I am planning to install a standard size high compression piston and an XR 400 cam. I have been told that running a piston with a compression ratio of 11:1 or higher requires the use of race fuel or octane booster. I am just wondering if using a JE 10.8:1 piston will cause detonation problems when using pump gas, considering it is very close to 11:1. My other option is using a Wiseco 10:1 piston. Using the Wiseco piston won't cause detonation, but it will also not provide as dramatic an increase in compression. I don't know what to buy. I want an increase in performance, but not at the cost of a decrease in reliability. If anyone has been in this situation before and can give me some advice I would greatly appreciate it.

Thanks

 

Every time I have had to replace my top end, I go Wisco. No if, and or buts about it! Wisco is a superior piston over stock. You can run High Octane Pump, Turbo Blue or CamII with great performance. Just me 2 cents!

 

Wisco

 

I ran a 10.8/1 JE in the 400ex I had.....and I had detonation (valve clatter)when I tried to run premium fuel. By the way, the JE piston is superior to a Wiseco in every way. Don't skimp on this one....the JE piston is more expensive, but you get what you pay for.

 

i heard that wiseco owns je pistons from a good source he also told me the difference between the 2.je pistons are built for torque and the wiseco's are flat top pistons built for revs..i personally am going with the je but haven't decided my compression yet..try magic racing for prices they beat je and curtis sparks prices on je's..haven't priced the wisecos...

 

Id suggest the JE piston ...Most if not all dragracers and dwarfcar racers use the JEpistons .....And look the IMS kit uses the JE piston ........hope this helps

 

I had a Wiseco 10:1 85mm in my 400EX last year. A couple weeks ago I pulled that one out and put in a new JE 10:6 86mm. I had absolutely no problem with the Wiseco and I didn't break it in properly either. The reason I got the JE is because I want a little higher compression to work better with a new cam shaft. I considered the 11:1 Wiseco but was wary of detonation problems with pump gas. That, and many people feel that the JE is higher quality than the Wiseco.

When I took the Wiseco out it looked very good. There was a bit of wear on the exhaust side of the top ring but virtually none on the skirts. When I compared the two pistons side by side the JE definitely looked higher quality. It looks stronger and the finish is better. The ring groove geometry and oil porting is more sophisticated on the JE. I haven't had any detonation with premium pump gas either.