car idles 1300 in park 600 in drive why? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-19-2012, 08:06 PM
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car idles 1300 in park 600 in drive why?

chevy 350, with 350c trans car idles at 1300 in park and fall down to 600 in park, ive tryed the timing at 2 degrees all the way up to 16 degrees made no difference, searched for vacum leaks couldn't find any, any suggestions?

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Old 03-19-2012, 09:36 PM
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Yep, lets time it like this:
With vacuum advance disconnected and plugged, set the base timing to 12 degrees before top dead center. Lock distributor. Reconnect vacuum advance. Connect it to a manifold vacuum source, one that pulls vacuum full time including idle. Now, recheck timing, it should be 18 to 24 degrees before top dead center. Now, idle it down on the idle adjustment speed to 750 RPM.
If this doesn't work then repost.
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Old 03-19-2012, 10:38 PM
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Converter is too tight.




.
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Old 03-20-2012, 06:43 AM
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Quote:
Originally Posted by 23 tbucket
chevy 350, with 350c trans car idles at 1300 in park and fall down to 600 in park, ive tryed the timing at 2 degrees all the way up to 16 degrees made no difference, searched for vacum leaks couldn't find any, any suggestions?
Also check to see that the vacuum at idle in gear isn't so low that the power enrichment circuit of the carb (step up springs/power piston/power valve) is coming in.

It's very important to give as much info as you can about the vehicle and engine. Choose any/all that apply from the list under Info needed to help diagnose a problem.
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Old 03-20-2012, 10:57 AM
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Set the timing w vac adv disconnecd, at 16 BTDC, set the idle for around 750rpm. Then Connect the vacuum advance to ported vacuum.

Get an adjustable vac advance .. The vacuum advance is changing the timing when droped in gear. The mechanical advance may also be dropping off when going in gear also. Both are too reaactive to the manifold vacuum fluctuation at near idle when dropping in gear.

The cure is to recurve the distributor advance curve for more inital base timing, a slower, more stable advance curve ( stiffer springs) that does not exceed 36deg at max advance.
And then using a adjustable vac advance and adjust so that is not all pegged at idle.

A big cam will need a high stall converter and poer valve swap as well as the distributor recurve. The bigger the cam duration the more inital timing at idle.

The timing must not change when dropping it in gear from neutral.

What cam?
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Old 03-20-2012, 05:26 PM
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all right guys I've tryed every timing senerio possible, I'm sure there's no vacum leaks, from picking everyones brain I've come up with, the fact that the turbo350c is a lockup style transmission, and I have not hooked the wiring up for the lock up does anyone beleave this could be the problem?
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Old 03-20-2012, 05:28 PM
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also its a very mild 350 motor,bored 30 over, 9:1 compression, performer cam and intake, mechanical fuel pump, summit 600 carb, gm hei distributer
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Old 03-20-2012, 05:33 PM
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o one more thing it has zoomie headers
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Old 03-20-2012, 05:39 PM
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I doubt the torque converter would be the problem,when they get worn they get looser.If they are locked it would stall.
I agree with F Bird here as far as an advance problem.
Check to see if the timing falls off when it goes into gear. Have someone start it while you watch the timing, have the vac advance unplugged.
When it is dropped into gear if the mechanical weights are sticking or the springs are weak you will see the timing fall off(retard)
Same for the vacuum advance,check it for vacuum at base idle in gear, if it has some plug it in while watching the timing, or unplug it while idling hi in park to see if it drops. This may help narrow it down a bit.
Vacuum brake boosters can be the source of hidden (and quiet) vacuum leaks.
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Old 03-20-2012, 05:44 PM
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Do you have a tach, and what carb you got?
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Old 03-20-2012, 06:56 PM
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can't add much to the other replies on timing, but for sure ain't the lock up converter. without that connected, it's just like a standard t-350
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Old 03-20-2012, 07:05 PM
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what if the converter is stuck in the locked position?
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Old 03-20-2012, 07:06 PM
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it a summit brand carb there new, the car really runs out great down the road its just this high idle in park thats driving me nuts, also ther is no brake booster full manual brakes
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Old 03-20-2012, 07:09 PM
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yes I do have a tach
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Old 03-20-2012, 07:10 PM
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Quote:
Originally Posted by 23 tbucket
what if the converter is stuck in the locked position?
Then it would stall out as a standard vehicle would when the clutch isnt depressed while coming to a stop.It wouldnt make a difference in park or neutral though.In drive it should stall.
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