Weird Carb Choke Issue

[DJ_Baar]

Previous Owner installed an Edelbrock performer carb (1406 I think) & manifold on this old '67 Chevy C20 PU. Previous Owner did not have a cable long enough to connect manual choke (& did not install electric).

I installed replacement correct choke cable. (Attached is picture of carb before I installed cable to choke.) Cut to correct length (and a little extra available in slack to have enough for repairs later if needed). Lubricated cable before install (motorcycle cable lube) and white grease at exposed end. Choke opens and closes with no binding - smooth operation. BUT does NOT affect engine either open (for running) or closed (for enriching fuel mixture). I can sit with air cleaner off and watch it open and close no problem but NO response to idle RPM either! Totally weird.

Only adjustment from Edelbrock is for electric choke. Just doesn't make sense? I'm not new to wrenching, have had my share of motorcycles & hotrods built ground-up (pushing 60 here & ASE certified), but this has me scratching my head.

R/DJ

[geezer#99]

If you want more rpm, Adjust the high idle screw. It's on the drivers side.
Check this vid.
https://www.youtube.com/watch?v=LtcBAUHJJBM

[DJ_Baar]

Hunh - just don't remember adjusting more out of the box for the choke. Always had choke or enrichners do just that enrich the idle mixture. I will check that out - ain't the internet something? Ha! Learn something new every day.

[BugzC10]

My first thought was .."do you have a vacuum leak under the carb" I don't see much of a gasket between the carb and manifold. ...Watched the adjustment video. I would think if you pulled the choke all the way it would have an effect, but you indicated it did not. Let us know if adjusting the choke fast idle screw fixed your problem.

[GASoline71]

There shouldn't be any adjustment of the cable actuated choke. It's either open or closed depending on which way you pull or push the knob in the dash.

Then again... what do I know... I've removed every choke out of every carbed vehicle I've ever owned.

Except an old '67 C10 I had with a 292 and a 2 barrel carb. If I wanted it to sound "racy" at a stoplight or cruising through a parking lot, I'd pull the choke halfway...

Gary

[DJ_Baar]

After work tonight I messed with the fast idle choke adjustment screw on this Edelbrock1405 (correction) manual choke carburetor & can close the choke enough to kill the motor and adjust choke just before to fine bit of slight rpm increase. Messing with screw did little. Brought it back to where I started.

Note it is rather HOT here in New Orleans area so using a choke is limited to start with, but used to being able to note a significant idle rpm increase with a choke/enrichener.

R/
DJ

[geezer#99]

Maybe somebody had it apart and put it back togethor wrong.
Burn us off some pics.
Both sides of the carb will do.

[pwdcougar]

If you push the pedal to the floor and pull the choke knob/cable out it should set the fast idle screw onto a stepped or cam shaped lobe. Doing this should open the lower throttle plates. The electric choke versions of the carb do the same thing only via a temperature activated spring. I'll take a look at the linkage on my Cougar carb tomorrow and see if I can get a picture of the assembly.

If you can close the choke plate and it has no affect on the idle it sound like a vacuum leak to me.

Paul

[DJ_Baar]

If I close the choke all the way it kills the engine.

I see the linkage and how the screw adjusts fast idle by how far it is screwed in or out resting on that cam.

No PVC was hooked-up so used manifold directly. PVC hose is connected directly to outlet on manifold under back of carb. Would that cause a vacuum leak. There is a plugged outlet directly above on carb for power brake booster. I can move nipple to that and switch booster and PVC hoses to correct spots. Thought manifold vacuum same? So left it that way temporarily. I can get that all switched correctly.

R/
DJ

[DJ_Baar]

Oh and spoke with previous Owner. He says he installed the performer manifold and 1405 carb straight out of the box on this 350 SBC. (Only change to otherwise stock '67 C20 from original 327.) I changed the valve covers to add the PVC - only had a breather and a little excessive on oil leakage there - highway.

[swamp rat]

The port in the back is manifold vacuum, i used this to attach the hose to my booster, i purchased the correct fitting to attach the hose. the front can be left connected to the PCV, its also manifold vacuum.

[DJ_Baar]

Roger that Swamp Rat.
PCV now on front and had to get another brass fitting for back of carb. Would you believe NAPA didn't have in stock. I have a temporary hose barb on back, but ordered correct fitting for brake booster, and getting a vacuum gauge too (thought I had one, but been too long). Only have distributor and transmission dashpot connected now, (have to work A/C later); so if a vacuum leak, it shouldn't be too hard to find?

R/
DJ

[swamp rat]

Could be the base gasket for the carb, or possibly the intake manifold gaskets leaking if you have a leak, i would install the air filter, housing and base gasket, fire up the truck and get a can of starting fluid, spray very short shots at the base of the carb and then the intake gasket, if the engine speeds up you have a leak, but be sure its not sucking into the air filter or thru the carb to filter base gasket, take your time and let any residual spray dissipate between shots. I have also heard you can do the same with wd-40 but i think its too messy.

