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Old 01-30-2008, 10:25 AM   #1
tx71smallblock
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High idle speed

My truck is running fine but it idels almost at 1200 rpm. the electric choke is not hooked up and the timing is almost at 18* btdc. whats going on?
really need some help with this
thanks ahead of time
cody
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Old 01-30-2008, 11:40 AM   #2
dadsbrew
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Re: High idel speed

check for vacuum leaks, either around the base of the carb or any vacuum lines, possibly internal vacuum leak in the carb. 18 degree's is advanced alot is the advance still hooked up when your setting the timing.
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Old 01-30-2008, 12:58 PM   #3
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Re: High idel speed

Turn down the idle speed?
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Old 01-30-2008, 01:51 PM   #4
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Re: High idel speed

I had a similar problem and fixed it by putting on a heavier return spring.

Danny
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Old 01-30-2008, 02:05 PM   #5
dadsbrew
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Re: High idle speed

yes, I would definetly return the throttle by hand to see if it can come back farther, if it does use a heavier spring, good idea shyguy
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Old 02-01-2008, 08:30 AM   #6
tx71smallblock
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Re: High idle speed

Has after market heavy spring, brand new carb, idel screw is backed all the way out
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Old 02-01-2008, 11:52 AM   #7
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Re: High idle speed

Your secondaries are partially open could be bent rod or just dirty or out of adjustment try to manually close them or look down in the carb to see if one of the screws has come off the butterflies. You should also check the choke cam to make sure it is not holding the throttle open
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Old 02-01-2008, 12:40 PM   #8
Kager67
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Re: High idle speed

Something you could try is to hook up the choke and turn the choke housing a quarter turn counterclockwise (lean). This should make sure the choke isn't part of the problem. My 72 did the same thing and this fixed it.


Kage
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Old 02-01-2008, 12:59 PM   #9
68gmsee
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Re: High idle speed

Quote:
Originally Posted by tx71smallblock View Post
Has after market heavy spring, brand new carb, idel screw is backed all the way out
Has it run normal before or is this problem since the carb install?

I would remove the carb and check to make sure that butterfly closes almost shut when at rest. Should have just a small clearance.

If all the mechanicals check out, then possible vacuum leak. Don't overlook cracked hoses or possible transmission modulator if auto.
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Old 02-05-2008, 10:56 AM   #10
tx71smallblock
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Re: High idle speed

ok fixed the high idel, the choke cam was holding the throttle open. but now i have a timing question, is the listed 8* btdc before or after you hook up the vacuum advance back up? should i be ideling at 8 with everything buttoned up? or ideling at 8 with the vacuum pluged and then it jump to 10 or 12 with it connected?
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Old 02-05-2008, 12:41 PM   #11
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Re: High idle speed

8* base timing, so with vac advance disabled.
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Old 02-06-2008, 09:46 AM   #12
tx71smallblock
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Re: High idle speed

thanks cruiserman, is that what most of you are running? with what i put on it should i run somthing different?
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