Carby problems

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Model T Ford Forum: Forum 2011: Carby problems
Top of pagePrevious messageNext messageBottom of page Link to this message  By Liam Cox on Sunday, December 18, 2011 - 04:43 am:

Hey peoples..
I have a model T truck that I inherited of my father, and I am in the process of getting it running (again!!). After sitting for 8 years, I managed to get her up and driving again recently - and it was going 100% spot on!! But then it got some gunk in the carby, and upon inspection it turns out there wasn't a fuel filter.

I have since upgraded the fuel hose, and installed an in-line filter. Meanwhile, I pulled the carby down (Holley NH), cleaned it out and replaced the parts with new ones I got from a "carby rebuild kit" from a local dealer here in Aussie.

I followed the instructions as per the model T workshop manual.. although no matter what I did (eg: adjust float levels, triple checking the needle and seat was sealing etc) the carby would fuel up that much, the engine wouldn't run. After stripping it down and checking everything around 5 times, I gave up and put the old (original) parts back in the carby - which made it run somewhat better.

Since then, I have picked up another complete carby.. so now I have some new parts, old parts and 2 carbys.

2 questions please.. should I be running a fuel pump, or will the gravity feed be enough? And finally, does anyone please have some further advise on this carby problem! All of the parts/carbys are now sitting on the bench, awaiting further work! Thank you heaps :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Sunday, December 18, 2011 - 07:42 am:

Liam:

The fuel filter is a screen in the sediment bowl under the gas tank. Take the sediment bowl apart & clean.

My advise, get rid of the paper fuel filter, it will only impede the rate of flow on a gravity system. No fuel pump needed, gravity system worked fine....... when clean & had a least 2 gallons of fuel.

There is a carby manual available from the MTFCA,,,, don't know what unit you have... standard issue or aftermarket.

Hope this helps to get you started


Bob J.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Sutton on Sunday, December 18, 2011 - 08:17 am:

You didn't say if you were using a starter or not, but if you're trying to crank start, your carb better be perfect! I tried several different carbs on my '15 a few years ago and could only get one to work. They all work just fine on my truck because it can crank over just slightly more with the starter than I could get the engine to do manually.

If you think you need a filter, I'd recommend either fixing the inside of the gas tank or replacing it. Having a cruddy/rusty tank is just asking for trouble later on.

Craig


Top of pagePrevious messageNext messageBottom of page Link to this message  By CharlieB Toms River N.J. on Sunday, December 18, 2011 - 11:25 am:

Liam, I've done a number of NH's and never had a problem with re-building or performance which doesn't do a darn thing for you. I only mention it because they are about as simple as it gets. I can only think something in you re-build kit wasn't correct. Putting the old stuff back and having it run better leads me to this. You must make sure all the air passages are open in the carb body. There aren't many but they must be clear. Float setting and main needle adjustment are critical too. 1 to 1 1/2 turns open for starters will probably get you running then adjust down when it warms up. I do run a paper filter though most don't recommend it. As mentioned, check/clean the screen on the bulb for full flow and make sure the tank vent in the cap is clear/opened. Soak the carb body and blow out the passages. Use all the gaskets in the kit: there's one under the needle seat and the main jet too. Make sure you've removed the old ones from the body before re-assembling. They get as hard as iron and look like part of the body. You sound knowledgeable. Take your time, ask questions and get that thing running!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andy Loso on Sunday, December 18, 2011 - 02:31 pm:

Did you drill out the three brass plugs and clean out the passages?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Liam Cox on Sunday, December 18, 2011 - 08:40 pm:

Thanks heaps for the replies everyone!! There is no sediment bowl, so I will look into finding one of those first. And could someone please tell me where these 3 brass plugs are that need to be drilled? I will take all of the other comments on board too :-) many thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark C. Vlasak on Sunday, December 18, 2011 - 09:25 pm:

Liam,
Andy has a simple thing to do. Drill out the three brass plugs, clean out the passages, and replug with 1/8" brass plugs. You will be surprised how much crap you will get out of these passages. Obviously you will have to remove the brass name plate to get at one of the passages. NH Carburetor Idle Passages I do not remember where I got this excellent picture and wish I could give credit to the photographer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa in Poulsbo, WA on Sunday, December 18, 2011 - 09:53 pm:

Photo by Be_Zero_Be - glad it is useful. Mark is right - you would be supprised what comes out of those passages.

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Monday, December 19, 2011 - 03:19 am:

Instead of replacing the plugs with brass, use 8-32 Allen head set screws. Tap the holes 8-32. They are cheap, easy to install and make it easy to remove them and clean the passages. Instead of trying to get those little pins to hold on the tag, tap the holes either 4-40 or 6-32 and use weenie little screws to put the tag on. Far easier. Also allows you to remove the tag to clean that passage.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce Peterson on Monday, December 19, 2011 - 06:38 am:

Inline fuel filter won't work period. Get rid of that.

I suspect the old part that makes it run better is the needle and seat. The "Grose Jet" sold by part vendors works very poorly unless you have a '26 - 27 with the cowl mounted fuel tank.


