Two quadrajet problems

[Peer81]

Hello everybody,

After getting the carb back together I did some testdrives last week.
I still have a problem I hoped I fixed by now but it's still there.
With the idle screw not touching the throttle blades she's running (when hot) around 700 to 800 rpm (around 550 to 600 in drive). What I have read is that she shouldn't run if the idle screw is all the way out.
So started looking for a vacuum leak. With a vacuumgauge around 20hg at 700rpm I checked all the (new) vacuumhoses but no difference is found there. Found one carb bolt that was in the intake by 1 thread didn't work so placed a coil on the thread to fix that. Retorqued the carb bolts.
Till now I didn't check the intake for leaks still need to do that.
When the carb was apart I looked at the throttle blades and found holding them against the light alot of light was visible between the throttle blades and throttle bore.

Pictures:

So I repositioned the throttle blades to center them better in the bores.
I think it should be a "big"? vacuumleak to cause this problem or am I wrong? Anybody a idea?

Second problem.
I rebuild the carb about a year ago. I also have a dual wideband meter to check the A/F ratio. At idle and normal steady drive the mixture is between 14:1 and 16:1 so not that bad. But at full throttle the mixture is steady around 9:1 so way rich! Weird thing, I still have a almost stock 350ci and the q-jet has the CH secondary rods. I didn't put in the DA rods (richer) to see the difference but it looks like I should go with a even leaner rod and not richer. Or could it be a problem in the carb like a blocked airbleed? Of course I compleetly cleaned the carb when I rebuild it.

Greetings Peter.

 

[damoroso]

Peter,

Seems like there might be a couple things going on. The pics that show daylight between the butterflys and the base plate make me wonder if they're closing all the way. Obviously there has to be some space, but this seems to be a little much. The next thing is that it's not exactly true that these won't run if the idle mixture screw is turned all the way in (according to Cliff Ruggles, the idle mixture screws on these had marginal impact to begin with). These carbs don't have an isolated idle circuit, so closing the idle mixture screws won't necessarily shut down the engine. I do beleive it will cause the MC selenoid to go richer though.

As for the second problem, are you sure the rich stop is correct for the MC selenoid? Is the cam on the air valve broken or moved? Doesn't make sense that the original metering rods would suddenly cause an overly rich condition.

And finally, you could always tag up with Cliff, you know he knows these things really well!!

 

[Peer81]

Thanks for your reply Damoroso,

To compleet the question. Dwell is perfect around 30 degrees in drive. TPS around 0.56V. Throttle blades are closing all the way. After centering them the space isn't that obvious anymore and evenly all around the blades.
For the idle screw I didn't mean the idle mixture screws but the screw to set the idle speed. It's all the way out and normally a few turns in to open the throttle blades a little for idle speed.
The lean and rich stops are perfect, secondary airvalve cam is new (good idea to check that!) The spring is around 3/4 turn in.
And I forgot: Also installed throttle shaft bushings.

Of course I already posted the same topic on Cliff's forum but the more idea's the better

Greetings Peter

 

[damoroso]

Peter,

Sounds like everything is good on the carb. Makes me wonder if there might be some issue with the throttle linkage or cruise control linkage? If you can't get below about 700 rpm with the idle speed screw, and the plates are all closing when you look at the carb off the car, maybe there's something holding them open a bit when the carb is installed?

Maybe disconnect all the linkages...throttle, cruise and TV cable and try then?

 

[73shark]

With that much side clearance on the secondaries, it seems like either the bores are too big or the butterflies are too small. Do you know if it looked like that before the overhaul?

 

[Peer81]

When I was working on the throttle blades I swapped one with another one I have around. No real difference between them so the blades are fine. The bores have no real indication that there is wear damage. I have know idea what it looked like before.

Cliff also gave the idea to check if the secondaries close all the way. So I'm going to check that ones the temperature is above zero

Greetings Peter

 

[73shark]

If there's as much gap around the throttle plates as there appears to be in the pics, I'd guess you're leaking so much air past them that setting the idle will not be possible beyond what you've done.

 

[black_81_vette]

Looks like the shaft may be twisted slightly allowing the butterfly on one side not to close fully.

 

[Peer81]

Thanks for the replies everybody,

I've checked the throttlebody with a good friend his good running crossfire trottlebody and compared to his TB mine was much better.

I took the pictures with as much as possible light comming past the throttle blades but IRL it isn't hat much. But I'll find the problem

Greetings Peter