EVO8 Piston Drop-in?

[tristanmb81]

Well, purchased a set of used Evo8/1G rods but to my surprised they do not drop right in, what's the catch ? I pulled my stock pistons out with no issues and never needed a ridge reamer. Now, my only options are to send the block out to be bored to fit the evo pistons Tried searching the threads I haven't found anybody else running into the same problem.\
Anyone wants to shine a light to this problem?

 

[hubz91talontsi]

Maybe you bought piston's that were already larger than 85mm?

 

[BLINKY619]

yea measure the evo ones and then measure the stock ones.... im pretty sure there oversize

 

[1995gsx20g]

did you compress the rings fully?

 

[tristanmb81]

i didn't put the rings on yet I was trying them out but the skirt won't even fit in the cylinder. But turning the piston upside down would barely fit.

i'm pretty sure they are stock 85mm pistons because they were off of a stock evo.

 

[1995gsx20g]

mic them up.

 

[donniekak]

Have you honed the bores yet? You will need to to make the new rings seat, yes you need new rings. Sometimes the upper 1/4" or so of the bores get a ring of deposits that need removed.

 

[RamenPride]

i'm pretty sure they are stock 85mm pistons because they were off of a stock evo.

used Evo8/1G rods

Not sure what you mean here. Stock EVO 8 pistons with machining done to fit on 6-bolt/90-91 "big rods" and a 7-bolt crank, or just stock EVO 8 pistons and rods?

Anyhoo, the only thing I could think of is that the EVO that they came out of had a stock rebuild done, bored over, and oversized pistons installed.

 

[tristanmb81]

I mic the top of the pistons and it's only a hair bigger than the 7bolt piston. However, the lower skirt of the piston seems to flare itself. The evo pistons were mated onto a 1g big rod. I know because this were removed from a 2g 7bolt motor. I'm still puzzled!

Did some researching and DSM piston size are 84.98mm vs EVO8-9 85mm. Do you all think honing my cylinder walls would do the job or should I just let the machine shop take care of it? Also, I accidentally dropped one of my pistons and crack a a little bit of the skirt lip. shit what a disaster!

 

[jking29]

They didn't have 1g big rods if they came out of a 7 bolt. If you cracked a skirt on one, that piston is junk. What exactly did the pistons measure? Got any pics?

 

[Stainbox12]

Im also interested on knowing about this issue. I recently bought some used evo 7-8 pistons for better compression, i would be mad if they wouldn´t fit. I have not installed them yet, as i know i need to machine the rod.

 

[jrohner]

The evo pistons were mated onto a 1g big rod. I know because this were removed from a 2g 7bolt motor.

You know they were modded to fit a 6 bolt because they came out of a 7 bolt? What are you talking about?

 

[tristanmb81]

wtf! you guys are thinking way too far into this question.

evo8 piston on 1g 6bolt rod.
prior to me purchasing them it was on a 2g 7bolt. the previous owner got the rods machined to fit a 7bolt crank.

now, this is why it is called evo8/1g big rod combo.

 

[RamenPride]

The evo pistons were mated onto a 1g big rod. I know because this were removed from a 2g 7bolt motor. I'm still puzzled!

so am I! I mean, I know you can get 6-bolt rods machined to fit on a 7-bolt crank and use EVO and 2G pistons, but not sure how the pistons/rods you have being removed from a 2G 7-bolt means that they are on 1G big rods. Do you mean that you know the pistons and rods should fit because they were already installed in a 2G 7-bolt? If so, maybe the person had their block bored and oversized pistons put in.

Did some researching and DSM piston size are 84.98mm vs EVO8-9 85mm. Do you all think honing my cylinder walls would do the job or should I just let the machine shop take care of it? Also, I accidentally dropped one of my pistons and crack a a little bit of the skirt lip. shit what a disaster!

If you cracked a bit anywhere on the piston, then the piston is junk. Anyway, honing the cylinder walls isn't going to take enough off the cylinder to fit an oversized piston. Honing is only to remove the glaze, not to put in a bigger piston. If you still plan on using what you've got (minus the one piston w/the crack) then take it to a machine shop.

