Nit-picking the Holley "G" carb part 1

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Model T Ford Forum: Forum 2018: Nit-picking the Holley "G" carb part 1
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham, Blackfoot, Idaho on Sunday, July 01, 2018 - 01:29 pm:

A couple of comments by Stan Howe, indicating that repro parts for the "G" are not spot on got me wondering - I recently picked up a couple of "junker" "Gs", one yielded a pristine cork float. Stan had commented replacement floats are larger than original cork, which is obvious from the picture. The cork float is 3/8" thick, the replacement is over 1/2" (.565" to be exact).

Question - is buoyancy a function of weight if displacement is equal ? Starting to guess, because I don't know what the needle lever and rivets would weigh, but the cork float with the fitting weighs 9.5 grams, the oversize float 7.5.

Question #2- the modern material float appears to be made of two laminated pieces - any problem if I opt to trim it down to original size ?

Question #3- Is there anything that can be used to seal the original float that modern gasoline won't destroy ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John T. Tannehill III, Hot Coffee, MS on Sunday, July 01, 2018 - 01:33 pm:

Red Kote


Top of pagePrevious messageNext messageBottom of page Link to this message  By Corey Walker, Brownsboro TX on Sunday, July 01, 2018 - 02:18 pm:

I don't know why cork would do this but this is coming apart like it was laminated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham, Blackfoot, Idaho on Sunday, July 01, 2018 - 02:33 pm:

Corey, I believe it was. The float in my picture appears to be laminated too, but it doesn't show in that view.

John, thanks for the tip. Red-kote sounds like it would do !


Top of pagePrevious messageNext messageBottom of page Link to this message  By Corey Walker, Brownsboro TX on Sunday, July 01, 2018 - 02:50 pm:

Maybe because it's made by gluing pieces together. I always wondered how tree bark could come in big enough uniform pieces to make larger things from. I googled it and found this


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Sunday, July 01, 2018 - 02:56 pm:

The agglomerate is what you get when you buy cork gasket material at the auto parts store.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Sumner lapeer mi on Monday, July 02, 2018 - 06:24 am:

I have a question about the Holly G. I restored several G's to spec's regarding float settings using replacement floats and good original cork floats sealed with gas tank sealer.The float needles are either NOS or very good originals. My speedster's 10 gallon gas tank sits on a riser about 9 inches above the frame. I have the standard 1/4 inch fuel line. With more than 2 gallons of fuel,the floats stick open intermittently while sitting, and sometimes while running and driving. I have not had this problem once with a N H. Is it possible the weight of the gasoline in the higher mounted tank affects the float operation on a Holley G ? Les


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham, Blackfoot, Idaho on Monday, July 02, 2018 - 11:22 am:

Les, your problem turns us back to questions I have regarding the floats, original cork and modern replacements, their size and relative buoyancy. It is possible the additional height of your tank increases fuel pressure past the ability of the floats to close the needle valve. You say the valves "stick" intermittently ? If they actually stick, perhaps there's some interference on the float and its contact with the needle. If it just won't hold against the additional pressure, and you've made absolutely sure the fit of the needle in the valve body is "perfect" perhaps the float setting needs an adjustment that will work with that additional pressure ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Monday, July 02, 2018 - 12:45 pm:

Les good question. I was wondering how the two materials compared. I have a Marvel carb that the cork float is past use. I was going to use a Model A gas tank float that is made from the modern material. While the surface area might be a bit smaller using the A float, I was wondering if it would have more buoyancy because it has more air bubbles in it's construction.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham, Blackfoot, Idaho on Monday, July 02, 2018 - 02:05 pm:

Perhaps it isn't all that critical ? I never studied physics, but I'm thinking buoyancy is a function of weight to volume - correct ? In Mark's case, if the Model A float is smaller than the original cork float, but weighs less, it may be at least as buoyant (?). I'm unclear as to whether the volume (i.e. size) of the float in a carburetor can affect its function in other ways ? A larger float means less gasoline in the bowl - a smaller one, more gasoline. That may affect how the carburetor performs. I'd also think a float that is less buoyant will not stand as much fuel pressure as one that is more buoyant.

If I understood him correctly, Stan Howe seemed to indicate that the size difference between the modern material replacement float and the original cork can affect the "idle circuit" in the "G" carbs. ?!? we take it on faith that suppliers of new parts give us stuff that will function equal to OEM parts, but I've found you really need to be your own quality control.

Re/ Les's problem, I rather doubt the slight gain in fuel pressure would over-ride the needle valve in a "G" carb, but maybe it does ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Pete Osmanski on Monday, July 02, 2018 - 03:00 pm:

Buoyancy is a function of shape and weight. An object will float when the weight of the displaced fluid in which it is floating equals the weight of the submerged part of the object. Shape is important. Take a boat as an example. A flat piece of steel that weighs the same as the Queen Mary would go right to the bottom. Shape it like a hull, and it floats. Density and weight are interrelated. Something less dense would have to be larger in order to weigh as much as something more dense. But I'm conflicted here. One train of thought has me thinking if the modern float replacement material is less dense than the old cork float, to displace the same amount of gas in the bowl, it would have to be larger. But on the other hand, is displacing the same amount of gas the goal here? Being less dense, it could float displacing less gas. But then wouldn't that mean that the gas level would be higher? So I'm back to thinking that the displacement of the same amount of gas as the cork float is the goal.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham, Blackfoot, Idaho on Monday, July 02, 2018 - 03:19 pm:

Thanks for that Pete ! Maybe we're getting somewhere ? I had not considered shape ! On the question of displacement, I think we have to consider that carburetor floats don't actually float - they'd like to, but the force necessary to close the needle valve works on the float partially submerging it - the point where the float's buoyancy is strong enough to close the needle valve ultimately determines the level of fuel in the carburetor bowl. If that adjustment is too high, or the needle valve is faulty, the bowl will flood over. In the case of the "G" carb, if the adjustment is set too low, the "puddle" will be inadequate at the mixture needle and jet where the idle "sucker straw" takes up fuel. The result will be hard starting and a rough idle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John T. Tannehill III, Hot Coffee, MS on Tuesday, July 03, 2018 - 01:15 am:

I had the cork float broken in several places but super glued them together and then dipped the float in Red Kote. It worked great. I did adjust the float level just a bit due to the added weight from the Red Kote.


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