Another Cam Timing Idea?

[LeakProof]

Just curious,

Couldn't you feasibly just put the dowel pin's back in the same exact spot you found them and call it a day?



Please consider the following:
Case split and reassembled, with new bearings.
Rebuilt rods.
Rebuilt rocker arms.
Heads completely re-done.
New timing chains.
One pitted cam, repaired.

Or is this a bit risky?

Thanks,

Mike.

[efhughes3]

Not after you've removed the sprocket. The pin is what locates it in relation to the cam. It can spin 360 degrees.

Also, if you changed chains, let's say going to a split chain without removing the cams, the chain length/stretch will be different and will need re-timing.

[LeakProof]

Thanks, Ed.

I suspected the sprockets being removed may play in to this.

And yes, they are new, no-link chains.

I guess there are no short cuts to the timing process.

Mike.

[efhughes3]

Exactly!

[Walt Fricke]

One could devise a "shortcut." Build a jig which holds the cam at exactly what it should be at when the crank is at the proper TDC. Put the crank to 0, set the device, pull things apart to do what you want to do, reassemble and set things, and put the pin in whichever hole will accept it.

This is kind of like how later cams are timed, with a fixture holding a slot in the cam's rear end.

However, timing the traditional way is really easy. Set crank to TDC, rotate cam until you have the desired reading on the gauge, insert pin, tighten nut, and recheck. Most of the time you will be within tolerance first try, at least on a rebuild where only one rocker arm is installed. About as quick as using a tool that doesn't exist. And for which there would be little market, considering its limited marginal improvement.

I once forgot to tighten the three 6mm bolts which hold the aluminum round gizmo. Instant oil leak loading the car into the trailer to go race. I pulled the cover off in the trailer in a Walmart parking lot, removed the tensioner and the nut, then the gear. Tightened the bolts. Put things back together. Set the dial gauge and spun the engine. Son of a gun - timing was still spot on. Of course, for this I didn't have to turn the crank or cam. How the cam stayed in balance with the various valve springs pushing on rockers I don't know, but it did. You never know.

Walt

[LeakProof]

Thats cool.

Mike.

[James Brown]

Great story Walt. Most piston aircraft engines stop in the same place not due to compression but due to cam/spring resistance. I assume this is happening on Porsche engines also. You can feel it if you turn a engine over without plugs, you can "feel" the camshaft lobes moving the valves. and you can find a sweet spot where most valves are closed. That's probably why you got away with that one!