What is the engine life of modded motors and what parts are usually the first to detonate(fail)? was thinking of possibly working the heads on my 27hp kohler.

Shorter than stock

My recent research for my 27 Kohler has revealed that will head work, carb swap, exhaust and an UN-TOUCHED governor that the Kohler would be a very reliable motor. Internal mods and an increase in compresson will equal a shorter life span.

Question- What mods (or combination of) typically cause the compression to increase to a point that you are sacrificing the longevity of your motor? Just curious what some of the guys would say that have pushed these motors to their limits and beyond.

my stage 3 is on it's 3rd rebuild in under 100 hours. decking the heads and cam work with flat top pistons all increase compression. I was running 225 psi
.
While it ran it ran great. Firsts rebuild a evt cam failed with in 2 hours, second rebuild due to fact the "boat Dr" did not want to do a complete tear down when replacing the first cam, third rebuild the fuel mixture leaned out due to a leak in the fuel primer bulb (my best guess).

I bought a spare stock 35 twin to run while the bomb is waiting to be rebuilt.

I am going back stock pistons 9 if possible), and having a thicker head gasket made to bring compression under 190.

JD

I had almost 80 hrs on stage 1 with no big problems only a leaking case gasket which alot of stock motors do. Stage 2 lasted UM 10 hrs......its fun while it last but mark my words a few years from now we will have reliable madded motors wunning 35+ that last 100's of hours.

later

[quote="craig"][quote="JD"]my stage 3 is on it's 3rd rebuild in under 100 hours. decking the heads and cam work with flat top pistons all increase compression. I was running 225 psi
.
While it ran it ran great. Firsts rebuild a evt cam failed with in 2 hours, second rebuild due to fact the "boat Dr" did not want to do a complete tear down when replacing the first cam, third rebuild the fuel mixture leaned out due to a leak in the fuel primer bulb (my best guess).
I bought a spare stock 35 twin to run while the bomb is waiting to be rebuilt.



I don't know for sure. In outboards a leaking fuel line can cause a loss of top end. The jetting was set up with out a leak and a consistent fuel pressure and set barely rich, a intermittent leak could cause a low fuel level in the bowel and loss of a fuel to the main jets. It was running fine at wot them it would miss and stumble a few times then kill, it would restart with out problems . It was acting like a water or dirt in the fuel bowel. It did it even in my drive way. The miss and stumble was detention.

JD

I

If that was the case every engine that runs out of gas would burn up. If you was detonatin' you had other problems such as low octane level.

Stock timing, cam looks new, I had 10 gals of 91 octane in the tank and added 5 of regular. Compression was 225 on each side. I had just made a plate to mount the mikuni like they do on Harley's, It did not act like it had any vacuum leaks. The fuel line would only leak when it was moved .
I don't think I ever know what happened.

JD