200 NA hP possible?

[Guest tejas74260]

ive been reading a few articles here and there about guys who have a setup from the l6 engines that get them 200 or more NA rwhp. Thats something that i'd really like to do in my 260. do you guys have any suggestions for how the setup could be like? I'm definitely thinking of putting these factors into consideration:

 

I'm going to budget anywhere from 3k to 7k dollars into this (or as much as a 16 year olds income allows)

 

i want to do high compression (N42 head)

 

I want to use carburetors (keepin it nostalgic)

 

and im willing to go with larger displacement (even sonic test to see how much i can overbore)

 

Do you guys think its possible and do you have any suggestions?

thanks in advance

Mark

[Guest bastaad525]

You can do it without upping the displacement. Dont bother doing a stroker motor if you're target is 200rwhp. If you want to up the displacement you can overbore the cylinders (I went .060 over on the N/A I built and ended up with 2.9L, i dont remember exactly but it was like 2850cc's, but even this is NOT necessary to get the power you're after) Just get an L28 block, flat top pistons...

 

and now here's where the debate starts... head choice. An N42 will give you instant high compression with the flat tops, about 10:1. However, a few of us are converting over to believing that a shaved P90 (turbo) head will flow better and make more power. It has a better combustion chamber shape (good for fighting detonation, very helpful with such a high CR) and is believed to flow better in general, as it was intended for the turbo motor, and it was also the final L6 head that Nissan designed, using all the knowledge they had gleaned during well over 10 years of L6 production. With the money you're budgeting you could EASILY afford to get the P90, shave it, and shim the cam towers to keep everything in spec.

 

At any rate, whatever head you choose, you're want to spend most of your money on IT. Headwork (porting and polishing) and a good cam are the main ingredients you'll need to get to your 200rwhp goal. Also get yourself a set of stainless steel, swirl polished and tuliped valves. Good headwork can cost upwards of $1000, but as most people will tell you, all the power in an L6 motor is made in the head, so plan on spending most of your money here. If you want to go really crazy look into running the bigger chevy valves.

 

For induction, a lot of people would recommend triple carbs, which flow a LOT and make good top end power, and should have no problem getting your hp goal. However, I've always felt that a) they are a pain to initially tune, they can be very costly to initially tune, c) they get horrible gas mileage, and d) they aren't the best compromise for around town driving... they are more geared for top end power. You CAN make over 200rwhp on stock 240 SU's, but with the budget you've set, I personally would recommend buying a set of the overbored SU's from Rebello. They flow much better than the stock ones, while retaining the advantages of SU's over trips, and aren't much more expensive than a rebuilt set of stock SU's. Well whether you go with stock bore or big bore SU's, I think they are the better choice for every day, good around town driveability, decent mileage, as well as being super easy to tune and much less finicky than the trips. They should also be cheaper (although used triples can be had cheap as well).

 

Then all you need is a good header and free flow exhaust (go mandrel bent 2.5") and think about some drivetrain improvments as well, like a 3.9 differential if you dont already have one, a lightened flywheel, and a stronger than stock clutch. Also be sure and go with a later ZX distributor.

 

All that and a good dyno tune should get you at least 200rwhp. I built an N/A motor, L28 block overbored to 2.9L, flat top pistons, BONE STOCK N42 head (no porting or polishing) with only the stainless valves, a .480 lift 270 duration cam (mild street cam), rebuilt stock bore SU's from Ztherapy.com with SM fuel needles, 3-2-1 header into crush bent 2.5" exhaust thru a resonator and cheapie muffler (I was running out of money...) ZX dizzy, lightened flywheel (stock lightened to 16 lbs), ACT six puck clutch and a 3.9 diff, and made 170rwhp and 170ft lbs of torque. Headwork and a hotter and I'd have hit 200 easy.

 

 

Well, hope this helps and good luck!

[Guest tejas74260]

yeah, the p90 has been on my mind as well too, but i didnt know how much work was involved with the shaving and shimming to keep it to spec. the better quench area did have good appeal to me, and it is a lot easier to find.

 

thanks for the advice on the SU's. the stock su's on my 260 i have heard are just really emissions choked and arent as good as the earlier 240 carbs. its just been hard for me to find a place that does something other than core exchange, they wont take the core from my 260's carbs. oh well, i'll figure it out. thanks a lot

Mark

[Guest bastaad525]

I dont think rebello or ztherapy make you exhange your cores, you just pay more for not having usable cores. A good alternative is to get some junked SU's from a junkyard car or cheap, used SU's from someone who is switching over to SU's, and using those as your core. Might save ya $100 *shrug*. The stock 260z carbs do suck but there are those who have gotten them to work reasonably well... better not to get stuck on them though.

 

Not much work to get the P90 to make good compression with flat tops... I think you have to shave it either .8 or .08" to get that... I forget. It's not much work though just shave the head and shim the cam towers the same amount, oh and you'll need thicker lash pads I believe as well.

[DattoZG]

my frens helped me with my build up a few years back and was a nismo 2.9L stroker motor using a L28 block with an mild port and polish e31 head with nismo valve springs, hks mild cam, the block was heat treated, with nismo dished pistons, 100 overbore, and was sleeved, the crank was knife edged, and counter weighted for faster rev, hks light flywheel, crane hi6 ignition, 6-1 headers, stocks SUs, nismo close tranny, 336 rearend, n36 intakes, 1mm hks gasket, car revved to 10K fine, made 200 +- 5 HP at the wheels on the dyno. if i had the 44 mikuni setup im sure id get a few more ponies....to bad i sold my head and headers and carbs, all i have left is the block and just got a set of 44 mikunis from my 73 skyline to put on my car but may sell my setup soon. =(

[Guest bastaad525]

All that and only 200hp to the wheels???? doesn't seem right....

 

 

must have cost a LOT to build that....

[johnc]

If $7K is your entire budget for the car, engine, interior, exterior, driveline, wheels, tires, etc. then you had better shop very carefully for a clean, rust free chassis. That, by itself, will cost you at least $2.5K. Wheels and tires will add another $1K. Getting the suspension and brakes back into a good stock condition will cost you another $1K. Cleaning up the interior and exterior will cost another $.5K.

 

That leaves you $2,000 to spend on engine, trans, diff, driveshaft, and halfshafts.

[Guest tejas74260]

i already have my car, its a 74 260z that i bought for $850 bucks from a guy in kansas. it only has one rust hole, but that is the only damage. it has a really good paint job though (repainted the original orange) The interior is kinda iffy, driver's seat torn, but its my project car. the 7k was my investment for the drivetrain, so i think im gonna be alright (i own my own business)

[DattoZG]

the 200whp was pretty respectable, i wasnt even runing flat top pistons, i was running nismo dished pistons getting about 10.7 to 1 compression...i didnt spend to much on the build up, you dont need much horsepower to have a fast car, 200whp can get you high 12 sec 1/4s on a good day...i raced my buddies nsx off the line at a dead start with a seeping head gasket, 1st gear dead even, 2nd gear he went up half a car, 3rd gear went up another half a car so at this point he was a car length ahead, 4th gear he would not lose me,,,bout to hit 5th then we ran out of track...i was running a 336 rearend, if i had geared the car better with my 4.44 r190 lsd id prolly jump off the line like a bat out f hell, and with running only SUs i think it was a cool deal for about $3500 of work done. nsx had comptech exhaust, monster flow and chip. not a bad run i think...we even ran twice same results, wish i had one the second time but that thing can revv! its pretty tough to get 200 whp out of a l motor with aout a good amount of work done, my motor was reliable and strong, had no blow by and started up everytime, very consistant, built well,.