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Old 08-02-2019, 11:22 PM   #76
cpnbnanamn
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Re: 1 barrel rochester carb 1967 problem

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Originally Posted by VWNate1 View Post
NO Problem ! .

The flat spot off idle is very common and you must take the steps to ensure everything else is *perfect* before touching the carby or you'll chase your tail endlessly and hate the rig .

You'll need a 12 volt, inductive timing light ($30 new @ O'Reilly's), a dwell tachometer (pawn shops have these cheaply) and a vacuum gauge (another $5 used tool at the pawn / thrift shop) and some new vacuum hose .

Have some patience, we'll walk you through it .
PROGRESS!!!
Finished a tune-up, and then kinda baselined the carb. Found that I had the mixture WAAAY too far out, so after the tune-up was done, reset the mixture to 1-1/2 turns, and she fired right up! Backed the idle down, but I still have that flat spot off of idle. If I go easy into it, it revs right up, but jump on it a little, it damn near drops out. I do see some improvement in running, though.
Ok, so to answer a few questions I've gotten: The accelerator pump seems to be working. Watched the throat while hitting the accelerator, opening the plate, I see a pretty good spray down the carb throat. I also sprayed carb cleaner around the base, intake manifold, vacuum line, anywhere I could think of that air might be getting in. I might be doing it wrong, but as far as I can tell, not leaking.
I'm in the process of gathering tools up. I have a timing light, but not sure if it's any good. And I think I have a vacuum gauge.
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Old 08-03-2019, 01:06 AM   #77
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Post Re: 1 barrel rochester carb 1967 problem

Progress ! .

Also check to ensure the distributor's vacuum advance line is connected so ot gets no vacuum signal at idle but gets lots of vacuum the *instant* the throttle is opened .

Suck on the vacuum hose and see if it holds vacuum1 as long as your tongue is on it, they're available new and plenty of good used ones out there too .

A new inductive dynamic timing light is under $40, I get good quality ones @ pawn shops for $5 because no one wants them, be sure to test before paying for any used light .

The ones with the advance dial on th back as the best .

Set idle timing to 8 ~ 10 degrees BTDC at 700 or less RPM .
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Old 08-04-2019, 09:50 PM   #78
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Re: 1 barrel rochester carb 1967 problem

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Progress ! .

Also check to ensure the distributor's vacuum advance line is connected so ot gets no vacuum signal at idle but gets lots of vacuum the *instant* the throttle is opened .

Suck on the vacuum hose and see if it holds vacuum1 as long as your tongue is on it, they're available new and plenty of good used ones out there too .

A new inductive dynamic timing light is under $40, I get good quality ones @ pawn shops for $5 because no one wants them, be sure to test before paying for any used light .

The ones with the advance dial on the back as the best .

Set idle timing to 8 ~ 10 degrees BTDC at 700 or less RPM .
Ok, so I had some help today, and we made a few adjustments. Verified that the vacuum advance was working, and checked the vacuum coming from the carb (22 psi). Adjusted the timing to ~11 BTDC - The engine seemed to like that. The flat spot has improved a little but is still very much there. It's running at about ~700 rpm at idle.

I also discovered I probably need to replace the throttle return spring. The friend that was helping me has suggested that I may need to rebuild the carb again - feels that the ethanol gas may be eating at the gaskets / plunger cup for the accelerator pump.

While I'm happy it's running better - I'm frustrated at the same time. Kinda feel like I"m chasing my tail.

Oh, and we damn near burned the truck and house down. The wire that comes from the starter solenoid to the positive side of the coil shorted, and damn near caught fire.
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Old 08-05-2019, 02:28 PM   #79
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Post Re: 1 barrel rochester carb 1967 problem

O.K., you're getting there .

The vacuum is measure in inches not pounds, 22"is fantastic ~

? Does the vacuum gauge's needle quiver or twitch at idle ? .

Did you gap the spark plugs to .035" ?.

Engine OFF peer down the carby throat and work the throttle once, the *instant* the throttle begins to move .

There should be a very thin stream of fuel not a spray nor stream of droplets .
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Old 08-05-2019, 02:30 PM   #80
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Ignition Timing

? Is there _any_ vaccum at the dizzy when the engine is idling ? .

