Engine won't idle with VA A/C on - Team Camaro Tech
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post #1 of 17 (permalink) Old Sep 1st, 11, 12:26 PM Thread Starter
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Engine won't idle with VA A/C on

I have a stoutly built 350 with Comp Cams 282S, edlebrock 750 and performer intake, TF heads. I just had the new Vintage Air charged up and when the compressor comes on it kills the egine unkless I keep the idle rpms way up about 1500. It idles OK w/o compressor on at 950. I also had them do some carburetor adjustments because I didn't think it was running like it should and he switch the distributor from ported to manifold vacuum. He suggested a step-up motor? Anybody have other suggestions or explanantion.

Wouldn't ya know I'd find this out on a day when it's supposed to get to 104 in the shade.
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post #2 of 17 (permalink) Old Sep 1st, 11, 12:37 PM
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Re: Engine won't idle with VA A/C on

Quote:
he switch the distributor from ported to manifold vacuum.
A ported dizzy VA is different specs to a manifold Vac one....it is very rare one can simply swap over like that... Doing so also means changing cent, intial, the whole config of the Dizzy....and yes it could effect the idle load and stuff depending on the specs.
Quote:
I also had them do some carburetor adjustments because I didn't think it was running like it should
Like what?
Your issue is very likely to be carb /advance related.

Also with the larger cam, the bottom end rpm range, including idle becomes very ineffient and unstable...adding extra load like AC is not good...maybe needs a fast ildle when A/C is turned on... or just more idle advance.

My Spelling is not incorrect...it is creative

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post #3 of 17 (permalink) Old Sep 1st, 11, 12:46 PM Thread Starter
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Re: Engine won't idle with VA A/C on

I should have mentioned it has a stock points distributor. When I first got this engine running years ago it seemed a lot crisper and idled smoother. It had no A/C at that time. The engine was only run a little every few months while I played with restoring it for abotu 7 years and then I let a pro take it to finish the body work 2 years ago. He had the engine out and back in and had done some messing with the carb and dist. With the A/C off now it does seem to run better but I'd sure like to have the A/C if possible. Is there anything that I can put on it to turn the compressor off if the rpms drop too low or some other way to get both working?
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post #4 of 17 (permalink) Old Sep 1st, 11, 12:55 PM
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Re: Engine won't idle with VA A/C on

Ya just install a fast idle solenoid, you wire it to your A/C so it kicks up the idle when the A/C is on
http://www.holley.com/46-74.asp


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post #5 of 17 (permalink) Old Sep 1st, 11, 01:07 PM Thread Starter
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Re: Engine won't idle with VA A/C on

This looks like what I would need for an edelbrock carb:

http://www.jegs.com/i/Edelbrock/350/8059/10002/-1

I only see one wire connection. Does it just connect to the wire the turns the compressor on and when it has power it activates the solenoid?
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post #6 of 17 (permalink) Old Sep 1st, 11, 01:27 PM
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Re: Engine won't idle with VA A/C on

From the installation instructions
"Attach the wire from the solenoid to the
existing idle compensator wiring connector.
If connector is not present, you may splice a wire from the +12 volt wire supplying power to the air conditioning
compressor (check with voltmeter or test light first). Use a 1/4" female receptacle and at least 18-20 gauge wire.
Some receptacles will require that the locking tab on the solenoid be flattened before the receptacle will fit."

Here is the instructions
http://www.edelbrock.com/automotive_.../8000/8059.pdf


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post #7 of 17 (permalink) Old Sep 2nd, 11, 07:31 AM
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Re: Engine won't idle with VA A/C on

You really should fix your carb/distributor problem first.

An engine idling at 950 shouldn't need to be stepped up to 1500 to keep it from stalling.

Sounds lean and when the RPMs fall along with the vacuum advance, the motor stalls.

Revert both systems back to their original configuration and just keep what works.
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post #8 of 17 (permalink) Old Sep 2nd, 11, 08:28 AM
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Re: Engine won't idle with VA A/C on

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Originally Posted by mahunt View Post
You really should fix your carb/distributor problem first.

An engine idling at 950 shouldn't need to be stepped up to 1500 to keep it from stalling.

Sounds lean and when the RPMs fall along with the vacuum advance, the motor stalls.

Revert both systems back to their original configuration and just keep what works.
X2 on this. I run a Hr282 cam but with 112 lsa cam and can idle at 800 with the ac comp on. I run a 8361 ready to run MSD with a 3310-4 Holley. Inital dist timing is set a 17, total 34 at above 2500 rpm. You should be able to do the same unless your carb is out of sync.

