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ant720

setting idle speed and timing

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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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Thanks Doctor. I have it set at 1000 rpm and 10* and it seems happy. Anything below 1000 it gets rough.

 

I understand what you're saying for total timing. Is that procedure a necessity or is it ok to just set timing at idle? 

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Do you drive the car/truck at idle????  Yes it is necessary for a happy motor!

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Doc510 knows what he is talking about.  He has been building Datsun engines for many years.  There are many Doc510 engines running down the streets of Arizona!

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should be about 800 RPM at Idle.  Something is not right when you have to idle at 1,000 to make it run okay. 

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^usually means too small of a primary jet with a weber.

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yep..captain sum tin wong.

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what I try to do is adjust the mixture as it will go high or low on the rpms then adjust the timming  to what it will run best at.

 

Napz motor do run at a lower timming BTDC.

 

I think your fine long at you not have the speed screw cranked all the way in meaning your bypassing the idle jet circuit.

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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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maybe you can adjust the speed screw out to get the idle down(maybe that's all that is needed.)

 

 

I wouldn't take apart a carb myself unless I have another ready incase one fucks up. Esp a stock carb. Far as I know they are Rubix Cubes waiting to explode

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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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I am pretty sure my 4wds tach is about 200 RPM

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I've got a laser tach reading off a reflective sticker on one of the pulleys. who knows how accurate it is though

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