Try setting the timing back to 9 ~ 10 degrees BTDC .
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Old 08-11-2019, 08:58 PM   #81
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Re: 1 barrel rochester carb 1967 problem

More PROGRESS! Installed an inline fuel pressure gauge, and a new filter. Gauge is showing basically no pressure, and if the see-through filter is full, it'll start, and run for a bit, but when that filter starts to empty out, she stutters, and eventually stalls. I still have the stock tank. Is there a sending unit in the tank? Wondering if I should replace the pump, or sending unit (if it exists). Or time to pony up the cash for the Boyd tank I'm wanting?
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Old 08-12-2019, 09:50 AM   #82
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Post Fuel Issues

First thing is to get what you've got working properly then move on to fancy fuel cells .

Otherwise you're going to be chasing your tail until you begin to hate this
simple old truck .

So, with about 1/2 tank or more of fuel, disconnect the steel fuel pipe in the engine compartment where the short flex hose to the fuel pump is connected~ fuel *must* gush out in a steam as large as the inner diameter of the steel pipe .

If it flows out and immediately makes a down ward 90 degree turn, there's something blocking the fuel flow that needs fixing .

The next step is to remove the fuel sender / pickup and check the screen/sock on the end of the pickup pipe, look into the tank with a flashlight to see if there's crud in there .

If the intake sock isn't perfect, replace it or make a new one using brass / stainless steel window screen but DO NOT run it sans intake screen ! .

If the intake screen is perfect (very unusual) try blowong the steel pipe running along the frame backwards and see what come out at the tank end .

I use flexible Mechanic's wire to plumb old steel fuel lines, it's tedious but not difficult ~ every time the wire stops moving, pull it back out and wipe off the accumulated crud and rust, after a while the pipe will be cleaned out and work like new again .

Take off the short flexible frame to pump hose and look through it ~ it *must* be perfectly round inside and easy to see through, if not replace it or grind / peel off the crimped collars on each end to release the standard hose barbs, discard the fancy flexible stuff and replace with regular hose, use good quality clamps, not crappo Chinese junk .

Until the fuel pump gets unrestricted flow to it, it cannot transfer the necessary volume .

This carby wants no more than 2 ~ 3 PSI so don't go slapping an electric pump on to force things, you'll create a whole new set of problems .
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Old 08-12-2019, 10:55 PM   #83
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Re: 1 barrel rochester carb 1967 problem

Thanks for the help thus far, Nate! More progress to report! Tested the fuel pump for suction on the tank side. MORE than enough. Found that the fuel line between the tank and pump was clogged. Blew that out, and made a helluva mess. I knew the last filter was nasty with black crap in it, so I decided to keep going and pulled the sending unit.
Attached, are pics of the sending unit's strainer, the crap that blew out, and a shot of the inside of the tank.
I know you used to be able to reseal a tank, but the amount of rust concerns me. Knowing full well that the tank is coming out at some point in the relatively-near future, not sure how much money I want to put into it. I also saw that the strainer on the sending unit is split open. No bueno.
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Old 08-13-2019, 08:16 AM   #84
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Re: 1 barrel rochester carb 1967 problem

How many gallons do these tanks hold?
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Old 08-13-2019, 10:33 AM   #85
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Post Routine Fuel Tank Service

You're welcome, once you get this rig running well you'll wonder why anyone wants a V8 .

The fuel intake sock is maybe easiest to hand make, I recently spent some time @ O'Rielly's , plenty of fuel socks, none I really liked, maybe the host here has them ? .

As far as the tank, this one looks very good and they're easy to clean out and de rust, the only thing is : you need to dismount it to properly do the job, ask and I'll walk you through it, under $100 and you can save and re use the cleaner / de rusting agent for a few years on all the other steel bits & hardware you're going to want to re use .

Carefully shake the sending unit's float, if you feel any liquid sloshing 'round inside it's junk, new ones are cheap .
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Old 08-13-2019, 11:22 AM   #86
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Re: Routine Fuel Tank Service

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You're welcome, once you get this rig running well you'll wonder why anyone wants a V8 .

