Warming up 396 - Team Camaro Tech
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post #1 of 12 (permalink) Old Feb 3rd, 08, 10:06 AM Thread Starter
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J
 
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Warming up 396

My '69 396 takes a good 3-5 mins to warm up so it can idle. Upon starting the choke is on and the car will idle at approx 1500 - 2000 rpms. If I tap the pedal before a good 3 - 5 mins the choke will dis-engage and rpms will drop to idle range but will die. Is this typicaL for big block cars?

If I allow enough warming time and tap the pedal the rpms will drop and the car typically will idle as it should.

Right after start up (when warmed up) my car will idle at approx 800 rpms. While driving for a while I noticed that the idle moves up a little to 1000 rpms or slightly above. If I sat at a light long engoug it appeared that the idle would slowly creep back down to 800 - 900 rpms. Is the normal?
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post #2 of 12 (permalink) Old Feb 3rd, 08, 10:33 AM
 
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Re: Warming up 396

My small block with edelbrock 750 ( no choke ) acts the same way...the more it warms up the lower the idle gets....
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post #3 of 12 (permalink) Old Feb 3rd, 08, 11:04 AM
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Re: Warming up 396

I had one that would do that at idle when warm and it ended up being a broken spring on the dist weight under rotor. Timing was moving at idle.

Dennis
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70 Nova SS 396, 4sp, 3:55 12 bolt
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post #4 of 12 (permalink) Old Feb 3rd, 08, 12:26 PM
 
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Re: Warming up 396

thats a good point...going to have to take a look at distributor....thanks
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post #5 of 12 (permalink) Old Feb 3rd, 08, 12:28 PM
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Re: Warming up 396

Normal? It's a 69 Camaro 396. Nope, no such thing as normal.

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post #6 of 12 (permalink) Old Feb 3rd, 08, 12:38 PM
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Re: Warming up 396

The choke disengaging before warm shouldn't happen either. If it's thermostatic, it needs adjusted or the coil needs replaced.

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post #7 of 12 (permalink) Old Feb 3rd, 08, 12:49 PM
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Re: Warming up 396

Most likely some basic tune issues going on if a mild engine won't idle after a couple minutes. I'm sympathetic with allowing the tune to decay on a street car. As long as it doesn't begin to do embarrassing things. A carb won't track ambient changes like a newer car will. I would play with the idle jets and check timing first. A little fatter and a little more advance. Winter you are getting cold/dense air so the combustion is leaned out AND more heat is consumed by the inlet air... so the flame front propagates slower. The colder the inlet air the more advance an engine will take before the dreaded risko'dets begin.

Tim Smith
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post #8 of 12 (permalink) Old Feb 3rd, 08, 02:11 PM
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Re: Warming up 396

Like Eric says, check the choke for correct operation first.

alan
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post #9 of 12 (permalink) Old Feb 3rd, 08, 03:55 PM
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Re: Warming up 396

My 396 has no choke setup on the carb so I have to babysit the carb for the first 1 or 2 minutes to keep it running. After a minute or 2 it will idle by itself. After it warms up the idle will climb to 700-800 rpm's.

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post #10 of 12 (permalink) Old Feb 7th, 08, 11:47 AM
 
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Re: Warming up 396

check if your throttle is sticking a little bit. same thing happen to me when i was at a light. carb was just stuck a little bit.
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post #11 of 12 (permalink) Old Feb 8th, 08, 07:45 AM
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Re: Warming up 396

I want to no more about your engine set up. Tell us about your engine.
Tell us about your driveline. Carb size?
I have a 427 engine with dual 600 on it. I set the front carb on fast idle with the choke plate remove. Takes 2 mins. and down the road i go. Have headers and 3 inch exhaust with L78 cam 4 speed.
I tried a test years ago with a 350 11:1 engine. I put a 600 holley then a 650 then a 700 then a 750 then a 780 and i could not believe the difference in the car idle and sound of car that changed. Also the thottle response. At that point i was into carb repairing. I just no at that time the best all around turned out to be the 750 carb for idle and response.
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post #12 of 12 (permalink) Old Feb 8th, 08, 08:03 AM
 
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Re: Warming up 396

As others have said, this sounds like something needs adjusting, or the choke isn't working right (you didn't mention your carb, so not sure what you have). I've got a '68 with a 396, and it had an old Edelbrock carb on it when I bought it. It had an electric choke that would never work correctly. It'd take several minutes before the car would idle on its own. I knew the carb had other problems though, so recently finally replaced it with a Holley Street Avenger 770... also with electric choke. And now things are perfect. The choke now works like it's supposed to... stays active and keeps the idle high while cold, slowly stepping the idle down to "normal idle" as the car warms up. No issues at all now with the car having problems staying running, and it's incredibly difficult to rev high enough to force the choke to step down prematurely (and even if it does, your next tap on the gas pedal puts it right again).

~Bob
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