Mike’s Carburetor

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We have a ton of technical information for just about any carburetor and new information is being added on a daily basis. Check back again.

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Mike

Tri-Power Carburetors

Rochester Tri-Power carburetor kits. These are
the 2G and 2GC carburetors. The 2GC is the carburetor in the middle and
would have the automatic choke attached. The front and rear carburetor
does not have a choke.Selecting kits for the tri-power carbuetors is straight forward if you
still have the tags attached to the top of the carburetor. Rochester
did not stamp the carburetor number in the side of the carburetor until
1968.Tri-power carburetors use two different carburetor kits. One kit for
the center and the other kit for the front and back carburetors. Each
kit services one carburetor, so to do all three carburetors you will
need three kits.

Be careful because chances are you may not have the original
carburetors. It is rare that we see a tri-power setup that has the
correct carburetors (numbers matching).

Here is an example of a tri-power setup. Notice that the front an rear
carburetors use the same carburetor kit, but the center carburetor uses
a different kit.

1959-61 Chevrolet V-8 A/T NO AIR

7013015 FRONT CARBURETOR Tri-Power Carburetor Kit K6121
7013017 REAR CARBURETOR Tri-Power Carburetor Kit K6121
7013016 CENTER CARBURETOR Tri-Power Carburetor Kit K636

What if you don’t have the carburetor tags?

You have to make the best guess and the suggested way is to take the
carburetor apart and carefully compare the old parts with the parts we
have illustrated in the photos, or videos.

Here are the typical carburetor kits used on the Chevrolet carburetors
(prior to 1968)

K636

K355

K427

K6121

Holley 1904 Problems

Here is a question I received from a customer recently.

I rebuilt my 1904 using kit #k4043, got new mixture screw and pump link. not having much carb experience I think I have some problems. I’ll list what I think is wrong.
Will idle only if choke partially closed, did it before rebuild too
Fuel dumping out of main metering port onto choke plate while idling
Inline glass filter always full, used to be half full
Vacumm hole in base of throttle body blocked, but intersects with hole in the bore
Idle mixture screw is ineffective whether screwed in or out
There is no dashpot lever spring
Carb doesn’t mount directly on the manifold, but on what appears to be a stack of gaskets, but everything lines up linkage-wise.
I did the fix for the warped body and now it’s flat.
In your video you mention the plastic ball in the main body sometimes not being there and not making a difference, I put mine in.
The only thing I didn’t replace were the balls for the main metering body because the balls and weight were moving very freely.
Any help would be greatly appreciated. Joe

The fact that the engine will only idle with the choke partially closed means that there is too much air due to a vacuum leak somewhere, or that it isn’t getting enough fuel. Since the problem was there before the rebuild, I would start by looking for a vacuum leak.

Spray carburetor cleaner around connections and if the idle smooths out, or the RPM changes, then you have located the leak. I would start with the non standard stack of gaskets. After that check all other connections such as the intake manifold. If the carburetor will mount with the standard 1 gasket, then I would take the other gaskets off.

Fuel dumping means that you are getting too much fuel in the float bowl. Did you seal around the inlet bolt with the Permatex anaerobic. If not, check out my instructions on how to  do that. Did you recently replace the fuel pump? A new fuel pump might have too much pressure. Test the fuel pump pressure and compare to the specification in your motor manual. I’m guessing somewhere around 5 – 6 lbs.

The hole in the base of the throttle body leads up to the vacuum port at the top of the carburetor. This is used for the distributor advance and needs to be open all the way to the intake vacuum. Having this covered up will cause problems. If you have to, make a hole in the gasket.

The missing spring from the dashpot is not the problem. The dashpot is used on automatic transmission type of cars and it holds the throttle open for a second or so when you let up on the gas, allowing for any left over gas mixture to be burned.

Weber Marine 4 Barrel Carburetor – Accelerator Pump Test

 Weber Carburetor Main DischargeOne of the most common problems on almost any carburetor is when the accelerator pump circuit fails to deliver the correct amount of fuel. The accelerator circuit works, you guessed it, when accelerating. Throttling up requires an extra shot of fuel and the accelerator pump forces that extra fuel up through the main discharge and out the venturi, mixing with the fuel already being delivered to the engine.

(a) illustrates the main discharge hole. This hole will either have a ball and weight, or a ball and spring. Replace with the same combination. Check ball 1st, then either the spring, or the weight.

There are several things to think about when rebuilding your carburetor, especially around the accelerator pump circuit. Make sure the pump well is polished so that the pump cup glides smoothly and clean out all of the small passages in the venturi. Using thin wire is about the only way, since cleaners and compressed air are not going to remove all of the ethanol deposits left behind.

With everything clean and you are ready to assemble the carburetor, it is a good idea to test the accelerator pump circuit before closing up the carburetor.

Test your accelerator pump circuit as follows:

  • Fill the float bowl with liquid. We use mineral spirits.
  • The accelerator pump well should fill up with liquid.
  • Insert the pump and press down. Liquid should come out of the main discharge.
  • Replace the check ball.
  • Hold the check ball down with a brass drift punch (gently).
  • Again, press down on the pump. You should feel a slight resistance since the check ball is not allowing liquid up through the discharge hole. If no resistance, then gently tap the check ball and the drift punch in order to seat the check ball.
  • Install the venturi cluster and gasket.
  • Press down on the pump again. You should get a good squirt out of the venturi. If not, then the passages are plugged. Use thin wire to clean out the passages.