The fuel intake sock is maybe easiest to hand make, I recently spent some time @ O'Rielly's , plenty of fuel socks, none I really liked, maybe the host here has them ? .

As far as the tank, this one looks very good and they're easy to clean out and de rust, the only thing is : you need to dismount it to properly do the job, ask and I'll walk you through it, under $100 and you can save and re use the cleaner / de rusting agent for a few years on all the other steel bits & hardware you're going to want to re use .

Carefully shake the sending unit's float, if you feel any liquid sloshing 'round inside it's junk, new ones are cheap .
Hey Nate - In further investigation, I've come to the conclusion that I should replace the sending unit. It's in pretty rough shape, and I think it'd be the best bet. Who makes the best replacement?
As far as removing the tank, I've been told it's difficult to remove, and that the filler neck usually gets bent. Is there a trick to it? I'm betting I'm gonna have to remove the bench to do it, right? I've been looking at kits to do it, and possibly looking at the idea of taking it to a local radiator shop to clean..
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Old 08-13-2019, 11:49 AM   #87
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Post Fuel Tank

Unless it's dead I really recommend retaining the original sender, once cleaned up (use aerosol electro contact cleaner) they usually work fine .

I've had bad results with any Chinese made senders .

Once you undo the tank straps and slide the seat all the way forward you lift the passenger side of the tank a little bit and wiggle it as you pull the filler nck out of the body, then it's clumsy but not heavy to remove .

Just don't get worried and the job will go O.K. ~ I'm crippled and still manage it .

FWIW, your '67 may have a folding backrest, if not go find a '72 with unbroken springs (yes, they do exist and are usually very cheap) , remove your old unhinged seat to do the tank, you'll find a lot of crud that needs cleaning and maybe some rust bubbles you should at least wire brush then encapsulate with Rustoleum because RUST NEVER SLEEPS .

There are many products to clean the tank with, the best ones have Phosphoric Acid in them, you cn buy Phosphoric Acid in the flooring dept. of any big box hardware store or gallon jugs of " CLR ",

Dilute it with tap water and fill the tank, shake it and allow to sit overnight, shake it some more and drain the now black and nasty liquid using a large funnel with some clean felt or old towel in it to screen out the rust flakes .

You'll be amazed and well pleased with the clean shiny rust free metal inside the tank .

Use the BLOW part of any vacuum cleaner in the open sender hole to dry it out before re installing the sender and tank to the body .

If it's really rusty inside after you've soaked and shaken it, add a hand full or two of BB's, pea gravel, loose small sheet metal screws, nuts and flat washers, fill it again with the same (now filtered) solution and shake the beegeebers out of it until your arms are sore then shake it some more, let soak over night etc. .

WARNING !! : this solution will stain and etch the concrete in your driveway and kill the grass it touches to choose carefully where you'll be working .

I wish I had photos of a seriously rusted 1959 VW tank I did recently, it had been left sans cap with 3/4 a tank of fuel for close to thirty years and I was told by the seller to scrap the tank but original is always better quality than re pop so I sent to days and it's like new again....

This solution is goof for ferrous metals and brass copper too but never EVER pot metal / alloys ! .

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Old 08-13-2019, 12:26 PM   #88
cpnbnanamn
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Re: Fuel Tank

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Originally Posted by VWNate1 View Post
Unless it's dead I really recommend retaining the original sender, once cleaned up (use aerosol electro contact cleaner) they usually work fine .

I've had bad results with any Chinese made senders .

Once you undo the tank straps and slide the seat all the way forward you lift the passenger side of the tank a little bit and wiggle it as you pull the filler nck out of the body, then it's clumsy but not heavy to remove .

Just don't get worried and the job will go O.K. ~ I'm crippled and still manage it .

FWIW, your '67 may have a folding backrest, if not go find a '72 with unbroken springs (yes, they do exist and are usually very cheap) , remove your old unhinged seat to do the tank, you'll find a lot of crud that needs cleaning and maybe some rust bubbles you should at least wire brush then encapsulate with Rustoleum because RUST NEVER SLEEPS .

