Inspecting and Machining Stock Pistons
02-21-2003, 06:08 PM
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Inspecting and Machining Stock Pistons
In a different thread, we began the discussion of modifying stock 944 turbo pistons to increase the volume of the dish to reduce compression ratio. I wanted to start a specific thread to have further discussions about modifying the stock pistons. Here are some things I would like done with my pistons:
1) Properly inspect them for integrity (are they cracked, etc), condition of iron coating (how much has been worn off and are they still usable) and specifications (are the ring lands within specs, wrist pin condition, etc)?
2) Increase the volume of the dish to the maximum safe size (by not going deeper than the stock dish but by making a full round dish the same depth as the existing dish). Perform accurate cc measurements on a before and after basis.
3) Lighten the pistons wherever possible. I have seen the newer 968 pistons where the lower skirt is removed under each side parallel to the wrist pins (but the skirts are full depth perpendicular to the wrist pins). Can this be done to the stock 951 pistons to some extent?
4) Balance the pistons to the sub gram level.
5) Apply recommended coatings such as thermal barrier on the top, oil shedding on the bottom and dry film on the skirts.
Looking at the above list of things I am interested in, does anyone know of someone who does a good job on this type of work? Any BTDT stories out there??
Thanks,
Jeff
1) Properly inspect them for integrity (are they cracked, etc), condition of iron coating (how much has been worn off and are they still usable) and specifications (are the ring lands within specs, wrist pin condition, etc)?
2) Increase the volume of the dish to the maximum safe size (by not going deeper than the stock dish but by making a full round dish the same depth as the existing dish). Perform accurate cc measurements on a before and after basis.
3) Lighten the pistons wherever possible. I have seen the newer 968 pistons where the lower skirt is removed under each side parallel to the wrist pins (but the skirts are full depth perpendicular to the wrist pins). Can this be done to the stock 951 pistons to some extent?
4) Balance the pistons to the sub gram level.
5) Apply recommended coatings such as thermal barrier on the top, oil shedding on the bottom and dry film on the skirts.
Looking at the above list of things I am interested in, does anyone know of someone who does a good job on this type of work? Any BTDT stories out there??
Thanks,
Jeff
