dand86951

Tony, I went back to my written records and the number I wrote on the sheet to order the pistons was .007 inches. My memory is real good but real short. That would be .178 mm. I am certain this is the correct number. That would leave .036 clearance from piston top to head. Plugging in the .007 into the calculator the stock configuration gives a 8.0 to 1 compression ratio.

Tony

My notes show 27.8 cc on the 968 volume

HTH

https://rennlist.com/forums/showthre...s&pagenumber=2

Thats a link to some mods im trying on a stock 928s4 piston to increase its volume to produce an 8.5-9.0:1 configuration for a SC engine.

As i type, my "practice piston" is finished. I pick it up tomorrow(tues). Ill CC it again to see what i come up with.
This is some pretty uncharted territory in the 928 and Ive gathered that piston machining in general is a somewhat frowned upon approach to lowering CR....I guess i will see!!

id value any and ALL of your inputs.

You see in the thread..and the pic below. The 928 piston sits ..003" or .076mm short of the deck also.

Tony

This the machined piston. It now sits at appx 30cc vs stock 24...and a new CR of appx 8.75:1

Any in input on what should be done with the newly machined surface?

Im looking at hard anodizing...ceramic coating...or perhaps a combo?

Do the stock pistons come from porsche with a andozized surface on them.? From what i can see on my piston i would be lead to say yes.
Gurus out there?





Sorry if im hijacking the thread a bit, but it does concern piston volumes..and perhaps changing them.

dand86951

I would think the thermal barrier ceramic coating would be the best. Lots of hot rodders and race engine builders have been using it for quite some time with good success. As usual getting it done properly is the best insurance so check the references of whoever you should choose to use.