My question has to do mainly with the Longbridge BN4 that is now back on the road after about 50 years disassembled and then under restoration for the past six years or so.
About four years ago, early in the restoration, I rebuilt the stock SU H4 carburetors, including installing new shaft bushings and various wear parts. Memory being what it is, I did not recall the bench setting that I used for the Jet Adjusting Nut. The car first went back on the road last week. When the car was not running well these past few days (due to a faulty condenser it turns out), I rechecked various carburetor and other adjustments.
I discovered that I had backed off the Jet Adjusting Nuts six flats, or one full turn, from all the way up. The Healey manual that I have mentions backing off the Jet Adjusting Nuts twelve flats, or two full turns as a starting point. So I tried that too. And I tried nine flats. I find that, now that the car is running well again, it doesn't make a lot of difference to the operation of the engine whether the nuts are backed off 6, 9, or 12 flats.
The engine does seem to idle faster with the nut backed out 9 or 12 flats instead of 6 flats, but I am wondering whether that is the only difference that I should expect. The engine has great power and sounds amazing, but I haven't driven it enough with the various settings to say much about differences in performance between the jet adjusting nut settings.
Wondering what other people know about this. For these relatively small SU carburetors, what setting might work best? And what difference will the settings make?
Learning as I go. Thanks in advance.
About four years ago, early in the restoration, I rebuilt the stock SU H4 carburetors, including installing new shaft bushings and various wear parts. Memory being what it is, I did not recall the bench setting that I used for the Jet Adjusting Nut. The car first went back on the road last week. When the car was not running well these past few days (due to a faulty condenser it turns out), I rechecked various carburetor and other adjustments.
I discovered that I had backed off the Jet Adjusting Nuts six flats, or one full turn, from all the way up. The Healey manual that I have mentions backing off the Jet Adjusting Nuts twelve flats, or two full turns as a starting point. So I tried that too. And I tried nine flats. I find that, now that the car is running well again, it doesn't make a lot of difference to the operation of the engine whether the nuts are backed off 6, 9, or 12 flats.
The engine does seem to idle faster with the nut backed out 9 or 12 flats instead of 6 flats, but I am wondering whether that is the only difference that I should expect. The engine has great power and sounds amazing, but I haven't driven it enough with the various settings to say much about differences in performance between the jet adjusting nut settings.
Wondering what other people know about this. For these relatively small SU carburetors, what setting might work best? And what difference will the settings make?
Learning as I go. Thanks in advance.