piston rings

[scruffy63]

i'm rebuilding a de with e pistons for a hc motor. i know I have to use the e piston rings, but how do I know what size piston rings to use??

[scruffy63]

can anybody help me??

[andrave]

use E rings, you answered your question.

[scruffy63]

well i know I need to use rings but there are different size rings. i don't know which size to get.

[Red coupe]

use the set that corrisponds with what size piston your useing,if you have standared sized e pistons use standared size rings if you are bored .010' use .010' oversized ring, ect...

[Tx-Sx-FS]

isnt the E a lower compression engine than the DE??

[scruffy63]

how do i find out what size pistons I have? I'm using the stock pistons out of my e so I guess i'm not overbored any.

the e is a lower compression motor but when you swap pistons it puts the de at a higher compression.

[Red coupe]

like he said iirc (Ive never seen the inside of any KA actualy...)the de has cupped pistons and the E has flat topped. With the shape of the E head and pistons the compression is less but in the de engins the e pistons take up more of the space in the chamber.

If you have standard sized pistons use standar sized rings, when you get the rings stick one inside the bore and square it up with a piston (grabe by connecting rod then push the ring downward a few inches) mesure the gap in the ring with a feeler gauge, then divide by 3.14 (3 will work fine if you dont want to use a calculator) this will give you the end clearance, Im not sure of nissans specs (check the fsm if you really want to know) but as a general rule it should be at least .003 - .004 for each inch of bore diamiter. Also becareful not to twist the ring when you install it, use a ringexpander or use a shop towl to pull outwards on the gap. Twisting the ring can make it fit more snug in the ring land by shaping it like a lock washer and preventing it from working right. Its also important toput the gaps over the wrist pin alternating sides with each ring so that it the rings will cause al little damage to the cylinder finish as possible untill they seat.
Modified by Red coupe at 1:49 PM 10/8/2004

[scruffy63]

thanx for the great info red coupe, that really helps.

the e has 2 different pistons.flat topped ones that had a compression of 9:1 and cupped ones with a compression of 8:6.

in the de the e pistons either make a compression of 11:7 or an 11:1.

[250sx]

If you know that the pistons (e) are from the a stock motor that has never been touched then thats standard. and make sure that the DE engine your putting it into has not been bored too. btw, never heard anyone mention here but all sohc ka trucks have flattops but with pressed in pins.

[scruffy63]

yeah I did hear that but yeah i'm taking the pistons out of my old broken KA that has not been touched.

[:: orion ::]

Bear in mind, there are 3 grades of stock piston...!!!

So you need to find out which grade they are, then order the proper rings. Or (if there's only one choice for rings) at least make sure the end gap is within spec before you install them...

- Brian

[250sx]

orion, what do lyou mean by 3grades of stock pistons?

[scruffy63]

i thought there only 2 "grader". the flat topped and the cupped.

[p00t]

orion, what do lyou mean by 3grades of stock pistons?

i thought there only 2 "grader". the flat topped and the cupped.

orions brain ->

you have to clean off the top of the piston it will have a grade number stamped on it (1 to 3). the grade number tells how wide the piston is. The higher the number the "fatter" the piston gets. this grade number effects the bore size of the block and the ring size used. The number matches up with a chart in the FSM. You have to look in the FSM for the clearances.

If you just slap pistons into the block without checking these things you can cause some major problems, mostly poor ring seal resulting in poor compression, lots of blow-by, and lots of burnt oil.

[250sx]

wow, thats some good info. I have a set that ill take alook at later.

[SX APPEAL]

thanx for the great info red coupe, that really helps.

the e has 2 different pistons.flat topped ones that had a compression of 9:1 and cupped ones with a compression of 8:6.

in the de the e pistons either make a compression of 11:7 or an 11:1.

just out of curiosity, What kind of power gains do you get respectivly from exchanging the pistons? And how safe is it running that high of compression in a stock engine?

[scruffy63]

I expect to be running anywhere from 16 - 180whp. its safe as long as I run 93 octane gas. 91 would be the lowest I would run but I wouldn't recommend it.

[SX APPEAL]

180 whp just from higher compression?!? Wow I didnt know they made that much of a difference. What other performance mods do you have?

[scruffy63]

well 180 to the wheels is really really pushing it but that is the max I can estimate. the compression itself is about 20-30 hp then with intake exhaust headers ecu and maybe upgraded fuel I believe you'll be up around 200hp. but i only have intake exhaust for power.stock hp is 155 , compression 25hp, intake 5hp, exhaust 5hp. 155+25+5+5=190 at the flywheel. this will add up to around 165-175 at the wheels.

[180fan]

you should ask Driftaholic, he's just recently swapped SOHC pistons in his DOHC motor. He says the motor is noticably faster and quite fun, aside from the problems he's been having with getting it to idle.

You might also want to check on the block itself for the piston ring sizes. Next to the piston itself, stamped into the block you'll see a number there too. Give those numbers to the parts guy at a parts dealership and they should find the appropriate rings for your motor.

Oh also if you're completely rebuilding the motor, be sure to get the rows of numbers stamped into the crank at the front, and also the number stamped into the bottom of the block for the proper sized bearings for your motor.

[deviousKA]

All grades of the oem nissan pistons (89mm) fall within the tolerance, meaning it doesnt matter which you use as long as they are standard bore. If grades are being described as 1:89mm 2:89.5mm 3:90mm, thats completely different.

More people should be boring their engines.

[scruffy63]

you more people should bore their engines. is this for power or to get the rings to seal properly?

[TrunkMonkey]

is this for power or to get the rings to seal properly?

to make absolute sure that you have the right clearances.

-demetrius

[TrunkMonkey]

well 180 to the wheels is really really pushing it but that is the max I can estimate. the compression itself is about 20-30 hp then with intake exhaust headers ecu and maybe upgraded fuel I believe you'll be up around 200hp. but i only have intake exhaust for power.stock hp is 155 , compression 25hp, intake 5hp, exhaust 5hp. 155+25+5+5=190 at the flywheel. this will add up to around 165-175 at the wheels.

GRRRRRRR....

no.

you'll gain 4-5% of power with every point of compression you go up. in other words, if you raise your compression ratio from 9.5 to 11.1 on a completely stock KA, you'll gain roughly 11-12 hp at the flywheel. the beauty of higher compression is that the more you modify (bolt-ons, boost, or nitrous) the more you'll gain.

-demetrius

[scruffy63]

but i'm going from 8.6-11.1, so wouldn't my guesses be close? also wouldn't boost or nitrous make the engine unreliable?(faster but unreliable)

[scruffy63]

but i'm going from 8.6-11, so wouldn't my guesses be close. also wouldn't boost or nitrous make the engine unreliable?

[TrunkMonkey]

but i'm going from 8.6-11.1, so wouldn't my guesses be close? also wouldn't boost or nitrous make the engine unreliable?(faster but unreliable)

if you're rebuilding a DE with E pistons, then you're going from 9.5:1 to 11.1:1.

-demetrius

[scruffy63]

sorry I had a moment of stupidity. so what about my reliability question?

[TrunkMonkey]

so what about my reliability question?

keep things in perspective. don't expect to run huge amounts of boost/nitrous on a high compression engine and expect it to last very long.

-demetrius