Category Archives: Fuel

WHAT TO DO IF YOUR MOTOR SUFFERS FROM VAPOR LOCK

Lately, I’ve been hearing more stories about ’49 Cads experiencing vapor lock. This ailment is due to engine heat causing gasoline to boil away or vaporize at certain spots in the fuel line. This makes for air in the fuel line, starving your engine of fuel, which will then stall or refuse to start. As ’49 Cadillacs were not known for having this problem in the past, it makes me wonder if it is not some new problem with the formulation of gasoline. The following may help and if any members have additional suggestions, please send them to the Times:

1. Check to see if air is freely flowing through the radiator and that the motor is running at a normal temperature;
2. Check your steel fuel line make sure it is not passing to close to the driver’s side exhaust manifold and check the flexible fuel line from the end of the steel line into the fuel pump to make sure it is not touching or passing very close to the oil filler housing or another hot part of the motor;

One possible solution is to wrap an insulating material around the rubber fuel line between the end of the steel line and the fuel pump. You can also do the same for the steel line between the pump and the carburetor. A good insulator is a length of rubber fuel line or, alternatively, insulated hose used for radiator return lines. It should be of the right diameter; that is, of course, bigger than the line to be wrapped. Cut it longitudinally (along its length) and place it around the length of the fuel line to be insulated. It’s expensive (at $4 / foot here in GA), but if it solves the problem is money well spent. Another insulation material is aluminum foil. I’m not sure about other alternatives to cover the fuel lines, but you can try McVey’s for some insulating material, as they do sell stuff of this type for exhaust pipes, or go to a hardware store and see what they suggest.
Another solution is to install an electric fuel pump. If you do so, I would not do away with the mechanical pump, but merely have the electric pump as an auxiliary. I have such a set up on 2 of my cars (but not my ’49 Cad which does not vapor lock yet). Install it so that the electric pump on a separate small fuel circuit with 2 “T” connections near the fuel tank and not merely in line with the mechanical pump. A more ambitious electric fuel pump installation involves installing a “T” connection just outside the fuel tank, with one branch of the “T” connection serving the existing steel fuel line and the mechanical pump. From the 2nd branch of this “T” connection near the fuel tank, install a short line to the electric pump. From the outlet of the electric pump install a second long steel fuel line, parallel to the long steel existing line, all the way to a rubber line going into a second “T” connection near the carburetor, thereby bypassing the mechanical pump altogether. This second set-up will look funny but will probably work well. The mechanical pump puts out 4 to 5¼ lbs, so the electric pump should not put out more than this.
If you suspect your engine temperature is too hot, a good way to accurately check it is to temporarily hook up a mechanical temp gauge to the same point on the rear of the passenger’s side cylinder head as the stock electrical sending unit. You can buy one and any necessary screw-in adapter inexpensively at an auto parts store. You install it by temporarily removing the passenger’s side ventilating tube, run the cable through the hole and gently close the vent valve over the cable to prevent most hot air entering the engine compartment. I’ve done this with my own car and have been surprised at the difference in readings between the stock electrical and auxiliary mechanical temperature gauge readings.
On the other hand, the motor’s symptoms may be due to something else altogether, a constricted fuel line. See John Washburn’s article in the May 2011 Self Starter.

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AN ALTERNATE VIEW ON IDLE MIXTURE ADJUSTMENT PROCEDURES

by Art Gardner

Jon at the Carb Shop in Missouri suggests a slightly different approach to adjusting the idle mixture screws on an old Cadillac carb. According to Jon, the Shop Manual’s approach of first setting the idle speed and then tweaking the mixture is backwards. He says you should set the mixture first and then adjust the idle speed to achieve the desired/specified idle speed. Jon says that on a Carter 722, the mixture screws should be somewhere between 3/4 of a turn from all the way in to 1-1/2 turns. He suggests that one should break that up into thirds, so you would have more or less discrete positions of 3/4 turn, 1 turn, 1-1/4 turns, and 1-1/2 turns. He says for a brand new engine, 3/4 turn is typically the right position. As the engine wears, 1 or 1-1/4 turn become the norm. Moreover, he says that there is almost never a need to turn a mixture screw more than about 1-1/2 or 2 turns out from closed. He says that with these relatively steep mixture needles, once you turn the screw out about that much, the mixture passageway is fully open and further turning of the screw doesn’t make it any more open (open is open, after all). I followed Jon’s advice in fine tuning the performance of the Carter 722 on my last 1949 (sadly now enjoyed by someone else) and found it to be very sound. Give it a try!

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AIMING THE SPRAY NOZZLES IN YOUR CARTER 722S CARBURETOR

by Art Gardner

Many of you may have rebuilt your 1949 Cadillac carburetor, the trusty Carter WDC 722S. Although the instructions in the Shop Manual are very good, in paragraph 10 on page 124 there is insufficient detail on an important tuning trick: aiming your accelerator pump discharge jets for optimum throttle response. The Carter 722S carburetor has two little dots cast into the carb body and the sprays from the accelerator pump jets are supposed to hit these targets. The Cadillac engineers figured out that when the spray hits these targets you get the best atomization of the accelerator pump spray and thus the best throttle response.