 

[FLASH1970]

If you are so cheap/ broke that you won't/ can't buy new pistons you shouldn't be trying to mod/ rebuild your car. I would never use used pistons in an engine build. Take your engine to a machine shop and let them tell you what size pistons you need. I doubt your cyliners are still perfectly round. If you have a bore gauge, measure them and see but chances are you'll need to go .020 over.

 

[tristanmb81]

If you are so cheap/ broke that you won't/ can't buy new pistons you shouldn't be trying to mod/ rebuild your car. I would never use used pistons in an engine build. Take your engine to a machine shop and let them tell you what size pistons you need. I doubt your cyliners are still perfectly round. If you have a bore gauge, measure them and see but chances are you'll need to go .020 over.

first of all money has nothing to do with my question.

second, there was already a thread on here about someone using evo8-9 pistons on their 7bolt motor.

if you have no useful input about this question please keep your comment to yourself. i'm trying to keep this thread as short and sweet and get my problems resovled.

 

[FLASH1970]

first of all money has nothing to do with my question.

second, there was already a thread on here about someone using evo8-9 pistons on their 7bolt motor.

if you have no useful input about this question please keep your comment to yourself. i'm trying to keep this thread as short and sweet and get my problems resovled.

I did have useful input. I told you to take it to a machine shop and let them tell you what size pistons you need. Problem solved. Buying pistons before you have your bores looked at is not a good idea. Same with bearings.

 

[1995gsx20g]

some people like to look at the bores themselves because they don't even trust a well known machine shop. people make mistakes. i only use my machine shop to bore, hone and resurface. but i tell them what needs to be done.

 

[FLASH1970]

some people like to look at the bores themselves because they don't even trust a well known machine shop. people make mistakes.

I agree. I have a bore gauge I check my bores with once I get the block back to make sure. And I check it before hand and tell the machine shop what I found and have them verify it prior to ordering parts. I make mistakes too and it's always good to have more than one set of eyes looking at it.

 

[tristanmb81]

thanks guys for all of the inputs will bring block to machine shop to get it looked at prior to build.

 

[DSMunknown]

Just a quick reference link.


http://www.dsmtuners.com/forums/newbie-forum/311850-any-2gs-evo-pistons.html

 

[tristanmb81]

Just a quick reference link.


http://www.dsmtuners.com/forums/newbie-forum/311850-any-2gs-evo-pistons.html

Thanks! Was reading that a while back and I was talking to the OP and he stated that it was a drop in process. Oh well, machine shop is where my block and pistons are going.

 

[dsm-onster]

No matter how "used" they are, if they are meant for the same bore, they will slide in. . . Bores wear bigger and pistons wear smaller.

Oh, and I've taken "used" pistons to 52lb/min and seen 500whp trap speeds based on weight. If they are ok, then well, they are ok. Everything is "used" the instant you start the motor. But more importantly, 200k all stock blocks have made 4-5-600whp. Those blocks had 200k pistons in them. Reringing them and honing the block in a rebuild would just help the situation for those high horsepower and mileage blocks

 

[tristanmb81]

No matter how "used" they are, if they are meant for the same bore, they will slide in. . . Bores wear bigger and pistons wear smaller.

Oh, and I've taken "used" pistons to 52lb/min and seen 500whp trap speeds based on weight. If they are ok, then well, they are ok. Everything is "used" the instant you start the motor. But more importantly, 200k all stock blocks have made 4-5-600whp. Those blocks had 200k pistons in them. Reringing them and honing the block in a rebuild would just help the situation for those high horsepower and mileage blocks

Thanks DSM-onster!
I couldn't stand others negativity and I know that you see where I was coming from with this build. I know that going with brand new parts will always have its advantages but, I have done enough research before attempting this myself. However, a road block prevented me from accomplishing my build because it did not fit for me. Good luck self!