wiseco 13:1 compression pistons

[jimbob8915]

I am wanting to install a drop-in wiseco ck104 piston kit.  It will bump my compression up to 13:1.  I will install a power commander  and get a map but was curious if this is too high a compression for pump gas.  I also need to know if my starting system is adequate for this. Anybody with this mod ?

[Professor]

J&E has a kit that is 12.3 to 1 for a stock bore.

[Lucky34]

just curious... what kind of performance increases can u expect with the 12.3:1 and the 13:1 ?

[mountainmotor]

(jimbob8915 @ Nov. 10 2006,14:37) I am wanting to install a drop-in wiseco ck104 piston kit.  It will bump my compression up to 13:1.

Welcome to the site . I see this is your second post asking about compression .



With the Cometic head gasket supplied in the CK104 kit and assuming your chamber volume remains stock and the block has not been decked you will not come close to 13.1 compression with those pistons . There's  a good way to target 12.8 with the Wiseco's , in which is just about the ticket  .  Actually several ways to go about it but i've ran out of time today . Will check back tommorrow.

Question:

Are you going to cam the engine and install a pipe ?

[jimbob8915]

I want to put in an intake cam in place of the stock exhaust and degree both. I will run a stock exhaust because I like the low profile stock look and sound. 12.8:1 will still be great if it will run on pump gas. 2 points of compression should equal about 7-8 hp and I hope the cam swap and intake mods to air box and velocity stacks anouther 7 can be found with mapping.

[Don Hardcastle]

There are several other options for a low profile stock look for exhaust. The stock exhaust is restrictive almost to the point of making the rest of your mods pointless.

Don

[mountainmotor]

(jimbob8915 @ Nov. 11 2006,15:38) I want to put in an intake cam in place of the stock exhaust and degree both.  I will run a stock exhaust because I like the low profile stock look and sound.  12.8:1 will still be great if it will run on pump gas.  2 points of compression should equal about 7-8 hp and I hope the cam swap and intake mods to air box and velocity stacks anouther 7 can be found with mapping.

Adding compression to the Busa engine is the best way to catch up with the increased overlap and resulting lower cylinder pressure from use of larger cams . Quantifying gains from compression alone is a little bit tough to do .

Your talking a 14-15 hp gain and it's not going to get there with an exhaust cam only and will need some more engine behind that stock exhaust system .

Honestly , i'd stick with stock compression if thats all your going to do to the engine . You might compute the compression with a .018 gasket but still not any appreciable gain there with that particular set-up .

[mountainmotor]

Slip-on's , Yoshimura Stage I cams and the CK104's will make a marked improvement in the power that goes to the ground  . Like a different bike . Been there n done it and they sound sweet and run much harder than stock .

The difference in just adding slip-on's with cams and such can be seen or felt when adding/subtracting 80-100% map numbers , the stock mufflers are that bad .

[Professor]

(mountainmotor @ Nov. 11 2006,19:39) Slip-on's , Yoshimura Stage I cams and the CK104's will make a marked improvement in the power that goes to the ground  . Like a different bike . Been there n done it and they sound sweet and run much harder than stock .

What octane pump gas did it require? What about hot starts with a single battery.

I just looked at my time slips from Saturday. I had several passes with only 11-14 minutes between rounds. Stopping at the trailer for fuel and to give it a once over caused another start in between some of these. I’d like to stick with the stock battery setup but still need it to start again as soon as I shut it down.

[mountainmotor]

Required 91 octane at 12.26 static compression during 90F ambient .

Another CK104 engine went fine @ 12.81 with 93 octane but took the 93 to do it . Best way to build them is to take away most of the negative deck height and then exact the compression another way or ... two .

No problems at all cranking either engine when at running temp or with some heat soak  .

Aside from this std bore topic ,I feel certain that "some" of these 1397's that require two batteries are just too tight , have a bit of starter draw and combinations of , ect to include mis-computed compression .