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Old 06-21-2014, 04:47 PM   #26
C10_ustacould
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Re: 1 barrel rochester carb 1967 problem

Ok, I'm going to have to change my name to Monkey's Uncle because I just could believe that gaping my plugs to .060 would clear up my stumble under load at higher speeds (55-70). It did! Just for kicks I pulled the plugs and re-gaped them this morning. Took it for a ride just now and there is a huge difference. It's no barn burner but it accelerates fairly smoothly up to 70. Sorry I doubted you guys... kicking myself for not doing it sooner. Maybe now I'll enjoy taking the truck out for a ride!
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Old 06-21-2014, 05:43 PM   #27
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Re: 1 barrel rochester carb 1967 problem

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Originally Posted by VWNate1 View Post
Before touching the carby you *must* go back and check and adjust all the tune up stuff ~ points ? .016" or 33 dwell , timing 0 ~ 10 BTDC @ idle and there *must* be no vacuum signal to the dizzy @ idle , if there is , you have the vacuum advance hose on the wrong carby nipple.
Not always. If you have a vacuum leak elsewhere or your carb is sufficiently messed up (or a giant cam) you sometimes have to turn the idle screw in so far to get a decent idle speed that you uncover the transfer slots. This is when guys (rightly or wrongly) start drilling holes through throttle blades and so on.

I think as soon as you do that you wind up sending a vacuum signal over the ported line (you're essentially at part throttle, even though you call it idle).

So you're 100% right that there shouldn't be vacuum there at idle, just it's not always caused by being connected to the wrong port.
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Old 06-21-2014, 06:29 PM   #28
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Re: 1 barrel rochester carb 1967 problem

Ozzie,What kind of gas do you use??? 100% gas. E-10, ???
If the vital components in the carb can't stand ethanol, then you could be in trouble..

The accelerator pump diaphram, and inlet needle can cause problems w/ even e-10 gas.
This isn't an every time, all the time deal, but can test your patience.

Theres a guy in Eldon Missouri, business name The Carburetor Shop that may have parts to help you, if you need them...Call him, He doesn't do emails...

Kits from part stores won't be compatible with ethanol gas, the "know-it-all" parts guy might tell you other wise..beware!!!
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Old 06-21-2014, 09:49 PM   #29
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Re: 1 barrel rochester carb 1967 problem

Thanks 68 Gold /White i got it straitened out had a weak fuel pump and real fine rust from the gas tank.Purrs like a kitten!
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Old 06-21-2014, 11:28 PM   #30
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Smile Re: 1 barrel rochester carb 1967 problem

He said it was a stock setup so what I said was 100 % correct , ALWAYS check the basics or you'll wind up chasing your tail .

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Originally Posted by davepl View Post
Not always. If you have a vacuum leak elsewhere or your carb is sufficiently messed up (or a giant cam) you sometimes have to turn the idle screw in so far to get a decent idle speed that you uncover the transfer slots. This is when guys (rightly or wrongly) start drilling holes through throttle blades and so on.

I think as soon as you do that you wind up sending a vacuum signal over the ported line (you're essentially at part throttle, even though you call it idle).

So you're 100% right that there shouldn't be vacuum there at idle, just it's not always caused by being connected to the wrong port.
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Old 06-21-2014, 11:32 PM   #31
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Post Re: 1 barrel rochester carb 1967 problem

Glad to hear this ~

Rusty silt is almost always incredibly fine so it whistles right through filters then once it's in the float bowl it begins to clump up and clog things .

I was recently on a Vintage Car Rally and had just this happen , it was running fine until a lunch stop then it wouldn't idle , the clear plastic micronic fuel filter looked perfectly clean but when I took the Air Horn off the carby on the side of the road , there was a chunk of rust blocking the idle and main jets ~ blew them out with my mouth , re assembled and zoomed off again .

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Thanks 68 Gold /White i got it straitened out had a weak fuel pump and real fine rust from the gas tank.Purrs like a kitten!
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Old 06-22-2014, 12:18 AM   #32
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Re: 1 barrel rochester carb 1967 problem

Exactly rust is so fine it goes through the inline filter and gets in the carb!
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Old 11-24-2017, 04:21 PM   #33
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Re: 1 barrel rochester carb 1967 problem

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It is a better design , it's also made of Aluminum instead of the old pot metal so they last far longer .

They're out there on E-Bay very cheaply once you know what to look for .

Every year or two , GM made yet another improvement to them , just like they did to those old 'B' series carbys .
Don't suppose you can help me out with a part number? I don't know what to look for!

