Support the sides and lightly press the center. It will move like hot butter.

I'm trying to catch up in this thread so here's some commentary:

My 1978 B300 has a 2245, R7871A. For the 1979 (I don't have the service manual for 79), I see listed R7590, R8597-R8598, R8925, R9816. Not the one you listed, they appeared to be 2245s. You definitely have the stud upside down there, possibly someone in the past replaced the carb with a different one which just happened to be available but not the correct one.

I am still leaning towards timing / distributor being your issue.

Someone suggested a soft failure of the fuel pump, and these can be difficult to assess visually but I would expect a rough/lean run in that instance but not a "no start". I am assuming of course you have checked the coil? Sorry if you may have mentioned it but the thread is getting long!

regarding 4 bbl swaps, when assessing a problem I try to change as few variables at a time during the diagnosis!

Keep us posted!

I hope I have some flat enough surfaces...

I appreciate you keeping up on this thread! Going on page 6 now!
I searched for my carb numbers and I can't find them anywhere... not one mention of my numbers in the Holley Haynes Manual either.
I would also agree that it's the distributor/timing... The motor starts almost every time and actually idles a little on the weak side but it's when I accelerate that it backfires and stalls. It would make sense to me that the dis. is causing the issue. I know the fuel has good flow to the carb because when I installed it I installed a new filter and cleared out the line from the filter to the carb by putting a clear hose on the end of the fuel line into a clear container and cranking it for a bit... I could see a surge of fuel everytime the pump would spin so I know there's plenty of fuel getting to the carb...
As for the coil I ran a resistance test on it and it checked out...
On the 4bbl swap it was just a thought, I can't afford to buy a new manifold and carb right now...
I ordered a Cardone distributor which should be arriving today. I haven't heard the best things about Cardone distributors, I hope I get a good one!
I'll be back to post my progress!

https://www.carburetion.com/CarbNumber.asp?Number=R6765

These guys say 74 Dodge truck

https://carbkitsource.com/numbers/Holley/index8.html

Interesting, it says 74-80 Truck .. Maybe it's the correct carb after all... The "tag" on my van classifies it as a truck...
My pump lever is different though, it has two slots and I haven't seen any other carb with the same lever...

Dan, Several different carbs will bolt onto your intake and will function well. from about 1966 through 1983, These carbs used on the 360, 383 and 400 had more air flow and were a larger size then the carbs used on the 273 to 318 motors The smaller 318 carb and the larger 360 carb do not interchange. Mopar used either a Carter Carb in the early years and switched to Holey carbs in 74, I think, probably due to the emissions enforcement Both the larger Carter and the Holley both fit the intake and back then were not a difficult thing to interchange, I think the rerouting of the gas line was about the hardest part of the swap.

I suspect the biggest difference between the Holley carbs off a 360 and the Holley carbs off a 383 or 400 was probably the jets and the metering rod diameter. Over the course of time, several things changed inside the Holley carbs. I used the generic carb kits because those had all the gaskets and I would just use the gaskets that matched the carb in hand at the time. As the production dates of the vehicles and their OEM carbs moved on, the amount of adjustments the average person could make disappeared. The early 70s carbs were much more adjustable then the late 70s carbs were. Also of note is that many of the adjustments on the late 70s and early 80s carbs were more complicated to do correctly. It is my opinion that the earlier carbs were better carbs, but time has not done them any favors. Worn throttle bushings has become a huge problem with carbs and those worn throttle bushing have become a vacuum leak that is hard to detect. Gene

Alright Gene... everybody else... I have great news! It's alive! It was the distributor the whole time! With all the work I did cleaning and readjusting the plugs and especially rebuilding the carb, this thing runs better than it's ever run before!!! Seriously! My van runs so freaking smooth right now!
It use to hesitate and stall out some times and now it seriously runs like a brand new engine! The distributor and the carb were untouched basically since I bought it. I only replaced the needle and seat, the cup and gaskets on the carb when I bought it and also only replaced the cap on the distributor. That work was definitely due on this van and boy it sure paid off!
Thank You Thank You to everyone especially you old schoolers for your plethora of information!

You don't have to send me that carb anymore Gene! I appreciate it very much sir!

That van has more work that needs to be done on it so I'm sure I'll be back soon...
I'm very thankful for everyone hear on this thread! I couldn't have done it without you all!!

Glad to hear about your success.

a good outcome always deserves a "happy dance" !
don't be afraid to ask about something. lots of experience here willing to share.

Good deal. I'm happy to hear it runs well.

