FACT: thermal conductivity of a given material is closely related to electrical conductivity of that material...

LOGIC: Aluminum has a higher electrical conductivity than that of steel... thus it is a BETTER thermal conductor period.

A steel sleeve is going to transfer heat slower than a nikasil coated aluminum cylinder... the only consideration that may need debate is if a wet steel sleeve is "equivalent".

 

With the 351cc sleeved the coolant is closer to the heat source... that will help it dissipate the heat better.

 

^ maybe... but you can only assume, and have no proof. Thermal transfer is based on heat differences... yes the steel sleeve will have high heat gradient on the combustion side that drops rapidly to a cool gradient on the coolant side. However, steel is still a poorer heat conductor than aluminum overall... so its hard to argue that its more efficient than a solid aluminum wall.

 

That's exactly what I read when I googled it. I tried like crazy to copy and paste many of the different things I read but just could not figure out how to do it. Everything thing I read up on said a wet sleeve and dry sleeve is more of a personal preferance and there are many pro's and con's to each one.

 

Guys have 10,000+ miles on the 351 kit.... bill blue has them on his own bike. So not only does he make it and sell it he is using it himself.... Good enough for me.

 

Take a look at this site...

Thermal Conductivity of some common Materials and Gases

Notice how the thermal conductivity of aluminum is about 250 W/(m.k)... notice how iron is only 80 and cast iron is only 55.... you can have aluminum walls about 3 times as thick as and iron walls and it will still conduct heat just as well....

 

I'm not disputing that either the 331 or 351 is faster than the 250 KLX. What I'm wondering is if the 351 is really faster than the 331 or the 340. I'm sure it makes more torque but does it make more horsepower as well. I'd just like to see the dyno chart numbers for all three displacements or at least a you tube video of a drag race. I have a vague recollection that the KDX 200 was actually faster than the KDX 220. I was just curious if the 331 may actually be faster (albeit less powerful) than the 351. Personally with the type of riding I like to do on my KLX I'd really prefer more torque any way but I'm just curious.

 

I'm not arguing the 351 in terms of quality... I just don't want wrong info being passed... I'm sure its thermal properties are very sufficient, obviously steel sleeves were around well before aluminum on aluminum contact... Yet its just not as good at dissipating heat as aluminum, and you won't see this until the cylinder is heated until failure... which will never happen on this quenched klx.

So yea it really doesn't matter... pick either one their both great.

 

No offense to anyone... but this is headed down the typical "internet BS" IMO.... Do it or dont do it, 250, 300, 331, 340 and 351 have been proven to all work. Getting into heat dissipation of materials is a little over the top. I heard my cooling fan kick on with the 250 jug less than 5 times. Didn't bother me one bit to go bigger. I have also put in engine ice to help with cooling, but i did that before my trip to colorado....

 

There is no aluminum to aluminum contact. The contact is between the aluminum piton and the thin layer of nickel silicon alloy coating the cylinder. If you have aluminum to aluminum contact youv'e got problems.