Piston Ring Gap Question

[98mitsubishigst]

Okay, just clearing things up. I had my engine bored (20 over)and my friend who took an auto class said its fine to just put the rings on and put them in the engine because the rings i ordered were 20 over..

If my engine was bored 20 over does that mean i don't need to gap my rings?

I already assembled the engine... so i need to know if i need to take it all apart again..

thanks everyone

 

[92EagleAWD]

If they are for pistons .20 over then you should be fine, most rings are pre gapped for your application, you can check them with a feeler gauge, generally speaking rings for stock turbo engines have a smaller gap, the more power you make the bigger you will want the gap, if the gap is too small and the rings expand too much they can gouge the cylinder walls.

 

[92tsiawdguy]

i run .004 piston to wall clearance and .03 top ring .25 bottom ring. your rings WILL need gapped. because your cylinder walls will not be exactly the same. so your ring gaps may be too tight.

 

[Rob10_99]

I don't know how you can accept something from china to be suited for your EXACTING tolerances such as ring end gap.

I had my block machined/assembled locally(just the rotating assembly), and even the build sheet(i didnt have the time to build my own engine, or I would have at the time), said ring endgaps were in the .013 range, yet they were in the .008 range.

If you know anything about boosted engines, this would have scarred the walls of the block as well as possibly breaking the piston lands.

FYI, I'm now running .021 top and .022 bottom rings, bring on the boost.

Bottom line, if you don't check it yourself, your pushing your luck.

 

[Killa_dsm]

Like others have said, if you had your block bored you will need pistons that will fit that bore size. And definitely check your ring gaps, especially if your taking the time to rebuild your motor.

 

[95burgundyesi]

I used standard mitsubishi OEM rings on a standard bore during my rebuild and they were spot on all 4 cylinders, guess I am lucky.

 

[soulefood]

the whole thing is that you should have at least sent the pistons to the machine shop so when they final honed the cylinders they could hone them to within the manufacturers suggested piston to wall clearance. each piston although they are brand new are not the same size when your talking thousandths. so a good machine shop will mark each piston to each bore and make sure the final hone is within manufaturer specs. from there you should gap your piston rings. all you gotta do is put one of the rings inside the cylinder... flip the piston upside down and push the ring down a couple inches. this ensures the ring is square in the bore. then stick a feeler guage inbetween the two ends and you will know what your ring end gap is. if you are gonna have to take the engine apart to do it, then so be it. this is a 4g63t were talking about, and engine that if built properly, will stand the test of time when others wont. take the time to re-gap the rings. your engine will thank you!

 

[BogusSVO]

pull it apart and check them... if you run lean, and over expand the rings, the ends of the rings can butt and break ringlands and/or score the cylinder walls

most ring/ piston manufactures have a formula sheet in the package. use it and add.003 I have not had ring issues with this, yes it may oil smoke a little till the engine gets to op temp.

your friend in school is sort of correct, if he was building an engine for grandmas grocrey getter it be fine.... but your not.. so the clearance must be checked.

 

[98mitsubishigst]

Well i did send the pistons and main studs to the machine shop for clearances..


so i should just start all over?

 

[BogusSVO]

sounds like you need to atlest pop the pistons out, and remove the rings and check your ring end gap....

before you do that, check your rod to crank clearance too...

 

[98mitsubishigst]

my rings are scratching the inside of my cylinder walls.

wtf... im getting so stressed out.. i bought feeler gauges today..
so i put them in a few inches.. i did number 1 1st..

1st ring came to .020

is that right?

and the 2nd came to be .022..


BUT WHY DO I HAVE A SCRATCH DOWN THE CYLINDER WALLS IF THESE RINGS ARE SUPPOSE TO FIT?

 

[spooled_u_1st]

Did you spray your cylinder walls with wd-40?

Yes those are the numbers your looking for. Also you want to turn a piston upside down and slide the rings down an inch or so to make sure the rings are square in the cylinder.

 

[98mitsubishigst]

WHY are my rings scratching the sides of the bore then?

there is a scratch the whole way down for the rings ...
but if they are the right size wtf..?


and i oiled the walls with my oil

 

[BogusSVO]

how bad a scratch? it may be from a sharp corner of the ring..

 

[donniekak]

If the pistons are installed improperly an oil ring can pop out of its groove and bend down beside the piston and scratch the cylinder wall. Get a good piston ring compressor and this wont happen.

 

[rtincher22085]

So my instructions said to take my bore and x it by 0.0050 for the top ring and 0.0055 for the second ring. I have JE pistons and rings I ended up .018 top and .021 for the second and oil rings were .016 .015 minimum my block was bored over .20 = 85.5 mm I was just wondering with my setup 16g will i be safe to run the gaps that close seeing I ain't pushing the 400 mark? gas availaible is 93 octane