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setting idle speed and timing


ant720

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I'll start by saying I'm a total novice. Details:

 

I'm trying to set the idle speed and timing to spec on a z24 with a weber. Hood sticker says 800rpm and 3* BTDC.

 

Before adjusting, the idle was around 1200 rpm and it ran pretty smooth, not sure what the timing was. 

 

When I set everything to spec it runs a bit rough and sounds like it's misfiring (I'm guessing, I don't know what that sounds like...)

 

It seems like it wants about 1000rpm idle and 5 or even 10* of timing.

 

Any ideas? normal? Am I doing something wrong?

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Well I just found this after 1 second of googling. I'm not crazy. Will give this a try.

 

"Set the Timing...Generally speaking you need a little more advance with a Weber than with the stock carb. A good place to start for most cars with Webers on pump gas is 12-14 Degrees advance at 1000 RPM idle and 36 Degrees total advance by 3000 RPM...This is not cast in stone and you need to make sure your car does not Detonate at these setting. If you get any detonation then you need to back off the timing..."

 

Follow up: how does one measure total advance?

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Well I just found this after 1 second of googling. I'm not crazy. Will give this a try.

 

"Set the Timing...Generally speaking you need a little more advance with a Weber than with the stock carb. A good place to start for most cars with Webers on pump gas is 12-14 Degrees advance at 1000 RPM idle and 36 Degrees total advance by 3000 RPM...This is not cast in stone and you need to make sure your car does not Detonate at these setting. If you get any detonation then you need to back off the timing..."

 

Follow up: how does one measure total advance?

"Webers" usually means the Side Draft DCOE version for that timing... Try 10* - 12* BTDC at idle.. Idle speed 800-900 RPM, the motor will tell you what it likes.   TOTAL TIMING you need an advancing (adjustable) timing light.  Warm up the motor, set the timing light to 34-36*, increase the engine speed to 2,800-3,000 RPM,  turn the distributor until the (0)/TDC marks on the pulley and timing plate are pointing at each other, Lock the dist down a drive it.  You may have to adjust the idle speed after this. Make sure you under stand what you are doing before doing it.  The original idle timing setting may not be the same,, leave it alone, you don't drive it at 900 RPM anyway.

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I've got an adjustable timing light ordered. I will see if I can get a lower idle after I set the total timing. If not, I'll pull the carb off and see what's in it. 

 

So I'm looking for ~800 rpm idle and 34-36* total timing?

 

And the vac advance line is hooked up when I'm setting total timing?

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Everyone is taking for granted the 30+ year old tac is correct.  I can change tacs in my 86 720 king cab and very the idle speed 400 rpm just by changing tacs.  These old tacs are a guide and I do believe that 1 in five are correct rpms.

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