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Found these strange looking "phenolic" spacers in my LS6 #4803-1 Holley today.
One was stuck in the metering block and one was hiding behind the float.
???????
If I had to make a guess, I would say anti-slosh baffle. During hard braking or acceleration the fuel in the bowls likes to play games by uncovering jets causing fuel starvation and causing the float settings to whack-out.
On the 4150s Holley installed vent whistles to control sloshing fuel from exiting out the fuel bowl vents during braking / accelerating.
Neither Jeff nor I had ever seen them either over decades of playing with Holleys. But this carb looks very original inside and out, even down to the jets the power valves, etc. But this is also an over the counter CE carb, not OEM install, dated 1975.
These things would reduce the fuel volume a good bit, maybe 40% in the front bowl only. I don't think it is a slosh item, because most of this volume reduction is on the bottom of the bowl. At any rate, I will install the more traditional white plastic bowl whistle to control slosh on braking.
Oh just a thought, maybe we have it backwards, maybe they are to prevent the front jets from going dry under acceleration? Might actually work for that. This is a factory LS6 carb. Might actually need it. Makes the bottom of the front bowl sort of V-Shaped.
But then the back jets would starve right? (That's why Holley made the rear jet extensions tubes.)
I am still "baffled".
???
Bakelite is also a heck of a heat insulator. Vapor lock/heat transfer effect?
I'm not convinced its for volume removal. The more fuel in the bowl, the bigger the fuel bowl, the cooler the fuel remains = win-win.
Put a pot of cool water on the hot stove then a tablespoon of water and see which one heats up faster.
As far as insulating, millions of SBC out there which had or have the heat-cross-over under the carb. So which is it? Heat up the carb or insulate the carb from heat?
I've seen those phenolic spacers in at least a half-dozen original GM-installed Holleys. For as many as I've seen, I have reason to believe they were part of the GM OEM Holley configuration package. I can see no purpose for them other than to reduce fuel volume.
I'm pretty sure it was an emission piece back in the day (I was a cust. service counterman for a auto parts chain whse), I'm pretty sure I read about them in regards to pollution control but never saw them. I do know that if you are track/dragging this car you'll want to remove them, adding the whistles and extensions are well received improvements. Lower volume can lead to big changes in level during full load wot.
I'm not convinced its for volume removal. The more fuel in the bowl, the bigger the fuel bowl, the cooler the fuel remains = win-win.
Put a pot of cool water on the hot stove then a tablespoon of water and see which one heats up faster.
As far as insulating, millions of SBC out there which had or have the heat-cross-over under the carb. So which is it? Heat up the carb or insulate the carb from heat?
From an emission control standpoint, less area for fuel vapors to form = lower un-burned HC. The 70's saw lots of stop gap measures and this was one of them. The heat cross over was an emission/cold engine drivability addition and it works in conjunction with the heat riser. You want the engine to heat up as quickly as possible for lower emissions, longer oil life etc. (GM didn't like to replace engines under warranty).
Stop gap emissions attempt sounds correct to me. Especially since several have been seen on other "original" Holleys.
The chemist in me thinks the fuel surface area would remain the same and that would not reduce evaporative emissions, and volume is irrelevant. But the way the phenolic or bakelite would tend to insulate the remaining fuel in the carb sure could slow the evaporation rate after shut-off. And then other Holleys had bowl vents (why?) GM, and Chevy in particular often had a way of meeting these mandated changes so they were intentionally very easy for the real racers to un-do.
I am thinking of camshafts so big they were really designed for open headers, 2 inch (small block) exhaust on L88s, headers in trunk on 68 Z28s, and the goofy secondary throttle stop limit on 400 cu in Firebirds that knocked 30-40 hp off the GTO motor to stay under an arbitrary HP/CU in limit. Strange times indeed, the 70s! I put the severely retarded timing on 70-73 cars in this same camp. Just compare those spark-controlled timing curves to the fairly well performance-optimized curve that a factory 63 Fuelie had. They all helped emissions, or mandates, not performance, but were easy to change.
03-13-2019, 10:29 PM
Mystery Holley Part