I need to replace my carb on my 67.
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Old 11-24-2017, 11:01 PM   #34
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Post Rochester P/N's

Here are the part #'s for a 1968 with a manual choke :

Alternate/OEM Part Number(s): 17055531, 7028006, 7028007, 7028010, 7028011, 7028012, 7028013, 7029007, 7029011, 7029012, R1M

I hope this helps, you may have to fiddle the linkage .
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Old 11-25-2017, 11:04 AM   #35
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Quote:
Originally Posted by VWNate1 View Post
Here are the part #'s for a 1968 with a manual choke :

Alternate/OEM Part Number(s): 17055531, 7028006, 7028007, 7028010, 7028011, 7028012, 7028013, 7029007, 7029011, 7029012, R1M

I hope this helps, you may have to fiddle the linkage .
Thank you!! Ordering it up today and will let you know how it works!!
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Old 12-02-2017, 08:10 AM   #36
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Re: 1 barrel rochester carb 1967 problem

OK so I could use some help fellas. I have a 61 stepper with a 1971 250 and 3 speed saginaw out of a nova. It has a 1bbl Rochester on it with stock intake and exhaust manifolds. It was running rough so I checked the timing and re-set it at around 6 BDC without vacuum. Ran better but idle still seems rough. Dizzy looks like it was replaced recently enough. I checked the plugs and it is the typical center 2 are gummy and outer 4 are clean so I changed them all to be safe. Ran a little better. I left the gap at stock should I re-gap them to 40? I changed the fuel filter and run at least 2 tanks of gas through it including adding some seafoam to it. I also did the seafoam treatment to the intake manifold to clean out the carbon buildup. I noticed the carb had some holes plugged with crimped off hoses so I changed them out to plugs. It also had an exhaust leak at the down pipe and finally got it fixed too.
So this carb has all kinds of things on it that aren't hooked up because truck is a basic manual choke. I'm not sure if things are correct on it or what should be removed(solenoids?) and what should remain. So when its warmed up and I am on the road when I depress the pedal there is a instant half second hesitation before it accelerates. What would cause this? It also diesels when I turn it off so from reading your posts I need to fidget with idle and mixture screws but have no idea which one is which either. I did buy an HEI dizzy for it so wondering if I should drop it in or get it running smoother first? See pictures of current set up. Not sure why they are sideways...
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Old 12-02-2017, 11:54 AM   #37
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Post 1 barrel Rochester carb Adjusting

O.K., looks like you're on your way .

Me, I'd install the HEI dizzy before anything else, unless it pings when you stamp the throttle, set the base timing to 8 ~ 10 BTDC, idle speed below 800 RPM ~ then connect the vacuum advance hose whilst looking at the timing~ if it jumps forward, you have the wrong hose nipple on the carby ~ it shouldn't get any vacuum advance until you open the throttle .

If you're running points, do you have a dwell meter ? if so, remove the spark plugs and crank the engine, cap and rotor off, adjust the points gap to 33, this is the first step in points ignition .

Then gap the plugs to .035 (points) and re install them .

Once this is all done, stop the engine and look down the carby through as you gently work the throttle : the *instant* you move the throttle it's critical to have a solid if tiny spray of fuel out the accelerator pump jet ~ if it doesn't,take the carby apart and blow out the jet well, there's a BB in there that's finicky about tiny dust on it .

Now : engine off, turn the key on and see if that solenoid makes a 'click' and moves out a bit .

If so, you're on the right track, engine idling warm, back it off until there's a visible gap and then use the idle stop screw on the carby to set a 500 RPM idle .

Idling super slowly and maybe a bit roughly now ? fine ~ use the idle solenoid to raise up the hot idle to 800 ~ 1,000 RPM's , what happens is : that solenoid sets your idle and when you shut the key off it goes in and prevents the hot engine from dieseling .

As long as the key is on the engine should _barely_ idle with the solenoid disconnected .

I hope this helps, you have a GREAT carby there, keep at it remembering to FOLLOW THE STEPS IN THE CORRECT ORDER else you'll chase your tail forever .

Think of tuning like a clock ~ 11:59 is when you touch the carby and NOT BEFORE ! .

Everyone hears the carby popping and so touches it first, this is dead wrong every time .

Remember ; any HEI dizzy NEEDS A FULL 12 VOLTS and the original yellow coil power wire doesn't provide that .
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Old 12-02-2017, 02:30 PM   #38
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Re: 1 barrel rochester carb 1967 problem

The solenoid is not hooked up to anything. its a '61 and doesn't have this function. The choke pull off is not hooked up either.
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Old 12-02-2017, 05:10 PM   #39
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Post Re: 1 barrel rochester carb 1967 problem

O.K. so run a 12 volt fused wire to it, one that comes on with the key then follow my instructions .

You appear to have a choke cable connected so ignore the choke pull for now .

I sure could use the bimetallic spring ("choke stove") for my '69 .
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Old 12-06-2017, 02:52 PM   #40
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Re: 1 barrel rochester carb 1967 problem

The carb appears to be squirting instantly. Do you have a picture of your relay trick for HEI?
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Old 12-07-2017, 02:24 AM   #41
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Post Re: 1 barrel rochester carb 1967 problem

I don't, I'll try to get one before too long .

