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NMcKe97

Dished pistons for NA?

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I just recieved my new pistons and rings from the machine shop for my NA l28. I had to have the walls slightly honed so I required oversized pistons.

I recieved a set from safety pistons with hasting rings. The part number is "SP123 -2 nissan (datsun)81-83 : 280zx 6v 81-83 : l28e eng 2753cc / 86.0 mm"

The set of pistons I got from the machine shop were dished unlike my original flat top pistons and my uncle, who I'm building my car with, said that's how they are supposed to be even though it will lower compression.

Through all the reading and searching I've done I thought that you only really wanted flat top pistons on the NA set up and dished pistons for turbos because of the lower compression.

So my question is, are these the right pistons to be using or am I supposed to have flat tops for my set up.

I've had the head  machined .005" and the block machined, I need to figure out how much material the shop took off the block but it's not much. Im also using a fel pro head gasket which I've heard it is slightly thinner than stock. My uncle said we needed to use dished pistons because of those modifications is this the case?

If I do need to re order pistons what brand should I get or who should I order them from?

Thanks in advance for the help and input it's much appreciated!

-Noah M

 

Edited by NMcKe97

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Which head are you using?  Look between the #1 and #2 spark plug holes, down at the edge.  It will say N42, N47, P90 or P79.

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Sorry I got ahead of myself and forgot to mention which year and model I have. It's a 1981 280zx 2+2 with a f54 block and p79 head.

It's a stock engine with no work done on it up until now since I've been working on it. It's been a family owned car its whole life so I know exactly what has or hasn't been done to it.

Thanks for your time.

-Noah M

Edited by NMcKe97

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Tough call.  The 2+2s are heavier so the extra pep from flat tops would be nice.  The stock '81 (I think) 2+2 junkyard motor I bought and tore apart had a P79 with flat tops.  

You don't want to make your helper mad but most folks get flat pistons from ITM, they are all over ebay.com.  Are the pistons already connected to the rods?  If your not looking for a hot rod and I'll say you're not, 2+2 ZXs are heavy, just stay the course.  It may be a bunch of trouble for no noticeable gain.  If you're having fun you'll end up with an earlier and lighter car to build a hot motor for. :D 

Here's a compression calculator that I've never been able to figure out but you might have better sense than me.  http://www.ozdat.com/ozdatonline/enginedesign/

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It sounds like we are going to find another set that are flat top pistons, definitely will need the extra get up and go for the build as I was already using every ounce of hp she had stock so I definitely can't go backwards.

16 hours ago, siteunseen said:

 

You don't want to make your helper mad....

You hit the nail on the head with that one Siteunseen, he's given me an unbelievable amount of help so the last thing I want to do is cause a problem or stress him out!

Thanks for the link to that calculator, that will definitely come in handy at some point or another. Probably not this build cause I'm to lazy to gather all the numbers and plug them in right now LOL but nonetheless thanks for the tool.

Unfortunately the pistons have already been attached to the rods but I can't have compression drop from 8.8:1 to 7.3:1 so we will be getting the right flat tops. I don't even want to know what the hp output on something like that would be, it sounds awful.

If I had a different head or a turbo laying around with all the other little goodies needed then the dished pistons wouldn't be a problem but unfortunately that's not the case.

I wondered the same thing zed head but the box and website both specify it's for the l28e so I'm not really sure what to think, it'd make more sense if it were an early 280z but what do I know. They imaginably have a reason for it or maybe they are just out of touch with the z pistons, who knows.

I think you'd be modestly surprised to see how the 2+2 drives, I've pulled on a number of cars with more hp including evos, bmws, subarus, and more. Probably has something to do with me knowing how to drive but I'd like to accredit it to the ol' Daty puttin in work!

For now I'm going to stick with the 2+2, it's done surprisingly well for me so far and that's with it being stock. You'll have to take my word when I say I've driven the $^!# out of her and really put her through her paces.

I've nonchalantly removed 100+ pounds of interior from her before and it had a real nice get up and go so I imagine if I really wanted to lighten it up it wouldn't be to tough. I believe I recall people lightening it to 2600lbs or less if memory serves me correct.

I know most people aren't a fan of the 2+2 but I've genuinely enjoyed every bit of it, it has a nice get up and go as well as great steering and handling. I could care less for the cruise control and all the other luxury bs, especially cause most of it doesn't work, but it's nothing I can't remove or fix.

Do you guys want pictures of the build or should I save my time and forum space?

Thanks again for the help, advice, and taking the time out of your day to help me gentlemen, it's very much appreciated, hopefully I can return the favor someday!

