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Old 10-30-2008, 05:18 PM
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Compression for nitrous

I am trying to figure out what the standard CR is Ideally For a motor that will be with out NOS the majority of the time but can still handle it. I want to built one of my 400's for a good street/strip car. I'm looking for 500 HP no bottle, but have the option to run 125-200 shot if i choose to....

How much NOS can a stock 400 crank handle???? Hyper/ coated pistons/ forged rods?????

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Old 10-30-2008, 11:06 PM
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400sbc + 150 to 180hp shot nitrous +92-94 octane gas + a moderate amount of spark retard on the juice + 9.80:1 cr = reliable, true 480 to 500hp N/A and 650hp reliable hp on spray.
Thats more than enough horsepower to run solid, reliable 10second ET's in your average decently prepared 3400-3600lb streetmachine (at the track).

Anything more requires 100% 110+ octane racing fuel.

If you try to defy the laws of physics, you'll find out that racing gas much is cheaper than pistons.

The stock GM 400crank is plenty strong when prepared properly.
If you run the nitrous in a fashion that creates improper combustion, detonation,preignition, leanout, the crank will be the least of your worries.
The hyper pistons will need a larger than typical top ring end gap.
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Old 10-30-2008, 11:21 PM
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It really isn't a question of how much nitrous can your crank handle , but how much total HP combined. If you are going to add 200 extra horses to your 500 horse engine, then you need to prep it in all areas like you are buiding a 700 HP engine! The last thing you want to do is run over your crank in high gear when it exits out the bottom of your oil pan. Will a 2 bolt main block be satisfactory....maybe. Will adding splayed 4 bolt caps help....Do you need main studs.....probably. Would It be better to get a Bowtie block , or Dart block to start with....400's are very good engines, and you just need to follow sensible steps to ensure you get the most pleasure and satisfaction for your intended purpose. When the NMCA craze first started, I built many big cubic inch nitrous Small Block Fords and Chevies, some had compression as high as 13-1/2 to 1 and used 400 HP Fogger kits. There are as many ways build a nitrous motor the wrong way, as there are the right way. Just use common sense, and follow good thorough machine shop practices. If you want an extra 125-200 HP, just build it with that much to start with and dont use nitrous. Its not difficult to get that much power out of a 400. I've built some dirt track 400's that made a little over 600 HP with only 11-1 comp. and unported steel Bowtie heads and no roller cam. I think you are underestimating the potential with what you have....
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Old 10-30-2008, 11:26 PM
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CNC-Dude your right on in your response. I was going to go with a little giggle juice with my build but then after reading a lot on the boards I have gone against this idea I'm just going to build my 406 to be a nice street motor with gobs of tire boiling Torque!
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Old 10-30-2008, 11:31 PM
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Well I tried not to sugar coat it, I just stated the facts! 400's have awesome potential, and can be just as durable and dependable at high HP levels as anything out there, just use your noggin' when you pick your parts.... Thanks for the complement.
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Old 11-03-2008, 05:00 AM
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whhoooooo guys

Your talkin 150-200 shot??? I aint wantin all that.... I'd like to build it to about 10:1 with the comp 280 cam, I=beam 5.7 rods forged, 22cc dish pistons, 062 vortec heads 202/160, stock 400 crank, beef up the valve train and springs, 1.6 roller rockers w/ poly locks. I'd like to atleast gasket match and bowl blend the heads, but I'm kinda scared to do it myself, cuz I'm not that good yet and I hear the vortecs don't have much meat to work with????????? oh and bore .030

I heard that JE makes a coated Hyper piston that will take a 150 shot no problem, but I dunno how true that is.

I was really only plannin on 75-100 at the most.
I think the motor should yeild ~ 450HP then throw a 75-100 shot to it and I got 525-550. Can the Hyper pistons handle it if I stay below 100????????
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Old 11-03-2008, 10:08 AM
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Its been my experience that hypereutectic pistons aren't very compatible with even modest amounts of nitrous or boost from superchargers. When using either nitrous or boosted power adders, this is one area(pistons) that should not have any corners cut at all. Also, a good safety measure would be the addition of an MSD timing retard module, or timing box to remove set amounts of timing to prevent engine damage. Just running the engine one time on nitrous without taking any timing out of the engine, will be the only time you will run it. Also, as F-Bird has also mentioned, better fuel is also a mandatory requirement for your situation. Neither of these two issues is an option(timing retard or better fuel), they are absolutely required, no ifs, and or buts. Detonation can destroy an engine in a millisecond, even before you hear the first ping, so don't cut any corners in these two areas and you should be fine. You need to follow NOS' recommendations for amount of timing retard, fuel octane, fuel pressure, jetting of nitrous and gas for kit(plate or fogger nozzle) for HP you want to run, engine compression and cam selection to the letter. Any deviation will cause very costly repercussions. Nitrous can be a lot of fun, and provide long term reliability, only if you follow some basic guidelines for prepping your engine and getting your tune-up dialed in as they recommend.
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Old 11-03-2008, 01:00 PM
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chris mays from comp cams

Well I just got off the phone with chris mays from Comp, and He is gonna go through my ideas and help me decide the best way to go. Thanks for your help guys and keep the ideas comming. I'm still open minded.
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Old 11-03-2008, 11:04 PM
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Quote:
Originally Posted by eatonde
Can the Hyper pistons handle it if I stay below 100????????
That depends: Can you follow the piston makers directions and set ring end gaps as required to account for the extra heat created by nitrous?

