If you have a 50mm, a 52mm, and 54mm cylinder and all 3 are set up for a 42mm stroke crank, will the port top and bottom heights map out the same if traced over a rolled up piece of paper placed inside the cylinder????

And if all 3 cylinders are placed on a flat surface, will the deck height measure the same on all 3 (if set up for a 42mm stroke)????

 

If they're all set up for the same size stroke then the only difference should be the bore size right?You will probably have to measure them yourself to be sure.

 

the key word here is "set up for" if they are just decked to fit the port timing will be off. like building a poor mans ported cylinder. deck the cylinder more than it needs and then add an extra base gasket or 2 to get the port timing better. if you have a stock cylinder that is for a 45 crank and put it on a 42 the port bottoms will be above the top of the piston at the bottom of the stroke. you can deck it to get more compression but the material is taken off the top of the cylinder. the ports will still be above the top of the piston at tbe bottom of the stroke. hard to explain in writing but doing the best i can.. call billy at wrh or rich hetrick and they can explain it to you better.


Mark

 

To this date I have Not seen a 54mm bore, new cylinder, set up for the 42 stroke.
None of the 53mm cylinders were set up for a 42.
And only a hand full of the 52 mm cylinders were set up correctly port timing wise (polaris Best) all deck heights were incorrect.
Most all of the Eton/xtreme 50 mm cylinders were correct for the 42 stroke.
The new wrh 53mm aluminum nickosil cylinders are built precisely for the 42 stroke engine. Port timing and deck height.
None of the 52mm Aluminum nickosil cylinders currently available are set up for the 42 stroke engine.
I deal with them night and day, I know.

Deck heights would be the same.
Empirically, yes, port top and bottom heights would be the same.
In other words you desire the same exhaust duration, as in transfering from one cylinder to the other

Port maps (size of the hole)would not be the same due to the relationship of bore size -VS- percentage of port size.
I.E. exhaust size should not exceed 75% of bore.
The deck height is not your first concern. The first concern is to uncover the transfers as to gain the correct transfer duration #'s with out over shooting the exhaust port timing (duration). Possibly raising the cylinder.
Then try and determine how much material to take off the top of the cylinder to tighten the squish up.
For a 42 stroke the Gasket surface to gasket surface on the cylinder should be 77 mm. but all this changes when you space the cylinder up to correct the transfer port timing.
Most all your generic cylinders are set-up with what I call a Japanese industrial standard. A great big gap between the piston and head.

 

OK, then it's very clear to me that the best way to make power on my 42mm stroke 90 is to go with the 53mm.
To WRH16, I have sent you a PM.