In any case, get that anti - diesel solenoid hooked up and working then set the idle timing to 10 BTDC @ 700 or lower idle speed and make sure there's NO vacuum signal to the dizzy @ idle .
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Old 12-07-2017, 07:14 AM   #42
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Re: 1 barrel rochester carb 1967 problem

ok going to do that this morning when its warmer. Curious why 10˚ vs stock 4˚? I don't have a vac gauge but when I put the vac line from dizzy to my lip I feel a very slight pull but it does not change idle when I hook it back up.

what solenoid switch did you use? Ill pick one up from auto parts store.
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Old 12-07-2017, 10:24 AM   #43
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Post Re: 1 barrel rochester carb 1967 problem

10 BTDC because that's what the engine was designed for, 4 retards the timing over all and reduces exhaust emissions .

There should be zero vacuum signal @ idle, the usual port is behind the carby facing the rocker box at the bottom .

There is no switch for the idle solenoid, chose a power source that comes live when you turn on the key .
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Old 12-07-2017, 10:32 AM   #44
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Re: 1 barrel rochester carb 1967 problem

10-4. Im at 6˚ so will see if that helps. The vac is coming off the bottom left port on side that faces the valve cover (see pic).
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Old 12-07-2017, 10:47 AM   #45
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Post Re: 1 barrel rochester carb 1967 problem

O.K., sounds good .

Just for fun, suck on the vacuum line whilst it's attached to the carby, it *must* hold vacuum and when you suck on it @ idle, the engine should speed up a little bit .
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Old 12-07-2017, 03:52 PM   #46
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Re: 1 barrel rochester carb 1967 problem

Ok I put it at 10˚ BDC and it ran faster so I turned the solenoid counterclockwise until the idle was at a good sounding chug. I have no rpm gauge on my timing light. It seems to run smoother on the road but there is still a hesitation when accelerating. The engine doesn't diesel now. Oh and the solenoid electrical connector is gone. Must have broken off previously so I can't hook it up. Know where I can find one?
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Old 12-07-2017, 04:01 PM   #47
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Re: 1 barrel rochester carb 1967 problem

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Ok I put it at 10˚ BDC and it ran faster so I turned the solenoid counterclockwise until the idle was at a good sounding chug. I have no rpm gauge on my timing light. It seems to run smoother on the road but there is still a hesitation when accelerating. The engine doesn't diesel now. Oh and the solenoid electrical connector is gone. Must have broken off previously so I can't hook it up. Know where I can find one?
https://www.napaonline.com/en/p/CRB22081

But for $85 I'd be looking to find a good used one.
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Old 12-07-2017, 04:03 PM   #48
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Re: 1 barrel rochester carb 1967 problem

mine doesn't even look like that.... Mine is about a 1" diameter by 3 inch long tube see previous posted pic....
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Old 12-07-2017, 04:56 PM   #49
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Re: 1 barrel rochester carb 1967 problem

Any of those carb mounted solenoids are nothing more than BandAids. They're use to fix a problem created by some modification. Some engines require a solenoid to maintain a smooth idle when the AC compressor kicks in, but that is usually in conjunction with smog equipment already compromising the idle quality.

Did you connect the manual choke cable? Does the choke and the high speed idle cam function properly? Do you have to step on the throttle before you pull the choke cable? Most of the time that arrangement results in the end of the cable breaking off eventually.

Did your '61 Step Side have a 235 with a Rochester B? If you still have the Rochester B, I'd use it to replace that smog Monojet that has missing parts. If you must have a Monojet, I'd get one for a '68 with manual choke.

You seem to have manifolds from different applications. Hard to believe a choke stove on the intake manifold would ever get hot enough. A choke coil without a stove cover would never get hot enough to open a choke.
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Old 12-07-2017, 07:22 PM   #50
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Re: 1 barrel rochester carb 1967 problem

the manual choke was rigged to work. No idea if high speed idle cam works. don't know how to check it.

The original engine blew and my uncle did some horse trading and a friend of his put this 250 in from a '71 nova. No idea what the deal is with the manifolds. Pissed my dad off so my dad gave me the truck. I have spent the last few months fixing and replacing all of the "shade tree engineering" as I go through the truck. Eventually Id love to replace the manifolds with dual header and Offy or Clifford intake and carb. For now I just want to get it to run better. I can take apart a motorcycle carb in my sleep but just learning about auto carbs. Suppose its a good one to start on.
I do have to tap the throttle to get it to start and once it starts I leave choke on for a little while until it warms up. I have seen plenty of carbs for sale online but I prefer to get this more tuned since it isn't broken.
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