The Stovebolt Site Forums The Shop Area Engine Shop need replacement carburetor HELP !!

I want to change carbs on my 58 GMC truck.engine is 270 straight six.Carb is a Zenith 1 barrel#11275D.Center to center mounting studs:2&11/16ths.Is there ANY carb that will work on my truck?As long as I get one that fits??Having a hard time finding a carb that will bolt-up.Any way that I can "tune"this wornout carb?Been rebuilt twice in a yrs time.Has a adjustable needle valve;air fuel screw.What are basic settings?
Thankx in advance,Danny

There are a lot of enthusiasts that would kill for that carburetor ☺

Seriously, probably the very best carb you could have on a 270.

Suggested initial settings:

Idle - 1 turn from lightly seated
Main - 2 1/2 turns from lightly seated.

Jon.

Jon,
The idle was set originally at 2-1/2 turns.too rich plugs fouling bad.I read that turning counter-clockwise leans it out.
At any rate people convinced me to try a Holley 2300 2 barrel setup.claims of "ease to work on"
frustrating to say the least
Danny

Danny -

The most wonderful thing about the internet is that anyone can post!

The most frustrating thing about the internet is that anyone can post!!!

Adjusting main metering screw on the Zenith counter-clockwise RICHENS the mixture, not leans it!

If in doubt on what any mixture adjustment does; check it out. First follow the internal passages to determine if the adjustment is fuel or air; then determine which direction closes the adjustment and which way opens the adjustment.

If you still have the Zenith on the engine, readjust the IDLE to one turn as I suggested above; and the main adjustment to 2 1/2 turns.

One other concern. Different carburetors have different adjustment ranges; which is why I want to see an identification number posted (as you did) before I open my mouth (er keyboard). Beginning about 1969 (different companies, different years), original equipment carburetors starting using a long taper idle mixture screw. Often, the idle adjustment for such a screw would be 2 1/2 turns to 3 1/2 turns. Some would take this measurement and post as correct for all. But most of the earlier carbs used the short taper screw for which the common range was 1/2 turn to 1 1/2 turns. There is no "one size fits all" answer.

And while others may love Holleys, I find adjusting Holleys to be a case of how many gas stations one will pass (never as many as the Zenith). ☺

Jon.

Jon,
Thanks for the continued advice.So I might just need to tweek the Zenith,huh?I believe that the needle is somewhat long&tapered-BUT this is from an novice.The choke wanted to close shut every time pedal is pushed EVEN though choke cable wasnt hooked up.had to ziptie it open just to limp back home yesterday.BTW- you have actually taken time to help me--THANKS !!
Danny

Danny - the choke MUST be hooked up, otherwise you will run rich.

The needle in the main metering jet IS a long taper, which is why the suggested initial setting is 2 1/2 turns. The idle mixture needle is the short taper; hence 1 turn.

Jon.

Jon,
Shall hookup&check those settings.
Danny

Jon,
Okay did all that.Let it warmup &drove to store for a soda.shutit off&made a whoosh noise thru the carb.Returned home,shut it off(whoosh noise) outside of garage&now wont start. Waited til this morning;fINALLY got her to start.idled real bad for 10min before I could back her into the garage.Was very hard to start
Danny

Danny,

Have you check the other tune-up items? Timing, points, plugs.

Good point, and valve clearances too.

okay, regapped plugs&points;everytime I try to set the timing ;lined up marks,distributor"moves"back somewhat to where it was when I found it.Will follow up with setting the timing 5'BUDC(?)
using timing light.had timing "ear"set before.
Danny

Thanks Guys for all of the advice.That is what I like about this "site"Gonna send that Holley back to store&pursue tweeking&tuning more--

Humbly,Danny

Well I set the timing by the mark,on the flywheel.Had rotor pointing at #1plug wire.Seemed to run (idle)ok.Took it around the block(no problem)Went to store&it overheated&couldN"T hardly give it any gas.It kept "popping back thru the muffler&stalled out3times&quit idling..A 5min ride took 30mins plus it overheated.WHAT is going on??I am totally baffled.I replaced the thermostat about 4months ago-could it be bad?Does anyone know about these engines?I have(i thouight)a decent GMC270 with that Zenith carb that was(?) giving me fits--

Took the thermostat out&it runs better.Waiting on another one to arrive.Will be really suprised if the overheating issues havent damaged something-