Holley carb fuel bowl mods

[67 Tiger]

This is probably not the best idea, If you changed from a sec. metering block to a metering plate, then a stock float bowl would fit. Of course you would need shorter bowl screws, and I dont know if there would be any performance lost using a plate insted of a block. Holley does sell a number of different plates, and Quickfuel also sells some.

 

[cadreamn67]

Bob and Gary,

Thanks for sharing your very unique solutions. Tiger people seem to have special skills when it comes to being resourceful in dealing with the beast.

I took a close look at how my CAT headers (most recent non stainless steel version) fit. Curiously there would be absolutely no problem on the passenger side in moving the engine forward. As you guys point out, there is some work to do on the driver's side. On my car the header down pipes pass down by the hanger with about 1/8 inch clearance on both front and back sides. No way I could move the motor forward 3/8 of an inch without doing some metal removal on the hanger. At this point, this is something I really do not want to do. But I respect the fact that you guys have done it and to no obvious ill effect.

67 Tiger,

The metering plate is a very interesting idea. As you say there is a possible performance reduction of unknown dimension.

I would give you better than 50/50 odds that Holley tech support/assistance would not be willing or able to help identify a metering plate that would work or quantify the effect of such a change. In my attempts earlier to get help from them, I tried to put the questions in the context of using certain Holley parts in substitution of others.

The response I got,and I quote by copy from their e-mail response:

"Hello,
I would not be able to make any recommendations on how that would work do to the fact we are not carb modifiers.
Thanks Kevin"

Respectfully, I am very encouraged by all the data I found and shared from the Fisher book. I will at least go that route initially, with monitoring the fuel pressure at the carb during WOT as key part of the initial testing.

Thanks, everyone, for all the constructive feedback.

Gene

 

[Tiger tamer]

Gene, if quickfuel sell metering plates I would try contacting them. They are into carbs modifications and probably more likely to help.

 

[cadreamn67]

Mal,

Thanks for the encouragement to check with QuickFuel. I understand they are a pretty good company. At the moment I have everything I need to give the smaller bowl a try. I will make QuickFuel and the metering plate my Plan B if necessary.

BTW, I measured the distance from the attachment bolt seats to the metering block mating surface of both the side hung float bowl and the center hung float bowl. The distance is the same for both: 1.5 inches. The center hung float bowl looks much bigger because of the way the back protrudes out for the float hinge and needle placement. The actual fluid holding chambers does not look that much different from each other. I do not dispute that the internal capacity is 20% larger, but I cannot help wonder what the actual volumes are. A 20% of a relatively small absolute number for the smaller side hung float is also a relatively small number. Maybe in terms of the absolute amount of additional cc's of fuel the bigger bowl holds is not that significant. Especially when you consider that the bowls do not fill to 100% of capacity, but only up to the bottom of the sight plug hole. But I digress...

Gene

 

[Duke Mk1a]

I do not dispute that the internal capacity is 20% larger, but I cannot help wonder what the actual volumes are. A 20% of a relatively small absolute number for the smaller side hung float is also a relatively small number.

To clarify...My Ultra HP bowels are 20% larger than all other Holley center hung bowels. It is a new feature. They are more than 20% larger than a side hung bowel. The Ultra HP is a racing carb.

Gene, I am sorry but, the fix for you is to get a proper manifold that allows you to use the bowels that the carb was designed to use. That $200 investment may save you a toasted 347 engine.

my $.02.

 

[TigerBlue]

Capacity vs Flow

I agree? that the absolute volume of fuel in the bowl is NOT important.

If fuel delivery lags behind fuel consumption under sustained WOT the volume will never be enough! (Think of going for a land speed record.) The jets will eventually suck air.

As long as the jets are fully covered with gas by more than adequate fuel flow the engine will be happy and pulling hard. Another way to look at it is that the float and needle seat are controlling/limiting the volume of fuel to less than full pump capacity.

Rick

 

[cadreamn67]

Duke,

Thanks for clarifying the 20% number being referenced. And I really do appreciate your 2 cents. I assure you I value your input much more highly than that.

If my being hard headed about this costs me my 347, I do have a professionally rebuilt 6 bolt 289 long block (.030 overbore) sitting in the corner of my garage to fall back on.

Maybe it could be stroked to a 331?

Gene

 

[Bob Knight]

Gene,

I have the same headers from CAT and my hangers were also close. I had to grind off a corner of the driver's side motor mount, but my hangers cleared... barely. The headers may have some variation set to set.

I don't think I swapped hangers like Bob suggested.

Gary

I didn't swap the hangars, just the motor mounts.