Can you follow the nitrous companies directions and set up and test a fuel system that feeds the correct amount of additional fuel for the nitrous, pick the right spark plugs and set the spark timing accordingly.

If not, you will damage anyones piston in short order.
When things go wrong or are done wrong with nitrous, Hyper pistons shatter,
Forged pistons pinch the top ring land and evenually break too or get a hole burned thru them if you keep at it. Just takes a little longer.

When set up correctly, nitrous does not break pistons.
That being said, hyper pistons are good for 150 to 180 hp shot on 92 94 octane pump gas, easily.
I have exceeded that nitrous shot power level by more than two fold with cheapy cast and hyper cast pistons without damage. (on racing fuel) and made huge power.
I've seen the best forged pistons destroyed in a second when the nitous set up was incorrect.

Smooth, normal, controled combustion wether N/A , nitrous, turbo or supercharger does not break pistons.
Detonation, preignition, pinging , knocking, overheating, lack of fuel (lean) and or not enough fuel octane or high speed leanout, does.

Unless you are trying to make the most absolute power under nitrous, you don't need a "nitrous cam" Any cam/motor combo that works well N/A, will work very well under nitrous.

The NOS Power Shot and Superpower Shot systems are near goof proof.
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Old 11-04-2008, 07:43 AM
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fuel system

OK, I'm VERY un-educated when it comes to nitrous, I've never used it or really even researched it. So, what do you mean when you say set up a fuel system that delivers the correct amount of additional fuel for the NOS??

Will a mechanical pump not work?? Do I need a special carburetor??

OK lets use one of the engines I already have running just for theoretical purposes to give me an Idea of what you mean.

The 355 SBC, KB119 dome hyper's, forged I-beam rods, cast crank, Lunati bracket master II 300 246/246@050, 515/515 lift. 339 heads 76cc 194/150 valves, weiand X-elerater single plane intake, Holley HP 600cfm VS with weak Sec. diaphram spring and 4.5 powervalve and 10" vacuum at idle. (holley mech. fuel pump 6PSI) 185PSI +-5psi on every cylinder

What would I need to do to be able to run a 75-100 horse NOS kit...... I don't even know the difference between a plate kit and a fogger kit so please be as detailed as possible.

I have a guy thats tryin to sell me the hose and soelenoid, purge valve, ect for $20 bucks and a bottle for another $10. Its my brother in law, He bought a 99 f-bird with a 3.8 and a 75hp kit
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Old 11-04-2008, 09:11 AM
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Tell your B in law to keep his junk.
Go buy a new complete plate nitrous system. The NOS super power shot system is a good one for you.
Read the instructions. I prefer to use a "dedicated fuel system" to feed the nitrous system with the required fuel.
I use a separate extra 3/8" fuel line from the fuel tank with a Carter #P4594 or P4601 electric pump and a common Holley fuel pressure regulator.
The operating flowing fuel pressure is 5 to 6.5 PSI.
It is critical that the nitrous system fuel supply is a steady flowing 5 to 6.5 psi.
This is the right stuff for the typical 100 to 300 hp shot plate nitrous system up to 300hp shot or so hp.
Get this thru you head and you are going to enjoy your nitrous system for years, with no trouble.
That is the purpose of the separate dedicated fuel supply line pump and regulator.
Do it right the first time.

I do not recomend "piggy backing" off the engines fuel supply system.
Do it right the first time.
The minor extra cost and work involed in installing the correct fuel system to support the nitrous sytem is well well worth it, if you want trouble free performance.
Full instructions on how and why are available for your to read up on.
www.holley.com.
If the carb is jetted properly for N/A use, it is right for use under nitrous.
If its too lean you will m ake trouble for yourself.
A typical holley #1850 600Vs carb should have a 64 to 67 primary jet and a 73 to 76 sec jet (or equal sec metering plate) and a (its own) fuel supply that can keep up to the engines fuel demand at WOT.

