Topic: Adjust 68 2v 2100 Carb w/ Auto Tran & A/C

[keiken01]

How important is the vent hole on top of the carb?  The book says it's supposed to be open at idle then closed at throttle.

Also, when the engine is warm, should manually closing the butterfly cause the engine to choke off and run rough or cause it to run faster?  My old 1979 Camaro with a 305 2v would run smoother as the engine warmed up and the buttlerfly opened.  If I closed it manually it would make it run rougher and choke it.  This carb seems like the opposite in that when the engine warms up and the butterfly opens it. manually closing the butterfly increases engine speed which seems like it runs better that way.

[Soaring]

Then you don't have something adjusted right.  When the engine is hot and you manually  close the butterfly, it should choke it and eventually kill the engine.   Do you realize this thread is a year old?   

[keiken01]

That's what I'm trying to figure... and yes, I know I started this post last year, tried many adjustments, then had you rebuild the carb for me just a few weeks ago... but something just isn't quite right. 

I tried plugging the vacuum ports at the manifold, but it didn't seem to change anything.  The car runs at idle best/fastest when I hold the 'fly at about 1/8" open or from closed.  The mix screws are set 2 1/2 turns.  Also the 'fly never fully closes... the 1/8" open is about where it starts, then it quickly opens up after start.  it feels like there is spring tension holding the 'fly open.

I open/close the vent on top to see if it did anything, but I don't see how it has any effect on the car whatsoever.

This is really bugging me so I'm reaching back out to find some test to run or get answers.

[Soaring]

There is a spring tension holding the choke butterfly open after the engine warms up.  That's what that black round choke system is all about.  You can adjust that by loosening the three screws, then turn the black round thing until the butterfly goes to where you want it, then tighten down the three screws.  Do this when the engine is cold.  There is nothing wrong with that carb.  You must have a vacuum issue.  It is difficult to repair an engine on the internet.   

[keiken01]

Totally agree with trying to fix this thing over the internet  Folks that have lots of experience with this would probably find the problem in a few minutes, but for  a novice like me, I'm just getting frustrated.

It looks like my carb may not seat tight to the spacer/manifold as it appears to be a little wet around the base.  Is it ok to use "form a gasket" material that is for use with gasoline?

Any suggestion where else I should look for a vacuum leak?  I already have the vacuum ports blocked at the manifold, so I'm clueless as where to look now or what else might be causing the problem.

[Soaring]

You have a vacuum leak at the base of the carburetor.  Did you put a gasket down on top of the spacer before putting the carburetor on?  If not, then that is what you need to do.  Let me know if you need for me to send you one. 

[keiken01]

I have a gasket there, but it isn't sealing off.  I sprayed some carb cleaner around the base to check and it increased the rpm momentarily.

[Soaring]

Are you using a thick 1/4" or so gasket with dimples in it?  If so, that is the wrong gasket.  Use the flat very thin one.  It is almost paper thin.  Let me know if you need one. 

[keiken01]

I'm using the thin one that is like heavy paper.

[Soaring]

Then use a layer of black RTV between the carb and the gasket.  You need to seal off that vacuum leak. 

[keiken01]

I noticed that the spacer has a flat side that was facing up towards the carb.  Is this the correct position?

[Soaring]

I noticed that the spacer has a flat side that was facing up towards the carb.  Is this the correct position?

Yes, the flat side should be on both sides.  If not, then use the black RTV as I suggested.  You simply need to seal off any vacuum leak from underneath the carb. 

[keiken01]

Ok well it looks like RTV took care the carb leaks around the gasket but it didn't change anything.  Do you know recall if the throttle shaft was worn any?  Just wondering if there may be someplace else on the carb that might leak. 
Also, I noticed that with the rebuild it appears you swapped the accelerator pump assembly, so the one I have now doesn't have the arm that extends over to hold the vent hole open at idle and closed at throttle.  I played with this vent hole and it doesn't really appear to make a difference if it's open or closed, so what purpose does it serve?

Does the accelerator assembly have a vacuum through it?  Just asking as I had to tighten these screws a little to resolve a leak on throttle and I'm pretty sure I stripped one.  I stoped gas from shooting out but didn't know if it might be sucking in air.

