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Sat Feb 18, 2017 11:07 am

Trying to figure out what I have here and not sure how to read this number 87.96. The pistons measure 87.5mm, was told that it was a 1641 when I bought it used but that would have been 87mm? this is also a machine in kit from the mid 1980's that sat as parts until a few years ago.

Sat Feb 18, 2017 11:14 am

88's
69x88=1679

Your mic is not centered correctly on the piston

You might check your cylinder wall thickness to also see what you have

Sat Feb 18, 2017 12:00 pm

Thanks, cylinder wall is 3mm.

Sat Feb 18, 2017 12:07 pm

X2 on the measurement method.
Slide the calipers on with the flats at the widest point on the piston. Using the tips is no wise. The get stressed over time and can give you incorrect measurements.

Trust me on this. I have literally inspected several hundred thousand SS fittings in my career using the method described above.

Good Luck.

Edit: Also make sure the measure all the way around the piston. You want to find the highest and lowest measurements.

Sat Feb 18, 2017 4:47 pm

You have the thin wall 88's. I would really consider getting a new piston and cylinder set, then you can do a really nice upgrade by going to a 5mm wall thickness cylinder for durability and have fresh good conpression again. You just have to open the heads up slightly to the 90.5 size. For $180 its money well spent. Before ordering, you will need to also check your engine case id to see if it was really machined or not.

http://vwparts.aircooled.net/mobile/Product.aspx?ProductCode=VW8800T1K

Depending on your case id, if its not really machined then you could always put some fresh 85.5's back in and have a 1600, which would again be a thicker cylinder wall then your 3mm 88's

Sat Feb 18, 2017 6:13 pm

jpaull wrote: You have the thin wall 88's. I would really consider getting a new piston and cylinder set, then you can do a really nice upgrade by going to a 5mm wall thickness cylinder for durability and have fresh good conpression again. You just have to open the heads up slightly to the 90.5 size. For $180 its money well spent. Before ordering, you will need to also check your engine case id to see if it was really machined or not.

http://vwparts.aircooled.net/mobile/Product.aspx?ProductCode=VW8800T1K

Depending on your case id, if its not really machined then you could always put some fresh 85.5's back in and have a 1600, which would again be a thicker cylinder wall then your 3mm 88's

What are you seeing here, that indicates these are thin wall 88's?

Sat Feb 18, 2017 6:21 pm

The number stamped on top the piston is the size of the skirt, not the ring area.
Measure the bottom of the piston, 90 degrees to pin, and it should be the same as the size marked.
The bore size, (88mm) refers to the size of the cylinder. The piston needs to be smaller than the hole or it won't move very well!

3mm wall is thin!
IMO 4mm should be the minimum

Sat Feb 18, 2017 6:26 pm

Ans: A novice on the cheap asian caliper.
Learn how to measure a cylinder wall - check it @ 4 places/90* apart - both top & bottom, then report back here w/ an average or else all figures?

ach60 wrote: What are you seeing here, that indicates these are thin wall 88's?