Camshaft orientation question - Page 2

Travelin Man · 04-11-2015, 12:34 PM

You'll see in the pic the dial gauge I rotated the cam to get the 2.49mm the same as the left cam and it went all the way around to the cam lobe again and only read .05???

Trackrash · Trackrash's Garage

Confirm that the crank is at TDC firing for #4.

Confirm the punch mark on the right cam is aimed down.

Without looking at the dial indicator, put the pin in the hole that lines up.

Rotate the crank clockwise two turns stopping at TDC. Watch the dial indicator. It should go to zero then back up to close to the cam's spec. If not, then you have some double checking to do.

If it is close to spec when you turn it one more turn then remove the pin and turn the cam till it is in spec and replace the pin.

Report back.

Travelin Man · 04-11-2015, 01:41 PM

Will do right now and let you know. Thanks for you help

Travelin Man · 04-11-2015, 01:49 PM

Did what you said rotated it and the dial was a .01?

Trackrash · Trackrash's Garage

Forgot to mention. When you rotate the crank make sure that the dial indicatior's tip is always in contact with the valve retainer.

And set the dial to zero when the cam's punch mark is in the down position.

Travelin Man · 04-11-2015, 02:29 PM

Yeah I did that

Travelin Man · 04-11-2015, 02:34 PM

I do rotate the cam clockwise to get the valve overlap correct?

Trackrash · Trackrash's Garage

Depends. You should be close to the correct number. Turn it so you get the correct value. It shouldn't need to be turned more than a few degrees, if all is well you are just fine tuning it at this point.. Try turning it either way watching the dial.

Replace the pin. Turn the motor over two more times as a double check.

edit: to be clear, to get the valve overlap correct you are turning only the cam, make sure the crank stays at TDC.

Walt Fricke · 04-11-2015, 04:04 PM

I have had the same problem Gordon has had - on one occasion I set the left bank rotating the crank counterclockwise, which meant the cam was going clockwise, and my measurements were for the intake valve being the specified lift away from being closed. Rather than the specified lift as it was being opened. Valves hitting heads, of course, saved me before I got too far into installing all the rockers. Hand slap to forehead, start over. This mistake was easier since my MO is to put the crank at TDC on the pulley, and rotate the cam so I get the readings I want, and then lock it. Easy to forget which way the cam should be going if you are off to start with.

So one approach would be to do the trial setting - both cams dots up, soft lock with the big nut so they are connected (doesn't take much with no springs pushing on rockers etc), and rotate the crank clockwise, watching the cam intake lobes to see how #1 and #4 compliment each other. Then you will have a better idea of where the left intake cam is just starting to come off the base circle. Stock motors don't come off it much, yours with 2.5mm spec will come off it a bit earlier.

While you are sure that the cam is presenting its base circle to the rocker for #1, put that valve in and do a trial setting at the 0.1mm level. Books always call for doing this at TDC firing (when both intake and exhaust valves are closed), but the fact is you can do it any time the rocker is on the base circle, and that is a rather large number of degrees. If you were to set the rocker when the cam is not on the base circle, that would mess up all attempts to time the cam correctly.

Anderson has a good diagram of how to decide which cam is the rabbit ears, and which isn't, and which goes on which side. Dempsey does also. I like to look at that, with the book propped up on the bench, when I put the cams in. I have an engine apart about every other year or so. I remember a lot, but some things one just should not trust his memory on. Right = rabbit?

Walt Fricke · 04-11-2015, 04:08 PM

Also - if somehow the crank pulley, with its Z1 mark, wasn't set right, that would cause troubles. Since it is positively located by a pin, and can only be in one position, that's probably a pretty remote possibility - you'd have to leave the pin out to do it, and who pulls that pin out of the pulley? In a running engine, after, say, a missed shift and a zinged motor, the pin can have sheared and the pulley moved. It will still turn the alternator/fan fine, but it has turned on the crank so it can't be used for timing. But this is after a rebuild?