Z22 piston ring gap question...

[budsaipan]

Does anyone know what the piston ring gap should be for a stock Z22? I need the exact number for the top and bottom rings. I'm building a Lz22. Any help would be appreciated! Thanks

[banzai510(hainz)]

thery are usually in the instructions in the pakaging

[budsaipan]

It only says .003" to .004" to per inch cylinder diameter... Anybody?

[banzai510(hainz)]

internet is your friend

 

http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

[budsaipan]

Does the link provide a universal measurements for all piston rings? Z22 has a 3.43" bore size. Now I ordered a standard size piston rings for the z22. Do they even need to be gapped? In the paper from the package says that it has to be .003-.004 per inch bore diameter. So 3.43"x.003= .01029 rounded to .010. Do the gap on the bottom compression be bigger or smaller?

 

From the chilton,

top compression gap is .0098-.0157

bottom compression gap is .0059-.0118

[banzai510(hainz)]

Be HONEST I dont know.

I have my bottom end done at the machine shop and they do it. I had 2 motors done and both needed a rebore and new pistons so they had to press them on the new rods so I have them do everything on the bottom end including new ARP rod bolts.

 

However a early NWDE member that used to own a 620 truck did his rings and not gap them. The piston broke on the top land cause I guess the ring butted together when they got hot.

 

the bottom rings will be less as the taper of the bore will be less.But i think this was also in the writeup.

[hang_510]

Do the gap on the bottom compression be bigger or smaller?

last motor i did them the same (which does NOT mean its correct for your application)

[budsaipan]

Thanks guys, I'm trying to swap the rings out this weekend and hopefully I'll find an answer to that. But if I do find out that the gap from the new piston rings are within the factory limits, I might try that. Or I might even try the specs from the link. Hopefully everything wont mess up

[RoadRace]

OEM specs are for OEM rings and OEM driving applications. like anything, when its different from the OEM specifications, then the tolerances can change - but that doesn't mean they have to change. if your are doing a stock motor with no mods and using it for normal use then read no further. but if you are planning a high performance application, then you have to ask a couple questions:

 

1) did you buy 'file fit' rings?, usually id'd with a ".005" over the finish bore size on the box

2) Are you using a cast top and 2nd ring? are the sealing surfaces black? are they shiny, are they different?

3) Are the top and 2nd rings different material? are they Chrome - no, not the shiny stuff, Chromium alloy.

4) Are they Plasma-Moly filled top rings? you can look at the bore face of the top ring and see a stripe in the middle if they are (there's a good pic of this in the link from wiseco).

 

the metalurgic make-up of the rings determines the co-efficient of expansion and therfor has an effect on the ring gap - based on the bore diameter (bigger bore = more ring material to expand = more gap required). the ".0XX" per inch of bore" guidline is a good reference point. but if you turbocharge the motor - this brings more heat and heat changes things, NOS changes it again, high RPM has a huge effect on ring choice and gap, so does the ring location on the piston - the ring height and spacing between the rings will also have an effect on the gap, some aftermarket piston manufacturers will change the ring locations based on their research for the application they are intending it to be used for. An example of this would be moving the top ring further away from the top of the piston because they found a larger than normal gap was required to stop the top ring from closing in service, so the fix was to move it away from the heat source so they could run an acceptable gap to keep cylinder sealing to an optimum level.

 

hope this helps.

[budsaipan]

"using it for normal use then read no further" - roadrace

 

I think it's safe to say that I won't be gapping my rings since I bought standard rings for stock pistons. It it just a stock rebuild. Bore and everything stays the same. Thank you very much. Just in time too! Really appreciate the help.

[datzenmike]

'Stock' means they are mass produced. In order to make them cheaply and fast in large numbers the pistons and the bores are graded for size. (for example) No piston is exactly 85mm. They range from 84.985 to 85.035mm. A difference of almost 2 thou inch. Not much but the difference in circumference is about 6 thou inch. A stock ring gap could be anywhere in that 0.006" range depending on the bore tolerance.

