Inline Main Jet Sizes

[Clams Canino]

Looking through the various parts catalogs, I'm seeing widely disparate listing(s) for the inline 6 main jet sizes.

All the 1500's are stable at .080 (.082 for XS), but the later 140's (1979+) are all over the place from .074 to .080 depending on whether the serial number is US, Aus, Can and the year and ... and.

Going on the premise that the 140's were just relabeled 150's - why all the main jet changes?

I've been telling people building "frankenmercs" to use .080 on any of the 150 / 140 powerheads. Have I made an error?

-W

[stan merck]

140s had low dome pistons, 150s high domes. High domes burn down so easily ya want to run them a little richer. Some people say 140s are the same as 150s but all the ones I seen apart had low dome pistons and some of those engs had never been apart before. Other than that they are basically the same eng.

[Raceman]

I'm not sure exactly when the piston dome change took place but it's DEFINATELY not true that all 1400s (78 and newer) were low domes. I think your advice on the jets is solid. There's not much downside to runnin' em a little fat, especially with today's gas.

[crazy horse]

I've been running .084 in my XS for about ten years now;) .