Losing idle at traffic light with A/C on.

Cupid

Member

Mar 30, 2006

162

0

16

Apr 29, 2009

#1

• Apr 29, 2009

• #1

Okay,
I'm in the tune phase of my rebuild. I went with the vintage air a/c. With the A/C off I idle around 800. However, with the A/C on, I loose idle tremeduously....to the point of stalling the motor.

No problems with driving around. It just dies occasionally at the light. Any ideas?

If I run the idle up w/ the A/C on, it climbs too high when I turn the A/C off....around 12-1400.

How high can I/should I idle? Worried about fouling plugs, flooding, etc. Somebody metioned an idle solenoid. Anybody use that?

Engine Info:
Newly built

351C bored .030
Eddy Aluminum Heads
Harland Roller Rockers
Eddy RPM Air Gap Intake
Eddy 1407 Manual Choke Carb 750cfm
Cam: Eddy 7168
RPM Range 1500-6500

234/244 @ .50 lift - 312/322 Advertised
.562/.568 exh lift

 

Cupid

Member

Mar 30, 2006

162

0

16

Apr 29, 2009

#2

• Apr 29, 2009

• #2

Found this for $100. *sigh* Anybody have a less expensive option. If not, no biggie. You hardcore guys probably don't run A/C!

Edelbrock 8059 - Edelbrock Intake Manifold Installation Accessories

 

2

2+2GT

10 Year Member

Apr 25, 2009

3,333

10

79

Southeastern Pennsylvania

Apr 29, 2009

#3

• Apr 29, 2009

• #3

Whats' your vacuum at idle?

 

Cupid

Member

Mar 30, 2006

162

0

16

Apr 29, 2009

#4

• Apr 29, 2009

• #4

My vacuum is appox. 13-14 @ 800 RPM

 

SadbutTrue

Founding Member

May 1, 2002

2,390

4

49

Granada Hills, California

Apr 29, 2009

#5

• Apr 29, 2009

• #5

Cupid said:

Found this for $100. *sigh* Anybody have a less expensive option. If not, no biggie. You hardcore guys probably don't run A/C!

Edelbrock 8059 - Edelbrock Intake Manifold Installation Accessories

Click to expand...

That vacuum looks about right based on the cam. Mine makes a little more at idle (and isn't tuned right) but your cam has more lift and a bit more duration.. the RPM cam is pretty aggressive.

What does vintage auto say you should lose RPM-wise at idle when you turn the A/C on? With any A/C, you will lose some.

You could simpy try to finish tuning... you might find that it won't die as easily if the timing, idle mixture, etc are set right (assuming they're not quite there at the moment).

To be honest, unless you live in the deep south or in Death Valley/Pheonix, its generally best to just roll down the window around town (more fuel efficient plus having your arm in the door/window way is kinda part of driving a classic ). On the freeway it actually saves you a little gas to use the A/C versus rolling the windows down.

 

2

2+2GT

10 Year Member

Apr 25, 2009

3,333

10

79

Southeastern Pennsylvania

Apr 29, 2009

#6

• Apr 29, 2009

• #6

Cupid said:

Somebody metioned an idle solenoid. Anybody use that?

Click to expand...

Ford did, quite a bit, on a lot of cars.

 

Cupid

Member

Mar 30, 2006

162

0

16

Apr 29, 2009

#7

• Apr 29, 2009

• #7

2+2GT said:

Ford did, quite a bit, on a lot of cars.

Click to expand...

The search is on then!

 

2nd Mustang

Founding Member

Feb 24, 2002

2,488

0

46

Southern California

Apr 30, 2009

#8

• Apr 30, 2009

• #8

I had a Crapmaro that did that. It was a time in my life when money was scarce, so didn't turn on the AC until I got on the freeway or didn't have too many traffic lights.

It turned out to be a relay according to the AC repair shop.

 

Bullitt

Packin' Heat

Founding Member

Jan 13, 2000

2,743

0

47

Houston, TX

Apr 30, 2009

#9

• Apr 30, 2009

• #9

Ford put those idle solenoids on most early 80s carbed engines. You can probably find one and rig it up.

Edelbrock makes one too that's a direct fit. Believe they call it an "idle compensator" which is the link you posted earlier. Had one with my Edelbrock and it solves the problem you describe.

I would not tune your carb to idle high just to not die with the AC on. Fix it properly with a solenoid!