Just when I thought I was on the easy part - Team Camaro Tech
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post #1 of 24 (permalink) Old May 6th, 15, 11:56 AM Thread Starter
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Tony
 
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Just when I thought I was on the easy part

I didn't realize on a Demon carb the air cleaner stud is a different size. I bought a 1/4 by 20 stud and it doesn't fit. Plus the same hole as the stud is an idle screw at the bottom that I don't know how to adjust.

According to the directions for tuning a Demon the fuel air mixture screws should be set outward 1.0-2.5 if I read it correctly. I set them at 1.5 outward. What about the idle screw at the base of the carb? Any advice on that one?

My engine (to the ear because I don't have a tach) seems to be idling about right but stumbles when I put it in gear. So when I adjust the idle screw by throttle linkage up it seems to hight and wants to squeak tires to go in gear. I'm doing something incorrectly.

My vacuums lines are all in the right place (I think).

Trans and brake booster vacuum hoses to a tee on intake under rear carb bowl. Pcv hose on driver's valve cover to the back of carb.

Ideas?

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #2 of 24 (permalink) Old May 6th, 15, 12:14 PM
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Re: Just when I thought I was on the easy part

Quote:
Any advice on that one?
Buy a Holley?

I kid!

Sounds like your idle air mix might be a bit off. Do you have a vacuum gauge you can put on it to find the right mix? Made a difference on mine when I went from N to D. I used to have that same problem.

http://www.harborfreight.com/fuel-pu...ter-93547.html

$15 and it'll help you figure things out.

You want to adjust the idle air screw(s) to get the highest vacuum at idle. Then you can play with the idle speed.

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post #3 of 24 (permalink) Old May 6th, 15, 09:22 PM
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Anne
 
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Re: Just when I thought I was on the easy part

Quote:
Originally Posted by TClovis View Post
According to the directions for tuning a Demon the fuel air mixture screws should be set outward 1.0-2.5 if I read it correctly. I set them at 1.5 outward. What about the idle screw at the base of the carb? Any advice on that one?
Here is a link to the instructions :
http://www.demonfuelsystems.com/Asse.../LIT350rev.pdf

The street demon would have been a better choice. The speed demon is for engines with a cam over 220* duration and has a 4 corner idle setup.

But it might work ok once adjusted correctly.

Here is what they say about the center idle screw :
----------------------
On engines that idle below 1,000 RPM, set the primary butterflies open to the .020” (square) as
described above, but the secondary butterflies should be set to the bottom of the transfer slot. In
other words, at idle speed the secondary transfer slots will not be visible when viewed from the
bottom, but any movement of the secondary butterflies will expose the slot.
The next step is to provisionally set the Idle-Eze™. Insert a screwdriver through the air cleaner stud
hole to engage it, and turn the screw clockwise until the screw stops. Now, reverse it counterclockwise
by 1-1/2 turns. This will serve as a good baseline.
Use a screwdriver through the air cleaner stud hole to control the engine’s RPM. Once the RPM is set
approximately and the engine is running at normal operating temperature, begin to adjust the idlemixture
screws. Adjust the screws either in (leaner) or out (richer) until the engine reaches its
optimum idle. Adjustments in small increments of, say, approximately 1/4-of-a-turn at a time is
recommended. Once the idle mixture has been set, adjust the Idle-Eze™ by using a screwdriver
through the air cleaner stud hole to reach desired RPM. Once satisfied, install the air cleaner stud
and air cleaner and make sure its presence doesn’t change the idle settings or RPM. If it does, the
carburetor will require readjustment so it performs properly with the air cleaner installed. Once it does,
you’re finished and ready to enjoy your carburetor.

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post #4 of 24 (permalink) Old May 6th, 15, 10:04 PM Thread Starter
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Tony
 
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Re: Just when I thought I was on the easy part

Thx for putting up directions. Is my cam far off? Sum-1103? I don't understand the duration piece. I had planned for a retro roller later.

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #5 of 24 (permalink) Old May 6th, 15, 10:58 PM
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Re: Just when I thought I was on the easy part

I just went through the same learning curve. Take George's advice above and get a vacuum gauge (I'm not sure about the Harbor Freight part, lol). Note in the directions you set the transfer slots with the carb off the car. Then use the idle-eze screw under the air cleaner stud to adjust the idle speed. You only use the idle screw by the linkage to adjust the primary butterflies before install. After setting the idle mixture screws, re-adjust the idle speed with the idle-eze screw.

Your cam is 214 int./224 exh so you should be able to make this carb work pretty well.

68 RS Coupe 355/350 TH, Detroit Speed, Hotchkis, Vintage Air, 8.5" 3.42 posi 10-bolt, MagnaFlow 2 1/2" exhaust, etc.

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post #6 of 24 (permalink) Old May 7th, 15, 12:56 AM
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Tom
 
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Smile Re: Just when I thought I was on the easy part

What carburetor did you get ? Which Demon ? I see people giving you all sorts of information and we don't even know what you have ! I hope you went with the 750 cfm street demon like you were talking about.

I don't believe that the street demon even has transfer slots to set !