I'll take the carb back down to the lower garage and throw it back on the shelf. Gene

Appreciate it!
I'll take you up on that now!

Can anyone tell me how to adjust the fast idle??
Do I adjust the choke when cold and fast idle screw when it's warm? I thought I heard to adjust the fast idle cold but that maxes out the screw before it can reach 1600rpm...

Any tips and pointers for timing?? Do I time when warm?

What should I do warm? and what should I do cold??


I have the manuals it's just I have trouble making sense of instructions some times... Between the videos I watch and the books I can get some conflicting information...

There should be two screws on your throttle arm. One screw makes contact with with the carb's body, that is the hot idle speed adjusting screw. You adjust the motor RPM with that screw after the motor is up to operating temp and the choke plate is wide open.

The second screw seats against a plastic cam piece that moves with the choke plate by means of a rod linkage. That plastic cam piece has 3 steps on the that the screw can sit against. To set that screw for proper position, With the motor not running, you will need to open the throttle about 1/2 way open, and manually close the choke plate. The closed choke plate should lift the linkage up and lift up the plastic cam piece so when the throttle is released, the screw sits against the highest step that the screw can contact (but you need to be sure the throttle was open far enough for the linkage to lift the plastic cam all the way up without the screw touching the cam before the throttle is released). The information on the carb rebuild kit will give you the proper way to set that screw for the "fast idle". Things have changed enough through the years, you need to set "the fast idle speed" the way the info instructs you to set it.

There is one more important note here. While setting the fast idle speed, there is also a vacuum diaphragm called "the choke pull off" that needs to be tested. The diaphragm has a rod linkage the connects to the choke linkage. There is also a vacuum hose connected to the diaphragm that also connects to a vacuum port on the bottom throttle body. The vacuum hose needs to be soft, pliable, and without cracks or it needs to be replaced before the test can be done. You need to disconnect that vacuum hose at the carb base, and push the plunger on the diaphragm in all the way, then while its pushed in, cover the end of the hose with your finger to seal the hose. When you release the plunger, the plunger should stay sucked in until you release your finger from the hose end. If the plunger does not remain sucked in, either the hose or the choke pull off plunger is defective. Replace either (or both) of the defective parts. If the plunger remains sucked in until you remove your finger covering the vacuum hose, the choke pull off and the vacuum hose are good
The purpose of the choke pull off is to open the choke plate enough for the carb to get enough air when the motor is cold and the choke is in operation, so the motor can run. If the choke pull off and the hose are good, the next thing that needs to be checked is how much the choke pull off linkage is opening the choke plate. This test needs to be done with the plunger fully pushed in on the pull off diaphragm. You either need a vacuum pump to keep the plunger in, or you can push it in manually, and use something to temporarily plug the end of the hose. You will need both hands to check the gap between the choke housing and the choke plate. That gap is normally checked with a drill bit of a specific size (the instruction do lay out the process and the drill size).

The process is: Motor not running and choke rod from the intake disconnected. With the fast idle set screw positioned on the highest step on the plastic cam, and the throttle in the closed position against that screw, you insert the correct size drill bit along the inside of the carb body, and apply slight pressure to close the choke plate. The drill bit should slide in and out between the carb body and the choke plate with a slight drag. The little rod between the diaphragm and the choke linkage is either bent together at the U bend for more opening, or spread farther apart at the U bend to close the plate more. A slight bend can make a huge difference in the amount the choke plate opens and closes with this adjustment. After the adjustment is complete, reconnect the vacuum hose to the carb base, and reconnect the choke rod from the intake.


As a program note, after a few engine cycles (warm up and cool down, if there is a slight stumble leaving a stop, while the motor is cold and the choke is closed, a slight closing of the choke pull off rod may improve the cold engine operation, if the motor seems to run pretty rich while the motor is cold and the choke is closed, a slight opening of the the choke pull off rod can improve the cold motor operation. These adjustments won't make any difference once the motor has warmed up and the choke is no longer in operation. If the motor is warmed up (read that at or very near operating temp) and the choke is still under pressure to close, either the choke spring pressure needs adjusting, or the intake crossover the choke uses to function is plugged up.

Another program note, most chokes do not function well until the outside temp gets below 50 degrees. They were designed to function in colder weather. Gene

Gene laid out the adjustment procedure very well.
follow his instructions, and you should be ok.
you may have to tinker with it a bit, but don't get discouraged.

Good morning B300,

I had a feeling you would be back sooner rather than later. If there's anything working on these cars teaches you is not to celebrate prematurely!