The original type needle and seat work far better and are trouble free if in good condition. Some of the vendors sell a new reproduction needle and seat made to the original specs by Larry Smith. If you can get one of those you will also have no problems with fuel flow.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark C. Vlasak on Monday, December 19, 2011 - 09:16 am:

Stan,
I like the ideas and it comes at the perfect time to help me.
Mark.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace on Monday, December 19, 2011 - 09:40 am:

These exploded view of the NH can help too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Monday, December 19, 2011 - 02:10 pm:

There should be one more drawing to make some of those diagrams make better sense. On the second drawing, where the low speed tube is; that little circle is the beginning of the passage that goes to the front of the carb to feed the idle passage ahead of the throttle plate. When you are cleaning these tubes, be sure not to drill them oversize. If you can, clean the passages with pieces of acoustic guitar strings rather than drill bits. The size of the passages is more critical than you might think and it is easy to drill them oversize when you are cleaning them. Get some brass or bronze wound guitar strings. If you have to, go to the music store and buy the cheapest medium gauge set they have. It will cost 5 or 6 bucks. Cut pieces off the different size strings to clean the passages with. They are brass, so they won't enlarge the holes, they are rough, so they clean just like a file and they won't get stuck and break off in the passage or jet holes. Be sure to clean the tiny little hole from the idle passage to the inside of the carb throat. That is where the idle mixture comes into the intake chamber to supply idle mixture to the engine. Note that the passage is the jet. Do not enlarge it. I had a bunch of pictures of doing this in all the pictures I lost. One of these days I'll take more and post them on my web site as a "How to rebuild an NH." I will also be showing this at the Hutchinson Seminar. Old NH, ready for the garbage. NH all apart. NH rebuild and ready to install. Also 40+ Model T accessory carbs, carburetion in general and specifically, several stock Model T carbs, etc. Jan 20-21, Hutchinson, Kansas.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dennis Seth - Ohio on Monday, December 19, 2011 - 02:28 pm:

Stan,

I went to the hardware store and ask for a weenie little screw and she slapped me and called the manager... Please send bail money.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Liam Cox on Monday, December 19, 2011 - 03:18 pm:

Wow, heaps of info!! Thanks again everyone, I am looking forward to giving this stuff a go. Will keep you all posted! :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Monday, December 19, 2011 - 05:23 pm:

Now, Denny, like Larry the Cable guy says, "That's funny right there, I don't care who ya'll are."

I can think of a dozen funny follow up lines but this is a family forum so I'll let them go but you know there are some great lines in that post, Denny!!

I've had a bunch of emails today about the screws and passages so as soon as I get time this afternoon I'll go take some pics and post them of how I do this.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthony Bennett on Monday, December 19, 2011 - 09:25 pm:

G'day blokes,

I've used a grosse jet in a number of different model T's for over 20 years and had no problems whatsoever. I never turn the fuel off and have only ever had a flood when filling from dry, which a tap on the carb sorts out promtly.

The most recent restoration we have done uses a neoprene tipped needle and seat and it simply will not seal. You can hold it shut with your finger, but no matter how low the float setting, the carb floods in around a minute. Tried a number of different floats for the same result.

Grosse jet on order next.

Cheers;)

Anthony


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph Magedanz on Monday, December 19, 2011 - 11:34 pm:

Adding to what Royce said: "Some of the vendors sell a new reproduction needle and seat made to the original specs by Larry Smith."
I put one in, and it took care of my problems...
Just a thought.
Joe


Top of pagePrevious messageNext messageBottom of page Link to this message  By jack daron-Brownsburg,In. on Monday, December 19, 2011 - 11:37 pm:

Most float valve problems I've encountered are the dang hard gasket leaking. Nothing much wrong with the valve.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Tuesday, December 20, 2011 - 01:50 am:

Many, not all, of the seats are rusted and pitted to the point where the hard fiber gasket supplied with the new seats will not make a seal against the carb body. That seat should be ground flat and smooth with a 90* jig on a drill press or mill to make sure it is flat and perpendicualr to the threads of the seat. Virtually every NH that I've had sent to me because the needle and seat continues to leak has one of three problems.

1. Body seat is pitted or not flat to where the gasket will not seal. ANY pits or low areas WILL leak.

2. Seat area or carb body is cracked to where it allows a little gas to seep.

3. Float has so much solder on it what while it will float it will not apply enough pressure to the seat to effect a seal.

I personally will not use Grose jets. I see no reason to and I have had problems with them. The Original Smith ones work well as do the Viton tipped ones from the vendors.

Many of the original floats have a spot worn in them where the tang of the float rides against the bottom of the seat. If the wear is in just the right spot it will stop the needle from moving up into the seat and sealing. That area should be filed flat, then slightly curved for best results.

Some of the problems attributed to the needle and seat are not its fault. Check very carefully in the carb body below the inlet area for cracks. Many NH bodies are cracked there from too much pressure from the fitting being threaded in too tight. You can't see the crack with the fitting removed, can't see it with the fitting in place but if there is a crack it will leak. The only way to find the crack is to seal the seat area, feed gas into the inlet and watch for a seep below the inlet area. It is pretty easy to seal the seat, just solder the old seat hole shut and reinstall it. Get a gas line into the inlet and watch from the bottom side. It will show you where it wants to leak. It doesn't take much of a crack for gas to seep through it.

Many new seats are ruined installing them with a screwdriver. Few screwdrivers fit the slots of the seat well enough to tighten it without doing a little damage to the brass seat. A tiny lip will keep the needle from moving freely. The seat should be installed finger tight and then tightened either with a special piloted wrench or by holding a washer that just fits in the slots in a pair of pliers and turning the washer.

Again, the seat area of the body must be flat and smooth, a fine finish, if you expect the gasket washer to fit well enough to keep gas from leaking past it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Liam Cox on Wednesday, December 21, 2011 - 04:28 pm:

Thanks heaps Stan.. greatly appreciated!


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