Evo Pistons on 1g rods

[mach4g63t]

Okay, I've read all the threads on evo pistons on this forum. From what I gather, there is the simple feat of having the rods machine 1mm larger (as in the case when using 2g pistons) to have them fit on the 6-bolt big rods. I was also reading that the wrist pin of the evo pistons is off set 1mm in the other direction when compared to our stock 1g and 2g pistons. Can't remember if it's 1mm to the exhaust or 1mm to the intake, but it's in the opposite direction. Some people say it might 'cause piston slap, other people say they bolt in just fine.

Can anyone confirm this information and/or add in some advice on what they did to their rods to fit the Evo pistons. I can potentially get a pair for 75 bucks, which is uber cheap considering that forged 8.5:1 rods from wiseco or other places are over 400 bucks.

Thanks Guys.

 

[90laserRSfwd]

any update?

 

[mach4g63t]

Unfortunately, I never went this route. I just purchased a Wiseco/Eagle Combo for about 600 bucks and was done with it. Sorry.

 

[90laserRSfwd]

Not sure if EVO pistons will fit but the pin diameter is .866" (22mm - just like the 2g pistons).

 

[Big Woo]

The reason for the off set wrist pins is to reduce the shock loads to the piston and the reciprocating portion of the connecting rod. Off setting the wrist pin causes the piston to reach TDC at a slightly diffenrt time than the recipercating part of the connecting rod, effectivly speading the shock load over a greater number of crankshaft degrees.

Most OEM engines use off set pins thereby allowing them to use lighter components, and atain higher RPM's with those lighter parts.

I would suspect
that the EVO 4G63, and the 1G-2G 4g63's are opposite in terms of pin offset becasue the pin is most otfen offset toward the intake side of the piston, and the EVO has it's 4G63 mounted opposite from the 1G & 2G's.

 

[Big Woo]

I was thinking perhaps the piston slap issue should be addressed as well.

Since the connecting rod spends most of its time at an angle to the crank pin axis there are what is called major and minor thrusts. A major thrust is the downward movement piston's force against the cylinder wall, during combustion, due to the connecting rod angle. A minor thrust is the pistons force against the opposite cylinder wall during the compression stroke. also beacuse of the connecting rod angle. These forces very firmly push the piston against the cylinder wall. At TDC the piston forces will flip flop, this flip floping causes the piston to hit the cylinder wall during the changeover from minor to major thrust forces, this change in applied force makes noise (piston slap).

By offsetting the wrist pin and effectivly causing the piston and connecting rod to reach TDC at differnt times in terms of crankshaft rotation. This creates more time for the piston to change from minor to major thrust, thereby lessening the impact. Additionaly instead of a sudden lateral shift, the piston actually rolls from minor to major thrust. This effectivly translates to the piston first shifting from side to side at the skirt then gradually up the piston, instead of all at once.

 

[90laserRSfwd]

so will they work?

 

[JessGST]

Companies like Wiseco and Manley use their same piston for the Evo and the 2G. They just made larger valve reliefs in the 2G pistons to fit the Evo. Nothing else was changed.

 

[90laserRSfwd]

So it's possible that they infact would work them. I'm going to go down to the local Mitsu dealership with a micrometer and someother tools and compare the turbo 2g pistons and the EVO VIII pistons. I'll report back.

 

[Freerevving]

There are a ton of people running these in their six/seven bolts (I'm not one of them)... they work fine with no major modification

btw, 8.7:1 compression

 

[90laserRSfwd]

Stealership says they won't work. I disagree. Though they won't tell me (and I can't seem to find out) if the EVO VIII pistons are forged or cast.

 

[Freerevving]

yeah don't listen to them, parts people are almost programmed to say that... if you ask around you'll see that some people are running them, the main difference between them and the 2g piston is that they're 8.7:1 compression

 

[Freerevving]

and IIRC they're cast

 

[xi Talon ix]

yeah don't listen to them, parts people are almost programmed to say that... if you ask around you'll see that some people are running them, the main difference between them and the 2g piston is that they're 8.7:1 compression

actually they are 8.8:1

 

[Freerevving]

hey you need to get to work on the Evo cams... I'm getting anxious

 

[90laserRSfwd]

are the pistons cast or forged? No one will ever know I suppose....

 

[Freerevving]

they're cast from what I hear

 

[xi Talon ix]

hey you need to get to work on the Evo cams... I'm getting anxious

haha..well im still waiting on the machine shop. my local shop takes forever because they are always slammed with stuff this time of year. believe me man im anxious myself i havent driven my car in about a year.

 

[Freerevving]

haha..well im still waiting on the machine shop. my local shop takes forever because they are always slammed with stuff this time of year. believe me man im anxious myself i havent driven my car in about a year.

Well valve jobs are usually at the bottom of their list (not fun)... And can take weeks if they're backed up... but you can speed up the process by giving the guy in charge a cash incentive... or should I say, an early gift... Even $20 bucks is usually enough to say "here, just do my head before the others... See you later"

 

[90laserRSfwd]

Pistons are cast, they're 8.8:1 compression ratio (stock head and deck height, on stock gasket). They are $90 per piston and $59 per piston ring set at Mitsu.

 

[mach4g63t]

Unless you can come across a really good set out of a still good motor, it's more worthwhile to just go with a set of pistons from Wiseco or Ross. And if you're going 8.8:1 might as well go 9:1 (not that it's much of a difference) and then have the forged part guranteed with a piston designed for your motor. Saves time, money, and headaches. Plus, they're SHINEY when you buy them!

 

[Freerevving]

or just get some 86mm Mahle's... they're 8.7:1 at that diameter... plus the Mahle's are way more high-tech

 

[groundPork]

Pistons are cast, they're 8.8:1 compression ratio (stock head and deck height, on stock gasket). They are $90 per piston and $59 per piston ring set at Mitsu.

I'm not one to ever trounce on someone else's new ideas. i'll just say, by the prices you just posted (i did not verify myself though) it is overall better to get aftermarket forged. They will work for a pressed fit rod with no problem (i would prefer full floating, but pressed has been done w/o probs). it will be much stronger than stock. and if you must bore your rod out, use the ROSS evo std bore replacement. it does not have pin offset (you can use it in your DSM), and it does not require the block be bored. but you should hone it for the fresh rings.

my two pieces of burnt bacon...

 

[groundPork]

whoops. the majority of the last part of the post was for the original poster.

on another note... i have not checked my self, and judging by what dsm's i have done vp to piston checks on... it may not even matter, but good to keep in mind, that you will have to flip the pistons around if you use stock evo's... don't know what that'll do to your valve to piston clearance, but it may not be a good thing.

 

[90laserRSfwd]

The moment I found out the evo pistons where cast, I gave up on the idea. As 2g turbo pistons (8.5:1) can be had brand new for less then $100 (set of 4)