Hello,

TLDR; Can I use 79mm wiseco second rings on 78.5mm Supertech pistons because the 78.5mm second rings have 0.023" gap instead of 0.017"?

Some info:
Exocet with 1.6L stock engine, Ebay Turbo, FM DIY turbo manifold, MSPNP, up to 15PSI of boost, was running it for a few years with no issues, until it started overfilling the catch can way too fast under boost.
Figured that rings are gone, decided to rebuild the engine, engineering challenge mostly. Bought 78.5mm Supertech pistons with Wiseco 78.5mm rings from fab9tuning, bored and honed the block according to the pistons recommendations at a reputable machine shop. Started gapping the rings and the top rings seem to be fine, had to file it a bit to make the gap to be 0.016", The seconds rings' gap is way to big, 0.023" instead of 0.017" as per Wiseco chart.
Called fab9tuning and they suggested that the block was bored out of specs (which is questionable, but ok) and I need to go with 79mm second rings to compensate for it. Called Wiseco and they said that I must never do that as the rings won't seal, however, they said that 0.023" gap is fine for 15PSI+ and sent me the following chart down bellow.
I called the Toll Free: 1-800-321-1364 from Top Rated USA Customer Service - Wiseco Piston Inc. page, but the chart I got from this person who apparently works for www.racewinningbrands.com which is confusing:

Thomas Hanna
Tehnical Sales Department
Office: (440) 497-3170
Fax: (440) 951-6606
RWB - Home

So the question, what do I do, listen to fab9 or wiseco?
Any help would be appreciated. Thanks!

 

Buy the set of rings you need from another vendor.

Don't set yourself up for a full teardown and rebuild immediately upon cranking the engine and realizing it's fucked up. Build it right and only do it once.

FAB9 has a history of selling open box return items to many people on the forum, including me, and not disclosing and flat denying it. Beware.

And it was a very telling that he:
1) Didn't make it right
2) Told you to do something anyone with engine building experience would know won't work

 

And I would never gap them that loose either.

 

Thank you guys for the input, appreciate it.

How would you gap them for 25PSI+?

 

To the manufacturer's specifications

 

From the piston manufacturer specifications, not some random total seal chart.
I bet your gaps are correct for extreme boost, pretty sure mine were set at 017 top and 022 2nd. I kinda think CP and Wiseco are similar material, but I might be mistaken. Look up a Wiseco chart for your specific pistons.

Edit:
Oops I mean a supertech chart. And the are not a similar material.