How much NOS for stock?

[Nealio240z]

I have a mild built 355 sbc in my 240. Iv put a mild cam in it and done an intake manifold (edelbrock proformer) and im running a 750 Q-jet carb, block hugger headers, and a flame thrower HEI dist. It is only a TWO BOLT MAIN engine... (Year 1986-1984) My question is how much nitrous can I run safely and not risk engine damage??? Stock -pistons, rods, heads, crank, ect...

[a6t8vw]

most say 100hp

[grumpyvette]

on most engines 75hp-100hp is no huge increase strain on the engine provided youve backed off the timing advance slightly and jetted the nitrous a bit on the rich side, but Id suggest you never set the nitrious to hit at under about 3000rpm either, and install and ignition rev limiter.

Id further advise NOT useing nitrous if your not running a minimum of 15-20 psi OIL PRESSURE at hot stabile idle once the engine warm or your engines not running an ABSOLUTE MINIMUM of 50 PSI oil pressure at 5000 rpm, either probably indicates some wear and clearance issues you may not want to dump a good deal more bearing loads on.

Id also suggest a baffled 7-8 qt oil pan and a high volume oil pump as oil does a good deal of the cooling on the engines critical parts like pistons,rings,bearings, and under nitrous the heat tends to go up fast

 

take the time to read thru this

 

http://www.chevytalk.org/fusionbb/showtopic.php?tid/49752/

[Pop N Wood]

on most engines 75hp-100hp is no huge increase strain on the engine provided youve backed off the timing advance slightly and jetted the nitrous a bit on the rich side, but Id suggest you never set the nitrious to hit at under about 3000rpm either, and install and ignition rev limiter.

Id further advise NOT useing nitrous if your not running a minimum of 15-20 psi OIL PRESSURE at hot stabile idle once the engine warm or your engines not running an ABSOLUTE MINIMUM of 50 PSI oil pressure at 5000 rpm, either probably indicates some wear and clearance issues you may not want to dump a good deal more bearing loads on.

Id also suggest a baffled 7-8 qt oil pan and a high volume oil pump as oil does a good deal of the cooling on the engines critical parts like pistons,rings,bearings, and under nitrous the heat tends to go up fast

 

take the time to read thru this

 

http://www.chevytalk.org/fusionbb/showtopic.php?tid/49752/

 

 

Man, now that's an answer!

[Pyro]

I have a story for you.

 

A friend on mine bought an AutoZone 350 short block. Then he installed a CompCam 292H (244/244 at 0.050), sportsman II's heads, victor JR intake, 750 Holley, and a 275hp shot of n20. He put his engine into an 3500 pound 1980 Camaro with a LSD 4.56 gear and 8 inch 4000 stall converter.

 

He raced that thing every weekend and street raced it during the week. He used 20 pounds of N20 every week for over 2 years! That is over 2000 pounds on N02 through an AutoZone short block using 275HP at a time. Plus shifting at 6500 rpms! And he drove it to work everyday. The bearings finally got hammered out but it took a long time and a lot of full throttle runs.

 

If the n20 is set up right, your engine will last a long long time. Run the proper fuel, ignition timing, and the right n20/fuel mixture and a 200 or 250hp shot is no big deal for a 350.

 

I ran a 275hp shot for a few years with no issues using a 2 bolt main block and hyper pistons.

[rustorbust]

Check this out......

 

http://www.chevyhiperformance.com/techarticles/148_0303_small_block_nitrous_blow_up/index.html

[grumpyvette]

STRESS is CUMULATIVE, you can run a 100hp shot almost forever, double the shot and youve significantly increase the stress and shortened the engines expected life, starting with an engine in good shape with little wear and the correct clearances adds a good deal to the probability that the engine will last a long time.Ive yet to see a correctly tunned 100hp shot hurt a decent engine but Ive seen guys who have run that 100hp shot get greedy, and kick it to 200 and several experianced blown head gaskets or busted pistons, what many guys fail to realise is as the power goes up so does the heat generated, STOCK RING GAPS don,t take this into account, STOCK RING GAPS tend to close,letting the rings butt, locking the piston in the bore and busting the upper ring land.

cast pistons were never designed for the extra heat,

that junkyard jewel test probably had well worn rings with large, perhaps excessive clearances for a N/A engine that allowed the engine to opperate under the higher heat (at least temporarily)

Ive seen guys drop a 250 shot on stock engines and make a couple runs -to a few dozen before they had problems also, BUT they eventually DID break parts.

100hp is almost 100% safe, over 150 gets IFFY fast on a stock engine with stock clearances

KEEP in mind the ease with which an engine on nitrous revs can get you into serious valve control issues also

 

 

http://kb-silvolite.com/article.php?action=read&A_id=32

 

http://kb-silvolite.com/article.php?action=read&A_id=7

 

http://victorylibrary.com/mopar/nitrous-tech.htm

 

you might want to read thru this also

 

engines designed for nitrous use forged pistons, a thicker deck piston and larger ring gaps, theres a reason, and that reasons MORE HEAT and HIGHER PRESSURES

[Nealio240z]

Wow that is alot to swallow, but it answers my question in full...

[sick240]

i asy just work your way up and see what she will hold.

[grumpyvette]

i asy just work your way up and see what she will hold.

