Kohler K valve lash- straying from oem spec?

[Greentored 3,220]

Anyone ever tried 'tightening' the lash further than oem spec to get a little more duration/lift? Two reasons come to mind for the relatively 'loose' oem recommended settings- wear, and (obviously) not holding a valve off the seat when metal expands and clearance shrinks with running temps.

Getting it up to running temp and performing a HOT adjustment to a couple thousandths perhaps? The up side wouldnt mean much for lift, but a lot more duration. The down side would be a lot more lash checks as parts wear, but its a pretty straightforward job on these Ks.

Input?

[WHX?? 51,744]

I do know some guys go to the tighter side of specs and even a couple .001 under min spec. Mostly to help with valve clatter noise than lift. 

[ebinmaine 72,671]

Scott, what's the spec from the factory and how much would you change it?

 

Do you have any websites (other than Miller's), or videos or whatever that shows what can be had from these engines?

[lynnmor 7,817]

I wouldn't deviate much from the specifications.  I did a quick calculation for a 3.5 inch long valve that has an average 500 degree temperature over its length, the result was a growth of .0108".  Note that the valve head may hit 1000 degrees while the opposite end will be a few hundred.  Also, the engine block will grow as well changing the distance from the cam to the valve seat.  There is too much going on to just throw out a figure and trust that a burnt valve won't happen.  You can't do a hot adjustment and trust that it will give good results, the valve head will cool considerably in seconds while transferring that heat to the block.

[953 nut 59,990]

    I don't think Kohler or any other engine manufacturer randomly selects numbers and prints them up just for grins. A lot of engineering went into establishing specifications for these engines to provide us with dependable operation. What makes people think that they know more than the research and development teams. You might achieve some measurable short term gains (though I doubt it) but will probably pay the price in the long run.

[ebinmaine 72,671]

40 minutes ago, 953 nut said:

    I don't think Kohler or any other engine manufacturer randomly selects numbers and prints them up just for grins. A lot of engineering went into establishing specifications for these engines to provide us with dependable operation. What makes people think that they know more than the research and development teams. You might achieve some measurable short term gains (though I doubt it) but will probably pay the price in the long run.

 

 

All of what you write is true and I agree 100%. 

 

It's important to remember that Scott isn't necessarily going for an engine that'll last thousands of hours without adjustment or even full disassembly.

 

Higher HP street/competition/race machines are OFTEN adjusted.

Many are even  completely disassembled after every use/race.

 

Engine/vehicle/consumer end user machinery in general MUST be made to last whatever length of time the consensus believes to be acceptable.

 

If a 16 HP engine lasts 2000 hours but CAN make 25 HP ... only for an hour... no retail user would buy it.

But those looking for max HP would.

 

For the most part the Kohler research and development teams over the years have done a wonderful job and given us - the end user - a line of engines with a dependability rating second to none.

 

The process of experimentation and usage or elimination of good or bad ideas or parts of the whole to create even a miniscule improvement is highly satisfying to some.

 

 

 

It's all good.....

 

 

[tom2p 2,394]

 

there is almost always room for improvement 

much has been learned over the years (since the design and manufacture of the old Kohler engines)

 

and just a simple blueprint can make a difference 

 

[Greentored 3,220]

14 hours ago, ebinmaine said:

Scott, what's the spec from the factory and how much would you change it?

 

Do you have any websites (other than Miller's), or videos or whatever that shows what can be had from these engines?

Millers site, wow, that guy spent a LOT of time putting all that info out there! Ive scoured the interwebs here and there for hours and hours, just not a whole lot of Kohler K performance since a lot of folks are concentrating on the OHV. Theres a lot of 5hp Briggs info out there as thats been a kart racing staple for decades, so applying some of that info along with the little bit of Kohler info, plus 30+ years of 'what will happen if I do this' haha.

 I raced karts in my teens, built my own Briggs engines and was a consistent top 3 finisher- for a while was building them for my competitors as well. That ended when I did some experimenting on another guys engine and he beat me 3 out of the next 4 races. HUGE compression and a cam grind to match. Wouldn't rev worth a crap but the torque put him so far ahead on the green flag and off the corners, by the time it would go 'flat' he was so far ahead nobody could reel him in! Thank God it finally grenaded

 

[Greentored 3,220]

Fellas, make no mistake, this is not an attempt to outsmart Kohler haha. Millions of those Ks running 30+ years or more with plenty of power on tap and very little maintenance required- yep, pretty sure they have a better handle on it than the average 'backyard Joe'

When we start playing with engines to increase their output, dependability goes down, maintenance goes up, but if someone is willing to DO that maintenance, there is a ton of power left on the table, up for grabs.

The idea here is not to end up with a bomb 45 minutes into its life cycle, but more of a "it doesn't grunt as bad in thick grass/it pulls a plow with throttle remaining, but I have to check the valves and replace the spark plug at every oil change."

 

[Greentored 3,220]

14 hours ago, lynnmor said:

I wouldn't deviate much from the specifications.  I did a quick calculation for a 3.5 inch long valve that has an average 500 degree temperature over its length, the result was a growth of .0108".  Note that the valve head may hit 1000 degrees while the opposite end will be a few hundred.  Also, the engine block will grow as well changing the distance from the cam to the valve seat.  There is too much going on to just throw out a figure and trust that a burnt valve won't happen.  You can't do a hot adjustment and trust that it will give good results, the valve head will cool considerably in seconds while transferring that heat to the block.

That is VERY good info and a point not considered!