Wiseco pistons

Hi, has anyone experience with wiseco 80" pistons with 9.5:1 compression ratio?

schnof

I used to use a lot of these back when more shovels were being hopped up more often. They are a good forged piston, kind of spendy and pretty much overkill for most street motors as far as strength goes. Make sure you run at least the recomended clearance or they will score. (being forged they expand more as they heat up, so need more initial clearance. Also, take off all the sharp edges, both on the dome and skirt.

My personal experience is that 9.5:1 comp ratio is about the tipping point on a shovel for running without dual plugs. 9:1 you will probably get by without dual plugs on pump gas and no pinging. 9.5:1 without dual plugs on pump gas and you will probably have an engine prone to pinging. All of this can vary with cam duration and timing, bike weight, altitude, and even driving habits, but that is the rule of thumb I always use for shovels.

I used them in various forms and never had a problem. My brother used them at 10 to 1 in a '74 74 and they worked fine with no pings.

Thanx for reply.
Pinging is exact what my engine did when it gets hot. I have tried to change the fuel (octane) it gets better but it doesn't stop.

Still heard a noise that sounds like huhhuhh when the engine was cold. Maybe the piston fit was to tight. Is that possible. I didn't check that measurement because I thought my engine builder made it correct.

Now I change to stock specs and everything works fine. But I still want to now what was wrong.

If the fit had been too tight you would have found scoring on the piston skirts when you took it apart. I'm not sure of the noise you are describing. If the pistons were fit too loose it could give piston slap (which sounds like kind of a knocking noise) which will be worse when cold and can be detected by placing the bike in gear with the brake on and easing out the clutch. Piston slap will be amplified by putting a load on the engine in this manner.

I had Wisco's in my 74" pan, The first set was set up to tight , they probably would have been OK if I had let the bike warm up good before thrashing but when riding with evos, sometimes yer in a hurry! The second set had .0025 if I remember right, and lasted a lot longer. Mike