Two 81's on a Burns Manifold - Results

[emf]

Thought you guys might like to see this. Got my Burns installed today with two Stromberg 81's. Other than playing with a return spring here and there and cleaning up the linkage, they started right up and I was flying...

It runs fine without a pump, but I was at 1/4 tank and ran out of gas at the carbs. The Walbro pump has a bad diaphragm, so that will need to be replaced. Like I said in another thread, the piping isn't as elegant as I would like, but with the distributor in the way of just about everything, it will have to do. I'm quite pleased, it was really bolt and go...

Frank

[CarlG]

emf -- what fuel pump are you using?

[Flathead]

Is the motor stock or are there other mods besides the Burns twin?

[emf]

The pump is a Walbro 6 volt electric I bought on Ebay. the diaphragm is shot, so I ordered another kit. As far as I know, the engine is a B engine with a Model A Brumfield Head. Not sure of the compression ratio. It has a stipe cam and the papers I have with the car tell of a 'balanced rotating mass'. It came to me the way it is, so I don't know much more... I felt this baby was crying for the Burns...

Frank

[2manycars]

Have you considered using a model B fuel pump?

[emf]

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If I could get B pump at a reasonable price, I would.

[emf]

Just checking in... The set-up is completed without a pump. The bellows failed due to sitting on a shelf for a long time... ordered a rebuild kit. For now I'm running gravity feed. The car runs well with plenty of pep, but just one problem that I hope someone has seen before. With the idle speed screws backed off all the way, the car idles at 1000 rpm as measured from the tach. I can't get it down to 650 where it was with the Zenith updraft. It kind of tells me that the throat butterflies are open just a bit, but I closed them with the levers before setting the throttle arms on the linkage. Could the vacuum be sucking them open enough to idle that high??? Doesn't seem possible, but what else is there???

Frank

[PC/SR]

The vacuum is not opening the throttle butter flies. First suggest you check the idle screws. Then suggest you first disconnect all linkage and try adjusting the carbs individually. Then connect the linkage and test and adjust the air flow through each carb with an air flow device until it is equal in both carbs. You may also have an air leak somewhere. (Assuming all internal passages are clear which may need a check too.)
Carb tuning is art, not science. Keep trying. Lets not even talk about float level and jets.
FWIW, I think it should idle around 800 rpm. I know I know, it has idled at 400 for 80 years, but you are going to get more splash to the cam and cylinders walls and pins with the higher rpm. As someone said, maybe Herm, never heard of a failure from too much oil.
Edit: What Stipe cam, although any but the most radical should idle below 1000. Just a thought, is you tachometer accurate? I had a problem with that once. Also you are probably not going to get it right until the pressure is around 3 #.

[Kurt in NJ]

i have seen twisted throttle shafts, one butterfly is closed, the opther stays open some -----another problem could be wear on the edges of the butterfly , or centering, i have had to loosen the screws and shift the disc to fully seal the hole

with the throttle body assembly held up to light you can see any gaps

[midgetracer]

I am watching this close as I have the same problem. I always attributed it to the connecting rod between the carbs as it seemed to bind a little. Maybe there is another answer. I had the carbs rebuilt by Jere Jobe and they run perfect other than the idle. I have used the carb balancer and have them set equally, but still a bit high on the idle.

[Tom Wesenberg]

My stock carb wouldn't fully close most of the time. It was caused by the throttle linkage cross shaft support on top of the flywheel cover being bent. It doesn't take much of a bend to cause the shaft to bind, especially at idle where he spring has the least tension.

It was easy to find when I unhooked the linkage and found the cross shaft arm didn't move any more towards the closed position.

[Jim Brierley]

With multiple carbs it is sometimes difficult to get a slow enough idle. Make sure all linkage is right and check the butterflies to make sure they are closing completely. You may have to loosen the butterfly screws and re-center them. You may never get exactly what you want as the carbs weren't designed to work in multiples although my three 81's will idle pretty good.

