Triumph Repair: TR6 CAM TIMING, cam sprockets, exhaust stroke

Question
WHAT IS THE CORRECT WAY TO TIME A NEW CAM SHAFT IN A 1975 TR6 (SIX CYLINDER) I HAVE REBUILT THE ENGINE WITH NEW CAM AND TIMING CHAIN AND GEARS BUT THERE WERE NO MARKS ON THE GEARS AND I HAVE NO SPECS ON THE NEW STOCK REPLACEMENT CAM. THANKS FOR ANY HELP

Answer
Hi Robbie,
Some aftermarket cam sprockets do not have any marks so you need to do this.

If you have the head already on.----
Remove all of the push rods except the two on #1 cylinder. Set the crank so the piston of #1 is just short of TDC. With the cam, lifters, only two pushrods and rockers installed set the valve clearance of the intake and exhaust on #1 cylinder at .050" accurately. (unless your new cam is a competition cam and they will quote the procedure) Turn the cam to the center of "Overlap" (what would be TDC of the exhaust stroke) Now you will notice that you can't rotate the cam much in either direction. With a marking pen, mark a tooth on the cam sprocket and rotate the sprocket by hand counter clockwise until it stops and put a mark on the backing plate opposite the marked tooth, then rotate the cam sprocket by hand clockwise until it stops and put another mark on the back cover opposite the marked tooth. Use a caliper or rule to measure the distance between the two marks and put a mark in the center on the back cover. At this time I punch mark the back cover. (This is the cam timing mark of TDC) Move the cam sprocket until the marked tooth lines up with the punch mark on the back plate. That is the cam timing for TDC of the number one or number six piston (Depending on where you set the distributor drive)

Now be very careful not to move the cam and turn the crank to exactly TDC. do a fit check of the cam chain. If the cam mounting holes don't line up correctly, turn the cam in the sprocket 180 degrees in the chain and check it again. If it still don't line up remove the cam sprocket from the chain and flip it over and try again and if it still don't line up rotate the sprocket 180 degrees in the chain and try again. There are 4 different positions in between one tooth movement by rotating the sprocket and flipping the sprocket over and rotating again 180 degrees. So one of the 4 options should get you very close. You must not move the cam nor the crank while doing all of this.

When finished you should be able to rotate the crank clockwise until the clearance is taken up on the valves and mark the crank pulley opposite the TDC mark and rotate the crank counter clockwise until the clearance of the other valve is taken up and mark the pulley again and you should have a mark on the pulley evenly spaced on either side of TDC if you were accurate.  

If you are familiar with the use of dial indicators and degree wheels you are just "Splitting Overlap". and you can use a degree wheel and dial indicator to do the whole thing.

Howard