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Old 04-14-2009, 09:46 PM   #1
STiGMATA
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Default ross pistons problem =( !!!!

hey everyone.....i bought some ross 100mm pistons part#99886 and i send them out for HPC coating on the top and sides....i get them back today, and i start assembly and i install the first piston and go to rotate the crank to make sure there isn't any binding and i dont even get to do one full rotation and the crank just stops so im wondering whats the deal.. then i rotate it the opposite way piston comes up then back down and same thing it stops so i decide to look at the other pistons and seee that the skirt on the ross pistons is .215 taller than the stockers...so the skirt is hitting the bottom of the bore before the rod reaches the bottom so now i have to call ross and see what they can do, cause now im stuck without a car ....

any ideas from any experienced builders or someone else that has used the ross pistons....thanks

did some quick measurements.....


from the top of the piston to the top of the pin (stock .7555 / ross .746)
from the top of the pin to the bottom of the skirt (stock 1.2575/ ross 1.3985)
pin diameter .905......



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Last edited by STiGMATA; 04-15-2009 at 01:37 AM.
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Old 04-14-2009, 09:55 PM   #2
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Where is the deck height at right now?
Are you above or below deck with these pistons?
I wonder if the set you got was previously ordered with a custom pin height or something like that.
Rotate to TDC and measure the deck height.

Also measure the pin heights between stock and teh Ross.
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Old 04-14-2009, 09:55 PM   #3
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hitting oil squirters?
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Old 04-14-2009, 10:07 PM   #4
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from the pin to the top of the piston is exactly the same as stock its the actual skirt is .215 longer.....ill take a pic and post it up
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Old 04-14-2009, 11:03 PM   #5
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measurments added to first post, and pics soon to come
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Old 04-14-2009, 11:06 PM   #6
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Well if that's the case then they may be able to be machined down, assuming the skirts are (will be) as long as they are supposed to be to keep the piston square in the bore at rpm.

oooops just saw that you added measurements.
That Ross is damn ten thou shorter, which means your compression ratio is going to change if you use them.
Not by much but it will change a slight bit.

Last edited by Team Scream; 04-14-2009 at 11:18 PM.
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Old 04-15-2009, 01:39 AM   #7
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yeah i used my starrett calipers and depth mic to get the measurements....plus bump for pics
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Old 04-15-2009, 02:06 AM   #8
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Dude, if I am right, you are going to feel like an idiot. But at least an idiot who doesnt have to mod something.

I just put a stock STI piston into a spare block and it pushed 3/4" PAST the access hole.....

So, rotate the crank and make sure the rods that DONT have pistons attached are not catching....

Not saying your are an idiot, just that you make hit yourself in the forehead.
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Old 04-15-2009, 02:16 AM   #9
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Hmm....

Last edited by Team Scream; 04-15-2009 at 02:22 AM.
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Old 04-15-2009, 07:08 AM   #10
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Quote:
Originally Posted by reddevil View Post
Dude, if I am right, you are going to feel like an idiot. But at least an idiot who doesnt have to mod something.

I just put a stock STI piston into a spare block and it pushed 3/4" PAST the access hole.....

So, rotate the crank and make sure the rods that DONT have pistons attached are not catching....

Not saying your are an idiot, just that you make hit yourself in the forehead.
You're probably right
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Old 04-15-2009, 07:52 AM   #11
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Agreed
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Old 04-15-2009, 11:32 AM   #12
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nope your wrong ....cause i thought of that yesterday, and decided to drop a ringless piston in the bore without the pin in the rod and the piston is actually all the way down when its lined up with the pin hole.....
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Old 04-15-2009, 12:15 PM   #13
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well i just called ross, and i guess its a design flaw, he said they will fix the prob for me.....i guess they designed the piston with too robust a skirt,lol
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Old 04-21-2009, 05:41 PM   #14
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Quote:
Originally Posted by STiGMATA View Post
well i just called ross, and i guess its a design flaw, he said they will fix the prob for me.....i guess they designed the piston with too robust a skirt,lol
Hey that is great news that they will fix it for you...I hope that means they are going to make you a new set properly and not mod the ones you have?
Furthermore, I hope they turn it around for you most ricky ticky.
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Old 04-21-2009, 05:48 PM   #15
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heh, its too bad, if only you could get a custom crank and rod combo, it could work!
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Old 04-21-2009, 08:01 PM   #16
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Quote:
Originally Posted by STiGMATA View Post
well i just called ross, and i guess its a design flaw, he said they will fix the prob for me.....i guess they designed the piston with too robust a skirt,lol
Do you get a discount for testing parts for them?
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Old 06-23-2009, 11:47 AM   #17
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Do you get a discount for testing parts for them?
ha ha ha , no!!!! just a new free set of correct pistons......
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Old 06-23-2009, 04:05 PM   #18
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I've seen this happen from a number of piston manufacturers. For whatever reason they make the skirts too long and they either hit the base of the block or the rod itself.

As you found out the fix is to have them machine the skirts down.

Thanks,
Phil
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Old 06-23-2009, 11:05 PM   #19
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Do you get a discount for testing parts for them?






That kind of integrity doesn't exist in this field.
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Old 06-23-2009, 11:17 PM   #20
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Quote:
Originally Posted by Element Tuning View Post
I've seen this happen from a number of piston manufacturers. For whatever reason they make the skirts too long and they either hit the base of the block or the rod itself.

As you found out the fix is to have them machine the skirts down.

Thanks,
Phil
Element
Really?!! From who?


...when did he add the comment on the skirts? my reading fails as I missed the entire part on rotating and then stopping

Last edited by Homemade WRX; 06-24-2009 at 10:06 AM.
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Old 06-23-2009, 11:46 PM   #21
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Wrist pin holes ?
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Old 06-29-2009, 11:34 PM   #22
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Wrist pin holes ?
yeah the holes on the block that you use to slide in the wrist pin to connect the piston to the rod....
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Old 06-30-2009, 04:37 PM   #23
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Quote:
Originally Posted by Homemade WRX View Post
Really?!! From who?


...when did he add the comment on the skirts? my reading fails as I missed the entire part on rotating and then stopping
All have fixed this except Ross I guess

I have had problems with CP, Ross, and Manley pistons hitting. Our CPs at the time, keep in mind this has to be more than 4 years ago and this hasn't been a problem now for years, had to clearanced the bottoms by hand (do what you have to when a race is around the corner). The Ross pistons we had clearanced a little (this had to be 7 years ago), and the Manleys we just sent back. I get tired of fixing %$* for people and honestly when you tell them you usually get the, "we've never had that happen before we've sold many...." . I remember also pulling someone's built motor apart and you could see where the skirt was kissing the block but I don't remember the piston manufacturer. Most now have these issues figured out but when the 2.5 STi block was new this wasn't the case.

Also keep in mind not all rods are the same length but honestly all the above hit so bad it wouldn't have mattered which rod you used
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Old 06-30-2009, 09:57 PM   #24
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Quote:
Originally Posted by Element Tuning View Post
All have fixed this except Ross I guess

"we've never had that happen before we've sold many...."
I HATE that line

But alas with doing only custom parts now, that issue has gone down greatly
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