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Ram Air/Electric Choke Problem Revisited

Joined
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As you may recall I was having problems with my Ram Air causing my choke butterfly to partially close and set the fast idle cam to it's first step at speeds of 45-50 mph. I solved that problem by modifying my choke housing so manifold vacuum would force the choke butterfly open but that created another problem.............my choke butterfly would open too quickly about half the time; causing my engine to die after about 3 seconds of running. Knowing I had to slow the opening I have been experimenting with different sizes of "vacuum reservoirs" to delay the choke butterfly opening.

I tried a 1-1/2" X 8" piece of steel tubing but that made almost no difference whatsoever. Then I tried using a one-pound coffee can and that helped but the butterfly still opened way too fast. Next I tried a 1-1/2 pound coffee can and that wasn't nearly large enough either. Then I tried a 2 pound, a 2-1/2 pound, and finally a 3 pound coffee can (actually a one-gallon can) and the 3 pound can appears to be the right size.

I tried the 3 pound coffee can "reservoir" this morning and my choke was forced open after about 3-1/2 to 4 seconds which may do the trick. I mounted the coffee can under my blower motor for the time being just to see how well it performs over the next week or two.

The Air Gap intakes and real cold weather make starting pretty difficult at times so I want my choke to operate good enough to allow easy starting but I also want it to COME COMPLETELY OFF and that's why I am pursuing this unusual problem that was caused by my Ram Air.
 

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Antz81

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Auckland, New Zealand
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Why not just use an electric timer to switch a solenoid and use that to control the vacuum? You could set it to however long is needed then, which is probably still longer than your coffee can is giving you.
 
Joined
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Messages
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Ram Air Causing Choke Problems

Sometime in the next several days I'll make a short video showing my choke butterfly in the closed (cold) position then opening once the manifold vacuum purges the reservoir so you can see how the manifold vacuum forces the butterfly open.
 
Joined
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Why not just use an electric timer to switch a solenoid and use that to control the vacuum? You could set it to however long is needed then, which is probably still longer than your coffee can is giving you.


Because I already have the coffee cans to experiment with and my time is free. Now I'm hoping the coffee can won't collapse when I coast down a long steep hill when 25 Hg can be encountered.
 

dougelam

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So I take it your choke pull-off is not adjustable!

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Joined
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Messages
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So I take it your choke pull-off is not adjustable!

Sent from my SM-T530NU using Tapatalk


No, it's not adjustable. The 3-pound coffee can appears to be about the right volume to slow the choke butterfly opening. I'll know more after I have had the chance to observe it's operation over the next couple of weeks. I just need my choke to stay closed for about 4-5 seconds before it gets forced open. All of this trouble being caused by my Ram Air; something I didn't anticipate when I was fabricating it last summer.

The #3310 Holleys don't use a "diaphragm" type of choke pull off but rather a .515" diameter brass piston that is incorporated inside the choke housing. By installing two silicon o-rings on the piston and using manifold vacuum to pull on it the choke butterfly gets forced open with a lot of force. The trick is to use a vacuum reservoir with enough volume to slow the butterfly opening enough to allow the engine to keep running. If I can keep it fast idling for 4-5 seconds it'll continue running even with the butterfly pulled fully open. If I have to I can always "daisy chain" another coffee can into the system to further increase the volume but I think this 3-pound coffee can will do the trick.

The real test will come when the temperatures drop down into the low 20's because that's when it's the hardest to start. Yes, I could always convert it to a manual choke but I want it to operate automatically and I'm having fun experimenting with it.
 

dougelam

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I still don't get it!
Since Hib won't let my Google it I can't be 100% sure BUT without doing that I am sure that your electric choke coil has a rolled end that captures the lever pin. It sounds to me like it is not installed correctly!

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Boom

I took it out onto the highway and at about 30 mph I heard a huge BOOM under my hood. Uh oh! I brought it back home and found the force of the vacuum had broken the solder loose and the end got sucked all the way to the other end. So I made a new vacuum reservoir out of a one-gallon paint can that is made out of a thicker gauge of steel and has the press-in lid. If the force of the vacuum isn't enough to implode this can it should work.
 

bill81vette

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Wow!!!!!
That must have really sucked!!!!

