Ive been trying to find out about this set-up, Im on a budget while putting together this block for #650. I want to run a Evo Piston/1g Rod combo but im unsure if the Evo piston will work with a stock bore block or the block needs to bored over .020. I already have a .020 over block that has been cleaned honed etc, but would it be easier to just shell out money for aftermarket pistons and rods. or pick up a cheap set of evo pistons and have them machined to fit the rods. Thank you

Don't quote me on this, but I've heard the evo piston diameter is bit larger and would require your block to be bored for proper fitment. It might just be that the wall to piston clearance is larger due to being forged. Although, you should ask someone who has personally done it.

If you pick up used Evo pistons I would have the piston to wall clearences checked before anything. Also have the pistons checked to make sure they are still round. I'm not sure, but I don't think the stock Evo pistons are forged. I think they are just cast with 8.8:1 compression. You will need the 1G rods machined to accept the larger wrist pin. I would also have the rods and pistons balanced to match each other for better engine life and better performance. Balancing with the crank is nice, but just have each piston/rod weigh the same will save your rod bearings.

Honestly, you it may cost just as much as getting some JE pistons. Maybe.

EVO IX pistons are supposed to be forged

A lot of shops charge somewhere in the neighborhood of $125 to hone out the small end for a larger pin. Ive had it done for as little as $70 myself, i've done it myself when i worked in a machine shop for essentially free. I've also seen places quote as high as $250 to perform this work. Add to that, the reconditioning of the big end, plus balancing the rods, and you're already approaching Eagle rod pricing, brand new with ARP fasteners. This initially may lead you to believe it's honestly not really worth the time and effort unless you can do some of the machine work yourself. EXCEPT... eagle rods are set up for a floating pin. Stock pistons have an interference fit pin. Once you buy eagle rods, you're stuck having to shell out another $400+ for pistons with pins and locks.

Also.. this has been discussed before (see link below). Having never personally seen evo ix pistons, i cannot say with 100% certainty that they use an interference fit pin, but i'm 99% certain they do.

click

If your block is already .020 over, then you'd need to get pistons in .020 oversize as well. If it's already been honed, then you'd need to get your PTW clearance checked with anything other than stock replacements at .020 oversize, assuming the machinist set it up according to factory spec for the bore. You want to make damn sure the PTW clearance is correct, regardless of what pistons you're running. A good machinist likely would not even finish boring/honing without pistons on hand. Armed with this knowledge, you may want to opt to go with 1mm oversize pistons instead, and have the machine work done again, properly this time. Of course, if everything checks out at .020 (.5mm), then you're fine.

Hopefully, our new resident machine work expert "BogusSVO" can chime in here as well and add some more helpful information.

Well I just happen to have a set from a failed DSMGraveyard 7 bolt, but that is a story for another day Boys and Girls.





Where stock NPR pistons for a 6 bolt are marked 63DT , and 7 bolts are a 63DTF1

The Evo VIII/IX are engraved with a E9K1




They are a cast or a hyperplastic piston I will confirm that they are NOT a factory forged piston.

When you look on the inside and you see grids, it is a cast piston.

Yes the E9K1 is a press fit piston, not a floater with clips


In simplest terms, the Evo VIII is a flipped around 7 bolt 4g63

Piston selection is just one of the 5 main variables needed to calculate CR
(BTW From what I have measured, the 63DTF1 pistons will make more compression than the E9K1 by 1cc /ubbthreads/images/graemlins/ooo.gif )

If all you want to do it raise compression find a 1g head that is about 5.160 thick, and add +1mm valves, that should give you a combustion chamber size of 43-44cc

But for the expense of going to the Evo VIII pistons, and modified rods, I just can not justify the expense to HP cost ratio.

Also if you do buy a used set, make sure they skirts are not collapsed. Abused pistons will look just fine by the nekkid eye, but a mic will tell the truth.

The set I have, I just popped one out the block to look at it. Is a .020/.50mm over
Std bore is 85mm or 3.346
so a .50mm should be 3.366

Subtract .0035 for PTW, I should mic the piston around 3.3625

The one I mic'ed is 3.351 so it is collapsed by appox. .011 meaning the pistion is now junk scrap weight. In the past few months I have had 2 sets of used forged pistons come in and be .005-.007 from where they should be.

So there is no difference between EVO VIII and IX pistons?

Heyoooo, did someone say evo pistons? The 8 pistons have a minimum weight of 476g vs. the 9's minimum weight of 485g. The only info I really have is that the 9 pistons are newer, heavier (presumably stronger as well), and cooler to brag about than the lowly 8 pistons /ubbthreads/images/graemlins/laugh.gif Oh, that and you want the 1110B pistons as apparently there was some kind of revision? Anyway...

Here, have some part numbers!
Evo 9 .20 over pistons - 1110B076
Evo 9 .20 over rings - 1110A661
Evo 9 .40 over pistons - 1110B077
Evo 9 .40 over rings - 1110A662

How about some Evo 9 homologation papers regarding said pistons?!?


Evo 8 .20 over pistons - 1110A226
Evo 8 .20 over rings - MN155260
Evo 8 .40 over pistons - 1110A227
Evo 8 .40 over rings - MN155261

Evo 8 piston homologation paper!

StreetSurgeon, Do you have, will you post the other page for N5660 ?

If you pull up the pic of the piston on both pages, N-5688 and N-5660, You can see that both have E9K1 engraved on them. The revision you mention may be the added weight. But they both look to be cut from the same blank.

There is no secondary page for the Evo 8 piston. The reason the 9's had two pages is because of the revision, since the 8's had no revised pistons there is no second page /ubbthreads/images/graemlins/smile.gif

Here's where you can look at all that stuff.
click

I ran them in my laser build with 1g rods. Had to put them in backwards to clear. I loved how that thing ran. I sold it before i had any problems though. I blue printed everything and just used a little looser than factory specs.

Update with a little more info I found whilst digging through the Evo 9 supplemental information covering some changes between the 8/9. Of particular note is number two.