[Dollar Bill]

I have no solution to offer regarding your high idle but only a concern for the proximity of the fuel line to the manifold - Could be camera angle but appears too close given the vapor lock tendencies of ethanol.

Nice looking setup! Any plans for an air cleaner?

[emf]

Thanks for the suggestions, all of you. Yesterday I removed the pump because the bellows gave up. While waiting for the new pump kit, I replaced the pump with a union and let it gravity feed. It ran poorly, like it was starving. We noticed that the rear carb was not getting gas. We then replaced the 'big dip' in the line with a straight piece from the sediment bulb to the front carb. Now both carbs are getting enough gas by gravity feed. Took it out for test and it runs beautifully, to say the least. I may run it gravity for a while to see the results. Tomorrow I'll remove the carburetors and check the float butterflies for centering. Each day gets me a little bit closer...

The air cleaners are in a box that the mailman has in his hands... It should arrive first part of the week...

Frank

[emf]

One other thought, the front gas line from the pump is about an inch and a half from the exhaust manifold. It might be the camera angle. I'm still unhappy with the lines to and from the pump, but that is another day...

[Tom Wesenberg]

In the late 70's and early 80's my Renault R12-GTL went through 6 AC bellows fuel pumps before I got rid of the car. It wasn't until years later I realized it was the crap gas destroying the bellows in the pumps.

Now I buy Carter and Holley rotary vane pumps with no parts that the crap gas can destroy.

[emf]

I'm about at the end with this change... I put a pair of air cleaners on it and I decided to run gravity for a while to avoid having one more part to fail (the pump). I'll make my final decision on the need for a pump after a few tank fulls. The fuel line is just about straight out of the outlet to the carburetor input. Not sure how they will run with minimum head pressure from an almost empty tank. I still have a high idle and I may have discovered the issue. Timing appears to be spot on and it runs well at all different speeds, but when I back off on the pedal, the throttle plates don't return to the zero point. I can push on the throttle arm and reduce the idle quite a bit. It may need a heavier spring. When I put a spring on the throttle, the pedal is stiff. I may remove the pedal spring and just experiment with throttle arm springs for a while. All in all, very pleased with the results. Any thoughts on throttle arm springs???

Frank

[emf]

oops, need a photo...

[Bob-A]

Slick!

Bob-A

[hardtimes]

Originally Posted by emf

I'm about at the end with this change... I put a pair of air cleaners on it and I decided to run gravity for a while to avoid having one more part to fail (the pump). I'll make my final decision on the need for a pump after a few tank fulls. The fuel line is just about straight out of the outlet to the carburetor input. Not sure how they will run with minimum head pressure from an almost empty tank. I still have a high idle and I may have discovered the issue. Timing appears to be spot on and it runs well at all different speeds, but when I back off on the pedal, the throttle plates don't return to the zero point. I can push on the throttle arm and reduce the idle quite a bit. It may need a heavier spring. When I put a spring on the throttle, the pedal is stiff. I may remove the pedal spring and just experiment with throttle arm springs for a while. All in all, very pleased with the results. Any thoughts on throttle arm springs???

Frank

Hey Frank,
You are on the right track, with both gravity feed and throttle arm spring tinkering. I've gone thru all of that some time back. I also took off the pressure regulator and elect gas pump and gravity feed now. So far, so good ...as long as you do not allow tank to get tooo low of fuel. I did that once and once is enough,eh !!
You and I have it better than the '29 owner, in that that gas tank sits lower and thereby defeats gravity flow, more than '30/'31 tank up higher.
Just remember that the higher your intake manifold and carb(s) sit, the gravity feed will get more iffy...so keep a full tank, especially if going up steep hills ! I suppose that there are great looking/working low pressure (2/3 lbs) elect pumps out there, just that I haven't found one yet. If you do , let me know. I've tried to 'hide' mine, when used, down inside frame.