Need Help With 1990 LS 400 Timing Belt (please)
05-04-13, 11:14 PM
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Need Help With 1990 LS 400 Timing Belt (please)
How do I find TDC on My 1990 LS 400 ? I know where piston 1 is and can see the top of the piston and all marks line up , but my Question is that when I look at this video on youtube the rotors on the distributor did not point to the number 1 piston , it looked 180 degrees off is that possible ??? Please Help And Thank You
05-05-13, 05:12 AM
#2
Since it is a four-stroke engine, the crankshaft must rotate twice for a complete cycle.
So, the distributor rotates at half the speed of the crankshaft (to make one revolution per cycle).
It sounds like you have identified the TDC at the end of the exhaust stroke, rather than the (correct) TDC at the end of the compression stroke. Therefore, continue rotating the engine - in the forward direction - until the crankshaft goes through 360 degrees more and the camshafts + distributor rotate through 180 degrees more. You will then be at the correct TDC.
Post again if you would like more detail.
So, the distributor rotates at half the speed of the crankshaft (to make one revolution per cycle).
It sounds like you have identified the TDC at the end of the exhaust stroke, rather than the (correct) TDC at the end of the compression stroke. Therefore, continue rotating the engine - in the forward direction - until the crankshaft goes through 360 degrees more and the camshafts + distributor rotate through 180 degrees more. You will then be at the correct TDC.
Post again if you would like more detail.
05-06-13, 12:17 AM
#3
Lexus Champion
you should also verify the timing mark on the crank pulley, TDC is the same as 0 degrees before TDC
by the way, make sure to always rotate the crankshaft clockwise (looking at the crank from front of car) and never the opposite direction
by the way, make sure to always rotate the crankshaft clockwise (looking at the crank from front of car) and never the opposite direction
Last edited by LScowboyLS; 05-06-13 at 12:23 AM.
05-07-13, 11:04 PM
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what would happen if i start this , or should i say i found tdc by going counter clock wise . i hope i didn't ruin my car . thanks for all the help
05-08-13, 04:08 AM
#5
Lexus Champion
there is never any need go counter-clockwise, just go another revolution clockwise to get to the same point - Toyota is very adamant about turning the crankshaft clockwise only, so I follow what they say, as their engineering skills surpass even mine and yamae's, even though we have had to correct their work from time to time. 
05-08-13, 08:09 AM
#6
Might as well put it back together and hope for the best. What I do to find TDC is pull the NO.1 plug, then use a long screw driver and lay it in the hole. Be careful, you don't want dirt or any other debris to fall in the hole, Slowly turn the crank bolt clock wise until the screw driver stops moving up. it may help to reinstall the balancer and lower cover so you can watch you marks. hope this helps.
05-08-13, 10:38 AM
#7
Since it is a four-stroke engine, the crankshaft must rotate twice for a complete cycle.
So, the distributor rotates at half the speed of the crankshaft (to make one revolution per cycle).
It sounds like you have identified the TDC at the end of the exhaust stroke, rather than the (correct) TDC at the end of the compression stroke. Therefore, continue rotating the engine - in the forward direction - until the crankshaft goes through 360 degrees more and the camshafts + distributor rotate through 180 degrees more. You will then be at the correct TDC.
Post again if you would like more detail.
So, the distributor rotates at half the speed of the crankshaft (to make one revolution per cycle).
It sounds like you have identified the TDC at the end of the exhaust stroke, rather than the (correct) TDC at the end of the compression stroke. Therefore, continue rotating the engine - in the forward direction - until the crankshaft goes through 360 degrees more and the camshafts + distributor rotate through 180 degrees more. You will then be at the correct TDC.
Post again if you would like more detail.
a little counter clockwise turning wouldn't hurt but how much did you move to get to TDC?
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