MTFCA Forum

My Simmons Super Power carburetor has given me a great deal of grief and I gave up trying to rebuild it.

When I bought my 1925 T Touring it came with the Simmons and it seemed okay, but I suspect that it has been the source of much of my problems over the past two years or so. I am not interested in yet another summer in the garage or getting flatbeded back to the driveway. I want to drive this car.

Today I broke down and ordered a rebuilt NH carb. Fingers crossed, I'm hoping it works.

The point being, does anybody rebuild Simmons Super Power carburetors?

They are basic as the Nh but with the flapper, and most of the times people remove the flapper and then you have a crappy idle. I am no carb master but have played with a few and every once in a while you get one you just give up on!

May just have a plugged passage. I wonder is someone installed the wrong spray needle jet, they are a different length then NH but fit the same, along with shorter needle. If you go down to the drawings, it show the length of the jet tube. The shorter one in the photos is the Simmons/Western Auto/Duplex jet.

Now I know why the 1913 runned as crap as it arrived here to tune up. It had a Simmons carburetor on the engine. I tried to rebuild it but could make it run right. Build a rebuild NH pre 1923 on it and it run as new.

Thanks
Andre
Belgium

I have rebuilt several of them and have had no problems with them. I like them a lot and they are what I run on my T's.

I ran one once. Did not seem to get extra performance. Do they move more air than a swayback nh? more speed, smoother running? what is the draw?
I do know the internal differences.
30 years ago i tried running a straight thru. Top end was good, but it needed constant readjusting for idle & high speed settings. I did not know back then how to fine tune the float setting. That may have been my problem.
I figured, since it was only issued for part of 1 year, it was a design failure.

I would love to get the view points of those who have run either or both.

This maybe little off topic but just asking.
I heard that the Straight bore NH do not idle good. Is the flapper in the Simmons a way to try and fix that problem? Dan

yes dan, but does the flapper impede enough air flow volume to possibly flow less volume than a swayback?? Then whats the advantage?
The cfm difference is 29 for swayback & 31 for straight thru as i recall.

I have NH straight bore carbs. on 3 T's - all seem to idle just fine.

Is there a "noticable" performance difference over the swayback?

Three carburetors have a flap that I can think of; Simmons/Western Auto, Kingston and Marvel. All three work the some what the same way, when the flap is closed it forces the air thru the idle circuit, giving a richer mixture. My thoughts/OP; When fully open (Simmons and Marvel), the narrow profile of the flap should not be blocking that much air flow and should still force air down over the puddle and act like a variable venturi. I know the Marvel ran pretty darn good on the rebuilt engine in the 21. I have not road tested the Simmons on my 25 that still has cast iron pistons (got some rear end work to do before that). Reading some older post on the Simmons, they are very touchy when it comes to start up adjustments I have found that to be true. Good question re the comparison between the NH sway back and Simmons, can't help there because I don't use the NH in any form.

The simons flap is rather thick, plus there are 2 weighted stubs that will effect air flow. the question would be to what extent. I wonder if there are any air flow specs out there.

Revisit this thread and found that the Simmons carburetor on the 1913 runabout was missing the flapper. The bolt was there to close the hole but had no axle and no flapper.

Andre
Belgium

Those Simmons carbs have one passage. It’s function is to add air to the mixing chamber itself. That same passage on an NH would be the one that goes from under the ID tag to the mixing chamber.
You can see on top of the carburetor to plugs, one is to plug the hole where they drilled this passage from the top and then sealed the top of this passage which is intersected by another. The other is where a stop for the flapper is inserted. The passage that intersects this one comes from the choke side of the carburetor.
It is placed in such a way that when the choke plate is fully closed air can still be drawn through it through a recess in the carburetor throat that leads to the passage opening. I drew a diagram and put chalk marks where the passage is.
The main opening is under where the flap is located. As more air volume rushes through opening the flapper wider, less air goes through this passage and all the air needed mixes with the gasoline drawn through a jet that is inserted into the carburetor throat. This is where the spray needle seats unlike the NH where the longer needle goes down and seats against the spray nozzle itself,
Instead of an idle circuit like an NH, and it functions a bit differently than the Kingstons but the same principle, the flapper regulates the air providing a richer mixture at lower speeds and just enough in the mixing chamber while choking.
If you mess with the heating element make sure it is sealed or it can cause a vacuum leak or dripping fuel at shut off. There are several rubber washers there to seal it from the factory.

Thanks Cory, I for got about the brass seat in the passage.

I wonder how it would run if you drilled the brass jet out, opened the hole, installed an NH spray jet and needle!