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #7 of 24 (permalink) Old May 7th, 15, 07:25 AM Thread Starter
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Tony
 
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Re: Just when I thought I was on the easy part

I went with the speed demon 650 with vac sec and elec choke. I had no idea that the idle screw by throttle linkage wasn't the main idle screw. I just turned the baseplate idle screw 1.5 turns outward and all four fuel air mixture screws 1.25 turns outward. Then adjusted the wrong idle screw I guess.

What do I do with the idle screw by throttle linkage if the baseplate is the one that matters?

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #8 of 24 (permalink) Old May 7th, 15, 09:56 AM
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Tom
 
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Smile Re: Just when I thought I was on the easy part

Ok... The Speed Demon is basically a Holley, so yes it would have the transfer slots. Follow Lawrence454's advice and set them 1st.


69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #9 of 24 (permalink) Old May 7th, 15, 12:13 PM Thread Starter
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Tony
 
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Re: Just when I thought I was on the easy part

I'm not sure if that was done so I guess I'll take it off and follow that procedure.

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #10 of 24 (permalink) Old May 7th, 15, 01:54 PM Thread Starter
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Tony
 
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Re: Just when I thought I was on the easy part

Quote:
Originally Posted by TJS69 View Post
Ok... The Speed Demon is basically a Holley, so yes it would have the transfer slots. Follow Lawrence454's advice and set them 1st.

I know I sound ignorant here because I am but is it the butterfly adjustment that makes the square (transfer slot)? I can't remember if that was done or not.

Since the idle screw is down the air cleaner stud hole and is the main idle adjustment. What's the purpose of the other more obvious idle screw and what is supposed to be done with that one? I'm confused on this thing.

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #11 of 24 (permalink) Old May 7th, 15, 03:15 PM
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Smile Re: Just when I thought I was on the easy part

The thing with the transfer slot is so not too much of the slot is exposed. If too much is exposed, it will bypass the idle metering circuit. You want the slot to look like a square below the throttle blades and not long and rectangular ! I alway's thought this was about .040", but the height should be the same as the width. This is just a baseline, and a small adjustment to your idle screw will be needed. When you have the carburetor off and are setting the butterfly's notice how much more is exposed with 1 more turn etc.

If the engine wants more air, you then crack open the secondaries until you are close to adjusting your idle with a small adjustment.


69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1

Last edited by TJS69; May 7th, 15 at 03:30 PM.
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post #12 of 24 (permalink) Old May 7th, 15, 06:32 PM Thread Starter
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Tony
 
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Re: Just when I thought I was on the easy part

I took off the carb and it looks right. I have the square transfer slot on primaries and can't see slot on secondaries as instructed. Must have been the screws. I'll get it back on tomorrow.

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #13 of 24 (permalink) Old May 7th, 15, 08:05 PM
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Re: Just when I thought I was on the easy part

Tony, By now you should have read the instructions on your Demon carburetor.The first thing you should do is remove the carburetor to check the transfer slots and adjust if necessary. See page 3 in the instructions. Adjust the idle mixture screws, first gently turn them closed then open them 1 1/2 turns to start. Start the engine, set the float levels and fuel pressure to 6-7 psi to the carburetor. Get a timing light with advance to check the initial timing. Unplug the vacuum line to the distributor and plug it. Set the initial timing to 12-14 degrees BTDC. Check the total timing by revving the engine to above 3500 rpms. Set the knob on the Timing Light to 36 and shine it on the scale on the timing chain cover. The line on the balancer should be on zero. You can rev the engine to 4000 rpms to make sure that the timing is all in. Your mark should still be on zero. If by chance it is not on zero after revving the engine to 4000 rpms turn the knob on the timing light until the mark line up with zero. If the timing light mark is over 36 you will have to adjust the distributor to bring it back to 36* I will post a link to an article that helps explain all this better than me. Use your vacuum gauge to set the idle mixture screws to the highest reading you can get on the gauge. Now if the idle needs to be adjusted use the Idle-Eze screw. This article will help you understand setting the advance curve for the distributor, transfer slots, and timing. http://www.crankshaftcoalition.com/w...EI_distributor BTW if you are having a stumble when you hit the gas pedal see page 16 figure 24. If that doesn't help go up 1-2 sizes on the squirters.
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post #14 of 24 (permalink) Old May 7th, 15, 08:35 PM Thread Starter
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Tony
 
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Re: Just when I thought I was on the easy part

I read it. Some is Greek to me if not most. I'm going to get some help on this too tomorrow. I'm also wondering if my cam is in deed to small for this carb.

If the speed demon 650 works well with 220 duration and mine sum-1103 is advertising 214/224 I'm suspicious. Most searches I do for mild cams with this carb bring up the comp xe262 or 268.

I'm hoping it works for now.

1969 Camaro SS350, original motor/12 bolt/interior and build sheet in Fathom Green.
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post #15 of 24 (permalink) Old May 7th, 15, 08:38 PM
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Tom
 
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Smile Re: Just when I thought I was on the easy part

There isn't a transfer slot on the secondary side, so you are good to go !

Just a comment on your title, The easy part is buying the parts ! Making them work for your application is the challenge !

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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