Carb issue on my 85

[Travis T]

I know the needles in my Advance kit were made wrong and they never worked right. Yours being Holley parts I would think that they would work.

[Renegade]

Well I picked up a new needle and seat and that fixed the problem. Now I just need to take it out on the road and see how she runs. Thanks everyone for the help on this.

[Renegade]

I was able to get out and drive it today and noticed a couple of issues. First, I don't think the choke is working right because it takes forever to get it started and warmed up. Second, it has a slight surge at cruising speed and neither of these were present before I rebuilt it. Any suggestions?

[bscottie]

well I gotta say that you made a mistake somewhere in the rebuild from all the issues you have described, I rebuilt my carb 3 or 4 times total, only once did I use the GP Sorensen kit and every time I really thought I did everything right, I just finished rebuilding the carb a few weeks back and I spent the extra time to really pay attention to what I was doing and the carb is as near perfect as I can imagine, one thing I noticed along the numerous rebuilds is to pay attention to dirt and debris, removing every piece of old gasket everywhere and watching out for the position and shape of the O rings as you assemble the pieces, if you are 100% sure you didn't make any mistakes in the rebuild you need to look at possible leaks (vacuum and fuel) or fuel pressure

[WilliamCapri]

Hi Renegade,

Check choke operation when the engine is cold.

Take off the air cleaner, and plug the vacuum line that operates the air valves.

While looking down primary throat, completely open the throttle, as if you are pushing the gas pedal to the floor.

There should be a pretty good shot of gas (a tablespoon or so) going down the primary throat from the accel pump and the choke should snap shut.

If there is not enough gas from the pump shot, you may have a torn accel pump diaphragm or the transfer tube between the metering block and the throttle body may be leaking. The transfer tube gets 2 O-rings which can get buggered up at assembly.

If the pump shot looks ok and the choke is shut, it should fire right up, assuming no other issues. After the engine starts, the choke should open about 3/16" or so. The choke pull off is internal but there may be some missing O-rings or damage there.

Once the engine is running, you need to check for vacuum. If the engine is pretty much unmolested, the vacuum at about 800 rpm should be over 19" Hg.

Anything less than that and I'd be looking for vacuum leaks.

Get this nailed down then we can go on to the next steps.

W

As always, "it ain't what you don't know that gets you, it's what you think you know that just ain't so."

[Renegade]

williamcapri I think you may be on to something with this.

"the transfer tube between the metering block and the throttle body may be leaking"

I have taking it apart so many times it is very possible that I damaged one of the o-rings.

[WilliamCapri]

Renegade,

That reminds me of something else.

The accel pump shot originates in the front fuel bowl then goes into the metering block. Between the two is a gasket, of course. Trouble is, the gasket looks to be reversible but it is not. There is a hole that has to align with the accel pump port.

And, when I was working on mine, the transfer tube was usually pretty good at holding the metering block away from the throttle body and would only snug up with the bowl screws. If the metering block is just sliding on, the o-rings may be pretty worn.

W

As always, "it ain't what you don't know that gets you, it's what you think you know that just ain't so."

[Renegade]

What power valve should be on this car? Kit came with a 4.5

[Ethyl Cat]

What power valve should be on this car? Kit came with a 4.5

1/2 vacuum in drive idle +1

[84GT350CONV]

My Holley kit came with a 4.5 power valve. However my carb needed a 6.5 valve.

[bscottie]

my new kit came with a 4.5 also, I installed a 6.5, my car runs 15"+ vacuum


@ renegade, the orings on the transfer tube should have been replaced during the rebuild, that was one of my issues, I ASSUMED that since they looked OK they were good, the kit has new ones, on this last rebuild I only had a couple of pieces left from the kit, the first few times I did the rebuild I had over a dozen "extra" pieces.

[Renegade]

I really don't know what is happening with this car. I bogs down at shuts off at low rpm. Bowl levels are good and everything checks out but I am missing something somewhere. Its really acting like its running rich when it bogs down and shuts off I have to mash the gas all the way to get it started again.

[8ballEinstein]

First off, did you solve the problems with the choke? I would start there.

[Renegade]

The choke appears to be working as it should. It still doesn't like to crank though.

[8ballEinstein]

OK, I was curious because I didn't see any resolution concerning this after post #28. On cold startup, the choke should be closed then after about 90 seconds it should be fully open. If you have that, you're ready to move on.

[Renegade]

It opens a little but not alot. How much should it be opening?

[8ballEinstein]

All the way. You have to solve this for sure. It may be the cause of all your problems.

[8ballEinstein]

I guess I should follow up with HOW to solve the choke problem.

If you have a volt meter, check the voltage on the wire going to the choke housing. You should get 6-7 volts. Do this and report the results.

[Renegade]

I will check the volts tonight. I know last night it was blowing white smoke out of the tailpipe while I was trying to keep it running.

And no it doesn't have a blown head gasket.

[WilliamCapri]

Hi Renegade,

Don't forget to check continuity from the pin to ground. No continuity, no current flow, no coil heating, no choke opening.

The white smoke you saw may just be normal exhaust water vapor. Pretty normal to see it all the time here at this time of year.

W

As always, "it ain't what you don't know, it's what you think you know that just ain't so."

[Sinister]

Hi Renegade,

Don't forget to check continuity from the pin to ground. No continuity, no current flow, no coil heating, no choke opening.

The white smoke you saw may just be normal exhaust water vapor. Pretty normal to see it all the time here at this time of year.

W

As always, "it ain't what you don't know, it's what you think you know that just ain't so."

yub, my blow white smoke look like a head gasket at cold start, when weather is really cold, it all gone after 10 min idle.

[WilliamCapri]

Renegade,

Another reminder; if the choke coil has been removed, it is possible that it was not put together properly.

You need to make sure the loop at the end of the coil is put over the choke actuator tab before putting the screws in.

If this is not done the choke will not snap shut but it may tend to want to close. It will definitely not want to open and you will not feel any spring resistance hot or cold.

[Renegade]

Renegade,

Another reminder; if the choke coil has been removed, it is possible that it was not put together properly.

You need to make sure the loop at the end of the coil is put over the choke actuator tab before putting the screws in.

If this is not done the choke will not snap shut but it may tend to want to close. It will definitely not want to open and you will not feel any spring resistance hot or cold.

I checked last night and it was on correctly. I watched a video online and it was said open the throttle all the way up and then turn the choke thermostat clockwise until the choke valves close and then tighten it up. I am not sure if that applies to this choke and carb combo but I haven't done that yet.

I have been though the carb twice and everything on the inside looks correct so if its not the choke I may just buy a new carb.

One thing positive about this I guess is I am learning a lot about carburetors.

[8ballEinstein]

I checked last night and it was on correctly. I watched a video online and it was said open the throttle all the way up and then turn the choke thermostat clockwise until the choke valves close and then tighten it up. I am not sure if that applies to this choke and carb combo but I haven't done that yet.

If your carb is anything like the 4180's I've seen, you don't have the option for adjustability. That's because there's a plastic plate that is keyed into the choke housing. Still, many people fail to catch the actuator tab in the coil loop and have problems much like you've described.

[Renegade]

Well today it fired right up go figure. The choke it getting good voltage and opened up but it took a while.

When the car idles it goes up and down about a 100 rpm and if I give alot of throttle and let off the engine will die.
Something is wrong somewhere for sure.