This freaking carburetor…

[6f40j9]

Is driving me nuts.
Rebuilt 03-09/69 2 barrel.
A week ago, I finally got to drive into town. Running great, but 50mph top speed.
I ask around, poke around, lo and behold my secondary isn’t opening because I put the spacer on wrong and the linkage was blocked.
Fix all that, secondary opens, but it idles at ~2000+ rpm. (Guessing, as I don’t have a tach)
Pull the carb off again, clean off the spacer, manifold, carb. New gaskets. Put it all back together. Still high freaking idle.
The idle stop screw is backed all the way out. Throttle cable disconnected.
The air/fuel screw is 1.5 turns out from stop. (Doesn’t make any difference how far out I unscrew it though)
I pulled timing out until it wouldn’t start and dialed it back in so it starts and runs smooth. I can’t see my mark on the flywheel with the timing light to actually time it though.
I have wasted too much money on this oddball to replace it, but at the same time I’m not happy. I feel like I’m missing something simple because I mess up everything I touch on this truck.
Any ideas on what to look for next?

 

[Subterranean Nik]

Just to start.
Any underlying issues for the original need to rebuild carb?

As I read, once rebuilt all was running great up to 50mph which is what identified secondary, linkage, etc…

You’ll get it!!! Don’t give up…

Nik

 

[6f40j9]

Just to start.
Any underlying issues for the original need to rebuild carb?

As I read, once rebuilt all was running great up to 50mph which is what identified secondary, linkage, etc…

You’ll get it!!! Don’t give up…

Nik

I had it rebuilt while it was en route to me. I bought it used, it was replacing a leaking Rochester. It ran great until I pulled it off and dealt with the secondary issue. They open and close great now, even with my fabricobbled linkage. I just don’t understand the high idle. It’s like a vacuum leak but I can’t find one.

 

[6f40j9]

Idle video

 

[charliemeyer007]

I know nothing of your carb, but have you looked at the needles and their seats. Ever tried to adjust an oxy-acetylene torch that some ham handed gorilla torque the knobs down like it was for head bolts on a nitro methane fire breathing beast. The smooth taper shaft will have a big gouge ring cut in them and the seat will be damaged too.

Cold engine freshly started, spray the intake gasket areas lightly and quickly with wd40 - listen for the rpm increase which will indicate the leaking spot. Good plan to have a fire extinguisher handy, just in case.

 

[6f40j9]

I know nothing of your carb, but have you looked at the needles and their seats. Ever tried to adjust an oxy-acetylene torch that some ham handed gorilla torque the knobs down like it was for head bolts on a nitro methane fire breathing beast. The smooth taper shaft will have a big gouge ring cut in them and the seat will be damaged too.

Cold engine freshly started, spray the intake gasket areas lightly and quickly with wd40 - listen for the rpm increase which will indicate the leaking spot. Good plan to have a fire extinguisher handy, just in case.

I’ve tried. It idles higher cold. I’ve gone around the base, intake manifold, etc. nothing jumps out.

 

[igotta40]

I see a rubber boot that’s half missing. Someone rebuilt that for you? Possible air leak. Have you adjusted both idle stop screws or just one?

 

[charliemeyer007]

Ok, that would be a good sign that the intake gasket on the head and carb are good. Put a hemostat on the brake booster, dizzy and pvc hose, see if that makes a difference.

 

[6f40j9]

Ok, that would be a good sign that the intake gasket on the head and carb are good. Put a hemostat on the brake booster, dizzy and pvc hose, see if that makes a difference.

I don’t have a booster, the distributor is capped off. I tried the pcv hose, it doesn’t seem to leak.

 

[6f40j9]

I see a rubber boot that’s half missing. Someone rebuilt that for you? Possible air leak. Have you adjusted both idle stop screws or just one?

It’s been missing for awhile, didn’t affect anything before. Only one stop screw is operational, there’s a vacuum one that’s been disconnected from service. The throttle goes all the way to nothing right now.

