25-11-2018, 10:45 PM
Aspects of SU were covered at length on the old website. It may be appropriate to rake over a few points. Following refers primarily to the horizontal versions.
There are several variants and major components can be interchanged, notably pistons of different types and weights. So when comparing needles it important that details stated so like considered. And that the needle orifice not worn. The body and piston of 1 and 1 1/8 seem the same size, just the output dia differs so needles presumably similar for same pistons and cars. The needle calibration beyond the lift range is only in use when enriched for starting.
Early carbs had heavy brass pistons and no dashpot. The piston spring generally only appeared in mid 1950s with ohv Minor and semi downdraught. I dunno how the piston of these compares with earlier.
I found with the common initial postwar 1 1/8 dashpot model the standard EK needle was fine, the listed “weaker” option hopelessly so.
Part operating the enrichment whilst running is a test for mixture. Plotting needle shape can be much more informative than just comparing figures.
1 1/8 seems seriously oversize for a standard car but very many run these with satisfaction. (The horizontal models look more period and with no vent rib can be more easliy polished!)
There are several variants and major components can be interchanged, notably pistons of different types and weights. So when comparing needles it important that details stated so like considered. And that the needle orifice not worn. The body and piston of 1 and 1 1/8 seem the same size, just the output dia differs so needles presumably similar for same pistons and cars. The needle calibration beyond the lift range is only in use when enriched for starting.
Early carbs had heavy brass pistons and no dashpot. The piston spring generally only appeared in mid 1950s with ohv Minor and semi downdraught. I dunno how the piston of these compares with earlier.
I found with the common initial postwar 1 1/8 dashpot model the standard EK needle was fine, the listed “weaker” option hopelessly so.
Part operating the enrichment whilst running is a test for mixture. Plotting needle shape can be much more informative than just comparing figures.
1 1/8 seems seriously oversize for a standard car but very many run these with satisfaction. (The horizontal models look more period and with no vent rib can be more easliy polished!)