# Wants to Stall When Stopping



## peahrens (Jun 7, 2010)

Hi all. This is about my '66 GTO w/3 Rochester 2Bbls, manual trans, no A/C. Crane cam is a bit hotter than stock. In the first 250 miles since cam replacement, etc, I've managed to put in Pertronix II w/coil, get the valvetrain adjusted ok with locking rocker nuts and eliminated the slight valve cover oil leak using the cork/rubber gaskets. 

Now that I'm taking it on spins, it wants to stall after warmed up when slowing for a red light. Before it gets to steady temp it runs on fast idle, but when at temp, while coasting to a red light with the brakes on it tends to drop rpms to the stall point once when the clutch is depressed. If I goose the gas a bit (need 3 feet for the pedals) it will keep going. The rpm's are probably at 600-700 (on tach) if I get it to steady out. Is this likely a idle /mixture adjustment that needs fine tuning to keep the rpms from dropping so far? Or another problem? Should I set idle a bit higher than the 600 rpm per the manual? Suggestions welcome.


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## likethat (Oct 5, 2007)

I like 750 to 800 on my cars. Does the car idle well with out pushing the brake and when you do press it does it always want to stall the car?

You might have a leaky brake booster or line if your car has one. I would up the idle rpm on full warmed engine first. Recheck for vacuum leaks.


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## jetstang (Nov 5, 2008)

Just readjust the idle and needles when the car is warmed up, you might have it leaned out too much. Carbs are finicky and you may need to adjust it a few times before you find the sweet spot. I wouldn't worry about having it at 600 RPMs, that's really low, 750 or 800 is fine.


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## peahrens (Jun 7, 2010)

No power brakes, so that's not a complication. 

Last week, I tried the adjustment process for the Rochester 2Bbl, and took it for a spin. It died at the 2nd stop sign, and wouldn't turn over. I assumed the worst possibilities...my new Pertronix distributior stuff had failed, I had messed up something else, etc. I called a shop that works on old cars...they had no room to take it. Towed to the house ($50 for 3/4 mile). I changed my insurance last week to Haggerty, and opted out of the $29 towing option, so I'm $31 behind! 

The good news...the battery had died a natural death at 4 or so years...a new one got me in business. Today I took it out after adjusting...it still wanted to die at stops a bit, so I again did the old trial and error adjustments...this time starting at 1-1/2 turns out on the mixture screws, etc. After a few adjustments and trial runs, it makes it thru stops ok at 800 rpm warm idle. It may be a bit rich or lean, but it works, for now. I have trouble discerning when it may get too rich, even thought the rpm seems to be increasing as I back the screws out. I think I'm in the ballpark, but not at optimum.

A few lessons for me here...I need to enjoy the challenges more than get frustrated by them, and not always assume the worst. Plus, be persistent. 

Again, those that advise on these forums are most appeciated...there's a wealth of info readily available that was not the case 20 yrs ago!


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## jetstang (Nov 5, 2008)

To tune the carb, turn the screws in til it stumbles, then back it out 1.5 turn on both needles. Redo them again. This should get you a good tune. Adjust the idle speed after every tune.


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## likethat (Oct 5, 2007)

I like to hook up a vacuum gauge and an rpm gauge and tune till I get the most vacuum I can at 750 or 800 rpm. Then check it with the air cleaner on.

I like my idle on an automatic to just barely pull the car in gear as long as it is with in the 750 to 800 range. As for a manual I like it to be that when I let the clutch go slowly with out the gas peddle that it starts to move the car and I can feather the clutch so it will not stall.


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## dimitri (Feb 13, 2009)

On a fresh motor or cam I never run the idle below 1000 rpm for the first 500 - 600 miles.


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## geeteeohguy (Feb 2, 2008)

All good advice. With a "hot" cam, you need more than 600 rpm at idle. My '65 389 barely idles at 900 rpm in neutral. Jetstang's carb adjust method works. I always hold my body to the car when adjusting the mixture, and after I lean out one side till it runs rough, I go ever so slightly counterclockwise until it smooths out. Then do the other side.


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