Carb rebuilt - I’m afraid to crank it....

[jabborabbo]

I haven’t been on the boards for a long time - long story, truck essentially in storage (I could drive it but couldn’t spend sufficient time doing things like a carb rebuild). That is thankfully over now, so the first thing I’ve done is a... wait for it...carb rebuild! Rochester B carb on my 67 GMC...I followed the directions, carb is back on the truck, but since this is my first carb rebuild I’m apprehensive about cranking the thing. Other than having a fire extinguisher handy and doing the first crank outside of the garage, what advice do y’all have that will ease my mind?

Thanks in advance for all replies!

[68Gold/white]

What is a "B" carb???

When starting it, crank the engine over for about 10 seconds, WITHOUT pushing the gas pedal. This fills the float bowel with gas, which is obviously needed for carb operation. The engine might start in these 10 seconds. If it does, shut it off.

Next, if the engine does or doesn't start, look at the carb to make sure float is not stuck. Look at outside of carb for fuel leak, and inside for excessive gas.

Next, as you are looking down carb throat, pull back on throttle to see if accelerator pump is squirting gas in carb. If acc pumps works, that is a good sign.

If all this goes well, pump the gas pedal twice and try to start it. Hopefully all goes well. Look at carb as engine is running to make sure there are no leaks, anywhere.

[jabborabbo]

Rochester B carb photo attached...it’s a one barrel for a 250 6 cylinder. It now looks a lot better!

Thanks for the advice!

[kwmech]

Go for it, God hates a coward



have extinguisher sitting by

[Killer Bee]

more likely to have a carb fire from drastic timing issues creating backfire through carb..

I've seen many external gasoline leaks on engines at running temp that never made a flame..

however, if you're concerned, no harm in being prepared..

1. if internal fire starts, continue cranking engine with no throttle input and should suck flames down and go out
   
2. if fire can't be sucked down or starts/spreads externally, cover with damp towel to smother without mess and damage
   
3. chemical extinguisher would be my last resort but may be necessary for large fire from external leak

good luck!

[garyd1961]

Start it up and let it run a few seconds then shut it off. Get out and check for leaks then crank it and let it run.

[HO455]

Having your air cleaner on is good insurance against a carb fire. At the very least the base plate. Lots of good advice already posted.

[Coley]

If you have confidence in what you did and you followed the instructions step by step you should have no issues.
As for fear of it exploding......very, very, very unlikely if that is what you are thinking.
Simply take a fire extinguisher with you or something like a blanket to smother it if you think it might ignite something.

The only way that is going to happen, as mentioned, is if it backfires with the air cleaner off and even then there has to be fuel nearby to be ignited.

Get in, crank it over a few times....because it won't start until it fills up with fuel delivered from the fuel pump.
Then stop, leave it for a few minutes to see if anything is leaking....then maybe see if it is squirting internally.
Then hit the go button and start setting it up and away you go.

All good
Coley

[brown7373]

I always fill the fuel bowl through the top vent on a Q-jet. Not familiar with the 1 bbl, but I assume it has a vent also. With the choke set, it will fire almost immediately.

[jabborabbo]

I appreciate all the advice. The good news: I didn’t burn the truck up or burn the house down. The bad news: fuel is leaking out between the float bowl and the air horn, which I assume means that the float isn’t set right or the float needle, seal, and/or gasket ain’t right. So it’s off to the auto parts store to get another rebuild kit and try again.

One separate issue: the choke knob on that truck has always been hard to pull out - so much so that I stripped the knob off a while back and jury-rigged a couple of nuts and washers to replace the knob and be able to operate it. With the carb off and not connected to the choke the cable pulls in and out easily - when I put the carb back on and connected the choke cable it was hard to pull again...what’s up with that?

Again, thanks for all the replies!

[RustyPile]

I see you're in Palestine, TX.. I'm a little south of you, down here in Elkhart.. Your carburetor is a Carter Mono-Jet... Commonly found of GM I-6s for several years.. I'm very familiar with those carburetors and I'd be glad and honored to help you remove any bugs in it.. If you're interested, contact me through the site's PM Message feature..

[RichardJ]

That is a Rochester B. Not a MonoJet.

What makes you think you need another kit?

