Yamaha F250 valve clearance -- all exhaust valves too tight?

[thedillybar]

2005 F250 w/ ~2,000 hours. Unknown maintenance history.

Checked all valve clearances per the service manual. All intake valves are .178-.203 mm (within .17-.23 tolerance). All exhaust valves are .229-.279 mm (all tighter than .31-.37 mm tolerance).

Seems a bit unusual. I've pulled the shims ("adjusting pads") and they measure 2.50-2.59 mm. Anything I should check before ordering new shims and swapping them out?

13 (or 16) pads time $15 is a little rough but better than burning exhaust valves.

[panasonic]

Cam lobe height....

[thedillybar]

I checked all the lobes on the port side, tall & short parts of the lobe. Don't have the best setup, just a pair of calipers, but appears everything is within spec. 45.35-45.45mm and 35.95-36.05mm. Any wear on the lobe should increase the clearance not decrease.

[Punch953]

Worn valves and seats would tighten up the valve clearance. I don't know how much wear is permissible.

[panasonic]

I checked all the lobes on the port side, tall & short parts of the lobe. Don't have the best setup, just a pair of calipers, but appears everything is within spec. 45.35-45.45mm and 35.95-36.05mm. Any wear on the lobe should increase the clearance not decrease.

Hello Mr Dillybar,

You are correct, worn lobes would cause an increase in valve clearance not a decrease.

I do not know why just your exhaust valves clearances have closed up and not the intake valves. But valve clearances generally close up as a engine builds a lot running time and the valves pound their way into the seat, for lack of better terms.

So your engine calls for 0.31 - 0.37mm which is 0.012"- 0.014" (I have to work in imperial)

And you have measured 0.229 - 0.279 mm which is 0.009" - 0.010"

So they are not terribly tight and only a few thousands below spec. I don't see any reason why you shouldn't just shim them, as you are doing, to bring them back into spec.

Can I ask why you are checking them? Just maintenance or engine rebuild???

You do a leak down test and see if the cylinders/valves are sealing well.

Please post the exact engine model and serial number in the future, it helps.

[thedillybar]

2005 F250 TXRD, 6P2 1000001–1002894

Checking them per the maintenance schedule -- 500hr or 2.5yr. I bought the boat and engine about a year ago, and who knows what maintenance was done before me. I am planning to pickup some new shims and put it back together. I don't have a feel for what's "terribly tight", but figure it's worth doing if it's below the service manual spec. After all, why bother checking them if you're not going to adjust when you're out of spec.

I spoke with a machine shop today. He said the exhaust valves will wear faster if the engine is mounted low and water can push in when you come back to idle. When I bought it, the jackplate was almost all the way down and I would occasionally see white smoke (steam?) on startup. I've moved the engine up three inches since then.

[zenoahphobic]

Not sure what exactly your mechanic is implying.
Is he suggesting water entering cylinder “lock” pushing the exhaust valves, sudden cooling contracting the value make it hammer more in its seat, or that just moisture makes the seat or valve corrode a bit more removing some material off the seat or valve face.
It is certainly possible that someway water adds further stress that a very hot valve and seat is already under. That aside I would expect exhaust valves recede more than intakes, and what you measure is normal and therefore you would shim back to a wider gap to the maximum gap specified.

[99yam40]

I can see water in a cylinder would cause a piston/rod problems(Cannot compress water) but I do not see how it would affect a valve

[thedillybar]

I was thinking moisture/saltwater some additional corrosion on the valve face, but who knows.

Plan is to re-shim. I found a machine shop in FL that has most of the shims I need. Unfortunately, can't find any 2.42mm shims (69J-12168-50-00) anywhere in the US and back-ordered from Yamaha until mid-May. Apparently a dealer in CA has some, but they're closed due to the virus. Still looking...

[panasonic]

If you really get stuck and cannot find the proper shim, a good machine shop with a surface grinder could take the next larger size shim and precision grind it to the thickness you require...

Just a thought.

[TownsendsFJR1300]

This company makes/sells shim kits for all type of machines: http://www.hotcamsinc.com/

Although Yamaha outboards are not specifically listed, if you can measure your shim(diameter) , I'm sure they find you what you need..


.

[thedillybar]

I've sent an email to hotcamsinc; we'll see if they have something comparable.

As far as grinding..sounds like these are hardened so best to get the right size rather than machine them down.

[panasonic]

I've sent an email to hotcamsinc; we'll see if they have something comparable.

As far as grinding..sounds like these are hardened so best to get the right size rather than machine them down.

Yes they are very hard. They are machined to rough dimensions while in a soft condition, heat treated to the proper hardness and then surface ground to the precise dimensions required. That how they are manufactured.

[thedillybar]

Job is done. If anyone finds themselves in need of these shims, send me a message.

[99yam40]

Is there a reason you cannot share what you found on the open forum for all to see?