QuestionI have a 64 MGB that has 32,000 miles on it has been sitting in my garage in AZ for the past 2 years starting once every month starts fine but when I try to take it around the block has no power and starts to backfire thru the carburetors and when I adjust the timing still misfires now out the tailpipe and has less power. do you think I might have bad fuel? I have had the SU's rebuilt and the fuel pump is rebuilt and I changed from points to eletronic ignition system any ideas?
AnswerHi Patick,
If the mileage is correct, you should not have any major fault with the engine especially if you started the engine every month or so.
Do this, set the timing at 10 deg BTDC static. The timing should never be altered to correct for a running problem even if it improves a problem. All CB (chrome bumper) MGBs will run good at 10 deg BTDC. The only time you should alter timing is when you make engine, intake & exhaust modifications.
Fuel / carburetors are the most likely problem at this point. The 64 "B" has a drain plug in the bottom of the fuel tank so drain the old fuel and dispose of it. Put in fresh high test fuel (Amoco high test), Remove the three screws from each top "Pot" and carefully remove the top pot and the long floppy spring from each carb. Remove each piston with the needle in the bottom being careful not to damage the needle. NOTE! DO NOT MIX UP either piston or top pot and keep them with their respective carb. Do not worry about upsetting any adjustment just handle with a little care. Now, loosen the hose clamps on each fuel line on each float chamber lid and force the fuel lines off of the float chamber lid. (One lid will have the fuel line from the pump and another going to the other carb.) Then remove each vent hose (the smaller hose) and remove the three screws holding each lid on. Lift each lid off being careful not to damage the float attached to the little arm. A shop towel will soak all of the fuel out of the float chamber. Note the smell of the fuel and the level of fuel in each float chamber. They should have about the same level.
Now to test the fuel supply and flush the long line from the tank. Locate a piece of 5/16 in pipe. If you don't have any you can get a piece of 5/16 copper line from any auto parts store. Smooth the edges of the pipe and force it into the fuel line from the tank that you removed from the float chamber lid. (If you have a fuel line system with a "T" connection and each end goes to each float chamber remove the tank fuel line from the "T") Put the other end of the pipe into a can or jar. Work outside and keep a fire extinguisher at hand. Have someone else turn on the ignition but not the starter motor. If you still have the "SU" fuel pump you should see a strong flow into your can in pulses. Let the pump run about a quart of fuel into your can to flush the long fuel line of stall gas. If everything is OK reassemble the float chamber lids and reinstall all lines and tighten each. Now put each carb piston into each carb. note that each has a groove and a tooth so it can only go in one way. Be gentle with the needle. The piston should drop in freely, DON'T force it in. Put in the long spring and gently put each pot onto each piston. If you remove each plastic cap from each pot they will also go on very easily. Rotate each pot so the screw holes line up (only one way) Put the three screws back in and be sure the pot is seated all the way down BEFORE you tighten any screw.
Now! Slide in the piston on the end of the plastic cap you just removed and see if you feel hydraulic resistance. If not get a little engine oil and put it in first and try again. You should feel hydraulic resistance about half way down or so. (this is a "Shock absorber" necessary for quick throttle movements and for Idle pulsations.) Plus it lubes the shaft it rides on.
This does not cover any adjustments of the SUs. If they were correct when they were rebuilt they should still be correct. Now, restart the car and if you still have a problem you can contact me via e-mail at longez8@bellsouth.net
I hope this helps. Let me know.
HMF