There are many products to clean the tank with, the best ones have Phosphoric Acid in them, you cn buy Phosphoric Acid in the flooring dept. of any big box hardware store or gallon jugs of " CLR ",

Dilute it with tap water and fill the tank, shake it and allow to sit overnight, shake it some more and drain the now black and nasty liquid using a large funnel with some clean felt or old towel in it to screen out the rust flakes .

You'll be amazed and well pleased with the clean shiny rust free metal inside the tank .

Use the BLOW part of any vacuum cleaner in the open sender hole to dry it out before re installing the sender and tank to the body .

If it's really rusty inside after you've soaked and shaken it, add a hand full or two of BB's, pea gravel, loose small sheet metal screws, nuts and flat washers, fill it again with the same (now filtered) solution and shake the beegeebers out of it until your arms are sore then shake it some more, let soak over night etc. .

WARNING !! : this solution will stain and etch the concrete in your driveway and kill the grass it touches to choose carefully where you'll be working .

I wish I had photos of a seriously rusted 1959 VW tank I did recently, it had been left sans cap with 3/4 a tank of fuel for close to thirty years and I was told by the seller to scrap the tank but original is always better quality than re pop so I sent to days and it's like new again....

This solution is goof for ferrous metals and brass copper too but never EVER pot metal / alloys ! .


It's not dead, but the siphon tube is REALLY blocked up, and corroding. I'm concerned about it causing further issues.
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Old 08-15-2019, 01:00 PM   #89
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Thumbs up Basic Fuel Flow

Use some CLR on the various tubes to dissolve the crud .

As I said, I use Mechanic's wire and / or old unbent coat hangers because at least 1/2 of the vehicles I touch have been sitting a while and the crappy Foo-Foo 'motor fuel' they sell here as regular, degrades very quickly and after a few years is solid .

Like everything else, YOU are the best one to do the job because you care and won't rush nor skip steps .
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Old 09-07-2019, 12:59 AM   #90
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Re: Basic Fuel Flow

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Use some CLR on the various tubes to dissolve the crud .

As I said, I use Mechanic's wire and / or old unbent coat hangers because at least 1/2 of the vehicles I touch have been sitting a while and the crappy Foo-Foo 'motor fuel' they sell here as regular, degrades very quickly and after a few years is solid .

Like everything else, YOU are the best one to do the job because you care and won't rush nor skip steps .
More PROGRESS!!

Got the original tank cleaned up, and managed to salvage the sending unit. I was seeing the fuel filter empty out, and I thought that was part of my issue - the flat spot off of idle.
Got it all back together tonight, and got it started. I also installed an inline fuel pressure gauge. Filter is staying full now, and when she's choked a little, the fuel pump runs at about 4 psi. After pushing the choke all the way in, fuel pressure drops to 2 psi, and is pretty steady there... are they supposed to stay solidly at 4 or 5 psi? I still have that flat spot off of idle. I remember testing the suction side of the fuel pump and it was holding a solid 22psi IIRC.
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Old 09-07-2019, 07:09 AM   #91
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Re: 1 barrel rochester carb 1967 problem

Have you checked for a worn throttle shaft. They cause a vac. leak off idle.
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Old 09-07-2019, 08:57 AM   #92
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Re: 1 barrel rochester carb 1967 problem

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Have you checked for a worn throttle shaft. They cause a vac. leak off idle.
Yessir. Sprayed carb cleaner around the shaft area. Didn't seem to make a difference, but I can't check it again.
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Old 09-07-2019, 09:33 PM   #93
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Thumbs up Progress Indeed !

Yes, 2 ~ 4 PSI is plenty, be sure to do a volume test too with the ignition off you crank the engine with the carby feed pipe disconnected and there *must* be a solid stream of fuel the same diameter as the inside of the fuel pipe/hose that sprays straight out a few inches before it turns and turns down .

It sounds to me like you're getting there .

NO vacuum signal to dizzy @ idle, and vacuum as soon as you open the throttle, right ? .

You're looking for 4 ~ 10 degrees BTDC @ 700 RPM idle and no more than 32 degrees all in @ 3,000 RPM .


All six spark plugs have the exact same color on the center insulator ? . should be white to tan/beige ~ black or blistered is bad .
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