What should I do?

[P.I.M.P.]

Ok here's the deal. I have a 04 660 with a Stage 1 hot cam, Yosh pipe, K&N and Big gun rev box. I think it's about time for a new piston before this one takes a shit and does more damage. I want to upgrade to a 12:1 and possibly a little bigger on the bore so I'd like to know what size I could go to keep the reliability but still make the most power and not have to bend over on the price. I still want to run 91 and think I'll be ok with an average elevation of 4000-6000 ft.  I have a buddy that just went out and got a new 700 with a pipe and thinks he's pretty hot shit. So I'd like to run with him if not kick his ass. he weighs about 70 pounds less than me but isn't beating me to bad considering the weight difference and bigger bore. I want to get this done before Easter weekend so I can tell him I just adjusted the valves, fuel mixture or something like that. My budget is about $500 maybe $550 if that is everything tax, labor etc. Oh, I don't really want to upgrade cam or crank. Is this possible?

So big questions are
1. What piston? Weisco, JE or something else? (Reliable but cost effective)
2. 12:1 with my elev.  91 ok or not?
3. P&P while I have it apart?
4. What bore to keep it reliable and if I need to bore it later to put another in if this next one goes.
5. With these things 12:1, bore, P&P, pipe, intake, rev box, stage1 cam should I beat a stock 700 with a pipe?
6. What price range with your suggestions? What if any problems have you had with yours if you've had similar things done to yours.

Thanks for the info!

[Caliraptor]

piston wiseco 102mm 11:1, if you go 12:1 u would need to run vp or 91 with octane booster. do the P&P because it does make a noticeable  diff. having a 686 is the last cut on the cylinder, so u might want to go 101mm 11:1 that way u have more life on the cylinder. with those mods you should be beating him. piston retails for like $130 on ebay, gaskets around $70 for both, plus labor 

[P.I.M.P.]

So no 12:1 at my elevation? I'm already runnin 91.

[Peelz]

I would stay at 11:1 but go bigger bore. Buying race gas is not for me though.  Stage 2 cam for top end. 660 already has enough low end.  P&P if you have the cash. But the biggest gain will be compression jump and bore.

[P.I.M.P.]

So I talked to my machine guy today and he said here I could run a 13:1 if I want to do race fuel. I know I'm not going to do that but if I went to the 12:1 102bore I would be cool. Still not sure I want to do that because I still want to be able to ride in Glamis sometime. Is anybody over there running a 12:1 and if so what kind of gas?

[Colorado700R]

piston wiseco 102mm 11:1, if you go 12:1 u would need to run vp or 91 with octane booster. do the P&P because it does make a noticeable  diff. having a 686 is the last cut on the cylinder, so u might want to go 101mm 11:1 that way u have more life on the cylinder. with those mods you should be beating him. piston retails for like $130 on ebay, gaskets around $70 for both, plus labor 

Not at 4K and higher he won't, especially since the wisco will not be a zero deck true compresssion ratio will be around 11.5-1. 

Some stock 450's run a 12-1 ratio and have zero issues with preimum fuel at sea level.

[Mad Dog]

And you know that you can't compare the compression ratios of dissimilar motors in order to make generalizations.

Yes he might be ok with 91 and a 12:1, but that stage 1 is going to crank up the dynamic compression.  If he's at significant elevation his chances are good.  Could he get by with 91 octane and pump gas with a 13:1 in high elevation, it's possible but I think he'd need a lot more cam to do it safely.


A four stroke is an air pump, more air through the motor = more power.  If you don't want to run race gas and you're at a high elevation you'd get more umph with a 12:1 101 or 102mm piston and a stage 2 hotcam along with upgraded valve springs.  Your stock valves and seats aren't going to like it though and it's not exactly easy on the connecting rod either.

You're at the point now where a cheap build and a reliable build don't go hand in hand, 500 bucks only gets you started on the next step it won't do it all.  Unfortunately with each upgrade another part becomes the weakest link, and you're the only one who can decide how strong and reliable you need vs how much you can afford.