This tuning can be done while rebuilding the carburetor or simply by removing the air horn (the very top of the carb) to gain access to the accelerator pump jet nozzles. Indeed, once you take off the air horn, you have good access to the nozzles. The targets are little dots cast into an upper portion of the lower half of the carb. You just take a pair of needle nose pliers and gently bend the jet nozzles until the fuel sprays directly onto the “targets”. If there is fuel in the carburetor bowl, manipulating the rod from the gas pedal a little causes fuel to be sprayed from the nozzles and you can see if it is hitting the targets or not. The carburetor does not have to be totally disassembled or even removed from the engine to do this.

So on my own car, I removed the air cleaner and the air horn from the top of the carb and tweaked the aim of the nozzles to hit the targets exactly. It really made a difference. We also did this with Jay Friedman’s car and he reports that his car is running better than ever as a result. By the way, I didn’t figure this out myself; I found the details in an old carburetor user guide.

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49 FUEL PUMP OPERATING ROD AND OIL FILLER HOUSING

Besides warning ’49 owners whose cars have engine numbers between 85392 and 88800 (the last 5 digits, that is) of possible camshaft problems, the Cadillac Service Bulletin above has several interesting facts:

1. The 4th paragraph explains how to remove the fuel pump and oil filler housing as one assembly, which is an easier way to remove and replace the fuel pump. The reason is that when replacing the fuel pump with the oil filler housing still on the motor, it’s a bit tricky getting the pump bolts started because of the pressure the fuel pump operating rod exerts on the pump actuating lever, even with the rod in its lowest position. To do it the easier way, before installing either on the motor, first bolt the new fuel pump to the oil filler housing, then insert the operating rod in the motor, then bump the starter until the rod is in its lowest position and lower the pump and housing over the rod as one assembly. At this point it’s easy to draw the assembly down over the rod by progressively tightening the 2 bolts holding it to the motor. Don’t forget the gasket that goes under the housing;

2. Also, this way you can inspect the operating rod and replace it if worn, as they can still be bought new. The rod has a top and a bottom with a smaller diameter cast iron insert at the bottom (see diagram in service bulletin), so be sure you insert it with the cast iron insert down;

3. If the last 5 digit’s of your ‘49’s engine number are indeed between 85392 and 88800, then heed the instructions in the next to last and last paragraphs, particularly if you have had camshaft problems.

fuel sep 11

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THREE ITEMS YOU MAY WANT TO BUY

1. Jeff Maltby writes that one of the above brass fittings is a “must have” to seal the main fuel line into the gas tank fitting. This part often falls out when servicing the gas tank, and when it is missing the tank will leak badly at the fitting. Jeff had 2 extras made, but can get more if needed. $35 shipped in the USA. Contact Jeff at gljeff1@earthlink.net or 209-595-5152.

2. Jeff also reports that NAPA, the nation-wide auto parts company, sells the 1948 and the 1949-50 flexible rubber fuel line, as follows:
Make & Model NAPA Part Number Factory Part Number
1948 Cadillac, All Models WH 11076 144 2527
1949 – 1950 Cadillac, All Models WH 11093 145 4597

3. Chapter member Bob Knutson has sent in a web address of a scanned ’49 Cadillac sales brochure. The site is: http://www.lov2xlr8.no/brochures/cadillac/49cad/49cad.html Hard copies of this brochure are occasionally seen for sale on ebay or can be bought from literature dealers who advertise in Hemmings Motor News. It’s a beautiful publication and is usually not very expensive to buy, so all members should get themselves one if they don’t have one already.

jun 10 fitting

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NEW PROCEDURE FOR TESTING GAS GAUGE TANK UNITS

Chapter member Joe Foerster found a copy of, as he called it, “a snip” from the Nov.-Dec., 1948 Cadillac Serviceman’s bulletin, as follows:

A PROCEDURE FOR TESTING gasoline gauge tank units, which included lowering the gasoline tank in order to make the tank unit accessible, was announced on page seven of the February, 1948 issue of THE CADILLAC SERVICEMAN. In order to shorten the period of time required to replace this unit, the factory Engineering Department now recommends that the following procedure be used, which omits lowering of the gasoline tank. This new procedure takes less time than that allotted for lowering the tank in the old procedure. The new method is as follows:

1. Disconnect one of the battery cables.

2. Using a standard 4″ sheet metal saw, drill a 4″ diameter hole in the body floor pan directly over the gasoline tank float unit.

3. Disconnect the wiring from the tank unit.

4. Remove the screws which fasten the tank unit to the tank.

5. Lift out the tank unit. The float and arm will come away with it. Test the old tank unit against the dash unit. Failure may have been caused by poor ground.

6. Set the new tank unit with gasket, float and arm in exactly the same position on the tank. Install all screws and tighten securely.

7. Reconnect the wire to the binding post of the tank unit.

8. Fabricate a sheet metal cover for the 4″ hole in the body floor pan. Install this cover, seal with 3-M body sealer and secure it with at least six self-tapping screws.

9. Connect the battery cable.

Joe concludes, “Believe me. Once you’ve done this, you will wonder why the factory didn’t punch a hole there in the first place”.

gass sep 09

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CONVERSION OF AIR CLEANER TO USE A PAPER ELEMENT

Joe Foerster of N. Hollywood CA has converted the oil bath air cleaner on his Series 62 sedan to use a modern paper element. He did the job in such a way that it is not visible. Joe put together a series of photos and descriptive text regarding the air cleaner’s conversion which can be found at the following web site: http://bobnjoe.com/car/1949/blog2/archives/2007/11/entry_125.html Below is a picture of Joe’s car, appropriately named “49er”, with its converted air cleaner ensconced under the hood.

air cleaner jun 09

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