CP piston mahle nikasil clearance specs

[stubble88]

3.2 race motor
What are acceptable or maybe rebuildable tolerances for 95mm CP pistons with mahle cylinders?

My race clearance is over 0.2mm! Wondering what to do.

Cylinder ovality is over 0.05mm.

Thanks

[Old H2S]

Well your cylinders look round enough..
.008" on the pistons is a little big for race clearance that is not a turbo.
Set the pistons on 2 VEE blocks and look for total size on all sides and taper size on the north/south
12 &6 o'clock positions.
Then call Total Seal pistons rings and get a new set that they recommend.
Then call Calico Coatings in North Carolina and get the pistons coated with abraidable Moly .002" thick all around and change your oil after 2 minutes of break in.
OR....
Get a new set of super duper trick pistons from FAAPGAR here and laugh at your enemies.

[MST0118]

Some builders send their cylinders to Jerry at CP to get measured

[Dpmulvan]

Originally Posted by Old H2S

Well your cylinders look round enough..
.008" on the pistons is a little big for race clearance that is not a turbo.
Set the pistons on 2 VEE blocks and look for total size on all sides and taper size on the north/south
12 &6 o'clock positions.
Then call Total Seal pistons rings and get a new set that they recommend.
Then call Calico Coatings in North Carolina and get the pistons coated with abraidable Moly .002" thick all around and change your oil after 2 minutes of break in.
OR....
Get a new set of super duper trick pistons from FAAPGAR here and laugh at your enemies.

How are his cylinders round enough?

[Dpmulvan]

Originally Posted by stubble88

3.2 race motor
What are acceptable or maybe rebuildable tolerances for 95mm CP pistons with mahle cylinders?

My race clearance is over 0.2mm! Wondering what to do.

Cylinder ovality is over 0.05mm.

Thanks

Your cylinders are out of spec, isn’t the max .04 for ovality? Buy new cylinders or have them bored and plated. I’d buy new if you can afford it and use mahle pistons and rings.

[stubble88]

I’m going 3.4 hopefully just boring out my current cylinders. Was thinking CP pistons. 964 cam

[Old H2S]

.002" is good enough on a race engine for roundness, the new rings will be low tension, thin and wear in - wear out way before the cylinders are a problem. The rings will move to a happy spot and stay there in the first 5 minutes of run in.
The Cp pistons are fine, Henry says to knock off the sharp edges on the top for 5 extra HP.
If you're worried about the bores get the piston sides coated.
Ceramic top coating is cheap and would actually help on a race motor.
Call up Wiliam Knight and see how much you can save.

[Dpmulvan]

Originally Posted by Old H2S

.002" is good enough on a race engine for roundness, the new rings will be low tension, thin and wear in - wear out way before the cylinders are a problem. The rings will move to a happy spot and stay there in the first 5 minutes of run in.
The Cp pistons are fine, Henry says to knock off the sharp edges on the top for 5 extra HP.
If you're worried about the bores get the piston sides coated.
Ceramic top coating is cheap and would actually help on a race motor.
Call up Wiliam Knight and see how much you can save.

My race clearance is over 0.2mm! Wondering what to do.

Cylinder ovality is over 0.05mm.

Thanks

[Old H2S]

Look at the comments above on Henry's 930 for sale on BAT.. go to BAT comments.
Ovality problems are a myth.

[Dpmulvan]

Originally Posted by Old H2S

Look at the comments above on Henry's 930 for sale on BAT.. go to BAT comments.
Ovality problems are a myth.

Because comments and or opinions on a car auction website? How many motors have you built?

[Henry Schmidt]

The "ovality" conversation is a rather interesting one.
If you're not measuring the cylinder at temperature with a torque plate the number is rather ambiguous. The .004" number has been a standard for year but measuring used cylinders is hit or miss.
Malhe doesn't actually measure ovality they measure an air gap. When measuring old cylinders, the more important number is taper. The next most important issue is surface cross hatching. If you focus on this mythical "ovality" number, there is a good chance you will throw away a good set of cylinders.
As for proper clearance, the manufacturer will tell you the clearance spec and where that measurement should be taken.
When working with used Ps&Cs your most important consideration is ring groove clearance and ring end gaps. A little bit on the lose side may rattle when cold but in a race motor, all the pistons are doing is creating compression and holding the rings.