Ok my most recent build the Wiseco 10 to 1 40 over pistons were hitting the head. The area machine shop doesn't like to cut pistons. He is pretty anal about stuff especially forged pistons and hates dealing with most of the aftermarket ie Wiseco JE whatever. So given my location and limitations here locally in Maine I found some Keith Black 40 over in flat tops. Website says they are .8cc but list their dome pistons -12.9ccs or something like that so using the Big Boyz calculator I'm assuming being flat tops they would be -.8cc. So my heads currently measure 74cc and I'm running a Tman 590 cam. How much more off the heads do I need to mill to get near a 10.5 CR or playing with BB calculator around 68cc with a .030 HG. Assuming 0 deck height. Thanks. This current build due to the piston to head contact I was chasing a noise. Thankfully wasn't my lower end but still been a pain in the butt. Thabks for advice and help
Post up some pics of the contact area on your Wiseco's to show us.
Any clue as to how much contact?
Were the heads at one time chambered to a certain set of pistons?
Carbide bur on a die grinder as a last resort maybe.
Find a more competent machinist.
Check your base gasket thickness. Some kits are thinner than OE. Were the cylinders ever trimmed before for zero deck?
Quote from: cheech on June 30, 2020, 08:10:05 PM
Post up some pics of the contact area on your Wiseco's to show us.
Any clue as to how much contact?
Were the heads at one time chambered to a certain set of pistons?
Carbide bur on a die grinder as a last resort maybe.
Find a more competent machinist.
On our DragBike, we needed to employ said carbide burr, to create a Divot for the Right side Spark plugs!!!
You should have a minimum of .030- .040 clearance between the head and piston faces with all gaskets installed at TDC.This will give you the quench desired. You will need min 10,5:1 with that cam also good choice.
Quote from: Deye76 on July 01, 2020, 06:33:21 AM
Check your base gasket thickness. Some kits are thinner than OE. Were the cylinders ever trimmed before for zero deck?
:agree:
I meant to ask in my prior post, where are the pistons ending up? In the hole, proud? How much?
Wiseco pistons need to be deburred due to sharp areas.
I believe the term is "mill em to death".
40 over EVO flat tops with a .030" Cometic HG would need combustion chambers around 67.5 cc to get to ~10.5:1CR, so almost 10 CCs off of a stock evo head. If you're at 74, some cutting has been done already. You can cut .050" more, reassemble, re measure the chambers, determine how much more need to be cut, dissemble, then trim again, repeating the process until you get to desired volume, then modify the intake to fit, along with the exhaust mounts;
or
trim the piston for clearance/fit, and leave the intake/exhaust alone...