 

[Subterranean Nik]

Wondering if timing just too far advanced.
I see the comment in OP about timing:
“I can’t see my mark on the flywheel with the timing light to actually time it though”.
If timing off, would make tuning carb tough…

That’s good with no obvious vacuum leaks

Any chance any gaskets used in rebuild installed upside down? Saw this comment in another thread - blocked off some ports.

Lastly - methodically recheck all the carb settings after timing confirmed. Idle speed, mixture, etc…

Nik

 

[6f40j9]

Wondering if timing just too far advanced.
I see the comment in OP about timing:
“I can’t see my mark on the flywheel with the timing light to actually time it though”.
If timing off, would make tuning carb tough…

That’s good with no obvious vacuum leaks

Any chance any gaskets used in rebuild installed upside down? Saw this comment in another thread - blocked off some ports.

Lastly - methodically recheck all the carb settings after timing confirmed. Idle speed, mixture, etc…

Nik

I cleaned my spacer block and there’s nothing to block off via gasket. I was thinking similar but it had been like it was and running fine before, so that wasn’t it.
I pulled all the timing out until it wouldn’t start, then slowly back in to where I had started, hoping to find something there but no luck.
It’s just weird that it ran fine, then all of a sudden didn’t.
I’m going to pull the top off again and see if something isn’t stuck inside.

 

[royal cake]

I know this is not related to your carb issue, but eBay is full of the old school dwell/tachometers for cheap. Very handy.

 

[majdomo]

About the only thing I can think of is linkage. My '77 (rod linkage, however) had the tiniest bit of sticking that led to high idle. Pulling up with my toe on the gas pedal let it drop from about 1800 rpm (what it sounds like in your clip) down to 700 or so. Barely noticeable movement on the carb but it sounded exactly like that.

One idea is to disconnect your gas pedal cable and see if that changes anything when trying to start? EDIT - reread that you have throttle cable disconnected so that's ruled out. Maybe idle speed screw way down at the bottom of the carb, firewall side, though I'm sure you looked at that too...

EDIT EDIT - also try putting your air cleaner back on and connecting up the vent on your valve cover and all that jazz. I had a rough time with my '72 before I put those back on, with them on all was well. It was a first for me, it shouldn't matter but for some reason on this rig it does.

 

[Pin_Head]

Chances are that something in the linkage or the butterflies themselves is preventing them from closing fully because it is not going to run at 2,000 RPM with them closed. Check inside with a flashlight to see which butterfly is open and then find out why it is not closing. Did you remove the butterfly when you rebuilt the carb? If so, it may be reassembled improperly.

 

[6f40j9]

Chances are that something in the linkage or the butterflies themselves is preventing them from closing fully because it is not going to run at 2,000 RPM with them closed. Check inside with a flashlight to see which butterfly is open and then find out why it is not closing. Did you remove the butterfly when you rebuilt the carb? If so, it may be reassembled improperly.

I had a pro rebuild it, they’re both closed all the way.
I did back the idle stop screw all the way out.
Linkage is clear.
I appreciate all the tips, believe me.
That’s why I’m so frustrated. It ran fine last week.
I’ll open it up again and check inside next.

 

[fireflyr]

If like Pin_head suggested the throttle isn’t binding, and all the adjustments for idle are backed out, and your butterflies are closed it’s probably an air leak.
I’d even check the manifold gasket/torque.

 

[middlecalf]

An air leak below the throttle plates would not produce the high idle rpms, in fact it would reduce the rpms.

 

[6f40j9]

Pulled the top off today and it fell apart on me.
Now I need a new gasket and to figure out where the pieces go.

 

[6f40j9]

I’m guessing the spring goes over the brass piece, then that goes inside the silver piece, then inside the brass hole above the float.
The pin is obviously the ‘axle’ for the float.
The washer goes around the accelerator pump?
The gasket is broken around the accelerator pump section which is why I’m guessing it had started to puke gas out of that part.
The boot has been broken almost since day one.
I guess I need to try and find a rebuild kit for this thing now.