For your particular motor I would lock out the timing and set it for 26 to 28deg for 100 to 180hp shot while under nitrous. Your motor may want up to 32deg but 26deg is where you start. Or get a add on electronic spark retard box that retards the spark accordingly while spraying. Use the good 92-94 octane fuel or better. High octane racing fuel is cheap compared to busted pistons. Don;t waste your time or money with little cans of octane booster.
If you want to spike the fuel to raise the octane spike it with real 110+ octane unleaded racing gas.
http://www.klotzlube.com/
this is what I use: http://www.proracingfuels.com/ Mark II or Mark V
A champion RV8c non projected tip spark plug gapped at .035" is just right for the 76cc GM smogger heads and a bit of NOS.
Do not engage the nitrous for any reason at idle or at low rpm or at less than WOT.
Thats how you bend connecting rods.
It's all common sense.

Last edited by F-BIRD'88; 11-04-2008 at 09:43 AM.
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Old 11-04-2008, 09:20 AM
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OK, basics first. Think of nitrous as condensed or compressed air being sprayed into your cylinders. When it goes in to the cylinder it becomes uncondensed or uncompressed. Suddenly you have a whole lot of air molecules that need an equal amount of fuel to maintain a safe air/fuel ratio. The "dangerous" thing about nitrous is the very easy ability to create a lean condition. As I'm sure you know, a lean condition on a NA motor creates heat. Heat that, even without nitrous, can melt pistons. When you add nitrous to the mix, you run the possibility of doing the same thing, only with a magnifying glass on it. There are basically two kinds of nitrous systems, wet and dry. Wet nitrous systems use an enrichment injector to spray extra fuel in with the nitrous. These systems are usually safer than the dry systems, which spray only nitrous, and are easier to tune. The wet system takes a little longer to install, but can be used with NA or forced injection. Dry systems are easy to install, and are best suited for fuel systems that have a fuel return line to the tank like a fuel injected engine. Dry systems are a bad idea on forced induction.

Sufficient fuel pressure is very important. Some people make a T in the factory fuel line and pray that it works. Bad idea. Your fuel pump was designed to supply a sufficient amount of fuel for the motor to run under normal conditions. When you T off the line to run to a fuel nozzle for nitrous the biggest and most likely problem you will run into is a sudden drop in fuel pressure when the nozzle opens. The pump simply cant keep up with the demand, but the nitrous can. I've seen a lot of people add a high volume fuel pump in hopes of fixing this problem, and in theory it seems like it would work. However, even if the larger pump can flow 300 LPH unrestricted, it can't push 300 LPH through a factory fuel line. The line is simply too small in diameter to flow enough fuel through it. Think of pouring oil through a funnel and having to stop to let the level drop before you can add more, its because the spout on the funnel is too small to flow enough out to keep up with what your pouring in. So, the best way to remedy this problem is with a dedicated fuel pump and line from the tank to the NOS system.

Know the maximum amount of fuel you can get into the engine before you ever think about how much nitrous to add. Not knowing this equation is a recipie for disaster if you add too much, and your leaving hp on the table if you add too little. It's much more than adding parts, but its not difficult to do it right if you just take your time and are careful.

Last edited by DaSouthWon; 11-04-2008 at 01:32 PM.
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Old 11-05-2008, 01:37 PM
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the right fuel

F BIRD,
are you saying you just run the 110 or 114 octane in your nitrous fuel cell or do you run it in both tanks??

Could I just run the 93 in the regular tank and put some racing fuel in the seperate nos fuel cell?? With my CR bein what it is ~9.5:1 or so, could I just use 102 octane cuz I can get it locally for $4 a gallon
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Old 11-05-2008, 06:09 PM
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Depends on the shot level I'm using at the time.
Thats the beauti of running a separate fuel cell for the nitrous side.
I run 94 octane Sunoco up to 180hp. I can fill the nitrous cell with 110 also.
Not a bad idea even at this level. There is no such thing as haveing too much octane with nitrous. Don;t be shy with the octane.
Blend 92 octane with 110 octane race gas unleaded 50:50 gets you 101 octane fuel.

At higher shot levels I run both the nitrous and motor on 100% 110+ octane.
At very high racing levels, you get into multi staging, solenoid timers, methanol and water injection etc.
150hp is fine for a pump gas street motor on 92-94. 91 octane is not 92-94 octane. Learn to use it and put it to the ground right on launch. Get a simple Nitrous window switch and WOT switch to control the exact rpm it comes on
(eg right before or right after the stall speed rpm is reached on launch {3500stall})
and when it goes off. (just before the rev limiter engages)
This avoids putting undue stress on the motor at low rpm as the motor launches from near idle to the stall speed at launch, yet gets the most out of the nitrous boost. This along with proper fuel pressure, octane and flow and spark timing under nitrous is how you ensure your cast piston motor lives a long life.
The extra cylinder pressure (power) of nitrous does not break pistons. But the excessive pressure and combustion heat spike and load shock caused by detonation, priignition abnormal combustion or just injecting nitrous at way to low a rpm (which overloads the rods), does.

Last edited by F-BIRD'88; 11-05-2008 at 06:28 PM.
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