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Okay, after sucking the top of my one-gallon reservoir down to the bottom in a loud BOOM I made a new reservoir using a one-gallon paint can that appears to be made from a heavier gauge of steel. Hopefully it won't implode when I coast down a hill and put about 25" Hg to it. With the large volume I'm hoping it'll slow down the opening of my choke butterfly to 4-5 seconds after a cold start. It's 4:50 A.M. right now so I'll be installing it before I head off to my Fresno doctor's appointment this morning.
 

Attachments

  • 1971 Corvette Ram Air Choke Problems 001.jpg
    1971 Corvette Ram Air Choke Problems 001.jpg
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LLC5

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Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
As you may recall I was having problems with my Ram Air causing my choke butterfly to partially close and set the fast idle cam to it's first step at speeds of 45-50 mph. I solved that problem by modifying my choke housing so manifold vacuum would force the choke butterfly open but that created another problem.............my choke butterfly would open too quickly about half the time; causing my engine to die after about 3 seconds of running. Knowing I had to slow the opening I have been experimenting with different sizes of "vacuum reservoirs" to delay the choke butterfly opening.

I tried a 1-1/2" X 8" piece of steel tubing but that made almost no difference whatsoever. Then I tried using a one-pound coffee can and that helped but the butterfly still opened way too fast. Next I tried a 1-1/2 pound coffee can and that wasn't nearly large enough either. Then I tried a 2 pound, a 2-1/2 pound, and finally a 3 pound coffee can (actually a one-gallon can) and the 3 pound can appears to be the right size.

I tried the 3 pound coffee can "reservoir" this morning and my choke was forced open after about 3-1/2 to 4 seconds which may do the trick. I mounted the coffee can under my blower motor for the time being just to see how well it performs over the next week or two.

The Air Gap intakes and real cold weather make starting pretty difficult at times so I want my choke to operate good enough to allow easy starting but I also want it to COME COMPLETELY OFF and that's why I am pursuing this unusual problem that was caused by my Ram Air.




Do you read your own posts before you before you click on submit?
 
Joined
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Messages
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Location
Yemen
Once I leave my property I have a ten mile long 6% downhill grade to drive and my new vacuum reservoir will probably implode. If it does then I'll just have to find a way to strengthen the cans. The later C3's use what appears to be a 2-pound coffee can for a vacuum reservoir and they don't implode but maybe they're made from thicker material. Whether it works or not at least I'm having fun.
 

LLC5

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2,299
Location
Wa.
Corvette
98 black 6spd convert.
Once I leave my property I have a ten mile long 6% downhill grade to drive and my new vacuum reservoir will probably implode. If it does then I'll just have to find a way to strengthen the cans. The later C3's use what appears to be a 2-pound coffee can for a vacuum reservoir and they don't implode but maybe they're made from thicker material. Whether it works or not at least I'm having fun.



Clearly you don't.
 
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One Gallon Paint Cans Not Strong Enough

My one gallon paint can imploded before I even got out of my garage this morning and I had to make the 100 mile round trip with a vacuum leak; causing my engine to run poorly at idle. So it looks like I'll have to find something a bit stronger than paint cans. I'll see if I can find a 8" piece of 6" exhaust tubing and MIG weld some 16 gauge ends on it. It's not the vacuum that imploded it but rather the 14+ psi of pressure pushing against the outside.
 

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    1971 Corvette Ram Air Choke Problems 011.jpg
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LLC5

Well-known member
Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
My one gallon paint can imploded before I even got out of my garage this morning and I had to make the 100 mile round trip with a vacuum leak; causing my engine to run poorly at idle. So it looks like I'll have to find something a bit stronger than paint cans. I'll see if I can find a 8" piece of 6" exhaust tubing and MIG weld some 16 gauge ends on it. It's not the vacuum that imploded it but rather the 14+ psi of pressure pushing against the outside.



God dam, it never stops.....


My sides are hurting...........:L:L:L:L:L
 

LLC5

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Location
Wa.
Corvette
98 black 6spd convert.
Truly, no one can put hate on a paint can like good ole' toobroke.

That was actually tragically impressive.
 
Last edited:

dougelam

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Joined
Jul 19, 2011
Messages
453
Location
Michigan
Corvette
2002 Roadster
Funny thing is when he finally cries uncle we can tell him how to fix it!

That is if he'll listen!!!
7475d16a28096c8314e778fc628f044d.jpg


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