And please don't think I'm bagging on your carb work.  I'm very happy with the carb.  Acceleration seems more responsive than before and I was dealing with these issues before the rebuild. 

[Soaring]

Send me your address again. I will send you another rebuilt carb at no cost to you. 

[keiken01]

That's very cool of you.  I'll send you a PM. 
Are you thinking that if I get better results with another carb then it must have been a carb problem but if I get the same results it must be something else?

[Soaring]

That's what I'm thinking. 

[keiken01]

I got the package today.  Thanks again!

Setup questions...
What is this port here at the front for?  I don't have one there on my stock carb.  Do I block it off or run a vacuum line from it to
[attachimg=1]

There are two ports here on the back.  The angled one on the top looks like it should attach to the clean air line to the exhaust manifold for use with the heat line for the choke.  Yes or No?
The hole in the middle at the bottom is an open hole with no threads that leads into the carb.  I blew into it to see if it was an open airway and it is.  Do I just leave this alone and that's how it works or is something supposed to go there?
[attachimg=2]

Last question is in regard to the accelerator and throttle linkage.  The accelerator pump assembly moves a fixed distance but the throttle will move farther to open the bottom choke more.  When I hook up my throttle linkage, the only holes to connect to are on the levers to the assembly.  Should I make a hole to attach my linkage to the other arm?  The hole in the bottom is for a push throttle and mine is a pull.
[attachimg=3]

[Soaring]

I got the package today.  Thanks again!

Setup questions...
What is this port here at the front for?  I don't have one there on my stock carb.  Do I block it off or run a vacuum line from it to [attachimg=1]

There are two ports here on the back.  The angled one on the top looks like it should attach to the clean air line to the exhaust manifold for use with the heat line for the choke.  Yes or No?
The hole in the middle at the bottom is an open hole with no threads that leads into the carb.  I blew into it to see if it was an open airway and it is.  Do I just leave this alone and that's how it works or is something supposed to go there?
[attachimg=2]

Last question is in regard to the accelerator and throttle linkage.  The accelerator pump assembly moves a fixed distance but the throttle will move farther to open the bottom choke more.  When I hook up my throttle linkage, the only holes to connect to are on the levers to the assembly.  Should I make a hole to attach my linkage to the other arm?  The hole in the bottom is for a push throttle and mine is a pull.
[attachimg=3]

  Let's see if we can make that carb work for you.  The front of the carb has a vacuum port.  If you don't need it, then just block it off with a rubber nipple.  On the back, you have two ports.  The one leading into the top of the carburetor is exactly what you said it was for.  It hooks up to the manifold.  If you don't have a tube leading to the manifold, don't worry about it.  The big hole on the bottom is for your PCV hose to hook into.  If your spacer doesn't have a hole for that.  Just get a piece of copper tubing and hook it to your PCV hose, or if you don't need the hole for the PCV, just put a piece of copper tubing in the hole and squeeze it off so you don't lose vacuum.  Or if you have a dowel rod laying around that is that size, plug it with that. As far as the throttle plate, just drill a hole next to the knob if that is the system you have.  You do not have to drill a hole in the little plate with the small spring attached to it. 

[keiken01]

Ok, got it all together and got it running but had a leak around the top seal of the carb.  I stopped the motor, tightened the screws on top the carb and started the motor again and then it started leaking about 5-10 seconds after starting.  I tried tightening the screws again while running but couldn't get the leak to stop.  I didn't muscle the screws but did put some decent force against them to try to stop the leak.

The carb seemed to have a lot more power, but its really hard to tell with only a few seconds to hear it run without having gas just pouring out the carb and down the motor.

It leaks between the 2 screws on the driver side front top of the carb.  Any ideas on how to fix this?  Can I take the top of the carb off and slip like a thin washer under the 2 screws holes then press it down to bend that area down slightly giving better contact?

[Soaring]

What fuel pump do you have?  It sounds to me like you have way too much pressure for that float to cut off when the bowl gets full.  I set the level at 3 1/2 instead of 4, so that bowl should not be flooding.  You have other issues other than the carb.