secondary air valve being the problem. The best way to tune it is to have both the allen wrench and screwdriver in hand on the right hand side of the carb. Use a pencil to make a mark where the screw is starting out, loosen the allen screw (on the underside) then tighten the screw just a little bit (an 1/8th of a turn makes a huge difference) and take it for a drive. Mine was too tight and we loosened it. That little change was worth about a .15 at the track. Little test was to bang the screw driver on the carb to see it the flap moves a little. The heavier car will need the carb to open a little quicker. Like you said, it is an art.

[John Brown]

When I used to drag race a Q-jet car I made a tab that held the upper flaps open about 1/8" so air would instantly flow past the enrichment holes, making it act like a secondary accelerator pump. Some of the Olds and Pontiac carbs had square openings in the upper flaps that would do the same thing.

[Draginwagon]

Thanks Guys,
There is a LOT of help here.
Luckily the car does not sit Idle. I run it regularly even in the winter (though indoors) better to move and run than shut down for months, se we have a process we follow on all our cars.
It starts 1st turn of the key every time. On the road under normal acceleration it throws you back into the seat. The problem is when cruising say 50mph and you stand on it, it will bog then come on.
From the line if you stand on it, same thing.
this is all after a proper warm up.
Feather the pedal and she goes great but if you want to drop the hammer. Bogs.
I think between all I have read here we should be able to get it. Carbs are an art. I am in awe of anyone who has the talent. I had a friend who could tune a 6pack, Jags with multicarbs and make them run like bears. But he's long gone. But not forgotten.
Thanks for everyones help.
RICH. . .

[Donnie]

check the dwell