building the bottom end on the 280z
 

while im gatherin funds for the turbo swap....and the motor sits on the stand....i figured since im going through about a quart of mobil 1 synthetic every couple weeks id rebuild the bottom end of the old 2.8, in doing this i figured if it needs new rings why not just bore it...and up the compression a little?! so im trying to get some answers like stock comp ratio...and what aftermarket pistons are out there (ofcourse im trying to go cheap so interchanging parts would be optimal, like 240zx or something like that) and then im wanting to know if im going to have to change cams and the top end of the motor too? my dad will be buying this motor as none of the parts will work on the turbo setup and if he doesnt want to put it in his 280zx then ill probably buy another z and put this motor in it, but for now im daily driving my 280zx so downtime isnt a problem but i also dont want to spend over a grand when i wont get to use the motor for more than a couple months. and my dad will be buying it so i want to keep it cheap but peppy at the same time....any thoughts on maybe a 10-1 or a 10-5-1 or higher comp ratio and what all parts i could use without getting too expensive?

It's all up to you...

You could bore it 20 over (hard to find pistons now), 40 over (the more common bore), or do a 3L stroker (this is when you use the 240sx pistons).

A performance cam & head work is also up to you... it all depends on your hp goal & for what purpose you'll be driving the car.

10-5-1.... 10.5:1 lol. comon used flat top pistons and a thinner head gasket will get you around there. but, why not just build this motor for a turbo application? forged low comp pistons. all new bolts and studs ARP of course, and get an N42 or P90 style head and rebuild that. then just go standalone or get a ZX turbo harness and components. no point in rebuilding a motor your not going to even keep.

^^^ now who's not reading? :D

no i read that... but i still think its pointless. let him build the motor or at least pay for it.

IMO 10.5-1 is way to much for a street driven boosted engine. Pre detonation is the mortal enemy and will leave your expensive build scattered all over the street. Consider searching hybridz to save yourself some disappointing errors. The F54 blocks have a knock sensor that you can upgrade to use with an after market ecu like MegaSquirtnSpark. That way you can water or fuel quench or even retard the timing to prevent the melt-down.

I walked in to Airgas 2 years ago and asked the guy for the best deal. He had a 135 amp/110 volt Lincoln that was remaufactured with a full waranty. It looked brand new in the box to me. He threw in a auto dim helmet, gloves, spool of wire and small bottle for $550 including tax. I went back a month later and bought the .023 wire kit for sheet metal and the aluminum wire kit and bottle. I still can't weld forshit but I got the right tools.

lol, i think you skipped a few details there, he wants to build a higher comp engine then get rid of it to his dad and then get a turbo motor, which i think is a bit wastefull

ohhh god....here we go lets try this again.....dad has a 80 280zx gl that he just put about 5 grand into (new interior, kit, paint, wheels...the works) and hes wanting more oomph....i have the 280 with some mods now....but the rings are gone as its leaking oil (and the fact that its mobil 1 synthetic doesnt help) the clutch is also out so im changing the fly and clutch and figured id just pull it all and rebuild the bottom end while im there....i know you love the l28et and thats what i should swap.....BUT my dad will be buying this motor....for the same amount i put into it....HENCE why im doing it, its like me getting a more powerful car than i have right now im the meantime while the turbo is getting done (and did i mention it would be free) so i have no complaints with it....cause by the end of this year ill have a 400hp + turbo motor in my car forged pistons,megasquirt,methanol injection, blah blah blah so im not worried about going light speed right now....instead im doing all my body work and paint before may and then starting the turbo build....as most of my funding will be coming via this summe.....so like i said NO STROKING that involves crank,rods,and pistons.....just WHAT IS STOCK 78 comp ratio and a way to get cheap replacement pistons and rings to up it and still be safe im looking for around 230-250hp out of it as right now it should be making about 175-190 or so

We got the "why" part... :D

You're going to need a lot more than cheap pistons to get an n/a motor to 230-250hp... :paranoid:

for a 250hp range youll need the slight over bore for the aftermarket piston match and better sealing abilities, i dont recomend just going stock size again and new rings it might be out of tolerance for ring gap. and thats not a stroker or anything its a slight bore woopdy. your gonna need a standalone more than likely to get 250hp out of it. that or a Z31 swap should help maybe.... especially later ecu that can be reflashed what not.

as for me, i kinda lost faith in a turbo L motor for 400hp+ applications. they just want and want!

Indeed... lotsa G's to make 400hp w/ an L.

yea it takes some money to make it 400hp but maybe 4-5k with full standalone....and its well worth it name another swap that would be cheaper.....yea there isnt one.....cause any lsx motor will get that hp and so would a carbed 350 version but to change out all the suspension rearend and axles among everything else. especially wiring and standalone on an lsx motor is a big pita...and not even a datsun/nissan anymore...hence why i would rather spend the money, do it right the first time, and make more than enough power, but keep it all nissan.....but anyway back to topic...what piston/ring combo would you go with on the 40 over....and ive thought about it prolly only upping to about 220hp or so and thats fine....even if its only around 210-220 i can always put a small shot on it and easily get past 250

You're missing one important subject... RELIABILITY.

You can make a 400hp L28 motor for $4-5k... but it's not going to last long, because quality will be sacrificed for budget's sake. $7-10k is a better figure for a well built 400hp motor. We've had plenty of threads discussing that, so I won't detail further. If you want an example, see Jeff P's 450hp 280zxt... I think he's got about $15k sunk in that motor... http://www.angelfire.com/extreme/280zxt/

And as for the LSx motors... 350-400 is the base hp... you go up from there, so your $5k would be much better spent that way. I agree w/ you saying to keep it Nissan... but I also would add: Keep it realistic.

RB25 will hit those numbers with light and tasteful mods sound amazing and arent balls ass expensive like a 26 of 2jz etc and a fairly simple mount design. part of the reason i wanna learn to mig weld if you know where im goin with this :D

haha i can mig and have a brand new hobart.....hence why the rust will be fixed and im painting myself....and as far as the budget yes those are good numbers but im aiming for around4-5k for the build but we'll see how it ends up....and ls1or 2 is only about 330 so 400hp isnt base.....with cams intake and exhaust yes but not base....plus the mounting, drive shaft, rear end, u get the point....this is the way i see it simply put.....custom=pain in the ass and $$$$$$ and neither do i want to deal with so ill take my RELIABLE 400 hp turbo motor and call it a day

I'm not defending the motor... but in the words of Bleach: "do yer homewerk girlz." The LS2 is rated @ 400hp. The LS1 is rated from 305-350hp.

http://gilbertautoparts.com/ChevySmallBlockV8s/LS2.cfm

http://www.corvettemuseum.com/specs/2005/index.shtml

Again... Reliable isn't a $4k stroker motor. Did you click on the link from above about the 280zxt stroker $15k motor???

And building a custom motor is still called "custom" which you just said custom=pain in the ass.... :paranoid:

400+hp L will probably be the same cost as an RB25 swap honestly and probably be less reliable... maybe... yeah... idk bout that statement actually but i like the way it sounds. ud have to go stand alone thats for sure and that can turn into a PIA. its totally cool that u wanna do this, im just saying, i think u might think its a lil easier of a goal than it really is.

due yer homewerk gurlz.... Legandry Beast haunts you