new supertech pistons out of spec?

[poshatch]

I have a rb20 block that i had the machine shop bore and hone .5mm over and checked the clearance on the supertech pistons who are also .5mm over and it was good

checked the rings of two pistons in two cylinders, the top rings were in spec but the second rings were defiantly OVER the maximum allowed clearance for the ring gap

i dont remember the specs off hand but they were similar to 0.19mm to .48mm and these were reading in the .60's according to the feeler gauge

my question is should i trust supertech to know what they are doing and put them in or should i contact them and try to get some new ones?

Thanks everyody

[RRRRB]

who filed the rings?

[robbie2883]

who filed the rings?

+1 whoever gapped the rings did a crappy job. how did you measure gap clearance? did you put the ring down about an inch in the cylinder and make sure it's perfectly level?

[poshatch]

i put the ring in the cylinder and pushed it down both about piston height and to midway down using the piston itself to make it level then used a feeler gauge to measure it made sure it wasn't twisted.

and nobody filed them they came out of the packaging that way =/

since neither of you said it was OK im going to just assume that they are not safe to put in and will contact supertech to get some replacements. I hope they dont give me any trouble.

[robbie2883]

before you do that i would get a bore gauge and make sure that the cylinders were all bored properly. if the cylinders spec out properly then yeah...i would call up supertech and get a new set of rings. you can order them per cylinder so you don't have to buy a whole set of 6 if some are in spec.

[Darius]

+1

You have a ring filer, correct? If not, you should. They are only $20. You should be filing these regardless of what Supertech sent since each bore is slightly different and ring gap is extremely important.

[gawdzilla]

i put the ring in the cylinder and pushed it down both about piston height and to midway down using the piston itself to make it level then used a feeler gauge to measure it made sure it wasn't twisted.

and nobody filed them they came out of the packaging that way =/

since neither of you said it was OK im going to just assume that they are not safe to put in and will contact supertech to get some replacements. I hope they dont give me any trouble.

You need to file them yourself or have them filed by a machine shop using a ring filer. it's not an error from the piston manufacturer. if they're anything like my wiseco's, they do not come in the correct gap and need to be filed to your own bore.

[poshatch]

im sorry, but i have to say this

"i dont remember the specs off hand but they were similar to 0.19mm to .48mm and these were reading in the .60's according to the feeler gauge"

ill check all of them to see if i can get some rings to work with certain cylinders but the two that i checked were OVER they wont file to be smaller...

and if the bore is within spec of the piston, and the rings go on the piston, then it is a manufacturing error if everything else is ok but the untouched rings are too big off the bat.

in any case i did use a bore gauge to check it, my friends dad is a machinist and he brought home his work tools and he helped/taught/supervised the measurements and it was done correctly and he can vouch for they're accuracy.

thanks for the help i will contact supertech asap and i hope the customer service is legit.

[gawdzilla]

no one is saying you're doing anything wrong. all i am saying is that the rings will need to be filed and typically do not come pre-fit for the bore. they usually are shipped oversized and need to be filed down. this is so engine builders can customize the ring gap to their needs.

it is worth calling them to make sure what the ring gap is supposed to be, then file them to what is recommended by them. i wouldn't immediately accuse them of sending you the wrong rings or manufacturing error. it is not uncommon for piston manufacturers to send rings that are too large and NEED to be filed before installation.

[poshatch]

well somebody asked how i measured it so i wanted to be sure i let you all know how i did it

and gawdzilla your still not getting it

The only way that what your saying could be possibly true is if supertech designed the pistons and rings to work in different specs then FACTORY. The FSM says the gap can be NO BIGGER than .48mm and they are above .6mm

are you suggesting that i file them to make the gap smaller???????

I have not got a chance to contact supertech, the pistons did not come with they're own set of specs so i can only assume that i have to use factory clearances at the present time, which is why i started this thread in the first place.

But i think i got my initial question answered so i dont see a need continuing on in this circle. Thanks everybody.

[Darius]

You and gawdzilla are saying the same thing, he just phrased it differently. The rings come from any piston manufacturer so they can be filed to fit. Obviously you cannot file the gap smaller You will use the piston manufacturer's spec for the ring gap, not the FSM specs. This also dictates the ring gap location for each of the rings. If supertech did not supply this with the pistons, you need to inquire with them on what it should be. The FSM specs are based around the specific material of and use for the OEM rings.

[poshatch]

AWESOME! that is good news. but that may not be good news since i did not know that they would come with drastically different specs than stock

the machine shop put the bore/hone .5 over within OEM specs so if the pistons are different (possibly expand more with too small a gap or not enough and too big a gap) then that may be too undersized/oversized and may need more machine work =[

hope its just the rings!

Thanks for that bit of info

[robbie2883]

well...there's alot of variables there. what alloy are the pistons made out of? 4032 or 2618? different alloys have different expansion rates. the pistons should have come with a spec card. all machine work should have been based off that card.

as far as your ring gap. 0.6mm is only around 23 thousandths which is about right for a turbo street motor.

[RRRRB]

mine are at .022 and .019 87mm bore, being over and under a couple thousands is actually pretty normal, ive noticed this with mutiple manufactors i have used JE CP and weisco personally and not one set read identical even though the bore were within a thousands...

All my pistons were made out of 2618 which expands alot so being a little bigger is better than being smaller especially if this engine will see long runs of boost and or making alot of horsepower for a short period...

i suggest you pick the largest ring gap and file them all to that and be done with it, a couple thou wont hurt... oil expander rings are RARELY at the minimum .015 they state in the setup sheet... measureing in mm makes the specs look much farther apart than they really are... just FYI

[poshatch]

thats a bummer because they didnt come with a card, and i just looked on they're website its 4032.

and they dont have much on they're website to begin with so idono. hopefully it will be ok.

[robbie2883]

they DEFINITELY should have come with a card. did you buy them off someone else? you will probably need to contact supertech and see if they can help you out with a proper spec card (maybe they serialize their pistons) doubtful but worth a try. then you need to check the card specs vs what machine work you did. i'm REALLY surprised whoever did the machining though it was ok to just use OEM specs with aftermarket pistons and no spec sheet

[Shocker]

Do you remember you can have a ring gap that is "too tight" and during expansion the ends will butt and fubar your cylinder walls. A little loose wont hurt anything. Mine are #1 0.022" and 0.024" tho respectively for my Weisco's.

[robbie2883]

a hair lose is ok...but anything over a thousandth can cause warm up issues and blow by

[Shocker]

a hair lose is ok...but anything over a thousandth can cause warm up issues and blow by

I'd agree with this statement if ur making low power... But if your leaning on it with 20+ psi and big hp its better to be on the loose side vrs tight. Ill take a small amount of blow by. ( which in the big picture of.blow by will be null) vrs butted rings. Hp won't suffer and you will have a good reliable motor.

[robbie2883]

The term lose for boost or lose vs tight isnt in regards to rings. It's in terms of bearing clearances. Rings you want as dead on as you get them. Blow by is no where near reliable since you're going to blow fuel into the oil and make it a lot easier to wash out the walls and bearings. Not to mention the extra piston slap related with a lose piston. I'd just prefer to do it right. When your building with forged internals you're using chromoly rings anyway so there's no risk really of butting if you. Clearance right