 

The piston is measured and given a grade number from 1 to 3 or 4 (w/e). The same is done with the block. You may have seen a number stamped into the piston tops. A cylinder that was over/under size 3 can quickly be fitted with a close match piston from the number 3 box by the assembler.

 

Just throwing them in will likely work. But better safe than sorry and not that much hard work to assure a successful re-build that will last for many years.

[hang_510]

The piston is measured and given a grade number from 1 to 3 or 4 (w/e). The same is done with the block. You may have seen a number stamped into the piston tops. A cylinder that was over/under size 3 can quickly be fitted with a close match piston from the number 3 box by the assembler.

i asked so many people about this... guess you weren't one of them :ph34r:

[±~~∞]

internet is your friend

 

http://www.wiseco.co.../RingEndGap.pdf

 

No two sites seem to agree on piston ring gap placement. The site quoted says compression ring gaps at front and rear positions (where the wrist pins are), other sites say not to place any gap at wrist pin locations. Main agreement among all is that compression ring gaps should not be at "thrust" locations (in line with movement of connecting rod or 90º from front).

[datsunaholic]

Never, ever install new rings without gapping them. If they're too tight they'll bind, break, and tear the hell out of the cylinder walls.

 

If they are tight, you have to file to fit. BUT- big warning- test all of them first! Don't file until you're sure you have to. A ring that's tight in one bore might be perfect in another. Butif you filed it right away, and find a wider bore, you won't have that tight ring to go there anymore.

 

Since no 2 cylinders are exactly the same, nor are 2 rings exactly the same, I now am in the habit of trying ALL the rings in ALL the cylinders and figuring out which ones are the best match for a particular "hole". Actually I cheat- I measure the rings all in one bore, then measure the bores, the bigger gap rings go in the smaller bores and vice versa. But I generally am rebuilding 12-cylinder engines with 3 compression and 2 oil rings each- 60 rings total. But simply taking each ring and ensuring they're in spec in the bore they are slated for is sufficient.

[HRH]

Yes, ring end gap is important. You can probably throw them in and they'll work, but DON'T chance it if you're doing it yourself. To much leads to loss of compression and blow by, too little equals broken ring.

 

There are a lot of contradictory ring end gap specs. Some say bigger on top ring, smaller on second, some others say just the opposite. I go with the Datsun bible specs. Looser on top, tighter on bottom. However, if it's just a stock motor, you can run a tighter tolerance.

 

Check this:

 

http://community.ratsun.net/topic/25243-ka-z24-build-compression-questions-done/page__st__60

 

Post #65

 

Post #55 has the ring end gap per Datsun bible specs. Keep in mind, you can run on the tighter side of this if you're building a stock motor that won't see super high rpm.

[datzenmike]

No two sites seem to agree on piston ring gap placement. The site quoted says compression ring gaps at front and rear positions (where the wrist pins are), other sites say not to place any gap at wrist pin locations. Main agreement among all is that compression ring gaps should not be at "thrust" locations (in line with movement of connecting rod or 90º from front).

 

OK if you are on the left side (driver's side of vehicle) looking at the motor, the thrust side is away from you towards the pass side fender. The top compression ring end gap should be at a 45 degree angle away from you, slightly left towards the battery or slightly right towards the hood hinge. NOT towards the front/rear (piston pin direction), NOR straight away or towards you. (the thrust direction) Which ever angle you pick, the second compression ring end gap should be 180 degrees opposite the top one. Again: NOT towards the front/rear (piston pin direction), NOR straight away or towards you. (the thrust direction) For example if you have the top ring gap angled toward the battery then the second ring gap should be angled towards the brake master cylinder. The gap in the bottom oil control ring should be below the top ring end gap.

 

 

 

±~~∞ Does that help better ? :lol:

[Sealik]

FSM

 

 

Mine 'will be' installed as...front of engine, left side in pic

[HRH]

Yes, that! ^