so heres the deal guys. this spring i installed a set of se204 cams in my tc96 softail. and i love them. but like a lot of speed junkies i want more and want to go to a 103. here is my question. a lot of people say that the 10:1 compression of the se kit is to high for the 204 cams. however i did the math with the big boyz calculator and the ccp and corrected compression is higher with the 255 cams which is what stage 2 103 kit comes with.

so why would the 255 cams work but not the 204's?

to lower compression ive looked at the keith black dished 103 pistons. makes it about 9.5:1 compression. anybody ever used those?

 

10-10.25 is good for 204s in 103. Do not go below 10-1! If ya go with the SE 10-1 pistons go to thinner head gasket for a little more compression. Might think about high ratio rockers also for some more lift. 10-1 with 225s does cause problems...

 

........or bore to 107", using a .040" head gasket and install a set of S&S .570's.
You'll never wonder if you did it wrong.
Scott

 

Fair question and the answer is that the SE204 has 8* of advance ground into the cam profile; it can be finicky and tough to tune at high CCPs. However, you can run the 204 but keep static compression below 9.8; actually 9.8 is "on the cusp" and 9.6 would be safer. More than 9.8 or it will ping; guaranteed. The OEM flat top pistons and .045" MLS head gasket should get you in the ball park; or the KB pistons and whatever head gasket thickness you need to keep corrected compression about 9.3-9.4 which should also keep CCP about 190psi. Been there, done that with the 204 in a 95"er; ran great except in the summer when south Texas heats up to 100* and change. Don't forget to correct for sea level when using a compression calculator. The suggestion of using the 1.7 ratio rockers with the 204s is a good one.

The KB piston is a hypereutectic piston, so is the H-D OEM piston. I have never used them so I have no personal experience with them but lots are in use with no issues.

Then there is always Scott's option which is a good one as well; the 570 cams are great. Those cams in a 95" motor with decent heads will make 100TQ/100HP every time and very useable power. In either case, the tune will make the difference.

 

Have you already bought the pistons ?

 

The common mistake is believing the SE claim the the flat tops in the stage 2 kit yield 10:1 compression....not so. More like 9.6:1. Bottom line....204's in a 103" using the flat top pistons in the stage 2 kit. (which just happen to be the exact same pistons in all the newer 103"s from the factory) with stock heads and TB with proper exhaust and intake yields very good results.
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