Austarion

Found a set of second hand but brand new wiseco pistons for an eclipse, part no K559M85. The bore is right 85mm but i have no idea about the pin size which is 21mm. Any help advice would be greatly appreciated.

Those would be:
K559M85 Wiseco 1988-92 4G63 6-Bolt 21mm Pin - 8.3:1 - Standard Bore Forged Pistons


So they should also fit a 4g63 in a starion as it has the same bore & pin size as the 1G eclipse

Thats them, they appear to have recesses for a 16v head is this going to be a problem? i can't see it being one but better safe than sorry as apart fron some old air cooled V-Dub engines this'll be the first one i re-build.

Standard starion rods have 22mm pins. You'll need a set of vr4 rods or go with 1g forged eagles or similar to use them in the starion engine if im not wrong. As far as using them with the SOHC head theres no problem with valve clearence etc.

Starions have 21mm pins, so that'll be ok. Compression will drop if they are anything like the vr4 pistons.

hmmm my bad i always thought starions had 22mm pins!!! not to worry!!

Evos are 22mm while SOHC and VR-4 are 21mm.

Thanks guys.

Just remember when using forgies that they require less piston to bore clearance than cast one.

You need to measure all of you cylinder bores using either an internal micrometer or telescopic gauges and a normal micrometer, these can be picked up from hare and forbes machinery house for about $150 for both.

1 measure the bore a the bottom, halfway up and top then do it again but take the measurement 90 degrees from the first and note what the sizes are. Measure in thousands of an inch.

Work out if the bore is at true round by comparing all the measurements and their location in the bore.

If not it will need to be machined using a proper boring mill.
Honing it will not make it true round as a hone follows the contours of the bore.

Wiseco pistons need a piston to bore clearance of 0.0025" or 2.5 thousands of an inch any more than this and the engine will self-destruct.


So micrometer the pistons at the widest point of the piston skirt, for wiseco this is 1.300" from the bottom of the oil ring groove and at 90 degrees from the piston wrist pin (21mm)

Then add 2.5 thousands of an inch and this is what the cylinder bore has!!!! to be at.

If the bore is past this point then you will have to get oversized pistons and have the bore machined out to spec.

yes the VR4 type piston crown design works WAY better than the lumpy old starion crown shape. but as igotasicjb said, u might have to go for oversize ones...