There are several reasons you are getting some conflicting answers - One is that there are many different nuances for these procedures for the different vehicles that are out there and there is an element of trial and error necessary to dial in your ideal settings. Also, the factory settings may be designed to meet emissions requirements of the day and not ideal for running without emissions equipment. (early efforts at meeting emissions standards were disastrous and resulted in many owners disconnecting them immediately)

Hopefully, you have already completed the carburetor adjustments that are outlined in your carburetor rebuild kit. If you are a visual learner as I am, I have attached a PDF of the instructions included with the Hygrade kit. I have underlined the specs for my carb and you can disregard those - yours may be different. You can use drill bits as described by Gene, or use the included ruler but you will need to make sure to multiply or divide the spec appropriately, since the ruler is denoted in 1/32 increments.

In addition to the adjustments described in the rebuild kit, you'll need to adjust the idle mixture screws, the curb idle (the idle when hot), the fast idle (the idle at startup), and the timing.

Prior to placing the carb on the car, set the curb idle screw such that a thin sliver of the idle transfer slot is visible. This is just a starting point and will be adjusted later.

Timing:
I recommend you first assess the accuracy of your harmonic balancer. The video linked below describes this process and why it's important. Over time the dampener can rotate such that the timing marks are no longer accurate. Uncle Tony shows you how to do this although I know in that B300 it will be a little challenging due to the positioning of the engine in that doghouse!
https://www.youtube.com/watch?v=RBJOdiwjuQ0

Once you've done this, I set the timing when warm with your timing light.

Idle Mixture:
Bottom out the idle mixture screws (gently) then back out 1.5 turns. (also a starting point)

Once the car is running and warm, set the idle mixture screw such that manifold vacuum is maximized. You will need a vacuum gauge of course.

Now once you have set the mixture, put the car in gear and press the brakes. Set the idle such that the car can maintain a comfortable and stable idle. (Some trial and error) Note that this will be the curb idle!



Many guys do things differently according to their inclination and experience, I hope this is helpful. (I'm open to critique as well from any of the old crusty dogs up here)

Excellent description, I recall the OP stated that they replaced the choke pull off which couldn't hold a vacuum. Failures and maladjustments of these little things caused so much havoc back in their day!

Hi everyone! Thanks for all your replies! Just wanna say Merry Christmas and when I get back home I'll continue with each of your suggestions and instructions. Have a good one and be safe!

Btw I fixed the air cleaner stud, here's a pic of what I did...

B300 -
Hope you're having a great vacation! Your carb stud is still upside down but I guess I'll have to live with knowing that somewhere in the vast expanse of the Arizona desert, there's a carb stud installed upside down..

I came across the specs table for the Holley carbs on the '78. Yours may be a little different but this is a good starting point. See attached:

Thanks you too,
I actually ended up getting sick but not too bad... I guess I was due.

As for the stud I mentioned earlier that it can't be installed the right way on my carburetor. The stud probably belongs to another carb. The end with the lip is too short and doesn't reach the threads, that's why I put a sleeve on it...

Thanks for that specs sheet!
I'm really looking forward to getting back home to finish the tuning, I'm a bit worried that some mice will have made a home in my engine bay by the time I do...
That's a whole other issue I'll need to deal with. It's a constant battle with rodents where I live...

Hi everyone! Hope you all had a safe and happy holiday season.
I'm back home and luckily no mice made a home of my engine bay like they previously did when my transmission went out last year!

So anyway, I've done my best trying to understand and match all the different instructions for tuning the carb and I think I have it dialed in!
As for my understanding of the choke plate adjustment, that needs to be done cold and on the very highest step of the cam or detached from it right?
As for the fast idle adjustment and curb idle adjustments those must be done under operating temp. The instructions are to adjust the fast idle with the screw on the second step to the specified 1600rpm for my vehicle and once it's warm and the cam is cleared, the curb idle is set to 750rpm...
I've adjusted and readjusted the idle mixture screws pretty well I think. That process is to seat them and back them out about 2 full turns for reference and then one at a time close them to where it almost wants to stall then back out to find the highest rpm and then a 1/4 turn in or out for optimization, repeat on the other side...
It's running the best it ever has but I'm sure I'll be able make a few tweaks here and there as time passes...

I wonder if having the check weight and smaller jets will help conserve some fuel? I'm still hopeful even if it is just 1mpg...

So I think we're done here with the carb and adjustments.

Thanks again for all your expertise and knowledge!!!!

My near future plans are to do the brakes(whatever that entails) and idk what else...
I already rebuilt the tranny, the carb, the engine's pretty solid so I'm hoping nothing else will need to be done for a while.
That's it for now I guess, we'll see!