Ok, finally retrieved my digital camera from the twilight zone known as “the neighbors”. As promised (and if anyone is still interested), here is a photo showing the evolution of Holley center-hung float bowls over the past 45 years or so.
The one on the top left is the earliest design that most of you are likely to come across. In addition to the stiffening ribs (which disappeared in the next generation of castings but would reappear in the problematic “Asian” castings), these “vintage” pieces are characterized by a list of applicable U.S. patent numbers cast right in to the part between the two bottom screw holes, and the use of a ball-style accelerator pump check valve rather than the one piece orange silicon rubber “umbrella” used in later versions.
The bowl on the bottom left is the design that came on most Holley carbs which used center-hung floats from the mid 80’s through about 2004. These castings were produced for Holley by Empire Foundries here in the U.S., and were generally of good quality, although after making the decision to take their business offshore Holley was guilty of selling several thousand defective ones (bowl screw holes so far out of position that the bowl screws could not even be installed…or if they could, the heads of the screws would not seat on the sealing gaskets) before the new pieces became available.
The bowl shown on the top right however, are the ones you should really be wary of. They are the first of the “Asian” parts, and well over half of them we’ve seen exhibit the casting and/or metallurgical problems I mentioned in my earlier post.
The part shown on the bottom right is the current design (shown here with our surface finishing and dichromate treatment). While certainly not exempt from problems, most of them so far seem to be of reasonable quality.
If you find that you own a Holley carburetor with the problem bowls, keep in mind that strictly speaking, all of the versions of these parts are interchangeable. There are differences in the float bowls used on the primary and secondary sides of the carburetor, and float bowls originally equipped on 4500 series (Dominator) carburetors and most “HP” 4150 series carburetors can be plumbed for fuel into either side of the bowl.