-Noah M

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P79 head originally came with flat top pistons and was used for NA ZX cars. I personally would never build a P79 head with anything but flat top pistons. And, most folks who build the P79 head follow a process where they shave the head far more than you have.

Guy can speak to this more....

@Diseazd

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It's not uncommon to find bad part information out there in the aftermarket world.  I had not even heard of Safety Auto Parts until this thread.  99.999% chance that they just acquired the part specs somewhere and are having them made overseas, for cheap.  Doesn't mean they aren't good, but they're just sending numbers over there and receiving metal back.  Somebody misread a document and put bad info in their catalog.

They call themselves a parts "sourcing" company.  

http://www.safetyautoparts.com/

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Thanks for confirming that jonathanrussel, I knew that they came stock but I wanted to reaffirm that you aren't supposed to use dished pistons.

Good to know that my piston to valve clearance won't be a problem, I was slightly worried about that, I'll probably check just to be safe anyways.

Yea when I saw the box the pistons came in I got a little bummed out because it was a brand I never heard of and have never seen anyone talk about on the forums, so the quality was definitely a concern.

Upon more searching I couldn't find much about there quality, didn't read anything bad about them but I'd rather not be the guinea pig and use something tried and true.

I'm now in search for 86mm flat top pistons with .020" overboard(or any overboard at this point). I can't find ANYTHING. I've called my machine shop, ITM, motorsports auto, zcardepot, datsun california, and northern auto parts, all of them are on back order for a few months and wont have anything for 4+ months they said. I found a single .030" flat top piston but that leaves me needing 5 more and at 40 bucks a pop it's not cheap. I also found a engine rebuild kit with .050" over but its 500 bucks and I don't have that kind of money.

It would help me out sooo much if you guys could give me a hand locating some pistons. If you know of a company, private seller, or anyone that might have something please let me know or talk to them, I would greatly appreciate it!

Thanks as always for the information and help guys, you're always very insightful and resourceful!

-Noah M

Edited by NMcKe97

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Unless I'm able to find a good deal on a head I REALLY don't have the money for it, I just got laid off and am looking for new work so at the moment I have no income and a shallow savings account.

If I inevitably have to use these pistons then maybe it was ment to be and I'll be going turbo in the near future, but I don't see that happening.

Thanks for the advice rturbo, I hope that's not the route I have to take but I appreciate the recommendation, I hadn't considered that option beforehand. I'd like to stick with the stock head and compression if possible but we will see what happens.

Thanks for your time, advice, and insight, I sincerely appreciate all you guys helping me!

-Noah M

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Hit up the junkyard, and see what you can find. I can't imagine that a head would be too expensive. Or, are you actually interested in turboing the car in the future?

Given your current financial situation, I'm wondering if maybe it would be best to take a break while you gather your thoughts - and funds - before you make a decision. It sounds like there isn't much you can do right now.

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These guys might be able to help.  Looks like they have either side of what you need.  You might try looking for 0.5 mm over, instead of .020" over also.   Who knows if the people you are talking to are dong the conversion for you.  Confirm your bore size also, just to be sure that the machine shop got it right.  You never know.  Might find the right pistons but then find the bore size is off.

http://datsunspirit.com/shop/86mm-bore-flat-top-pistons/

 

 

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Rebelloracing.com would have them most likely, if you're in a hurry. I have seen tens of adds on ebay at a time for a small oversize ITM piston to fit a slightly cut cylinder bore. 

Zed Head has a great idea, search .5mm.

Or go balls out like Dizeazed and have it cut to .030 & shave the head as much as possible without shimming the cam towers. :D

Good luck, hopefully this won't be a big deal bump in the road for you.

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my 2 cents...

Don't get distracted by the turbo, if you savings account is shallow, then turbo is not the way to go. It takes money to go this route...

I would go flat top for sure and don't be lazy! Use some of the good online engine calculators to figure out what you will have when you're finished. Figure out what compression you want to run and how to get there. You are gonna have to spend some money to build the motor and if your dollars are as limited as mine then it would be a shame to spend that money and not end up with what you want...especially for just a little home work.

Read some of the engine build threads for Diseazd he has built a number of engines...

 

 

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Listen good to the advice you are getting NMcKe97.  You'll live with the engine for a long time. The P79 chambers are large....piston contact is not a problem, and even with the flat tops, you will still have a very low compression engine. 1 mm (.040 inches) overbore is the minimum I would bore....ITM Pistons have worked well for me. Nissan used flat tops in the 82 ZX's NA engines.....still was a very, very low compression engine.