With the test above completed you can feel confident that the accelerator pump circuit is going to perform as it should.

International Shipping

We have a big following when it comes to people buying carburetor parts from other countries, but shipping to other countries can be a challenge both in time and cost.

As of today we are offering a new shipping option for those outside of the US called Bongo. Many will already know about this service, but for those who don’t, this gives you another option of how to ship your order. We look at this option as being between our normal 1st class international (USPS) and FedEx. On our side we are simply shipping to another US address, using the shipping option selected by you. Bongo takes care of the rest.

The most economical shipping method is to use our USPS 1st class international shipping, but it takes 20 days avg to get your order, depending on customs and we don’t offer this service to all countries. Avg price for 1st class international is around $15.00. FedEx depending on the method you select is much faster, usually about a week, but costs can be $60 or more. Using Bongo, depending on where it’s going can cost around $25.00. Bongo typically ships to anywhere in the world in 1-5 days (+ time from our warehouse to your US address). You can even track your order all the way to its destination.

Bongo International provides our customers with their very own US address. Once you have a US address, you will be able to make purchases with us as well as other US based online retailers. Bongo receives your purchases and logs them into their online system which you can use to view your items and consolidate them with multiple orders.

International customers can save up to 82% off typical international shipping rates by following these four easy steps:

Register with Bongo and receive a U.S. shipping address.
Enter the Bongo address as both your billing and shipping address.
Use the credit card that you have on file with Bongo as the payment method.
Once the order arrives at Bongo, log into your account to forward to your country.

For more information about the Bongo service, or to get an estimate of what the shipping costs are visit Bongo International

Carter B&B Carburetor Lacks Power From Idle To Cruise

Carter B&BI would look closely at the main discharge. See #28 on the diagram to the right. Remove the aluminum clean out plug. If you purchased our kit you will find one was added but bagged separate from the kit.

Using  a flat blade screw driver remove the discharge jet. These are often frozen into the carburetor. In these cases I would leave it in the carburetor and clean it out while in the carburetor. You may have to use thin wire to get the jet cleaned out. I know one person that drills the jet out by 1 size to accomidate the current fuel, but personally I would do that only if you are having an issue when accelerating. These jets are not available so damaging one is not an option here.

Make sure the passage going from the main discharge to the accelerator pump well is not clogged and clean.

# 30 is the pump check ball. Make sure it wasn’t left out and is clean. This is the bigger check ball of the 2.

On most B&B carburetors there will be a check ball at the bottom of the pump well along with a clip that holds it in. This is where the fuel enters the well. Make sure the ball is there and that it is working. When you fill the float bowl with (mineral spirits), the ball should lift up by the weight of the fuel and fill the well.

Put the main discharge back in along with the pump check ball and plug, then fill the pump well with fluid. Insert the accelerator pump and press down. Fluid should come out of the main discharge and into the carburetor throat. It’s difficult to describe just how much should come out, but you will see it drip out the bottom of the carburetor in a good quantity.

Rochester 2 Jet Loses Power

Here is a question I got from one of my customers.

My Rochester 2 jet Has a stumble when pulling away from a light or stop sign. I purchased a accelerator pump and power valve from you. I thoroughly cleaned the carburetor and replaced those items. Now with the engine turned off I have a great pump stream. But if the car is running no pump stream. Turn the motor off and great pump stream again. Any advice on this would be appreciated!

I assume that when you say you get a good stream when the engine is off that you are pumping the throttle and watching the accelerator stream out of the main discharge. What comes to mind 1st is the main discharge and the check ball. Be sure the larger check ball is placed in the main discharge hole, then the copper colored spring, then the T.

The more likely suspect is that there is low fuel in the float bowl and the engine when running is using up most of the fuel and there isn’t enough to run over into the accelerator pump well. This could happen to the type 2 Jet that doesn’t use a check ball and feeds itself over the side of the well through the slit.

The 1st thing to do is make sure the float is set to factory specifications. While doing this use some teflon thread paste (NO tape) on the needle’s seat threads and wipe the viton needle tip with some no residual spray, or mineral spirits.

Another possibility is a bad fuel pump or some other impediment to fuel delivery. Check the fuel pressure of the fuel pump and make sure it is within factory specifications.
From my friend Jeff “Do you tell all of your customers (as I do) to use only fuel-injection-grade fuel hose (SAE 30 R9) or Gates Barricade hose?  This saves me a lot of complaints as internally-collapsing R6 or R7 hose is often miss-diagnosed as a carburetor or fuel pump problem; it is due to — what else — ethanol damage.”
So there you go, some possible remedy to a rather peculiar problem.

Carter WA-1 Check Ball Placement

The Carter WA-1, 1 barrel carburetor can have one check ball in some cases and in other cases, 2 check balls. Most WA-1 will need both check balls.

Both types will need a check ball in the main discharge tube. When you have two check balls in the carburetor kit, install the bigger of the two in the main discharge. When required and for most WA-1 carburetors place the smaller (and sometimes aluminum) in the accelerator pump well.

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Marvel Schebler Jet Removal

Marvel ScheblerSchebler

Schebler

Customer question.

Can you give me ideas on how to remove the main nozzle for a Marvel Schebler TSX-530 Type C carburetor?  According to the manuel it unscrews from the bottom.  I assume that the main jet and the nozzle are one piece.  I haven’t tried beating on it or cranking on it yet. I don’t want to screw it up until I know that I can replace it.

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