Question on newly rebuilt Holley 2818-1 carb

[BarryK]

I just got my Holley 2818-1 rebuilt and as i've been trying to get the timing and carb adjustments made I noticed a few things i'm questioning

1. the butterfly valve(?) on the very top that I thought normally opens and closes over the primaries is in full verticle position and it will not move at all whether the car is cold or fully warmed up to operating temp or if it's idling or revving. Shouldn't it move at times? I thought it did previously. Even trying to move it manually it doesn't budge at all like it's locked into place somehow

2. I can watch as I pull on the accelerator level as the primaries will open looking down into the carb, but the secondaries are not opening at all. is this normal without the car actually being driven? I would have thought that they would open as I revved her high enough.

3. even after the rebuild I don't think the choke is operating properly as it won't stay running unless I keep tapping the gas to keep the idle up until she is warmed up than she idles just fine.

are the choke and that top butterfly valve related to each other that could be working together to cause some of these problems?

I hope I'm using the right terms so you understand what I'm trying to describe and ask

 

[allcoupedup]

Barry,

1. You are looking at the choke butterfly. This should be closed when your car fist starts and blocking airflow and CHOKING the air supply. As the car warms up the bimetallic spring should loosen up and the vacuum (choke pull off) should open this butterfly. It feels locked in place with the engine running it because it is being held there by vacuum. If it feels locked in place with with out the engine is running, your choke adjustment is waaaaaay off.

2. Secondaries will not open with a "blip" of the throttle. To test their opeation you will have to use the grease trick or the paperclip trick.

3. If your choke butterfly is open when you first start the car (see #1) this is your problem. THe choke mechanism also operates the fast idle cam. When the choke is closed , your throttle assembly will rest on the fast idle cam and give you an elevated idle. As the choke opens (and you tap the gas), the idle will return to normal.



Assuming everything was rebuilt properly, all you have to do is adjust the choke. On the side of your carb you will have a black plastic cover held in place by a retainer and three screws. Loosen these three slightly and rotate the choke until the choke closes on a cold engine. Keep experimenting until you can see the car choking less and less as the car warms up. There is a 2nd adjustment on the fast idle cam that is very difficult to get to. Before you go there, we have to make sure your choke butterfly is operating correctly.


Barry - I highly suggest you buy a holley book. They will tell you everything you ever wanted to know. You're starting to ask questions that are difficult to explain without showing you on the carb so you can see the moving pieces and how they fit togehter.


Brian

 

[BarryK]

Thanks Brian
that was a huge help. it lloks like the choke adjustment must be way off because the choke betterfly won't close even with the car off and it's staying full open with the car starting cold.

can you explain to me the paperclip trick??

yep, I should get a book on the carb i guess.

thanks for figuring out what I was talking about even though I was using wrong terms or part names

 

[JohnZ]

Barry, assuming you have the 1965 Corvette Shop Manual Supplement, there's an entire section (6M) in it on your carb, including functional description, how all the systems work, how to rebuild it, and how to make all the adjustments (including the choke and fast idle).

 

[BarryK]

thanks John
you know, i was in section 6M earlier today as I was double checking the procedure for setting the carb with the vacuum gauge. Guess I should have kept reading!
i'll try to read more before asking.

 

[allcoupedup]

Barry,
The paperclip check involves bending a paperclip or something similar to fit onto the secondary diaphragm rod. If you place this clip directly under the secondary housing, you will be able to see the distance traveled by the rod. As the secondaries open, the rod will be pulled up into the housing and the paperclip will slide down.

Alternatively, you can smear some grease onthe rod and take her for a spin. A length of the grease should be rubbed off where the rod went into the housing. Both these are pretty primitive but I don't know how to do it otherwise without the car being on a dyno.

I believe you can adjust your choke by turning the housing clockwise. Rich = clockwise, lean = counter clockwise. The way it should work is the following. After driving around, your choke shoul be fully open. As your car sits, the spring gets tight and tries to close the choke. Since it came to rest in the open position, a quick throttle pump "sets" the choke and closes it next time you try to start it cold. This also sets the high idle. As it warms up,the choke will open and will allow the fast idle cam to reset position. This is why you have to tap the pedal to get the car off fast idle several times as it warms up... IF the carb is functioning properly.

I just rebuilt my 2818 again and FINALLY got this right. I don't have to feather the gas to get it running (no choke) or hold the pedal so it does not stall (no fast idle).


Brian


Brian

 

[BarryK]

cool, thanks Brian.
so, if i loosen the 3 screws slightly I should be able to rotate the black round housing and i want to turn it clockwise for more rich until it allows the choke valve to close?

I did read the section regarding adjustmentinng the chock adjustment but it's not really telling me anything I can understand. it just says to loosen the screws and align the cover scribe mark with notch mark specified in tune-up chart. In the specs listed in the back of the manual all it lists for the choke is "Automatic Choke Setting = 1 Lean".
you are making this make more sense than the book. With the choke on it's making it richer because it's choking off the air? So I want to turn the choke adjustment to a more rich setting to allow the choke valve to close?
or am I completely figuring this out wrong?

god I hate not knowing anything about this stuff and having to learn everything from scratch. SHEESH!

 

[allcoupedup]

Choke ON - same amt of fuel w/less air = richer. Choke should be completely closed with a cold engine. Choke should be fully open after running for 5 minutes or so.

there are two forces at work in the choke - a spring and vacuum. At idle the spring is cold and strong and it overcomes the vacuum and holds th choke closed. As the spring heats up, it gets weaker and the vacuum wins and holds the choke open. You need to find the right point. There is no absolute setting here - you'll have to experiment with it.


get the operation of the butterfly working first - at least so that that the choke remains close for the first 60 seconds and then we can go from there!
Brian

 

[BarryK]

ok, thanks Brian, I'll try playing around with it and see if I can get it to release to start off with