HS vs HD series carbs

[steveg]

Enquiring minds want to know:

Why are HD series carbs so much more expensive than HS series? > $1000 more for the replacements.

HDs are used on Jaguars, Aston-Martins, RRs, Rovers and most later Healeys. HSs are used for the most part on cheaper cars: Triumphs, Volvos, MGs - (also BJ7s but never mind).

HSs would appear to be more complicated with all their washers and seals.

The relationship between the needle and the jet would appear to be the same, therefore one would think the horsepower produced would be the same.

This I believe gets into the arcane knowledge of the ancients, about which we can only speculate.

 

[John Turney]

Probably for the same reason grade 5 fine thread bolts are more expensive than grade 8 fine thread bolts. Or why propane is cheaper in remote areas than in suburban areas.

 

[Bob_Spidell]

re: "Why are HD series carbs so much more expensive than HS series?"

To me, the HS is more complex and parts-intensive. I have cars with both; IMO the diaphragm jet on the Ds is probably more durable--and cheaper--since the seals on the Ses can dry and crack.

It may be an 'SU' thing: older costs more. The old SU pump used on early 6-cyl cars--with the big 'box' valve section--cost 3X the later ones (but the earlier 4-cyl pump, which could probably power a 6-cyl just fine, is less as well).