apex9

Hello every oneHow do i do that?

I am trying to find top dead center on rotary engine.

j9fd3s

tdc is when a face of the front rotor is closest to to the spark plugs. i used to have a kickass picture, but i dunno where it is. the keyway on the e shaft will be at 9 o clock if you are facing the front of the engine



mike

baracuda7

j9fd3s

found mah pic

Lynn E. Hanover

There are two TDC positions. If you want the one that shows up on the crank pulley and might be useful for timing, Assuming the engine has been running. Take off the distributor cap if any, and turn the engine by putting it in 4th gear and shove it backwards with your knees until the top part of the rotor button points at number 1 leading. It should be marked on the cap. At that point the pointer (the useless piece of wire) on the front case should be close to TDC. On most front pulleys the last mark in a row of marks is TDC except on those months where there is one mark at 5 after that nobody uses for anything or the 7 that came with a mark at 5 and 10 after. then TDC is one or two marks east from the very last mark.



Or since that TDC mark is so hard to see anyway only the guy that built the engine has ever seen it.



If you have a crank angle sensor the pickup for the leading coil (both?) will line up twice in one revolution. Rotate the engine with your knees and line up the pickup with a reluctor. It is either that one (now look for marks on the pulley) or if there are no marks, it's the other one.



Push it some more with your knees and look for marks. If you forgot to get under the car, take off a bunch of crap and clean off the whole pulley with a solvent that would not remove the paint from the little notches, at this point, get in the car and drive it back to where you started and clean off that pulley. And try again.



If the car has no distributor and no crank angle sensor, only the computer knows where TDC is, and it's none of your business. I believe there is actually a fine involved in California for asking about it.



But if it is just going to kill you if you cannot see TDC with your own eyes, here is one way to do it. If this worked out right there should be a keen picture below.



If you don't mind taking the engine apart to see it, (TDC is after all inside the engine) this rig gets you there in style. In this case this is a Mr. Gasket timing wheel, but any cam manufacturer sells these big ones. There is a slight paralax problem, but the pointer on the engine is a piece of wire for Gods sake. With this rig you can resolve TDC inside of one degree. (there are 359 others). You do this with the front case mounted and the pulley installed, so you can check indicated TDC on the stock pointer VS actual TDC from the dial indicator.



On the other hand, if you would rather not take the engine apart, there is a less costly way to do it.



Take a conventional 3/4" reach spark plug, and crush the insulator in the vise. Break off the ground electrode. Take a punch and drive out the ceramic from the threaded end. Now you should have an empty steel shell with good threads. Epoxy a short piece of brake line into the center of the shell. Have the inner end flush with the shell and the outer end about an inch longer than the shell. Go to Home Depot and buy some clear plastic tubing to fit over the brake line.



Mix up a batch (some bright color) of cool aid. Take a swig. Put the end of the tube in your mouth )(The clean end) and fill the tubing with cool aid. Clip both ends of the tube to the hood with a spring clamp. Remove either plug from housing one. Replace it with your bitchin new tool (the spark plug shell) tighten it 10 pounds no more. Slip one end of the tubing onto the brake line in the plug shell. With the engine in a position that is likely to be near TDC.



In 4th gear, rock the car back and forth, and watch the Coolaid in the hose. When the Coolaid is at it's heighest in the tube, that is TDC. If you engine sucks, and will not seal well enough to hold the water column while you look at it, dump in some motor oil through the intake and spin it until some oil squirts out the brake line. The reinstall the Coolaid line and just keep rocking and watching, and you will end up with the average null for the column movement, and that is TDC.



The Coolaid will not hurt the engine.



Lynn E. Hanover

White_FC

Just a quickie here guys....



How the hell do I find TDC?



My pullies are of no help whatsoever as there are no markings on them at all.



I need to stab my CAS in and it's a bit hard when you have no idea of where TDC is...



any ideas? sorry if this is an obvious and newbie question

kahren

there should be a groove where the markings are look close

White_FC

Cheers for the info, I have what _appear_ to be these marks you speak of, but im not 100% sure, they could for all I know be dents in it put there by me.

Is there any be all and end all of ways to find out?

I have the pully off now, so if there is a way to determine it use just the pully boss that is on there that'd be great, the pully boss has a small indent on it, could I use that somehow maybe? Obviously that mark isn't TDC is it? (I hope not because my timing was set nowhere near there. )

kahren

the keyway woudl be on the passenger side, and the mark to line up to is the one on the drivers side which is the leading mark (5 ATDC) then you line up the CAS withteh dot and put it in. you can open teh cover of teh cas and hold the shaft to make sure it doesnt turn as you are puttign it in. here are some pics to help u

kahren

one more