QuestionQUESTION: Just getting into my first mg!!! The car was parked for 23 years but runs well (needs valve adjustment). The previous owner removed the air pump system and installed an electronic distributor. Now the vac advance idles too high and the gas mileage is @ 17mpg arghhh. What will give me the 30-40 mpg I'm dreaming of? Different carb?
ANSWER: Hi Dan,
Something is wrong with your car if you only get 17 MPG but you can do all you want to it and never get 30 to 40 MPG. The air pump has nothing to do with that, nor the electronic ignition.
You can expect between 25 and 35 if everything is correct.
Start by running a compression test and let me know what the readings are. Set the valve clearance at .012" and set the ignition timing and run high test gas and be sure the air filter is clean or new. The Stromberg carb on your car requires that the air filter be good and in place as BLM took the amount of restriction of the air filter in account when they set everything up. You also need to be sure that the exhaust is free flowing meaning it must not have any more than 1.5" hg resistance at high RPM. If you are not familiar with that test procedure you can just do a vacuum test at full throttle at about 3500 RPM. must not be lower than 5" vacuum.
Unless the carb is at fault you will not correct anything by replacing it.
What is? "Now the vacuum advance idles too high" ????
Let me know,
Howard
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QUESTION: THANK YOU for the help!
Compression is as follows:
#1@130#, #2@128#, #3@120#, #4@128#
After a few drops of oil in each cylinder:
#1@140, #2@138, #3@128, #4@132
#3&4 plugs fowl considerably. As for the "vacuum advance" - Vacuum tube to the distributor seems to cause the engine to idle fast @15-20x100 when warm. Maybe the water choke is sluggish...
ANSWER: Hi Dan,
Even though #3 is a little low on compression, the wet test does not indicate a ring problem. So #3 & #4 should not be oil fouling, maybe a plug or ignition problem for them to foul.
Look at the distributor to see if it is a vacuum advance unit or a vacuum retard unit. Advance units usually have the hose out on the end of the vacuum unit and a retard unit usually have the vacuum hose on the distributor side of the diaphragm. If yours has an advance unit on it then check the port on the carb for vacuum at idle. It should not have vacuum until the throttle is slightly opened not at idle. This is called ported vacuum. If you have a vacuum retard unit than there should be manifold vacuum applied all the time even at idle.
The water operated Stromberg chokes have been noted for failing, especially the ones that use a wax filled unit to close the choke. These are identified by their shape as viewed from the side. They are an "L" shape. The other type that have a round cover with a screw in the center use a bimetal coil in them and can be adjusted by loosening the three screws around the edge and rotate the unit to get it in adjustment.
Let me know,
Howard
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QUESTION: Thanks AGAIN!!! Adjusted the valves and it runs much quieter, and smoother. Replaced the water pump - (some one had installed an aftermarket alternator that didn't have the proper pulley alignment)- after that, it runs at half the cold idle rpm than it did (weird) and quieter by far! Air cleaner is new now - and 93 octane gas - hot- BUT...still a relatively rough idle and too fast when warm. That vacuum line to the distributor causes it to run smoothest off the manifold port. I was told that the electronic distributor was factory retard... Dan
AnswerDan, the easiest way to tell if it is a retard unit on the dist is to look where the vacuum port is located on the vacuum unit. If it is out on the end of the diaphragm pointed away from the dist it is a vacuum advance unit, but if the port is pointed back toward the dist it is a vacuum retard unit.
Vacuum advance units are connected to ported vacuum on the carburetor.(ported vacuum only has vacuum when the throttle is opened off idle). Vacuum retard units are connected to manifold vacuum. On some cars the factory added in vacuum delay valves for emission control.
The procedure for setting the timing is different on different systems.
The sticker under the hood (if it is still there) is most correct and always overrides what your manual says. If the sticker is gone, use the setting listed in your manual.
I'm glad to hear you are gaining on the problem.
Howard
