exhaust port height

[headache]

hey guys i'm working on an 87 R cylinder that has had a thick sleeve put in. anyways i bored it to 68mm and am just wanting to "port" it back to stock because the ports in the sleeve are way smaller than stock and was wondering what the exhaust port height needs to be from the top of the cylinder down to the top of the exhaust port. right now its at about 1.740". any help would be greatly appreciated.

[k7mm]

Not sure on the stock exhaust hieght,but I have a brand new Hinson spacer plate,that would allow you to run a YZ 250 piston, 68mm in your cylinder.This is what Curtis Sparks ran in his National 265's.Sorry I could'nt help,but if your at 68mm then I would go with the YZ piston,with the long rod crank 87-89 and spacer plate.The YZ piston starts out at 68mm so your thick sleeve would benifit from this set up.The only hieght I could get you is from a Curtis Sparks Hi Rev cylinder.Keith

[headache]

thanks but this cylinder is for my brother, he already has bought a wossner piston for the 85-86 cylinder and he is running the short rod crank setup. I think ive got everything figured out already.