 

oh yeah, its always a great WARM FUZZY feeling while you stand next to a smoking busted , and expensive to replace engine , and thinking damn! it held up fairly well till that last little bit, now I get to spend money I don,t have replacing something I never should have busted,,,,,geee was that FUN!................NOT!

[Pop N Wood]

I remember one car mag article that tried to see how much nitrous a stock JY motor would take before blowing up. They put it on the dyno and started pumping larger and larger shots of nitrous through it.

 

Funny thing, what made them stop was fire belching out of the carb. They theorized that the stock smog motor flowed so poorly that after a point it was incapable of consuming all the nirtous that they were trying to send in.

 

They never did blow up the motor.

[grumpyvette]

BTW HOW TO CHEAT A LITTLE and get an idea where you stand..while tunning

 

http://www.professionalequipment.com/extech-high-temperature-infrared-laser-thermometer-501-ds-42545/infrared-thermometer/

 

this is not fool proof but a quality IR temp gun will give a good indication of getting into trouble ,IF you know how to use it, exhaust temps should be in the 1200F-1350F range with nitrous anything over about 1500F probably is a good indication your running wat too lean or getting into detonation, I usually play with the ignition timing curve and advance first, but after making reasonably sure thats close, you richen the A/F mix ratio to drop temps in the exhaust, your far less likely to have problems if you keep the exhaust temp range in the 1200-1350F range and the lower edge of the temp range may limit your power very slightly but it will tend to keep you out of trouble also, keep in mind A/F ratios close to about 12:1-12.5:1 generally maximize the torque, but try for about 12:1 or slightly richer, you really can,t afford to run lean for long, a couple of seconds can melt a piston land.

having an IR gun allows you to quickly check EACH exhaust header and locate cylinders that run lean or non-firing plugs

[sick240]

oh yeah, its always a great WARM FUZZY feeling while you stand next to a smoking busted , and expensive to replace engine , and thinking damn! it held up fairly well till that last little bit, now I get to spend money I don,t have replacing something I never should have busted,,,,,geee was that FUN!................NOT!

 

 

i was just joking, this is what my buddys tell me trying to be funny, i wouldn't think he would take my statement and run with it.

 

but if it helps i'm running a 250 shot on a stock 96 vortec motor and she has held up so far so good, but i do run 112 in the main tank to be safe on the 250 shot where on the 150 i run 93 in the main tank and 112 in the nos tank up front. i don't want that WARM FUZZY feeling

[grumpyvette]

Id strongly suspect that ignition timing would need to be retarded if you were mixing fuels, but TESTING with your combo will tell for sure.

OCTANE BOOSTERS like below can reduce the tendency to detonate, but your cat/emmission/ system and O2 sensors may not like a lead additive

 

http://www.gnttype.org/techarea/misc/octanebooster.html

 

http://www.prime-mover.com/Engines/GArticles/octane.html

 

http://www.elektro.com/~audi/audi/toluene.html

 

http://zhome.com/ZCMnL/PICS/detonation/detonation.html

 

http://www.kemcooil.com/products.php?cId=4

 

http://www.kemcooil.com/product_info.php?pId=54

[sick240]

yes sir, timing does pay a big role also, i have a 3-step retard box which handles the retarding of my timing. that way all i do is change the pills and no more messing with a timing light, cuts down on time at the track, just change the plugs for the 250 shot once i get to the track.

[Top Secret]

In my (limited) experience, a PROPERLY TUNED nitrous setup on a stock small block chevy will take at least a 150 shot all day every day. I consider 200 to be the beginning of the gray area. If you've all ready got good heads, mild cam, intake, and exhaust, I would just tune it with a 150 and leave it at that, personally. Of course, there will always be that one guy who doesn't want more.

 

 

Than again, I never really believed in nitrous. I always though you should spend that 500 bucks and get a better head, or a better cam. A stock shortblock shouldn't be pushed farther than 500 horsepower anyways. I would rather have 25 or 50 permanent horsepower than 150-250 substitutionary horsepower.

 

I may lose to the guy running the 350 horse motor + 150 shot of nitrous, but I am willing to bet my 400 permanent horsepower is more fun, and less expensive in the long run. But, this is getting into subjective conversation now, and away from facts. =) Nitrous isn't for everybody, and I am one of those people.

 

*Edit*

 

One more thing. I have always gone by my own personal formula for nitrous. This is not tested, nor am I saying you should do it, but everyone I tell this to agrees it "sounds about right." And that is, 30-35 shot of nitrous for ever 1 liter of motor will put you right at the beginning of the gray area.

 

If you have a B18C5 in your Honda Integra, that is a 54-63 shot. (Most honda guys run a 50 shot because they consider the 75 too dangerous, this would seem to fit here.)

 

If you have a 5.7 liter sbc, a 171-199 shot. Right between the a commonly acceptable 150, and the more risky 200 shot.

 

A mustang 5.0, would be a 150-175 shot. This seems to tie into what I read up on with the mustang forums.

 

A Mitsubishi 4G63 2.0 liter motor = 60-70 (Most guys seem to run a 75 shot, but these motors are just amazing, taking 400+ horsepower stock all day long.)

 

427 big block = 210-245 shot

 

You get the idea. It's just as grumpy said. Some motors just happen to be made with more acceptable clearances for nitrous and can take those 300 shots. But anything above 150 and you're just rolling dice in my opinion.