Adjusting valves questionIt is past time for me to do a valve lash adjustment.

[a64pilot]

Originally Posted by sandiegoskipper

Would a dial indicator work, screwed into the injector hole?

Yes, and is one way when you degree cams, when absolute precision is required.
On a Continental aircraft engine you install a rod that hits the piston, rotate until engine binds up, mark number of degrees on degree wheel, turn backwards until it again binds up, TDC is exactly in the middle of those two marks.
However a dial indicator takes a solid rod of course and often time your getting to the piston at an angle not straight down, so you can put the rod in a bind and if your not careful bend or break it.
Reason I use a soda straw, real tough to harm anything with one and they are cheap too, and we just need to ensure we are on the flat side of the cam, real precision isn't necessary

[Jimongee]

Wow! I only asked 1 question and all you sailors came to my rescue with great info. Thanks do much for putting this in common sense terms.
JIM
36' Hunter Boyne City, MI

[Wotname]

Originally Posted by sailcrazy

Maybe I'm not understanding what you want to do, but we just had an Onan mechanic (or so he claimed and advertised to be) adjust the valves on our Kuboto-powered Onan genset a few months ago-along with a few other issues we needed help with. I watched closely, so I could do it myself in the future. He turned the engine via a socket on the engine front until the valves were both closed and the gaps on the tappets were visible, and then adjusted both the valves on that cylinder. Then he rotated to the next cylinder and repeated. What I saw was very different from what you're talking about above.....what am I missing?

What you might have missed is that the OP has a 3 cylinder engine.

With a 2 or 4 cylinder engine, the angular distance between each piston is 180 degrees but with a 3 cylinder engine the angular distance is 120 degrees.

But is essence, this does not matter when using the method you described.

[Barney21]

Get youself a " Cam Timing Disc" it can be held in place with a magnet on the front crankshaft pulley, set it at TDC with timing mark. Then just rotate crank the required turn to line up with next required mark. No guess work no smoke and mirrors. You can make a Timing Disc out of a circle of cardboard if you have a full circle protractor.
Would not risk sticking a drinking straw down the injector hole. Really!
The injector may just go into the pre/ chamber , would give you a very short stroke.

[seabreez]

Originally Posted by Diesel Bill

Hate to throw this out as you guys will think it's nuts. Any way here goes.
Pick a cylinder, any cylinder. Rotate in direction engine runs. Watch the rockers. when one valve opens all the way, (full lift of valve off the seat) the other valve is fully seated and can be adjusted. After setting the lash mark the rocker with a yellow crayon. I have never seen a 4 cycle engine where if one valve is wide open the other valve lifter isn't on the cam base circle. This includes full race cams with a lot of valve overlap.

I will second the motion here... this is the way I have learned to do valve adjustments for 45 years on diesel and gas engines... again no burnt valves ever...

[Elie]

Naturally, this apply only for engine equiped with push rods. My Volvo Penta MD22L ( in fact a Perkins Prima in green color!) has a belt driven overhead cam shaft and adjusting the valve clearance is very different. It requires special tools, the removal of the fitted valve cover-cum cameshaft bearing top. The adjusment is made like cars, with insertion of shims between the valve and the cam. Quite complicated ! The only advantage is that all the valves can be adjusted immediatly without turning the engine.

[Kita]

Originally Posted by Elie

Naturally, this apply only for engine equiped with push rods. My Volvo Penta MD22L ( in fact a Perkins Prima in green color!) has a belt driven overhead cam shaft and adjusting the valve clearance is very different. It requires special tools, the removal of the fitted valve cover-cum cameshaft bearing top. The adjusment is made like cars, with insertion of shims between the valve and the cam. Quite complicated ! The only advantage is that all the valves can be adjusted immediatly without turning the engine.

That's called shim under bucket, very popular on motorcycles also...advantage is they don't really need adjustment as often...valves will get tighter under normal circumstances & as time goes by,if one gets loose, be careful something is up, .....

[Elie]

Originally Posted by Kita

That's called shim under bucket, very popular on motorcycles also...advantage is they don't really need adjustment as often...valves will get tighter under normal circumstances & as time goes by,if one gets loose, be careful something is up, .....

Wath do you mean that valves get tighter under normal circumstances?. How do they get tighter?
and by something is up? Trouble?. What kind of possible trouble?. Cameshaft problem?, timing?...
Thanks for your expertise!

[a64pilot]

Valves wear by wearing between the valve and the seat, that makes the valve seat deeper into its seat and the stem stick up more, that reduces clearance.
If your valves wear loose then something in the drive train is wearing, and that isn't normal, rare but cams do go bad and excessive clearance is one of the first signs.
On edit, some valve trains like the old Kawasaki 900 had the shims sit on top of the "bucket", made adjusting easy, but high performance cans would cause a shim to "spit" out and be thrown through the cam cover, so they went to shim under bucket first with the 650, drag racers back in the day fitted 650 buckets and valve retainers to their 900 drag bikes. Late 70's.

[Kita]

Originally Posted by Elie

Wath do you mean that valves get tighter under normal circumstances?. How do they get tighter?
and by something is up? Trouble?. What kind of possible trouble?. Cameshaft problem?, timing?...
Thanks for your expertise!

The valves open & close many many times & over time under normal circumstances the valve will wear a bit & the seat also & that pounding into the head as the spring closes the valve will seat the valve farther up into the head slowly & the rocker stays in the same spot so as the valve wears it will very slowly travel up closer to the rocker reducing the clearance or lash as some will say... if let's say one is very loose,make sure you are in the right spot to set that valve first & if it is then look at maybe the adjuster face that is contacting the valve for a worn adjuster screw or maybe a bent pushrod or something odd because getting loose is saying something is moving, but what!

[Elie]

Many thanks, a64pilot!.
This forum is like the Alibaba cave: You find everything, but mostly expert support!...

[a64pilot]

Knowing that they wear tight explains why when given a range of clearance like .004 to .006 for instance, why you should set it at .006, cause it wears closer to tolerance, where if you set it to .004 then real soon, your out of tolerance.
A little looseness in valve gear hurts nothing really, maybe make the valve train a little noisy but a little too tight means as the engine gets hot the clearance goes away and then the valve leaks and "burns" then you get to pull the head and do a valve job.

[Kita]

Originally Posted by a64pilot

Knowing that they wear tight explains why when given a range of clearance like .004 to .006 for instance, why you should set it at .006, cause it wears closer to tolerance, where if you set it to .004 then real soon, your out of tolerance.
A little looseness in valve gear hurts nothing really, maybe make the valve train a little noisy but a little too tight means as the engine gets hot the clearance goes away and then the valve leaks and "burns" then you get to pull the head and do a valve job.

Spot on! I am very happy with this forum. Great info! nice job!

[model 10]

This noise about valves only getting tight in a pushrod engine is a little too much. Rocker arm tips wear, valve stem tips wear and so do cam lobes. There is very little wear on a hard valve seat. Running with sloppy clearances wears out things out even quicker.
Anybody remember the Duntov 30 30 cam? Pretty noisy.

[four winds]

Wearing tight, I wouldn't say usually. It occurs mostly during the break-in period of a new or rebuilt engine. As the valve and seat get to know each other, so to speak.

After break-in wear there should be minimal for the life of the engine.

There are several wear areas in the valve train that can wear loose, as mentioned. But in my experience in a well maintained engine, particularly regular oil changes, valve adjustment is rarely needed. But of course must be checked to monitor for a problem.

Based on many hundreds of services performed at motorcycle dealers (Honda, Triumph, Harley), and my drag racing, flat tracking glory days, this is my opinion.