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IHateHacks · 04-12-2007, 03:36 PM

Ok you asked for it.

The crank pulley is keyed to the crank on the 7M with a woodruff key, so whenever the notch on the crank pulley is lined up with the 0 degree mark on the lower timing belt cover, the No.1 piston is at TDC. NOW, there are 2 TDC's on a 4 stroke engine, one on the exhaust stroke and one on the compression stroke. The TDC you need to install the CPS correctly is the one on the compression stroke. That is also the TDC when the cam gear matchmarks line up with the notches on the inner timing belt cover. If you have the upper timing belt cover off and spin the crank by hand, you will see that for every 2 times the crank revolves, the cams revolve once. So you hit the 0 degree mark once and the cam gear marks line up, then you spin the crank again and hit the 0 degree mark and NOW the cam gear marks are 180 degrees to the notches on the inner timing belt cover. So what I am trying to explain is, you can't just line the crank up to the 0 on the cover and think you are at the correct TDC. Like I said there are 2 TDC's on every single 4 stroke engine whether its SOHC, DOHC or OHV. SO, the only way to know what is the correct TDC on a supra is, 1. take the upper timing belt cover off and line the crank to the 0 when the cams line up with the notches. Or 2. take the no.1 spark plug out, spin the crank by hand and listen for when air rushes out of the spark plug hole when the crank nears the 0 degree mark. When it rushes out, the valves are closed and the no.1 piston is on TDC of its compression stroke. If air does not rush out then the exhaust valves are open and its on the exhaust stroke.

Obviously the method with taking the upper timing cover off is easier but you have to take the thermostat housing off and then you need to buy coolant. Either way will work and then you can properly install the CPS by lineing up the drilled mark on the shaft with the groove on the CPS housing and you are done.

04-12-2007, 03:36 PM	#14
IHateHacks 20psi boost Join Date: May 2006 Location: New Haven/Hamden Posts: 793	Ok you asked for it. The crank pulley is keyed to the crank on the 7M with a woodruff key, so whenever the notch on the crank pulley is lined up with the 0 degree mark on the lower timing belt cover, the No.1 piston is at TDC. NOW, there are 2 TDC's on a 4 stroke engine, one on the exhaust stroke and one on the compression stroke. The TDC you need to install the CPS correctly is the one on the compression stroke. That is also the TDC when the cam gear matchmarks line up with the notches on the inner timing belt cover. If you have the upper timing belt cover off and spin the crank by hand, you will see that for every 2 times the crank revolves, the cams revolve once. So you hit the 0 degree mark once and the cam gear marks line up, then you spin the crank again and hit the 0 degree mark and NOW the cam gear marks are 180 degrees to the notches on the inner timing belt cover. So what I am trying to explain is, you can't just line the crank up to the 0 on the cover and think you are at the correct TDC. Like I said there are 2 TDC's on every single 4 stroke engine whether its SOHC, DOHC or OHV. SO, the only way to know what is the correct TDC on a supra is, 1. take the upper timing belt cover off and line the crank to the 0 when the cams line up with the notches. Or 2. take the no.1 spark plug out, spin the crank by hand and listen for when air rushes out of the spark plug hole when the crank nears the 0 degree mark. When it rushes out, the valves are closed and the no.1 piston is on TDC of its compression stroke. If air does not rush out then the exhaust valves are open and its on the exhaust stroke. Obviously the method with taking the upper timing cover off is easier but you have to take the thermostat housing off and then you need to buy coolant. Either way will work and then you can properly install the CPS by lineing up the drilled mark on the shaft with the groove on the CPS housing and you are done. Last edited by IHateHacks; 04-12-2007 at 05:37 PM.