Which leads me to wonder if your actually idling on the idle circuit and not the off idle circuit cause air leaks require more fuel. The idle ports are below the throttle valve or butterfly's as they are sometimes called, if the engine won't idle on the idle circuits sometimes people will keep turning in the idle adjust screw in too far, opening the throttle valve too far where it pulls fuel from the off idle ports

http://4.bp.blogspot.com/-uKEdmgoSAS...2Bpage%2B2.png

Have you checked to see how many turns out from lightly seated the air fuel adjust screws are set at? should be somewhere between 1 3/4 to 2 1/2 turns out.

[dflarsen77]

Dj, one thing to look at for vac is the AC control. The big plastic ball on the evap box under the hood is a vacuum tank. The line on the bottom connects to manifold vacuum somewhere, or might be, and then goes to the back of your AC control in the cab, and then a hose goes back out from that unit to 3 spots. If any of those connections aren't in good shape, that could be a vac leak to cause a problem. I think the PO on mine ditched the whole system because of that

[DJ_Baar]

GREAT ideas Guys, BIG thank you for helpful advice.

I was thinking same thing and already disconnected A/C ball for now Dave, (A/C is another project to get fixed down the road). But it does in fact tie into same distr/transmission vacuum line connection right?

And Swamp Rat,totally agree, I've done similar with finding old Harley intake leaks. And don't trust adjustments on carb either so....

Plan is to go thru and completely repair/replace vacuum lines as needed and adjustments to carb. Waiting now on correct brass fitting for back of carb to go to brake booster, and a new vacuum gauge. Plenty to keep me busy as I'm going thru most all of this truck to get road worthy. (A little rust restoration later on what's patch panel repairs - rocker panel & cab corner passenger side.) Around everything else wet sanding & throwing some clear over "patina" to keep rust from happening.... Already got into cowling, rebuilt wiper arm assembly and treated in there before rust happened. And getting last of what I need to totally go thru brakes and put '71 GMC disc on front. I will be busy Labor Day weekend & following week's "vacation" as parts boxes are showing-up

Truly appreciate the help, I will let you know what I find further on this. It has been a while since I wrenched on an old Chevy PU. Seeing choke not do its things really surprised this ol'grey beard.
R/
DJ

['68OrangeSunshine]

DJ: I have a Carter AFB 9605S on the 350 in my '71 Jimmy K/1500 [like a K/5]. It's basically the same carb [made in the same plant iirc] 600 CFM w/ manual choke. Since I live in the SW Desert with a lot of external heat, I have a 3/4'' - 1'' tall phenolic 4-hole spacer between the carb and intake to eliminate vaporlock. You might benefit from a similar mod since it gets hot in LA.
A safety note also: I would replace the clear plastic in-line fuel filter with the steel kind. The plastic can melt and spill fuel on your intake. I lost a '67 K/10 Suburban w/454 that way.
GASoline71: I've restored, retro-fitted, corrected or installed a Manual Choke on every 67-72 Chevy or GMC truck I've owned. Automatic chokes always go on or off in the wrong places.

[DJ_Baar]

WoW good advice '68OrangeSunshine!

Haven't drove enough to get the vapor lock problem but it does get HOT and HUMID here.

What do you think about the glass gas filters? I noted a plastic filter under cab too with a fuel shut-off. I got the saddle tank with the truck and mounting hardware, but not installed. Note, this is a "Camper Special."

R/DJ

['68OrangeSunshine]

Originally Posted by DJ_Baar

WoW good advice '68OrangeSunshine!

Haven't drove enough to get the vapor lock problem but it does get HOT and HUMID here.

What do you think about the glass gas filters? I noted a plastic filter under cab too with a fuel shut-off. I got the saddle tank with the truck and mounting hardware, but not installed. Note, this is a "Camper Special."

R/DJ

I used to use the 1'' O.D. glass fuel filter with the sintered phenolic filters, but they don't sell those anymore. The replacement plastic screen inserts tend to distort with all the non-gasoline additives in today's US pump gas. Also the glass could break -- leaving you with fuel spilling on the intake deck and hot exhausts not too far away.
Really I do use the old phenolic filter and another plastic filter in-line on the syphon pickup end I put in a jerry can, before the Holley electric fuel pump and 6' of 3/8'' vinyl hose into my fuel tank. My collection of jerry cans is getting old and the new ''funny-fuel'' tends to loosen the paint from the inside of my old school gas cans.
Loose paint flakes and rust grains can jam the needle/floatvalve operation inside the AFB type carb.
Under the cab from the Aux tank, is less dangerous, but why not just get one kind of fuel filter for all apps? The steel can type. I write the year and month and sometimes the mileage outside the can so I know when it needs replacing.

[DJ_Baar]

WoW that's impressive.

I keep finding new things to fix as I go thru this ol new truck project. So distracted with wiring issues now before I get back to vacuum leak

But taking some extra time off after Labor Day to get thru most of this. Hoping to have all or most parts needed on hand by then

Will post as I find new beyond me issues for some helpful advice. Thanks to all who gave feedback.

R/
DJ