Sharp edges on new pistons

**thanhngo** · 26-02-2007, 04:23 PM

Hi all,

I just got a new set of pistons, but I noticed the valve cuts seem sharp? I have been researching about headporting and removing 'sharp' bits around the squish area of the 4age head. These pistons also seem sharp...is this something I should be worried about?

I was thinking of thermal barrier coat (ceramic) the piston top later down the track.

**Billzilla** · 26-02-2007, 04:25 PM

Yes you should smooth-off the edges a little.
I use 800 - 1200 wet & dry sandpaper to do that.
Just enough to take the sharp edge off, you don't need anything like a 1mm radius or anything.

**thanhngo** · 26-02-2007, 04:35 PM

Thanks bill that was fast and painless

Most of the piston seems well machined except for those particular areas so just found it abit odd.

**Billzilla** · 26-02-2007, 04:37 PM

Originally Posted by thanhngo

Thanks bill that was fast and painless

Most of the piston seems well machined except for those particular areas so just found it abit odd.

I've yet to come across a piston that doesn't need a tickle here or there.

**jeffro ra28** · 26-02-2007, 09:41 PM

If your not concerned about compression ratio and want maximum performace it is wise to put a large radius on the cut out. Large as in taking out the grinding burr and cut the sharp edge right off. then polish it with sand paper or Linishor. Probly like a 5mm radius.

About the only piston company that put a HALF sufficient radius on the valve releifs are CP.
It will maximise full valve lift air flow when the piston is approaching TDC and the valve is aproaching full lift. Something not so many people worry about but its just one of those little things that add up to the maximum output of the engine.

You would think that they would come perfect from the manufacturer, WRONG!

**GasedT18** · 26-02-2007, 11:38 PM

thanhngo,

what brand are they?

D

**thanhngo** · 27-02-2007, 12:50 AM

For reference they are 4age 16v Toda items . From their website listed as forged though I am not certain mine are (maybe old types?) Anyway thats another discussion all together

I certainly don't want these cut up to tell.

**Billzilla** · 27-02-2007, 12:54 AM

Originally Posted by thanhngo

For reference they are 4age 16v Toda items . From their website listed as forged though I am not certain mine are (maybe old types?) Anyway thats another discussion all together

I certainly don't want these cut up to tell.

Definitely not forged - you can see the casting flashes, and there's a hollow space between the gudgeon pin hole and head.