Originally Posted by xf351clev
I know a lot off u don't like them but i've got to do it anyway. My timing chain has stretched and am replacing it with a jp gear drive. Can i just alighn the timing marks on the old sprockets and remove them and replace it with the gear drive or do i have to get a degree wheel and start from scratch.
Thanks for ur time and brain power
A degree wheel won't help much without a piston stop. Someone makes them in the form that screw into a sparkplug hole, but I've never used one. Rather, I made one of that type by putting a 1/4" x 20 x 3" long bolt through a compression tester fitting and fitting a couple of nuts tightly to it.
You need a positive stop so that you can turn the engine in one direction and then around the other direction so that you'll know where the "middle point" is when calculating where TDC actually is for your engine.
I wouldn't recommend advancing/retarding your camshaft without rechecking your P/V clearances, which is a bit difficult with the heads on.
Timing chains stretch 2-3 degrees after first run in.
If you have a small plastic (half round) protractor, you can do it without buying a degree wheel. Go to a photocopier and make two readable copies of it. Cut out the pieces so that they line up properly and tape them to a thick paper plate. You now have a poor man's degree wheel. Mark one side of the protractor copy A and the other B so that you'll easily be able to tell which is which once you're turning the engine and/or have looked away.
Make a "timing pointer" out of a piece of wire that isn't going to change under its own weight. An old wire coat hanger works well. I use a pair of side cutters to make a nice point, then bolt it anywhere that is out of the way and that will stay put. Use the rest of the wire to shape it to where the pointer points at a fixed place on the degree wheel and, with your piston stop in place, you're ready to find TDC on number 1. Besure that you've already spun it 'round to the compression stroke before putting your piston stop in! Turn one direction, note the indication on the degree wheel, turn the other direction, note the indication on the degree wheel and half way between the two points (in degrees difference) is TDC. Pull your piston stop out, rotate the engine to the first degree mark plus half the difference between the two points and you're at TDC.
As a note, you probably won't need "two sides" of the protractor to make something that will get you fixed up. However, with two sides, you can easily use it to mark your dampener at 90* intervals from where it is installed to known good TDC. Be sure to remark at least the "0" (if it isn't the same place as shown on the dampener) with TDC so that you can use it for accurate ignition timing.
Of course, you could just buy a degree wheel...once you have one, you've always got one :)