Valve Adjustment Methods and Pros/Cons

[CR94]

Originally Posted By: Vikas
"Valve adjustment while the engine is still running"
You guys are pulling my chain, right?
Nope. I've seen it done on a Stove Bolt Chevy 6, and on a Slant Six. That's not to say I didn't wrinkle a feeler gauge attempting to duplicate that trick. It's not practical on most modern engines.

 

[robertcope]

I remember doing this with a 302 back in high school. It's just now it's done with those motors, I guess. I do valve adjustments however the factory service manual tells me to, personally.

 

[dmark]

Oh mighty Trav may I respectfully & humbly suggest the CB750 (both K & F series) did not use hydraulic adjusters. The K (SOHC) used nut & screw adjusters while the F (DOHC) used shims.
If I err I beg your pardon.


Originally Posted By: Trav
Its all been pretty much covered but the automatic ones you refer to are also known as hydraulic lifter or lash adjuster, they were also used in the Honda CB Seven Fifty.
There is another type that hasn't been mentioned and is the easiest of all adjustable ones and that is the wedge screw in the bucket like those used on Porsche 924 engines, Insert the feeler and turn the screw with an Allen key until its correct. It takes all of a few seconds per valve once the lobe is in the correct position.

 

[Vikas]

Isn't specified valve gap "maximum" clearance? If the cam is not at the correct angle, the gap is zero? Isn't cam always rotating? Isn't majority of the rotation, the gap is at zero? How do you measure the " open gap" if it exists for only fraction of second during each rotation?

Is it because all I know are the typical Japanese overhead cam engines???

 

[Jetronic]

if the feeler gauge gets between the rocker and the valve, the gap is bigger than the feeler gauge. you don't need much time to do this at a slow idle.

 

[Trav]

Originally Posted By: dmark
Oh mighty Trav may I respectfully & humbly suggest the CB750 (both K & F series) did not use hydraulic adjusters. The K (SOHC) used nut & screw adjusters while the F (DOHC) used shims.
If I err I beg your pardon.


I didn't say they did. I said the CB Seven Fifty, not the same bike that's why I spelled out 750.

https://de.wikipedia.org/wiki/Honda_CB_Sevenfifty

http://caferacersunited.com/honda-cb750-seven-fifty-cafe-racer-by-nelson-frances/

 

[bunnspecial]

Originally Posted By: Vikas
Isn't specified valve gap "maximum" clearance? If the cam is not at the correct angle, the gap is zero? Isn't cam always rotating? Isn't majority of the rotation, the gap is at zero? How do you measure the " open gap" if it exists for only fraction of second during each rotation?

Is it because all I know are the typical Japanese overhead cam engines???


In a four cycle engine, there is only movement of the valve for every 180º of camshaft rotation, which is 90º of crankshaft rotation.

I mentioned the "rule of 9s" earlier. It is applicable to 4 cylinder, 8 valve engines. When valve #3, for example, is open valve #6 is fully closed and be adjusted. For every given 180º of crankshaft rotation(90º of camshaft rotation) there will be one intake and one exhaust valve open and thus two that are full closed(at maximum clearance) and can be adjusted.

Here's a good video from MG guru John Twist. The procedure is applicable to any 4 cylinder OHV engine, and the principles explained in general are applicable to any engine.

https://www.youtube.com/watch?v=fezXUwVfH7U

 

[Vikas]

Pardon me, but the video does NOT show valve adjustment on a running engine! That was the part I was having trouble with.

 

[dmark]

In lieu of a witty response I stand corrected. That bike is too new for my taste. Did a search and did not see that one; should have searched for "motorcycle hydraulic lifters".
In other words "DOH!!".

Originally Posted By: Trav
Originally Posted By: dmark
Oh mighty Trav may I respectfully & humbly suggest the CB750 (both K & F series) did not use hydraulic adjusters. The K (SOHC) used nut & screw adjusters while the F (DOHC) used shims.
If I err I beg your pardon.


I didn't say they did. I said the CB Seven Fifty, not the same bike that's why I spelled out 750.

https://de.wikipedia.org/wiki/Honda_CB_Sevenfifty

http://caferacersunited.com/honda-cb750-seven-fifty-cafe-racer-by-nelson-frances/

 

[bunnspecial]

Alright, here's one of doing it on a small block

https://www.youtube.com/watch?v=CEV3Yz0kpDY

 

[Trav]

Originally Posted By: dmark
In lieu of a witty response I stand corrected. That bike is too new for my taste. Did a search and did not see that one; should have searched for "motorcycle hydraulic lifters".
In other words "DOH!!".



I wouldn't have known it either if I didn't buy one new in 93 as a second bike when i rode year round.

 

[Vikas]

Originally Posted By: bunnspecial
Alright, here's one of doing it on a small block

https://www.youtube.com/watch?v=CEV3Yz0kpDY
He measures nothing!

 

[Trav]

Engine running is usually reserved for adjusting hydraulic lifters, personally I don't care for that method. Mechanical lifters using rocker arms can be checked with them running with a feeler gauge that's no problem but doing the adjustment while theoretically possible is not something I want to mess with either.

Tools bouncing around all over friggin show, oil pi$$ing all over, A hole trying to hold the feeler while he tries to hold the adjustment screw while he locks it. No thanks.
Lash adjusters under the cam lobe of any type isn't something I want to check running.

 

[Silk]

We used to do it with 2 people on pre war cars like a '39 Chev - one on each side...one with the feeler gauge, one adjusting. Team work.