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Car Forum / Antique and Collectibles / Studebaker / June 2005Edelbrock 1406 quandry
I bought an edelbrock 1406 for my '63 Hawk Jet-Thrust and after installing it, the engine runs fine when at idle but misses like crazy when driven. (the idle, however, is too high even with the linkage idle screw backed all the way out). I have taken it to a couple of mechanics who should know what's up but I seem to be getting the run-around. Two of them just threw their hands up in frustration and another said I needed some sort of rebuild kit which I think is just an excuse. I checked out Ray Fichthorn's installation guide online and noticed that he had plugged the large front center vacuum connection on the carb. Where is the vacuum hose that attached there on the old Carter AFB supposed to go and could that be my problem? I had no problem with linkage clearance so am not using the 1/2" spacer he recommends. The points, plugs, wires and timing are AOK. Any assistance would be greatly appreciated. BTW, I have an electric fuel pump. One thing you might try is to get on the Edelbrock web site. You can print out a manual on setting up your carburetor and you also can send an e-mail to them for help. I had a problem with a carb I bought and found that the help they supplied was pretty good. If you cannot figure it out, they will rebuild it for you for $65.00 which covers parts and freight. My carb had a float way out of adjustment. It sounds like you may have a vacuum leak. Find a vacuum port on the base of the carb that is always open, or a port on the manifold itself. If you don't get 18-21 in.Hg. on the gauge you have a vacuum leak which will cause a very fast idle and a miss at speed. You may also have the vacuum advance hooked up to a continous vacuum port which would set the advance to far forward. The port for the advance should read different at idle than the continuous vaccum. Easy way to check for a vacuum leak is to use an unlit butane torch. Start the engine and let it idle. Open the torch valve but do NOT light it. Pass the tip around the carb base and intake manifold base. (wear a hat and glasses, ok?) If the rpm jumps up, you have a vacuum leak. Jeff "1949commander" wrote... > It sounds like you may have a vacuum leak. Find a vacuum port on the > base of the carb that is always open, or a port on the manifold itself. [quoted text clipped - 3 lines] > advance to far forward. The port for the advance should read different > at idle than the continuous vaccum. I put a 1406 on my car and I used that large center vacuum fitting to run to the PCV valve (inside a cool-lloking billet oil filler/PCV combination). That took care of the vacuum AND venting the valve covers. The instructions should tell you which of the two smaller vacuum fittings is 'ported' and which is constant. You need to use the 'ported' fitting to allow the vacuum advance to work properly in the distributor. This is, of course, assuming you have a distributor with vaccuum advance that is working properly to begin with! If you have the timing being advanced by the vacuum all the time, it will definitely cause problems. Remember to unplug the vacuum line (and plug the hose) to the distributor when checking or making adjustments to your timing. After the timing has been base-lined at @8BTDC ?, plug the hose back onto the distributor and see what your timing is. Has it changed the normal 4-6 degrees or more drastically? I put a 1406 on my car and I used that large center vacuum fitting to run to the PCV valve (inside a cool-lloking billet oil filler/PCV combination). That took care of the vacuum AND venting the valve covers. The instructions should tell you which of the two smaller vacuum fittings is 'ported' and which is constant. You need to use the 'ported' fitting to allow the vacuum advance to work properly in the distributor. This is, of course, assuming you have a distributor with vaccuum advance that is working properly to begin with! If you have the timing being advanced by the vacuum all the time, it will definitely cause problems. Remember to unplug the vacuum line (and plug the hose) to the distributor when checking or making adjustments to your timing. After the timing has been base-lined at @8BTDC ?, plug the hose back onto the distributor and see what your timing is. Has it changed the normal 4-6 degrees or more drastically? The center fitting can be PCV or power brake booster. There should be another one at the back, threaded and plugged if not in use. The passenger side fitting is ported vacuum, ideal for vacuum advance. Some GM's ran at full vacuum advance at idle and that would be the driver's side port. For your purposes leave it capped. To isolate linkage problems remove the linkage and set the idle. Adjust the length of the rod so that it's a little longer than necessary to insure the carb closes all the way. A carb that is way too rich will cause a miss and hesitation, I wouldn't think the 1406 is rich enough to cause that unless it's been set up for a different engine and you then bolted it on yours. Vacuum leaks are more troublesome at idle and part throttle, they disappear at full throttle and will cause a surge at cruise. I check for them at idle with a can of carb cleaner and a nozzle pointed at the usual suspects, I.e. base of carb fittings and the intake to head mating area. A leak will surface as a change in engine idle up or down. Keep the air cleaner on to avoid spray getting sucked in through the top and giving you a false reading. I have 4 old cars running with Edelbrocks, including my R2 Avanti. They are the simplest and easiest carbs I've ever worked on. There is nothing to rebuild on a fresh carb. Float settings could be off, dirt from fuel lines in the needle and seat but nothing really to wear out. BTW, if you plug a rubber fuel line with a bolt you may end up with small bits of rubber from the threads in the hose in the needle and seat, something to resist doing. Ernie >I put a 1406 on my car and I used that large center vacuum fitting to > run to the PCV valve (inside a cool-lloking billet oil filler/PCV [quoted text clipped - 14 lines] > distributor and see what your timing is. Has it changed the normal 4-6 > degrees or more drastically? -All good comments Ernie.. -ONE more thing: I have found this on SEVERAL Studebakers, especially with the Delco Distributor. As the car ages, often the VACUUM ADVANCE diaphram will get small cracks in it. It will still operate the advance, but when it pulls, a crack may open up- and you lose vacuum. This immediately retards the timing- and the process begins again. This causes surging, and missing- especially at constant speed. The only way to really tell, is a vacuum tester (hand-held pump)- Hooked to the vacuum advance hose. Pull a vacuum- and be sure the diaphram holds vacuum throughout it's full advance range. Ray Ernest Rizzolo wrote: > The center fitting can be PCV or power brake booster. There should be > another one at the back, threaded and plugged if not in use. The [quoted text clipped - 27 lines] > > Ernie >I bought an edelbrock 1406 for my '63 Hawk Jet-Thrust and after > installing it, the engine runs fine when at idle but misses like crazy [quoted text clipped - 3 lines] > of them just threw their hands up in frustration and another said I > needed some sort of rebuild kit which I think is just an excuse. I've had similar experiences with the AFB/Edelbrock. With the engine idling look straight down the bores of the carb to see if gas is dripping from the boosters. If it is it will account for the high idle and the miss above idle. I've had this phenomenon occur even when the floats are properly set and the fuel pressure is conservatve. |
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