MTFCA Forum

Hello all! It’s been quite a while since I’ve been on the forum, but I am just unsure where to turn next.

As a semi novice Model T tinkerer, I try my best to work with what I have, and troubleshoot the best I can. I have had a Holley G carburetor that every single time I start the car up and try to smoothie out the idle, everything is ok, but as I slowly push the choke rod further and further closed, it sputters, the car backfires relatively intensely, and I have to set it back to half choke just to have it run. I haven’t even driven it once this year due to that issue, and I have had it in the past, but this year, I thought I did everything right.

I made certain to disassemble and dip the carb in Berryman chart dip overnight this winter.

I added a new, less restrictive fuel line, because the older metal one had been almost bent off.

A new modern style float was added.

Does anyone have any ideas? Thanks!

Check compression, you may have leaky valves and or worn piston rings

Skyler

you are clearly running far too lean...why that is is pretty much a guessing game, but here goes:

1. you do know how to enrich the fuel mixture, right?
2. your new float can possibly be too buoyant and shut the float valve prematurely, keeping the fuel level too low in the bowl - this can leave the idle tube high and dry
3. read here and look for clues and tips: https://www.mtfca.com/phpBB3/viewtopic.php?t=22577

looking on some of your other threads, I saw your car...it's a dandy.

The engine was taken apart and roughly rebuilt about 7 years ago, but hopefully my brother has a compression tool.

I was taking in some of the reading, and I have noticed that if the idle tube must be fully submerged, and the float must be made in order to accommodate that, meaning I may need to adjust that. Before I did the clean out of the carb dip, it would often overflow the bowl, even though the bowl itself was tight. So far, I haven’t had that problem come back, but it does seem that the float may have to be more fine tuned.

Thanks for the advice Scott! I do wish I could iron out the laundry list of other problems, but this one comes first. Thanks!

Setting the float level is best done on the bench. The MTFCA Carburetor book tells you how.



Home made level setting tool. Crudely made, but it works.

Thank you Steve for that info. I do hope not to take the carb off again, but I may have to if the float is off. I always thought that the float should just stay level when the bowl is full, but I may need to read up more on a different position.

Fuel level is easily set as Steve shows with the top needle plate removed. The jet "bowl" has to have the proper level of fuel.
One can visually see the proper level. On carbs such as a NH its a guessing game tested by performance @ idle & hi speed. The G has a big advantage in this regard IMO.

Skyler

"level" on the float is usually a good point to aim for. However...what is the buoyancy of the new float? What is it's thickness? When it is level, what is the depth of the fuel in the bowl?

let's say an original float sat "level" when everything worked perfectly...now install a thicker float with increased bouyancy...by the time it becomes "level" it does so whilst sitting on a much lower level of fuel in the bowl.

So now the issue becomes "do I mercilessly bend the hinge and get a wonky angle on the float to get the fuel level, or what??"

In general, the float valve wants to see the lift mechanism relatively level when closed. If you can do that with tweaks to the hinge angle, then so be it...BUT if the float material is overly large or buoyant (or both) then you must experiment by reducing the size of the float so as to mimic the originally designed amount of fuel displacement vs size of float all the while checking fuel level down at the jet while in a static state...that is where Steve Jelf's bench set up comes into play.

The G is a commonly available carb and the commercially available floats vary from "near perfect" to "only close" as far as mimicking the original cork float. I doubt that too much work will be involved in getting things right. It does, however illustrate to some extent, why the restoration of rare carbs can run into serious money, as rebuilding them is more than just slapping a couple of gaskets on them.

Hang in there, whatever the problem is, you'll eventually solve it.

Thanks for your help Scott, this is the float I got from langs https://www.modeltford.com/item/6201GBQ.aspx I don’t know if it is to large for displacement or not. Does anyone else use that modern float?

Thanks for all your help so far! I decided to take off the needle valve and see if there was any fuel in the upper bowl, and there wasn’t any! It seems the float is set too low, I will try to just bend the float lever up first to see if that fixes things. If that is unsuccessful, I may try to trim some float off. Thanks again for all your help!

Here is a photo of how the upper bowl looks now with no modifications.

can't see much, but if the idle pickup is submerged in fuel and fuel height is not so high as to be flowing out of the (hidden) overflow pipe, then you've got it.

Thanks, it is now submerged, and not leaking out the overflow hole. Timing is another issue I should discuss in another thread…