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Discussion Starter #1
Hello,

Well, I'm trying to fine tune my holley 4160 (600cfm) and I have ended up with my idle in Park as 1,800 RPM (which is screaming) but then when I drop it in to gear in goes down to 900 RPM. Why the big change?

I guess my goal for both is 900 RPM in Park and in gear....any thoughts?

Thanks, Greg.
 

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What car, what tranny? C-4? Check all your vacuum hoses for possible leaks. Check around the intake for a vacuum leak.
 

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I guess my goal for both is 900 RPM in Park and in gear....any thoughts?
No street motor should idle at 1800RPM. You should either retard your timing, find the vacuum leak, or buy a new tach. ;)
 

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Or turn the idle screw down. You should look for a smooth idle at 750 in park, and 500 in gear, with the choke disengaged. If you're testing this when the engine is cold, you're adding another variable, the fast-idle cam.
 

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Is this a stock engine? It sounds like you have a healthy aftermarket camshaft and a stock torque converter. If this is the cas you need the proper stall converter but without more information it is hard to tell.
 

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Discussion Starter #6
The only other info I have is that I opened the secondaries a bit to try and get a stronger idle, but that should be the same in park and in gear. Unless.....Because I had a faster idle with the secondaries open, I kept backing off the curb idle screw to lower the idle speed and now when I put it in gear, it almost wants to stall.

So...is it safe to say that the problem would be solved if I close my secondaries a bit and crank my curb idle screw up again (which I was trying to avoid) and maybe my idles would even out? Or is there a bigger problem here?

Greg.
 

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I would definitely put the secondary throtlle blades back where they belong as there should be no need to mess with them to get a good idle. You still haven't told us what kind of engine this is and how many mods you have made.
 

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An automatic transmission will ALWAYS have a faster idle in park/nuetral than when in gear. Your carb should NOT be idling with the secondaries opening ... put them back to where they were and don't go bumping the idle speed up to compensate!

You should set your idle speed in drive (block the wheels, set the parking brake and have a helper stand on the brake while you're setting the idle speed). You're looking for the best idle at the lowest speed. Until you give us the engine specs, though, there's no way to tell you what that will be, although it should be somewhere between 600 and 800 rpms (800 means you've got a radical cam).

At 1800 rpms, you're WAY out of the idle circuit of the carb and on up into the cruise mode.
 

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Sounds like you have a vacum leak or a warped base plate on the carb alowing the butterflys to open up and cause that high idle.
 
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