My 103 built is coming together. Just got my heads back from the porter, and my TW-555 cams should be in tomorrow..The chambers are set @ 82cc. I have two choices for head gaskets..The first will give me .030 squish and 9.59 corrected cr..The second will give me .035 and 9.49 corrected...do I push the envelope, or give myself a little room for the odd tank of poor gas...What would you do?

 

That cam needs to set at 10.5 cr, to be fully effective.
FuelMotoUSA, just tuned a 107", with our Stage II heads, 555 cam.
That was set at exactly 10.5 cr.
109 hp/127 ft/lbs, with OE t/body, and Rhinehart duals, and dyno chart is posted in the Touring section.
Those heads need to be surfaced more, and use the .030" gasket.
Scott

 

we like .030

 

Tighter Squish can help with the fuel situation.

"Squishes" the mixture out of the edges and at about the point of ignition creates more turbulance. This can stop preignition and helps the flame burn better. Nice and tight.

This squish is not just,only, a compression issue. Its a good running issue.

 

My calcs show that .030" and 82cc put your static at 10.4; pretty close to the 10.5 that Scott says that cam likes; .035 is going the wrong way. Moving away from the CR sweet spot for that cam and opening up the squish band.

 

The closer you can put the piston to the cylinder head,(without contact during normal operating temps) the less chance of detonation, you'll experience.
Singh grooves also help.
Scott

 

My calculator comes out at 10.47, with the .030 squish..Its pretty close to 10.5 ? The Harley pistons have very small valve reliefs

 

Don'tforget the singh grooves per Scott's suggestion; cheap insurance.

 

And compression releases.

 

I am just worried the singh groves will further put the compression in the wrong direction..I dont want to have the heads milled again (cost), and the compression releases are already in..Thanks for the replys