throttle plate v.tubes filled

[F250 Restorer]

I am finished with the recalibration. Following Cliff's advice, I opened the idle tubes to 38, the down angle restriction to 52, the mix holes to 95, float level at 1/4", main bleeds are at 70, as is the idle bleed.

I'm anxious to find whether the small primaries deliver a bit more pep off the line. Today I'll toy with the throttle cable bracket and the adapter to a Holley style intake. I'll post my results.

I was a bit lost about which booster spring to use, but went with one that seemed about mid tension. I'll see if that works for the 14hg I have at idle.

[F250 Restorer]

I got it running. I was surprised to find that the AFR changed quite a bit from when it was warm in the driveway with the hood up, to when I brought it back after a drive. I attribute that a hot engine compartment and the hood being closed. I went from 12.6 AFR at idle, to 15:1 idling after a drive. I had to readjust the mix screws to get it back to 12.6. I opened the screws and it got back to desired ratio.

But, cool air is denser than hot air. So the engine should go rich with hot air supply, right? not lean?

Also noticed that my test drive was w/o vacuum advance hose connected; carb hose connection capped, hose not connected. I look forward to feeling the difference with the v.a. working, ha ha.

Cliff, how can you tell if the booster is not over-coming the engine vacuum and raising the power piston/m.rods?

[Cliff Ruggles]

Engine vacuum falls off WAY below the spring rate with any very quick throttle movements or going to heavy or full throttle.  With the later APT carburetors you can remove the plug over the APT and put a cut piece of a drinking straw down over the APT screw and against the pin on the power piston.  Move the throttle quickly to reduce engine vacuum and you can see the straw move up so you know it's working.

You can also reach in with a small flat tip screwdriver with the engine not running and push up and down on the pin to make sure the PP isn't stuck or sticking.......Cliff

[F250 Restorer]

I just want to say 'thanks' to Cliff for all the help. Had you not written your book, I never would have gotten over my hate of QJ's! Now that I understand it, I would rather have a QJ than a Holley, or any of the other name carbs out there.

I tuned today and found that I had to set the AFR mix for when the hood is closed, not for when it is open. It is funny, when I am sitting in the cab, hood shut, and the electric cooling fan comes on, I can see the AFR fluctuate as cooler air is pulled into the engine bay. Love this carb. I can't wait to dial in the APT for max mpg.

Oh, and Cliff, your specs for the engine/cam were dead on. It purrs.

[Cliff Ruggles]

 , I love the in-line 6 engines.  They were never all that popular but dead solid reliable and last just about forever.  Even cooler to see a 4bbl set-up on one!......

[F250 Restorer]

I can't seem to get any flow to my secondaries. I checked and ran a thin copper wire through the four tubes. The innner two are bleeds that vent through the airhorn. The outter two exit through a hole in the air horn. I thought those were the supply to the secondaries discharge tubes, but no. So, how do the secondaries get fuel?

Thanks.

[Kenth]

Fuel flows thru the metering discs in bottom of the float bowl were the secondary rods sits and up the channel were the secondary main well air bleed tubes (the small inner tubes in air horn) sits and out of the main discharge nozzles.
The larger (outer) tubes i air horn are the accelerator tubes that pull fuel out of the holes in front of the air valves when they opens to cover for the incoming air before the main discharge nozzles comes in. This pull over enrichment system acts much like a secondary acc pump.

HTH

[F250 Restorer]

Fuel flows thru the metering discs in bottom of the float bowl were the secondary rods sits and up the channel were the secondary main well air bleed tubes (the small inner tubes in air horn) sits and out of the main discharge nozzles.
The larger (outer) tubes i air horn are the accelerator tubes that pull fuel out of the holes in front of the air valves when they opens to cover for the incoming air before the main discharge nozzles comes in. This pull over enrichment system acts much like a secondary acc pump.

HTH

Thanks for the explanation. So, when I look up the discharge tube, I can see that the inner tubes meet the top of the airhorn. Shouldn't there be a gap so that fuel can be pulled out? And if so, how do drop them down a bit? Thanks again.

[Kenth]

The smaller tubes adds air to the mixture and are smaller than the channels for the fuel to pass.

[F250 Restorer]

Thanks again.

I think I got it, ha ha. Fuel is pulled in when secondary rods are lifted. That fuel passes the bottom of the inner tubes and air is then added as it is pulled past. It travels up the outer tubes and across the airhorn to the discharge tubes. Why is there a hole in that passage, in the airhorn, between the top of each outer tube and the discharge tubes? Each hole sits above each air flap. That has to be like an acc. pump squirt as the air flaps open, right?

I can't get air past those holes to the discharge tubes. If I plug each hole and blow through each outer tube, I got nothing coming out the discharge tubes.

[Kenth]

The outer tubes in air horn are parts of the secondary initial POE system using their own fuel wells in bowl and has nothing to do with the secondary main discharge nozzles.

[F250 Restorer]

Thanks for taking the time to lead me through this.

The inner supply tubes on my carb go directly to the top of the airhorn. No fuel can escape them into the discharge tubes. How can I pull/tab them down a bit so that they can supply fuel to the discharge tubes?

[Kenth]

The inner tubes are sitting fine and supply air into the fuel and the emulsified fuel feeds thru the nozzles.
Click on the picture to enlarge and see better.

[F250 Restorer]

We have a disconnect. I understand your explanation, but I don't think you are following what I am trying to say or explain. My secondary supply tubes are solid and extend to the top of the airhorn. There is NO way for the fuel to mix with air, unless it spews out over the top of the carb and is then sucked back down the secondaries. My understanding, as in your photo, is that the tubes have to terminate somewhere within the circumference of the discharge tubes so that the fuel can mix with air before being sucked down. Mine do not.

CLIFF, can you please tell me how to rectify this?

[Kenth]

The small brass tubes extend to the top of the air horn and adds air into the fuel in the fuel supply channels, not fuel to the nozzles.
The fuel to the secondary main nozzles are delivered up thru the fuel supply channels cast into the float bowl.