20B pulley and timing?
07-09-03, 02:29 PM
#26
Lives on the Forum
Originally posted by Jeff20B
Ted, sorry for the all the questions coming up, but my FC pulley has a yellow mark at ?? degrees and a red mark at 15 degrees after the yellow mark, which gives it 15 degrees of split. This is measured as 15mm with a cloth tape measure. Is this an accurate measurement method?
Did you mean 5 BTDC? If not, are you saying that the 20B pulley's L mark is actually at 0 degrees? It is advanced 5 degrees compared to the FC pulley. Is my pulley unique or somthing? Or are they all like that?
Ted, sorry for the all the questions coming up, but my FC pulley has a yellow mark at ?? degrees and a red mark at 15 degrees after the yellow mark, which gives it 15 degrees of split. This is measured as 15mm with a cloth tape measure. Is this an accurate measurement method?
Did you mean 5 BTDC? If not, are you saying that the 20B pulley's L mark is actually at 0 degrees? It is advanced 5 degrees compared to the FC pulley. Is my pulley unique or somthing? Or are they all like that?
FC is marked yellow = 5ATDC and red = 20ATDC.  It's actually *after* TDC and not *before*.  The split (at idle) is 15-degrees (i.e. 20 - 5 = 15).  This is verified in the Mazda FSM.
-Ted
07-09-03, 02:31 PM
#27
Lives on the Forum
Originally posted by Jeff20B
Thanks for the info. It will come in very handy to find 0BTDC or 0ATDC or whatever they call it.
Thanks for the info. It will come in very handy to find 0BTDC or 0ATDC or whatever they call it.
-Ted
07-09-03, 02:46 PM
#28
That makes lots more sense. Thankyou.
Ok, so the 20B has the same timing as an FC. The only difference is where the four mounting holes in the pulley are. All I've got to do is align the 20B pulley on the hub with the timing pin in the front cover. Then since I don't feel like messing with the mathematics to measure 5º of advance (to get to "TDC"), on such a large pulley, I'll just throw the FC pulley on there, mark it with a sharpie or whatever, measure 5mm or degrees of advance, mark it again with a file and rotate the E shaft counterclockwise untill it lines up. Then I'll have TDC for NA use. I'll double check the rotor compression bathtub location through the plug holes before I make any permanent marks of course.
I'm so glad I waited to mark the pulley.
Ok, so the 20B has the same timing as an FC. The only difference is where the four mounting holes in the pulley are. All I've got to do is align the 20B pulley on the hub with the timing pin in the front cover. Then since I don't feel like messing with the mathematics to measure 5º of advance (to get to "TDC"), on such a large pulley, I'll just throw the FC pulley on there, mark it with a sharpie or whatever, measure 5mm or degrees
of advance, mark it again with a file and rotate the E shaft counterclockwise untill it lines up. Then I'll have TDC for NA use. I'll double check the rotor compression bathtub location through the plug holes before I make any permanent marks of course.I'm so glad I waited to mark the pulley.
07-19-03, 06:21 PM
#29
Originally posted by rotaspec
According to the emissions plate in the Cosmo's engine bay, the timing is 5deg and 20deg ATDC.
Gary
According to the emissions plate in the Cosmo's engine bay, the timing is 5deg and 20deg ATDC.
Gary
The 1st gen 12a motor was at 0deg and 20deg ATDC.
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