Does anyone know the specs of EVO8 pistons and rods? I may be putting a set into a 6bolt motor. It seems there isn't a whole lot of information on the internet about this kind of swap.

Just real fast, I have a 6bolt 4g63. I am looking to maybe just use the EVO8 pistons on my 1G rods or possibly just keep the EVO8 rods as I heard they were the strongest of the 4G63 motors. I also heard that this would give me a 8.8:1 compression ratio over my 7.8:1 that I have now. I read somewhere a while back that the 2G 4G63 pistons have the same wrist pin diameter so if I were to use the 1G rods, it would bolt right up to the EVO8 pistons like they would the 2G pistons if I had the rods machined.

I'm not asking if this will work or asking for advice on this but if you have any, that would be awesome. I am more just curious on the specs of the EVO8 pistons and rods and will make my decision based on that information.

Any information will be greatly appreciated.

-K

 

I know it has been done before. I have seen a few write up on dsm boards

 

Information I found:

EVO8 pistons/rods specs:
Rod length: 5.906" (150mm)
Crank pin:
Piston pin: .866" (22mm)
Big end width:
Piston: 85mm
Compression: 8.8:1
Piston material: Hypereutectic Cast

Side Notes:
-Use EVO6 oil squirters?
-Turn pistons backwards?
-wrist pin of the evo pistons is off set 1mm towards intake
-Companies like Weisco and Manly use the same pistons in the EVOs and 2G T/E/L. Only difference is in the valve relief.

 

I believe the only company that uses an off set pin is Wiseco. If you were to use the EVO pistons on your 1G rods you would have to machine the 1G rod from a 21mm pin to a 22mm pin. The pistons are reversible as EVO 3 owners reverse newer EVO8/9 pistons for their application.

EDIT: At looking at Crower's spec's, EVO 8/9 stock spec rods fit a 6bolt and 7bolt crank.

 

So the OEM EVO8 pistons arent offset? Interesting. I read somewhere that they were. Let me see if I can dig up that info.

I know I would have to modify my 1G rods. I would let the machine shop do what they do. I know you have to shave .005" off each side of the rod and bore pin opening to 22mm to fit a 2g piston. I would assume this would be the same for an EVO8 piston but not sure about measurements. I think it would be the samebut again. let the machine shop figue it out

I would like to use the EVO8 rods as it would be an exact match as far as weight goes and would require no machine work thus saving money. Just drop in with new rings, bearings, and ARP rod bolts then call it a day. Just waiting to find out a few more details.

Do you know why they are turning the pistons backwards?

 

Here is that link regarding offset wrist pin and turning pistons:

http://www.galantvr4.org/ubbthreads/...&Number=513412

"Some will say to flip the pistons backwards but you don't want to do this because the wrist pin is slightly offset. Run them as normal, in the correct direction and replace the oil squirters in the block with Evo 6 squirters as they spray in a different spot. You could try to redirect the 1g squirters though."

This guy seems confident that the EVO pistons will work (and I am sure they will) but isn't sure about the rods. It seems nobody is sure about EVO8 rods in a 6bolt motor. Reading the link shows this guy Curtis tried it and had to add material to the big end of the rods to make it work with a 6bolt crank. There are 2 ways to find out. Get measurements or try and line it up and see what happens.

The thing with turning the pistons is that I am nervous about piston to valve contact. The reliefs in the EVO8 pistons are different intake/exhaust. I am running +1mm valves and BC 272s.

Just sucks that the information about this isn't out there. I would hate to have to find out the hard way. So far, it seems I am using the 1G rods on EVO8 pistons. Seems like the more reasonable thing to do at this point.

 

I would be cautious with the information that you are gaining from the links you provided. It seems to be quite dated, thus the opinion of the strength of an evo9 piston being better vs an evo8 is hogwash in my opinion. The stealership quoted me prices on stock pistons, rods, and crank, and said that they were the same between the 8 and the 9.

 

Well like I said, there really isn't much information out there. I have been trying to find out the piston and rod specs all night but cant turn up anything. Seems that this is going to have to be done the old fashion way... just see what works and what doesn't.

When it comes to stuff like this, I try and research as much as I can and usually I can weed out the stupid info from the right info but when there isn't much information out there to begin with and lack of knowledge regarding this swap then you really have no choice but to ask and see what other people say.

 

straight fit 8 piston and rod no need to turn them

 

I just put evo 8 pistons and rods in my 97 talon. Just flipped them around to match the valve reliefs. No valve to piston contact, no extra noise. Hopefully the longevity of the motor was not compromised. I'll probably pull the head after 10k miles or so and check the cylinder walls.

I just love that the pistons are lighter, have higher compression and the skirts are coated for less friction!

 

i has them in my dsm moda, rods have to be cut to accomodate pistons. Also got the pistons cut to accept larger 1g oil rings, but thats not a requirement.

 

It's better if you don't turn them around due to the offset pin. There is no clearance problem with valves/pistons, even when running HKS 272 cams on stock valves.

 

8 and 9 pistons are not the same. The 9 piston uses a different oil ring that doesn't work on the 8 piston. There may be other differences also.

 

I hear the wrist pin is offset, I hear it's not. Whatever, my motor has been running strong at 350hp for almost 5k miles (yeah, i've been driving a lot, especially in the snow!!) without ANY signs of abnormal wear, noise, etc etc. Bearing check and pulled the head last night to just double check everything is up to par.

Maybe 5k isn't enough to have a noticable problem, but i'm convinced that turning the pistons in a dsm/evo 3 is fine for a cheap rebuild... If i have any problems, i'll absolutely post them.