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Great idea rturbo, if I'm unable to find a set of pistons or some other alternative then I will most likley pull a head out of a yard.

I hadn't planned on going turbo (although I'd like to at some point, that or stroker) and still don't because as you and Patcon said, that takes money which is something I don't have a lot of. I more or less ment I would suffer with the low compression until I could get the parts, but forget that, sounds like it would be a while and would be a very slow and grueling time up until then.

As much as I wish I could do this build on my own time and schedule I can't because it's not my house and I currently don't have a place. I have enough funds to probably finish the motor but that's about it.

I've looked on Datsun Spirits website but it says they have no stock for 86mm or 87mm, I called them this afternoon and left a message inquiring about pistons and will follow up on it tomorrow.

I'll take a look and see if I can find any 86.5mm pistons, I hadn't considered that or done the math myself, so as you said Zed Head,  I doubt the people I'm talking to are either.

I believe we checked the taper with the new .020" rings and it all checked out within spec but I'll re do that, better safe than sorry.

I looked over ebay a few times siteunseen but I didn't see much in the .020" or .030" category, I'll give it another look and see if I missed anything.

I talked with Dave over at rebello racing and it sounded like he might have what I need, he said he would give me a call tommorow morning and let me know if he is able to get a .020" over or .5mm pistons. He recommended I use shaved turbo pistons accompanied with 240z rods if I cant find any flat tops. He said it will increase higher end torque as well so can't complain with that. The real problem then is finding l24 rods in a reasonable price range.

If you guys or anyone you know has some l24 rods laying around and are looking to part ways with them or trade them for some l28 rods I might be interested, if it sounds like somthing you're interested in send me a message or drop a comment.

I probably won't bore it out any more unless I have to just to save costs were I can, but who knows, I might have to go that route and I can't complain with a little extra umf behind each combustion cycle.

No matter which way I cut this cake money's being spent so I'm gonna do it right or not at all.

What's a safe amount of material I can take off the p79 head without having to shim the towers? I'll probably find the answer as I'm reading Diseazd's build threads but I'm gonna ask anyways LOL.

7 hours ago, Patcon said:

and don't be lazy!

Damnit Patcon that's not what I wanted to here LOL, but it's what I needed to here. I guess I'll be doing a little arithmetic in the next few days.

You couldn't have said it better Patcon, the last thing I want to do is assemble an engine I'm not satisfied with, I'd rather have not built the engine at all if that were the case.

I don't have any hp or compression ratio goal in mind. It's unfortunately not really a build for power, although I openly welcome it.

Mostly new oem equipment and upgrades where I can such as ARP hardware so that when I do really build it I'll have some experience and some upgrades all ready to go.

I'm rebuilding it because I already had half the block apart due to a head gasket leak so I figured I might as well go the extra mile. Plus I really wanted the knowledge and experience I'd gain from the rebuild. I figured mechanical work is a great life long skill to have so I went ahead and invested my time in it.

Up until several months ago I knew close to nothing about cars. I could change my fluids and basic maintenance but that was about the extent of it, I'd like to think I'm getting somewhat fluid in the vocabulary and understanding of things but I've still got a lot to learn.

6 hours ago, Diseazd said:

Listen good to the advice you are getting NMcKe97. 

I'm trying to digest and soak in every bit of it! I personally wouldn't invest my time and energy in something unless I was all in, so you guys have my full attention! I'm trying to put in my due time and gather all the info I can from you guys and these threads, thanks again for all the advice and info, it's really been a big help!

I assume that 87mm pistons won't be enough to throw the stock ecu off, correct me if I'm wrong,  so maybe that is the route I'll have to go, we will see.

I've only heard good things about ITM pistons so hopefully I can find some. Asides from custom and forged pistons what other brands are reliable and liked by you guys?

If the f54 p79 combo is already on the lower end of compression stock then I definitely can't go backwards and sacrifice hp, I was already using all that she had.

Unfortunately for me jonathanrussel they're out. I called and talked with 2 of their sales reps about it and they said they are out of stock and would have to call and order it from ITM. I informed them I had gotten off the phone with ITM earlier and that they are backlogged for several months and out of .020". With that in mind they said that would mean they have to wait as well.

So it sounds like I've got a few potential options now. I'll shoot for the original plan of using overbored flat tops but if that isn't able to work out atleast I've got a few other avenues I can take.

Thanks again guys for taking the time out of your day to give me a hand and share your knowledge and experience, I know I keep saying it but I really do appreciate it!

