4g61t.org

I got a free set of EVO pistons and rods to use in my 2G block (once I get a new crank) and I'm still searching for good reliable info on how to mount these. I find conflicting info on using them in the standard direction and reversing their direction. Which is correct? It all seems to revolve around a 1mm offset wrist pin. 1mm in the wrong direction could easily lead to excessive cylinder wear. I'm also find info saying that the compression ratio will be lower than 2G pistons and some that say it will be about the same. Stock EVO compression is 8.8:1, but using a DSM head, it's supposed to drop a little. Anyone have any info or experience with EVO pistons?

im doing a build now with evo 8 pistons on 1g rods.. its in a 6 bolt motor.. and yes the pistons need to be flipped 180 on the rods.... not to sure about the 7 bolt 2g blocks tho.



Steve

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Steve 89 colt 2.3 stroker stock top end. evo3@20 psi 13.489@99.30mph 3/10 2012
On drag radials.auto trans.launching @ 5 psi and no traction thru 2nd.

If using a 4g63 head will drop the compression (I can neither confirm or deny this), then install a 4g67 head and get the compression possibly higher or closer to the 8.8:1 that it started with.

I'm less concerned about compression and more concerned about the piston offset. I'll take a closer look at it and see which direction the offset is on the EVO vs the DSM block. I need to clean the excessive carbon build up on the piston tops so I can also get a closer look at the valve reliefs and what effect they will have on the direction in the block.

I'd rather not use another head, as the one I have is super clean and was rebuild just prior to bending some valves. I have since replaced the valves, seals etc. I will also have to get my head decked a little since I have a Cometic MLS head gasket. I might shave it a little more to make up for the compression if I see this as a benefit.

Right now my biggest concern is the piston orientation.

Further research says to just put the pistons in like normal with the "dot" facing the timing side. This would apply to EVO or DSM engines. Since the engine's rotation is the same (clockwise) then the piston and rod need to go the same direction no matter which engine you are using. Those that have said to turn the piston around are referring to the valve reliefs cut into the piston. The intake side of the piston in the EVO engine, has deeper valve reliefs cut into them. This does not appear to be an issue, so I will run them as intended.

go to here very good info
http://www.thedsmgraveyard.com/category_s/822.htm