Don
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post #9 of 17 (permalink) Old Sep 2nd, 11, 09:14 AM Thread Starter
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Re: Engine won't idle with VA A/C on

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Originally Posted by zdld17 View Post
X2 on this. I run a Hr282 cam but with 112 lsa cam and can idle at 800 with the ac comp on. I run a 8361 ready to run MSD with a 3310-4 Holley. Inital dist timing is set a 17, total 34 at above 2500 rpm. You should be able to do the same unless your carb is out of sync.
Are you using ported or manifold VA? I guess I need to do some reading and get the old timing light out. I thought I could rely on this shop that has always done good work on my newer cars but....
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post #10 of 17 (permalink) Old Sep 2nd, 11, 11:04 AM
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Re: Engine won't idle with VA A/C on

Although using a manifold vacuum source is the mantra for many on this site, I've always used the ported connection.

I find the manifold source varies with every flicker of the engine and can cause the engine to "hunt" as the variable vacuum signal causes the vacuum advance to seek. The problem is further compounded with a lean carb that falls off slightly during idle. As the engine stumbles, the vacuum drops sharply thus retarding the vacuum advance and deepening the stumble even more. A self reinforcing situation that ends in a stall.

As the ported vacuum connection is above the butterfly, it only provides vaccuum AFTER the carb has transitioned from the idle circuit to the main (much more predictable).

Don's recommendation is pretty standard and a great place to start.
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post #11 of 17 (permalink) Old Sep 2nd, 11, 11:19 AM
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Re: Engine won't idle with VA A/C on

Quote:
Originally Posted by Winch View Post
Are you using ported or manifold VA? I guess I need to do some reading and get the old timing light out. I thought I could rely on this shop that has always done good work on my newer cars but....
As with the 472 intake, I am using manifold vac, this would be the same as below the plates. But I dont think this is your only problem. Need to make sure your carb is tuned correctly . My dist is also recurved. My idle vac is about 10-11 hg. I run a 55 pv, with 70 /76 jets which is a little rich at 3500 Elev. I am on the money when I go to coastal areas at 2' .

Don
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post #12 of 17 (permalink) Old Sep 2nd, 11, 05:38 PM Thread Starter
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Re: Engine won't idle with VA A/C on

I just took it out and got on it for bit. It definately doesn't run now like it used to. When it winds out to higher rpms in first and especially second it starts misfiring but when I hit third it took off like a bat of hell which is how it used to run in every gear. It seemed like it was going to stay strong in 4th but on the stretch of road I was on I had to cut it off before I could let it wind out.

I need to learn how to tune it. I'll do some more reading. I've been working on getting rid of a vibration first.
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post #13 of 17 (permalink) Old Sep 2nd, 11, 10:30 PM
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Re: Engine won't idle with VA A/C on

If you are running pre pollution setup no eger etc, u must run manifold vac....sure u can use ported...but expect issues like burning out starter armitures and stuff like that...
Which is why Dodge, Ford , GM Austin, Damiler etc etc spent millions...(in to days money Billions of research and did so....
And Dont consider using a fast idle soleniod untill u KNOW (not assume) the timing /carb are dialed in as they are ment to be
If one patch fixes issues , like using ported when manifold should be used, and fast speed soleniods because tuning not dialed in...fully expwect other issues pop up and cost u far more further down the line.
OR simply put, do it once do it right, and just change the oil for the next 20+ yrs.

My Spelling is not incorrect...it is creative

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post #14 of 17 (permalink) Old Sep 3rd, 11, 11:14 AM
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Re: Engine won't idle with VA A/C on

I think using any kind of solenoid when using a VA comp. is a bandaid.
You have other issues me thinks, and using a step solenoid will mask the true issue.
The VA compressor (Sanden) is a baby.

I have a 350 with VA system, and I can hardly tell when the comp cycles on or off.

1969 RS/SS Vert

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post #15 of 17 (permalink) Old Sep 3rd, 11, 02:11 PM
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Re: Engine won't idle with VA A/C on

Quote:
I think using any kind of solenoid when using a VA comp. is a bandaid.
No not neccassry always....if some has a radical cam/ big carb, hi rise...or basically somethingh like a dedicated track engine in a street car, and darved, the bottom end becomes so iinefficient it doesnt have the HP to take on the extra load.....
It is then a step solenoid or similar device is used.....but a stock/ street strip does have enough and yes it definately indicates the carb /advance curves etc have not been dialed in correctly in the idle /fast idle rpm range

My Spelling is not incorrect...it is creative

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