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hod rodder
Joined: 04 Oct 2001
Posts: 15499
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 Posted: Mon Sep 24, 2001 9:21 am Post subject: timing --(Woz) |
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i was wondering if anyone out there could clear something up for me about how timing works...
how many degrees between each cylender spark is there? if your measuring from the distributer theres 90, but in fact the engine has actually travelled 180 degrees. when people say "ive set my timing at 12 degrees" does that mean 12 degrees after the pistons have started their decent via the distributer or the crankshaft?
just curious... |
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hod rodder
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| Posted: Mon Sep 24, 2001 9:54 am Post subject: Re: timing --(Paul) |
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Timing is generally measured BTDC. Before Top Dead Centre. Top Dead Centre is when the piston is at the absolute top, so the crank has pushed it up as far as it's going to go). Ok, thats TDC. BTDC is how many degrees the crankshaft has to turn before it's at top dead centre. So, if the crankshaft was "horizontal on that cylinder", then it would be 90degrees BTDC. Depending on the car, your timing has to be set differently. Not acutally sure on Gem's, but holden 6's are around 5 - 8 BTDC, 308's are basically the same..perhaps a little more advanced (more degrees btdc). Rotaries have leading and trailing spark plugs, so it gets even more confusing to describe, but thats a whole different story.
If your timing is set to 8 degrees BTDC, the spark plug will fire when the crankshaft is 8 degrees before it's "top of travel".
I hope thats what you were asking? I've been at the pub half the night...so if anyone can describe it better, be my guest....
Paul
Never late in a 308 |
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hod rodder
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| Posted: Mon Sep 24, 2001 11:57 pm Post subject: Re: timing --(Woz) |
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thanks, thats exactly what i needed to know  |
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hod rodder
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| Posted: Tue Sep 25, 2001 3:36 am Post subject: Re: timing --(Ben Wight) |
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What paul said!
Incase you are also referring to the marks on the mechanical advance plate within the dizzy, then they refer to distributor degrees, which is half that of the crank. There is a 12 and a 14 slot. Mine was set at 12 when i openned it up. It should be on 14 if using 8 degrees of static advance.
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