Quadrajet Starting Questions...

[MrSony]

have you measure the amount the air valve opens on start up?

Its about 1/4. Its certainly open too far.

 

[MrSony]

Ill adjust pull off and report back.

 

[RegalBegal]

And no they are not blocked.

well ya fooled me. I AM getting old.

 

[pontiacgp]

I AM getting old.

try living in denial, it is so much easier than to accept the inevitable....

 

[Bonnewagon]

Dual exhaust? It sounds like there is no restriction to cause the fuel to boil. That doesn't mean it can't. It may also be vapor lock. Are you using the stock steel fuel line? Is the fuel pump the 3-fitting recirculating type? The 2-fitting type can suffer from vapor lock. The air cleaner has nothing to do with any of this. Also, Rochester cured the leaking wells ages ago, so that condition is extremely rare unless you have a '60's /early '70's carb. EDIT: I checked the vacuum break setting for Buick carbs and they vary from .170" to .210" depending on engine size. That is why I suggest trying between 1/8" and 1/4" as a start.

 

[MrSony]

And in my air cleaner, there is a thing with two nipples on it with an A/C written on it. It's some kind of valve/plunger thing. What's it for? Part of the AC system of the car it's from? What's it do

The surging in startup could be many things. A vacuum leak, worn throttle shafts etc. you'll have to do some hunting. check this link here. The hard starting after sitting could be caused by the plug wells in the carb leaking down. This is a common Qjet problem. My guess is thats why when you look down the barrels, it looks wet. It could also be caused by modern fuel volatility. As for the hot air valve, it says AC as in Albert Champion, as in the spark plug guy. Part of AC-Delco. The function of it is to direct hot air off the exhaust manifold stove into the carb when it's cold and opens to let in cool air when the engine is hot.

Good info, but I meant this thing: the lil grey thing inside the filter area.

 

[RegalBegal]

And in my air cleaner, there is a thing with two nipples on it with an A/C written on it. It's some kind of valve/plunger thing. What's it for? Part of the AC system of the car it's from? What's it do

Good info, but I meant this thing: the lil grey thing inside the filter area. View attachment 94877

Thats the temp sensor. controls the vacuum going to the diaphram.

 

[MrSony]

Dual exhaust? It sounds like there is no restriction to cause the fuel to boil. That doesn't mean it can't. It may also be vapor lock. Are you using the stock steel fuel line? Is the fuel pump the 3-fitting recirculating type? The 2-fitting type can suffer from vapor lock. The air cleaner has nothing to do with any of this. Also, Rochester cured the leaking wells ages ago, so that condition is extremely rare unless you have a '60's /early '70's carb. EDIT: I checked the vacuum break setting for Buick carbs and they vary from .170" to .210" depending on engine size. That is why I suggest trying between 1/8" and 1/4" as a start.

Straight out with side exit tailpipes, thrush welded 2.5" duals. Stock manifolds. Stock steel fuel line. SBB line is routed like the 231, behind the dizzy and down the side of the timing cover to the pump. It's the 2 fitting pump. its a fresh m4mc qjet from everyday performance.

 

[pontiacgp]

Have you checked the timing?

 

[Bonnewagon]

With AC or not, the fuel line is routed along very hot engine components. Now add 90 degree days and you could have a vapor lock situation. The fuel boils, the bubble won't let liquid gas pass, hard to start. In severe cases the engine can shut off while driving, or at a red light. The 3 fitting pump redirects excess fuel back to the gas tank so there is fresh cool fuel going to the carb. Yours sounds more like a "hot soak" situation where fuel may be either evaporating or boiling over into the manifold. Did this start with the hot weather?