There's something hinky about the way the choke cable clamp is positioned. I think there is something assembled wrong with the choke mechanism that may be causing the leak as well as the choke operation.
Unlike many carb chokes with a step cam, your choke has a tapered ramp for the high-speed idle.

[jabborabbo]

Originally Posted by RichardJ

That is a Rochester B. Not a MonoJet.

What makes you think you need another kit?

There's something hinky about the way the choke cable clamp is positioned. I think there is something assembled wrong with the choke mechanism that may be causing the leak as well as the choke operation.
Unlike many carb chokes with a step cam, your choke has a tapered ramp for the high-speed idle.

I haven’t changed the choke mechanism...I guess I don’t understand how that could be the cause of my current problem....

[junksaver]

You don't need another rebuild kit. Just take it back apart and check your needle and seat to make sure it is clean. Then check your float level. The gaskets will be fine.
Couple of questions? You said the truck has been sitting. If it has been sitting for more than a year you may need to drain the tank. Did you put a new fuel filter and new rubber fuel lines on? Any little piece of trash can cause the needle not to seal in the carb.
Good luck and let us know how it goes. I just did all of that 2 weeks ago on my 67 with the same 250 1 barrel.

[jabborabbo]

Originally Posted by junksaver

You don't need another rebuild kit. Just take it back apart and check your needle and seat to make sure it is clean. Then check your float level. The gaskets will be fine.
Couple of questions? You said the truck has been sitting. If it has been sitting for more than a year you may need to drain the tank. Did you put a new fuel filter and new rubber fuel lines on? Any little piece of trash can cause the needle not to seal in the carb.
Good luck and let us know how it goes. I just did all of that 2 weeks ago on my 67 with the same 250 1 barrel.

It’s not been sitting for several years - I’ve driven it semi-regularly until about 2 months ago when I saw one drip of gas from the carb - that made me quit driving it until I was in a position to rebuild the carb.

The fuel filter is the sintered bronze type - I soaked it in carb cleaner - I haven’t put new fuel lines on it...I just thought I would eliminate the gas drip by rebuilding the carb.

[RustyPile]

Originally Posted by RichardJ

That is a Rochester B. Not a MonoJet.

Sorry guys, I stand corrected. It is a Rochester B.. I don't know why I typed "Carter"..Carter didn't make the mono-jet.. The Rochester Mono-jet has a more "square shaped" reservoir, with a single float/single needle & seat. The "B" has a dual float arrangement with a single needle & seat..

Too many days away from this stuff has caused my memory to fail me...

[68Gold/white]

Originally Posted by jabborabbo

It’s not been sitting for several years - I’ve driven it semi-regularly until about 2 months ago when I saw one drip of gas from the carb - that made me quit driving it until I was in a position to rebuild the carb.

The fuel filter is the sintered bronze type - I soaked it in carb cleaner - I haven’t put new fuel lines on it...I just thought I would eliminate the gas drip by rebuilding the carb.

I wasn't thinking about "B" carbs when I was reading your initial post, just V8 carbs, LOL

This as a cool carb to rebuild for someone without a lot of experience! I feel confident that it will run fine!!!

[bill3rail]

Originally Posted by Killer Bee

1. chemical extinguisher would be my last resort but may be necessary for large fire from external leak

good luck!

Water Extinguisher would spread any spilled grease, oil and fuel and just create a really big fire!

Suffocate fire with wet towel.

Bill

['68OrangeSunshine]

Carter did make a single Bbl ''YF'' carb for some GM L6 engines. You might try lubing your choke cable with graphite powder or WD40. But if it's really rusty, just replace it.

Correction: Carter YF one-barrel carbs were used on AMC, Jeep and Ford sixes, no documentation of use on GM L6s.

[bill3rail]

Originally Posted by '68OrangeSunshine

Carter did make a single Bbl ''YF'' carb for some GM L6 engines. You might try lubing your choke cable with graphite powder or WD40. But if it's really rusty, just replace it.

The issue is not his cable.
He needs to look at the choke functioning on the Carb.

Originally Posted by jabborabbo

With the carb off and not connected to the choke the cable pulls in and out easily - when I put the carb back on and connected the choke cable it was hard to pull again...what’s up with that?

[davepl]

BTW, I like to have a bucket of water nearby too. Small fires don't merit emptying a 10lb powder extinguisher, for example.