Valve adjustment

[Thumpower]

I'm building a slant and am ready to adjust the valves; the engine is sitting on a stand, so obviously I need to set them cold. I remember from back in the day that there was a procedure that allowed you to set valves on a 6 and only turn the crank 3 times - each cylinder has a "companion cylinder" and you can set 2 at once. I just don't remember how to tell which cyls are companions. Anybody remember how this is done?

 

[moe7404]

i dont know for sure. but i have seen that done on a V8 by cutting the firing order in half and put one half on top of the other. but that is all i remember about it. an old mechanic i knew would set the exhaust cold .002" wider than when hot. and the intake .001" bigger.

 

[OUTLAW]

If I remember right 1 and 6- 2 and 5 - 3 and 4 run together. On inline 4 and 6 and straight 8s are this way and I used the system of when rockers on 6 are both rocking(exhaust closing -intake just opening) set both valves on #1 follow the firing order for next cylinder and so on. As for adding .002 for cold setting- most manufacturers recommend this too. I hope this helps

 

[RustyRatRod]

I don't worry about all that mess. I adjust them one at a time front to back. Just get the cam lobe on the base circle and have at it. A little more work but to me much simpler. You want to add .002" setting them cold because everything expands when it gets hot.

 

[Thumpower]

This is what I did. I would watch the cylinder in question and see that the intake valve was closing. When it was fully closed I set the valves - still not certain that I was on the base circle, however. What do you think? I just had some doubt because in that position, you could turn the crank a good ways either direction and nothing moved.

 

[nm9stheham]

Your procedure will work if you move past the intake closure. The best way to be sure is to look for the exhaust to close and watch for the intake on the cylinder to just start to open; that is called 'valve overlap'. At that point, the OTHER cylinder in the 'companion' pair is for sure on the base circle of its cam lobes (and will be close to TDC on the compression/combustion cycle of that other cylinder, where the valves are surely well closed).

For example, rotate until #1 exhaust is closing and #1 intake just starts to open; then you know that #1 cylinder is at valve overlap, and you adjust on #6 at that point.

 

[pishta]

The base circle on a mechanical cam is only opposite the nose. There are ramps on either side of the lobe that "sets up" and "eases" the lifter on its way up and down the flanks so they dont bounce. if you look at a 6 cam from the nose with the dowel at 12:00, the lobes are clocked as follows to get the rocker lined up: 2,10~6,2~10,6~12,4~8,12~4,8. So when the first rocker #1 (1E @ 2:00) is at max lift, you can adjust the clock opposite valves that are at 8:00, #9 and #12 (7I and 8E) and so on, youll need to turn the cam 6 increments to set all 12. Add said .002 to E and .001 to I when setting cold to get you very close to spec.
tried to color code them but its like this:
Set #1 rocker to max lift and adjust 9 and 12
set #2 rocker to max lift and adjust 8 and 11
set #3 rocker to max lift and adjust 7 and 10
set #7 rocker to max lift and adjust 3 and 6
set #8 rocker to max lift and adjust 2 and 5
set #9 rocker to max lift and adjust 1 and 4

rayer:

 

[RustyRatRod]

And by the time yall are done with all that, my **** would be adjusted and runnin down the road.

 

[pishta]

And by the time yall are done with all that, my **** would be adjusted and runnin down the road.

well, it took me alot longer to research it and write it with the color codes that it would probably take to do it physically, but now everyone knows the procedure so it wasnt all a waste of time now was it.....

 

[AJ/FormS]

On a typical performance cam(like a 268/276/110) the valves are both closed for in the neighborhood of nearly 230 degrees, during the compression and power strokes. Thats a pretty big target to hit. On stock cams the window is even larger.
I pick what ever cylinder is at or near TDC compression stroke and make it so. Set the valves. Move to the next cylinder in the firing order,repeat. What could be simpler? Nothing to figure out. No chart to try and find. Works on any 4-cycle,gas engine.Right down to your Honda tiller/weed whacker.

 

[67Dart273]

EOIC That is all