-Noah M

Edited by NMcKe97

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Dave is a really smart guy and well respected but....given your situation I would encourage you to keep it simple and find the right pistons. They are out there on some shelf somewhere. 

And, honestly your best bet might be to take your time with this engine build and find a complete engine that is for sale but that was running recently. Folks do engine swaps in 280zs all the time. Craigslist typically has full engines for sale all the time. 

Here is a 75 L28 for sale. Not saying $900 is the right price but usually folks take less than what they advertise. Point is....engines are out there. And, if this is really a 75 L28 engine then it has a pretty nice N42 square port exhaust head. I bet in California Craigslist has lots of options.

75 L28

Edited by jonathanrussell
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You didn't mention the source below.

If you liked what you had before, and you're not looking for a big project then just rebuilding it to factory specs would be the way to go.  As soon as you start modifying, you end up on a trail of mods to make things work right with the last modification.

http://www.zcarsource.com/piston-set-280zx-020-50mm-oversize-81-83-non-turbo-new_8_55194_50979.html

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36 minutes ago, Zed Head said:

You didn't mention the source below.

If you liked what you had before, and you're not looking for a big project then just rebuilding it to factory specs would be the way to go.  As soon as you start modifying, you end up on a trail of mods to make things work right with the last modification.

http://www.zcarsource.com/piston-set-280zx-020-50mm-oversize-81-83-non-turbo-new_8_55194_50979.html

 Reminds me of a warning  that I remember in a heavy machinery operation manual. "Any primary adjustment (singular)  will be followed by secondary adjustments (plural) to compensate for the primary adjustment."  That tidbit of info turned out to be the most helpful sentence in the whole manual. I, of course, had to find out why.

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I'd say you guys got that right, the farther I stray from oem factory spec the more dollar signs I see. As all of you said, it's never just 1 mod.

I'd get a different block if need be but mine was in fine condition and I'm already a grip of cash deep into this build, it's almost finished, just need pistons and I'm pretty much good to go. I probably couldn't get a block if I wanted to anyways. I appreciate the recommendation though and will keep it in mind.

Unfortunately this whole build is on someone else's time so I have to get it out of there way as soon as I can, I really don't want to over stay my welcome, I've already had to have it towed a few times from other friends houses because of the time :/ .

 I knew there was another z supplier I was forgeting about, thank you Zed Head for linking me to that! I gave them a call and they only have a half set but he said they can get the other half in a week or so from ITM even though they're backlogged. He said ITM have some in a warehouse apprently, I don't know how that is because everyone I've talked to including ITM said they are out but hey works for me.

Yea the factory set up worked great for me so far so that's the route I'm looking to go. As I said earlier I openly welcome hp gains and will take them were I can but it's not my objective, later down the road I'll make my way there.

12 hours ago, Mark Maras said:

"Any primary adjustment (singular)  will be followed by secondary adjustments (plural) to compensate for the primary adjustment."

Some words of the wise right there, that will definitely come to mind anytime I'm considering mods. Thank you for sharing that great quote!

Please tell me that's a joke and you didn't get your finger lopped off siteunseen LOL, that would be one shitty day!

After a very busy day and a number of phone calls I've gotten closer to finishing my build. Dave at rebello racing said he has a set for .030" over if I recall correctly, zcarsource has half a set in .020" over and can get the rest of the set in the following week, and my machine shop said they might have found some sealed power pistons in .020" over so I potentially have a few choices right now.

I'm thinking I will  try and get the pistons from my machine shop to start off because of convenience and if that doesn't work I'll probably get the set from Dave over at rebello racing because it's cheaper than zcarsource and a little extra BANG for your buck, litteraly.

Not that I have a large selection here and I'll probably end up with whatever I can get my hands on, but what brands of pistons do you guys prefer? I know ITM is fairly well liked and commonly used, I've heard good things about sealed power, and I forget what brand Rebello has but I imagine if they're using them it's pretty good. If it where your choice what pistons would you go with?

Once again guys thank you very much for your insight and good words, it might not be a big deal to you but it's helped me out tremendously and I can't say that enough!

-Noah M

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No Noah that was my attempt at humor for Mr Mark Maras.

About a year or so ago I hurt my hand or fingernail or something really sissy and got on here complaining. Mark operates heavy equipment. While doing some maintenance on a front end loader or something similar he unfortunately lost most of a finger but never said a word until I get on here complaining about blue fingernail. 

I'll try and find the thread later today. His hands look like sledgehammers! If he's got a daughter and I went to pick her up for a date and Mark said have her home by midnight, 11:30pm and I'm there. :D

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