Idle Speed Varying? - Team Camaro Tech
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post #1 of 7 (permalink) Old Sep 26th, 14, 03:38 PM Thread Starter
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Brian
 
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Idle Speed Varying?

I have a 383 Stroker with MSD HEI... When I'm idling, the RPM will vary from 500 RPM to 700 RPM pretty consistently, like its on a cycle. Should I be worried (b/c I already am...)?
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post #2 of 7 (permalink) Old Sep 26th, 14, 03:49 PM
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Re: Idle Speed Varying?

Do you have the distributor vacuum hose hooked up to the right spot on the carb.
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post #3 of 7 (permalink) Old Sep 26th, 14, 03:58 PM Thread Starter
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Brian
 
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Re: Idle Speed Varying?

Yeah, think so... I've had it hooked up for +1 year but this just started in the last few months (I don't drive it a lot).
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post #4 of 7 (permalink) Old Sep 26th, 14, 05:43 PM
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Re: Idle Speed Varying?

Oh. Might check for vacuum leaks. And timing
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post #5 of 7 (permalink) Old Sep 26th, 14, 06:14 PM
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Anne
 
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Re: Idle Speed Varying?

Quote:
Originally Posted by Z28_302 View Post
I have a 383 Stroker with MSD HEI... When I'm idling, the RPM will vary from 500 RPM to 700 RPM pretty consistently, like its on a cycle. Should I be worried (b/c I already am...)?
Does your MSD distributor have a vacuum advance ?

How much vacuum does your engine have at idle ?

If you have a vacuum can, it may be "dithering in and out" at idle causing the engine to speed up and slow down.

Let us know what your setup is.

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Last edited by Lawrence454; Sep 26th, 14 at 06:24 PM.
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post #6 of 7 (permalink) Old Sep 26th, 14, 06:15 PM
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Mark
 
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Re: Idle Speed Varying?

Did you make any adjustments prior to the problem? Mine did that when I connected my B28 vacuum advance can because it shot my timing up past 50* at idle and the idle went crazy idling like a Pro Charger. I had to make a VA limiter plate for the B28 can to limit it to 8* at idle.

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post #7 of 7 (permalink) Old Sep 27th, 14, 04:52 PM
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Steps
 
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Re: Idle Speed Varying?

Quote:
I have a 383 Stroker with MSD HEI... When I'm idling, the RPM will vary from 500 RPM to 700 RPM pretty consistently, like its on a cycle. Should I be worried (b/c I already am...)?
No not worried , just inconveinant.
1 or 2 thngs
1/ The VA is not fully activated at the engine idle vaccuum...
The engine fires up on the intial advance, pulls a vaccuum , which pulls the VA, increasing the rpms... the carb is 'fixed' mixture on the idle circuit... the engine 'runs' out of fuel slows....vaccuum drops, VA goes back... and repeats
2/The counterweight springs (1 or both) are slightly light....the sperings should holsd the counter weights in till at least 200 to 300 rpms above the stable idle rpms.
If they do not.. like the VA.. they swing out after firing up, increase advance, increase rpms til the 'fixed mixture from the carb idle circuit 'runs' out... engine slows.

Note: a Non egr engine which I assume this is, runs VA on manifold vacuum with the VA being part of the idle advance (initial+VA) to give a stable idle, and easy fire up, low starter loads.

My Spelling is not incorrect...it is creative

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