Mark L. Warner

I have an '88 with rebuilt motor (355 now) that has, zz9 cam (212,226@.050 and .483, .520) 1.6 CC roller rockers, miniram, MSD, bosch +4, SVO 24#, rebuilt aluminum heads ported and polished with the big valves (2.05 - stainless), cold air induction with open box and K&N filter, 52mmTB, AIR pump delete, true dual exhaust with targa flow-thru mufflers, and the ususal small stuff. AND it has KB hypereutectic pistons - 10.25:1 compression. TPIS estimates 420 hp at the crank with this combo. The question is can I add nitrous with that compression ratio and the hypereutectic pistons or am I going to fry a piston. Any input would be greatly appreciated.

Follow-up question, I also have a ROD 6 spd - any guesses as to rwhp?

mos90

yes you can run nos on that setup. but considering the hypo pistons i would juice it past 125 hp. also i would pull 5 or 6 degrees timing out, make sure you have a good aftermarket high volume fuel pump and dont run platinum plugs and you will be fine. at that hp level the only thing that will hurt your engine is if you run lean or hit your rev limiter with the spray on.

i have a similar setup to your except i have afr heads and zz409 cam with 1.6 rockers, i am running a stock bottom end and i have a 125 zex kit in and have no problems. and im pushing 480 rwhp on the juice

but then i dont care if a fry a piston..then i can go with world 454 sb.

scorp508

Ugh... KB pistons. I wouldn't trust em' past a 100-125hp wet shot.

Mark L. Warner

480 at the wheels - incredo! If you take out the 125 shot (say 120 hp for argument's sake) that's about 360 at the wheels! What do you think that means at the crank? About 460-470 hp? I guess I am trying to back calculate what my hp is at the wheels if I have 420-425 at the crank. Whaddya think?

Mark L. Warner

Hey scorp - two questions. First, why dont you like KB hyp pistons? Second, what would you recommend as a max for nitrous on my set-up. Thanks.

mos90

i have 375 at the wheels with out the shot. and taking at average of 15% drive train loss tha would be about 440 fwhp. so take your 425 fwhp and multiply it bt .85 to get you rwhp so that about 360 rwhp for you. a 125 shot is giving me about 105 rwhp.

hope that helped.

there is nothing wrong with kb pistons, but they do tend to explode with large shots of juice. i think it has to do with the high amount of silicon in them.

for your next build spend the extra money for a good set of forged pistons

smallblock

with the cylinder pressure being generated by your setup. if you run NOS. it's not if but when your engine will frye.......

scorp508

They have their place and I am of the belief that it isn't in a nitrous engine if you want it to last a long time. I've also had two good friends have issues with the same KB pistons in their 383s in N/A form. One of which damaged the block so bad it had to be tossed.

amm0bob

You've already made a nice motor...

Juice will eat at the motor... that's what juice does... but it does make you move faster...

Mark L. Warner

Thanks for all the input guys. I think I will wait on the juice for now and just tune the crap out my motor as it is - I will do 1/4 miles but I also want to try autocrossing and road racing. I have a number of friends in the Porsche club and I am looking forward to doing some of their road racing events.

Hey SmallBlock. I love that picture of your '88. Mine is also black with ZR1 wheels. I can't tell - do you have 315s on the back? I do. What brand and type of tires do you run? The only difference is that I have red GrandSport hash marks on my front fender. It looks awesome. I'd post pictures but I don't know how.

Thanks again guys. Bye for now.

korvette4u

no kidding:


with Nitrous oxide wet induction spray @ 150 shot.. have fun !! best ride u can get with your pants on!.... but like every hot woman you pay in the long run

mos90

hey korvette, did you lean out to do that to those pistons. what kind are they? they look a little burnt.

TheStef

Are those piston's of your Cast or Forged?

I have cast Iron pistons (even was rebuilt a few years ago) would any of you consider running Nitrous on them? if yes, about how much would be the Max or how much would be safe.

mos90

im running a stock short block and it has gm cast pistons. i am runnig a 125 wet shot. but i pull 6 degrees timing and 1 step colder plugs.

korvette4u

did not lean out .. this is the result of a 150 shot with 6 degrees retarded timing and 2 sizes colder plug.....not only the forged piston burnt but the top ring support was completely blown into the oil ring.. if u look carefully you can see the broken pieces..

BTW The NOS kit #5151 is for sale,,,