Cam Timing Guidance

[Sway Bar]

I have a acquaintance that dropped his motor to do some seals etc. He got carried away and pulled the cams to do those seals etc and never marked their orientation and of course later changed/moved some of the valve lash settings.

So, of course we need to start over and time them properly. I have done this a few times on rebuilds and understand the procedure (install cams in the correct 'up' orientation, set TDC #1, set valve lash for Intake #1 and then watch the gauge for desired reading, etc). My question is since I have only ever done this during a rebuild with only #1 and #4 intake rockers in what do I do with the other rockers since their lash/settings are all over the place? Do I back them off as much as possible in order not to have them interfere/bind during rotation?

Thanks in advance

[gsxrken]

Yes. Get them out of the equation so you don’t possible bend any valves... makes it easier to turn over as well.

[Eagledriver]

Yes, back off the adjusters all the way. Be careful because it’s still possible to hit valves even with the adjusters backed off. Put the crankshaft about 30 degrees BTDC on number 1 while you bolt everything together and position the cams. That way all of the Pistons will be well below TDC and can’t hit valves. Turn the crank the rest of the way to TDC after you position the cams.

-Andy

[Jeff Alton]

If the dots are up in install position you can have all of the rockers installed. NO risk of hitting valves. As the cranks turns so do the cams. So if you are not hitting on #1 and #4 you are not hitting any other cylinders. Now, on high lift/overlap cams it can help to not have the other rockers installed/adjusted when it comes time to adjust timing as the cams can move when the pin is removed to adjust.

You don't say what motor/cams....
Cheers

[Walt Fricke]

I'm with both Andy and Jeff. We don't know what orientation anything was in when the cam gears were pulled off - where the cams were relative to the crank TDC. If all that was left strictly alone and not moved, I could see just putting the wheel back on with the chain, tightening the idler, and inserting the pin - maybe snug the nut or bolt. On both sides. Then rotate (slowly and carefully, feeling for any possible valve interference) so you have the two dots pointing up, as you would for fine tuning the setting. Then check timing and adjust accordingly as needed.

The fact that rocker feet were fiddled with is pretty much immaterial, assuming nothing silly like screwing one down as far as it can go.

However, it seems unlikely that the dots were up when things started getting disassembled, to to start the timing on 1, you are going to have to rotate everything. That's where the worry comes in: if one of the cams somehow got turned far enough one way or the other, it could be far enough out of time to lead to interference.

I once fixed a behind the cam gear seal leak in a trailer headed for a race. I don't recall being careful about where I rotated the engine and cams to before I started in on the big nut on that side. I did work hard at not moving the cam. Screwed the three bolts in (I had violated the rule of never installing a fastener without tightening it to spec - here spec for me is what my hand on the wrench tells me, but these were simply loose - finger tight), put the wheel and chain back on, and set up for timing #4 (leak on that side). To my pleased astonishment the cam had not budged, timing was spot on even after wrestling with that big nut when I finally turned the crank to the proper TDC as I watched the dial indicator. No fussing with lash.

So that's my take. I was in a hurry. I knew nothing had moved enough to cause problems, even though I anticipated I'd have to adjust the timing some. A few more variables here, and perhaps no time constraints.

[Flat6pac]

If you move the crank off Z1 35/40 degrees all the pistons are down in the cylinders so you can spin the cams to bring up the dot or the key way. Once the cams are up, you can return the crank to Z1 and start yer timing.
Bruce

[Walt Fricke]

Bruce - wow!