EVO 8/9 Pistons in DSM Block

[black92_tsi_awd]

So I bought a engine off Craislist that I was told came out of a running car. Since I don't trust anyone, I started tearing in partially down to check the bearing etc. Everything looked pretty good, little bit of junk in the bearing but nothing bad. I was told it had Kelford cams so I pulled them to get a part number and noticed the a couple of cam bearings were wiped out...as was the cams. So a total tear down was next. Which leads me to the the title of the post. This motor apparently had EVO 8 or 9 pistons installed at some point. Since there's no stock Mitsu part numbers I'm assuming they are from DSM Graveyard. The are mounted on 6 bolt rods with ARP bolts. I emailed them but got no response trying to figure out if they are 8 or 9 so I can pick up a new set of rings for the freshly honed/magafluxed block.

After hours of googling, I get alot of conflicting information on this setup...and most of it is 10 yrs old. So I was hoping to get some more up to date information.

1) Is there a reason not to run this setup, other than "it's cheaper to get aftermarket"?
2) Which way do the piston face since the Evo engine have the intake/exhaust flipped? From searching, It looks like the EVO piston sit lower in the bore than a 6 bolt piston so unless the cam is radical there should be an interference problem. This engine had the two dots facing the flywheel, which I assume is the "arrow" that normally faces the timing belt.
4) Has anyone actually calculated the compression ratio with a 6bolt rod/Evo piston/6 bolt head? Research says it's higher compression on the EVO but with the deck height in a 6 bolt setup it come out about the same 7.8 or 8:1
3) If these are Graveyard pistons, the website says the rings are different between 8 and 9? Hasting lists one ring set for both. Does anyone have the dimensional data to see if these pistons are 8 or 9.
4) I assume ring gap is set for the Evo piston dim?

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[BogusSVO]

The static compression is lower.

The 4g head is 47cc, and the evo is 43cc

Also notice how much lower the piston is in the block.

 

[black92_tsi_awd]

So it would be lower than 7.8?

The other issue is this block was assembled with the dots point rearward when the Graveyard Motorsports says toward the front. https://www.thedsmgraveyard.com/Graveyard-Motorsports-Specs-s/822.htm

When installing Evo 8 or 9 Pistons in your DSM Block, MAKE SURE Piston points tward the front of the engine. Rod Tangs should be on the exhaust side. You will notice that exhaust relives are backwards compared to a DSM Piston, this is how do the swap. The reason we do not point valve relives in the correct position, is because of the .040 wrist pin offset, which we want to keep.

I need to double check but I think the rods might be then assembled backwards if I flip them. Not sure why the rod tangs direction would matter on a 4 cylinder because they don't have another rod sharing the journal (not chanfered differently like v8's)

 

[lowell]

I ran Evo 9 pistons before with 1G rods, but had the machine shop offset bore the pins to raise the piston 1mm. I also cut the valve reliefs so there were no clearance issues.

 

[94awdcoupe]

I have run evo 8 pistons/rods in a 7 bolt engine. in an evo block they are 8.8 compression. in an early engine they will be approximately 8.15 compression. evo head is smaller at 43 vs 47cc. they also use .026 gasket vs .050 (felpro) dsm. I ran a one off turbo setup with it. a garret gt3071 bolted to bottom of fp manifold. it was a laggy setup. but made for a fantastic pump gas setup. I think it made 370whp 320tq 24psi if I remember right. the pistons are nearly flat tops. at most have 5cc dish. and the deck height is about .070 below deck. which is unusual in itself. they work really well if you ask me. maybe mitsubishi was on to something with the low deck flat top design. not sure. the also have a unique oil cavity under the piston that I believe is there to allow oil to stay on piston longer for better oil cooling.

anyone ever check compression after using these? i would be curious what cranking comp came in at? i have a new take off set of these and i am toying with the idea of running them again. just wish the comp in dsm engine was at 8.8

 

[black92_tsi_awd]

Well I ended up getting Wiesco Pistons since I had to bore the block. I guess I'll put these up for sale soon.