nick3

1991 240sx ka24de. i have a lot of upgrades (exhaust, cold air intake, cat removed, venom 400, header, pulleys, wires, ngk plugs, msd ignition system with 2 external coil, fidnaza flywheel, cenerforce dual friction clutch, mechanical fan removed, and a nx nitrous stage 2 (35-75 shot) kit with the digital rpms that you can set what rpms you want the nitrous to cut on and cut offand bottle warmer. and also spoiler, body kit, 19 in rims, and custom crome and black tail lights and dual hood scoops. i just got a new cylinder head with everything in it, timing kit, performace head gasket, eagle rods, and i havent got the arias forged pistons yet because the mechanic said to wait to see if it needed to be bored out first. i havent put it in the shop yet because im saving up the $1000 to get it done first. he told me that if it had to be bored then it would cost about $160 more. for that price i want to bore it out. i wanted to know what size to bore it out without going to much and with out using a lot of gas because i use the car every day. thanks

CircuitRacer

Just take off wat is necessary to have the cylinder bores straight. It all depends on the block's condition

wikd240

if you are getting forged pistons then you want to go .20/.5mm over bore...that takes your motor up to 90mm... that is the next size up piston and ring set... any company that makes the forged pistons for a ka24 will have them... take a look at this thread... it will give you some information about a na ka motor build ups...
http://www.club240.com/forums/showth...threadid=19485
this thread is pretty long but has a lot of info in it about the ka and the parts and where you can get them...
my block is bored .20 over as well as a lot of other internal work done to it...
everyone might get tired of me saying this... but here again... you are replacing your timing chain... i would also suggest that you replace the timing chain tensioners as well... i skipped this part and now i have 3900 bucks into a fully built motor that is dead... it is a small investment compaired to the rest of the motor...

nick3

the timing kit has the tensioners in it, but how much more power would boring it out to .20 give me? i dont think it would be much.

wikd240

thats why i was saying to read the post... get pistons from a 90 sohc... it will raise your compression ratio... a little more power... boring the block in itself will gain you almost nothing... but sticking in sohc pistons will... read the thread we have a lot of ideas and things to do to your motor to gain you more power...

nick3

ok, i will. and also i found out that eagle doesnt make a rod for ka and the guy on ebay i was getting them from must be full of crap for tring to sale my a set. where can i get a set that is nice and cheap?

wikd240

nice and cheap??? that aint gunna happen too easy... pauter rods makes a set... obx makes a set... they are all around the same price... expect to spend the most in this area...

nick3

do i really need them for a 75 shot? if i need them then ill go with a 100 shot

wikd240

you dont need them but it is good insurance... nos puts a lot of stress on the pistons rods and bearings... if you are going to use nos i would say yes you should get them... your motor is only as strong as the weakest part... i dont know if you have ever seen what a broken rod will do to a motor but do you really want it to be yours that is does it too???

nick3

ok i will get either get crower, or pauter rods. and how much horses will i get for the new timing kit, new cylinder head with everything new in it, rods, and forged pistons. i think the hp would just come from puting the new parts in, instead of the old worn out parts. maybe 5-15 hp

wikd240

you wont gain much in hp... even with all of the parts... where you would gain power is if you were to have the head ported and polished... better cams mafs bigger injectors better fuel pump and filter adjustable fuel pressure regulatorand a rechipped ecu...

even tho you have put on forged parts they in themselves wont add to horsepower... now if you raise your compression ratio then you will have some gains... but still there needs to be machine work done to the head and the intake manifold to get any real hp gains... tossin parts in there will not get you much other than an empty wallet...

you need to decide what you want out of your motor befor you start buying parts... i wanted 250 hp outta my motor and i had machine work and parts to get to that goal... if you want more than that then there are other avenues you will have to take... things like independant throttle bodies stand alone ems system or forced induction... might even come down to a swap...

what i want out of my motor might not be what you want out of yours... but in the end everything needs to work to that goal... all the parts machine work and TUNING need to be done to get the most out of your motor...

BigVinnie

iTrader: (2)

Expect under a 10% CHP gain by just installing the 1990 SOHC pistons......
Like wikd said the real power is in cams,fuel delivery, and ecu upgrade, and for insurance on high rev I would install CA18de titanium retainers, especially if you are running NOS...........

nick3

what about the jet performance computer upgrade? i had that on an old 240sx i use to have but didnt have many mods at the time. i didnt really feel any differnce. but i do have a lot more mods now maybe i would now. if not the jet, what can i do? the fuel upgrades im doing after i get all these things put in my car. upgraded fuel pump and fuel injectors. and with the pistons, all i have to do when i order them is just say they are for a 90 240sx, and even if there forged it dont make a difference? and is that 10% over stock or 10% over the hp im getting? i will look into the retainers. thanks

BigVinnie

iTrader: (2)

Honestly the cheapest way to go with more performance for less is an ECU piggy back.... Get an SAFC until you have all the work you have done to yur engine......
Then get a JWT biggest bang for your buck.......
It does make a difference if you increase the dish size of the 1990 pistons in the 91-94 KA, Raising the compression will give you the added donkey's, but then again you will need ecu reprogramming to get additional fuel for the new compression.
All an ecu does is calculate and determine mathmatical sequences.
If the ecu calculates fuel for 8.5 compression and then you install higher compression pistons your not making that much of a HP increase. Even with higher compression pistons the ecu is still calculating sequences for 8.5 compression. Hopefully that makes a little sense.......

nick3

i might sound stupid saying this but how do you piggyback the ecu, and can it be perment. what is a safc and why only until the work is done? the work will be done within a months time. and the jwt i guess is jim wolf, and is it another computer? and how much. thanks