High idle in park - Chevelle Tech
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post #1 of 13 (permalink) Old Mar 1st, 19, 10:27 AM Thread Starter
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High idle in park

‘98 350 block (880 casting)
Vortec heads from Scoggin Dickey .600 springs
4150 Holley
Lt4 Hotcam
.525 lift
279/287 duration @ .050
Stock 200r4 trans
‘85 Monte Carlo full weight

Idles in park at 2000rpm
Drops to 550 rpm when you put it in drive
How can I make this motor happier in park? I’ve been told it needs about a 3000 stall converter and it’ll be fixed. I’ve never had anything that needed a stall.

What’re your thoughts?
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post #2 of 13 (permalink) Old Mar 1st, 19, 11:11 AM Thread Starter
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Forgot to mention...I’ve adjusted the idle down when it’s in park, but when I put it in gear it dies. I’m a carb tuning novice!
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post #3 of 13 (permalink) Old Mar 1st, 19, 11:15 AM
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Re: High idle in park

The LT4 Hotcam is a byte of a little monster. I'd start by setting the Timing to Factory specs. Then adjust the Holley. You don't mention your Dizzy? Make sure it's working as advertised (vacuum hooked up to ported, etc.). Once you've got the Carb dialed in at Factory timing you can try bumping up the timing to where you get the performance you desire.

A 2400-ish stall converter should increase your driving pleasere, and help tame that cam at idle.
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post #4 of 13 (permalink) Old Mar 1st, 19, 12:14 PM Thread Starter
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What would be a baseline timing number? There’s not a factory spec for a Vortec engine as far as I know. You plug those distributors in and they set themselves.
I’m running an MSD HEI. Nothing fancy. It has a vacuum advance on it.
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post #5 of 13 (permalink) Old Mar 1st, 19, 1:01 PM
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Re: High idle in park

I would set the timing at 34* BTDC at whatever RPM the distributor stops advancing and note what the initial is at idle. Get the carb set and then connect the vacuum advance to manifold vacuum. Limit the vacuum advance so its around 50* at cruise rpm/vacuum.

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post #6 of 13 (permalink) Old Mar 1st, 19, 7:01 PM
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Re: High idle in park

Quote:
Originally Posted by 68malibeast View Post
What would be a baseline timing number? Thereís not a factory spec for a Vortec engine as far as I know. You plug those distributors in and they set themselves.
Iím running an MSD HEI. Nothing fancy. It has a vacuum advance on it.
Sorry, can't help with them fancy new fangled (post 1972) engines. Check this out: Installing and Setting a Vortec Distributor Correctly - GM Truck Central

Youtube has a 3 part series on Vortec Engine Distributors by Gary Linville that looked like it might be helpful.
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post #7 of 13 (permalink) Old Mar 1st, 19, 10:17 PM
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Re: High idle in park

Bruce, I don't think he's using that dist, it takes all the computer related parts for that system, I maybe wrong, but we'll see.

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post #8 of 13 (permalink) Old Mar 2nd, 19, 7:03 AM
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Re: High idle in park

First thing to do is check for a vacuum leak.
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post #9 of 13 (permalink) Old Mar 2nd, 19, 9:12 AM Thread Starter
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Quote:
Originally Posted by LeoP View Post
Bruce, I don't think he's using that dist, it takes all the computer related parts for that system, I maybe wrong, but we'll see.
Correct. Old school distributor. Very basic, non-computer controlled.
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post #10 of 13 (permalink) Old Mar 2nd, 19, 10:09 PM
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Re: High idle in park

12-14 degrees base timing is a place to start and 34-36 degrees at WOT at around 2500-3000 RPM, vacuum disconnected.
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post #11 of 13 (permalink) Old Mar 2nd, 19, 11:57 PM
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Re: High idle in park

It needs about a 2800-3000 stall converter. Your friends are correct. You'll also see a performance improvement as that cam starts pulling at a higher rpm than a stock cam. The cost is fuel mileage.

Your stock stall converter is too tight to satisfy your need for a low park idle AND a good in gear idle.

You can add an idle solenoid to bump up idle speed while in gear and that will kick out in park if you want both. The other option is a looser converter.

You can play with the timing and idle mixture to get the best results, but I don't think that will get you where you want to be by your description.
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post #12 of 13 (permalink) Old Mar 8th, 19, 5:32 PM
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Re: High idle in park

All this is without the vacuum advance hooked up and the hose plugged.
Adjust your idle speed down (screw on drivers/side of carb) as low as you can without it stalling in park then adjust your idle mixture adjustments (with a vacuum gauge attached hopefully) on the sides of the carb try to get it to idle smoothly to about 500-700 RPM then adjust your timing to about 10-18 base timing this should get it to idle better and a little faster.Then go back and re-adjust the mixture screws,if need be.
Be prepared to go back and adjust everything again if your starting points were way off.You're looking for about 750 to 850 in drive,as a starting point.
That idle speed screw on the D/S can cause more trouble than you think.Yes cranking it down keeps it running but at the expense of the carb idling correctly.If the engine is idling too fast the timing gets screwed up because its already advancing with the distributors centrifigal advance. Thats why adjusting the carb idle mixture and idle speed is important.
There are plenty of carb adjustment tutorals here on TC.Also Holley carbs has some more advanced tutorals to go by.
When all is done and its idling properly then you can decide between manifold vacuum advance or ported vacuum advance.Each has its own merits and either one can be right for your particuler combination.
Forgot to mention you may also have to adjust the float levels in your carb if they're way off.
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post #13 of 13 (permalink) Old Mar 8th, 19, 5:50 PM
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Re: High idle in park

Quote:
Originally Posted by 68malibeast View Post
Forgot to mention...Iíve adjusted the idle down when itís in park, but when I put it in gear it dies. Iím a carb tuning novice!
this is the reason I posted the above information.If the above method doesn't get it idling better you may have something else screwing it up.Either way make sure there aren't any large vacuum leaks before you do anything else.Like I said idling that fast (2000?)puts your centrifugal advance all in almost.Not good.

John
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406 SBC M21 3.31 12 bolt
"Quality is always remembered,long after the price is forgotten"
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