Car wont idle down after driven - Team Camaro Tech
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post #1 of 10 (permalink) Old Jul 31st, 02, 03:03 PM Thread Starter
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I have a fresh 350 with an edelbrock perf rpm cam and 750edel carb. The carb was untouched from previous engine along with the distributor and heads but everything else is new.
My ? is, when I start the car and just sit the car idles good, and the temp stays cool. After I drive it for abit the temp becomes harder to control and the car never idles back down when stopped.
I have messed with the timing many-a-time. It's only helped a bit. I'm thinking since the heads are crappy irons and I'm running 10:1 that somehow when the car is warm there is some kinda of detonation going on to keep it from idling down. I don't hear anything though, and the car runs strong?
any help would be great.
jeff
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post #2 of 10 (permalink) Old Jul 31st, 02, 04:58 PM
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Me thinks it's too lean! Set timing first, then use a vacuum gauge to set the idle mixture screws. Do not have the rpm above 800 for this or you run the risk of the primaries being involved. Reset mechanical idle as you adjust mixture.

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post #3 of 10 (permalink) Old Jul 31st, 02, 05:21 PM
 
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sound like possibly you have a vacum leak somewhere,to check this take a rag and cover the carb throat ,if the engine dies you don't have any problems

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post #4 of 10 (permalink) Old Aug 2nd, 02, 07:36 AM Thread Starter
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There are no vacuum leaks (it did die). Also I have 13" of mercury at 800rpm. As I adjusted the idle screws, a slight ticking noise coming from #2 cylinder got louder. I still can't figure out what it is. Might be valves. Would these to events correspond (carb adjustment)?
jeff
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post #5 of 10 (permalink) Old Aug 2nd, 02, 11:19 AM
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is the fast idle cam or choke not disengaging? i know it has a nice low idle when cold, but if the choke and/or fast idle isn't coming off, that will lead to a waaay fast idle when hot. my Nova did this a couple weeks ago when i drove it for the first time in a month. the humididty in the shop had caused some corrosion on the choke linkage, and it got sticky. had a 1200 idle when cold, which went up past 2300 when hot. scary. a little spray lube and wiggling it around a bit fixed it real nice.

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post #6 of 10 (permalink) Old Aug 3rd, 02, 06:02 AM Thread Starter
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I'll check that today. Also though, here is what gets me, after the car has been driven, and I go to stop the rpms climb. Seems like more fuel is entering the system or something. I have manual drum brakes so I don't see how they would be related. During braking the rpm can rise 300-600rpm??? Could this still be a vacuum problem?
urrgggg...
thanks jeff
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post #7 of 10 (permalink) Old Aug 4th, 02, 09:45 PM
 
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Vacuum leak / porous casting on the carb somewhere, allowing air to leak in when braking moves gasoline away from area where casting is bad??? I hear that some holleys are bad (quality control problems) for porosity. Also the fact that when it warms up the problem worsens seems to act like a vacuum leak/expansion problem on a seal or in the carb thats now hot.
Just grasping - hope this helps
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post #8 of 10 (permalink) Old Aug 6th, 02, 05:40 PM Thread Starter
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Here is another guess about what I think might be happening...
I am running the old cylinder heads off my 327 (for now) and the are obviously iron. Now, my CR is 10:1 +/- 0.2
I have read on here that running iron heads will cause the octane requirement to go way up if CR is over 9.5:1. Could this be the problem? Like I said before, the fast idle only tends to occur after street driving and it gets real warm.
I plan on getting edelbrock heads but I don't have the $$$ yet so they'll have to wait.
thanks again,
jeff
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post #9 of 10 (permalink) Old Aug 7th, 02, 03:02 PM
 
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Have you tried changing to a colder plug
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post #10 of 10 (permalink) Old Aug 10th, 02, 05:19 PM Thread Starter
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what brand and model plug would you recommend?
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