Reply to "Nitrous?"

Here's what happens when too much nitrous is used:

http://www.bacomatic.org/galle...ith_nitrous.JPG.html

That's a TRW L2379F forged flat top piston as used in a Pantera 351C.
The engine had closed chamber iron 4V heads, a Holley Strip Dominator
intake, a big Ultradyne solid flat tappet cam and was in the 490 HP
region without the nitrous. The nitrous unit was set up to add 250 HP.
When the engine was disassembled, the skirts fell off 6 of the 8 pistons.
While the engine was assembled, they were contained by the cylinder bore.
Oddly enough, the engine didn't make much noise. If you flip the pistons
upside down, there's a sharp edge stress riser where they cracked. FWIW,
L2379F pistons are available but are a different design from the originals.

If you get serious about nitrous, google up Mike Burch (a.k.a. n2omike).
He runs a 302-powered nitrous equipped '66 Mustang with home ported 289
heads. Nothing at all fancy but a load of nitrous and runs 10.63 sec @
129.3 mph in 1/4 mile. Some nitrous tips from Mike are below.

Dan Jones

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Before you start, make sure to have a bottle heater and pressure gauge,
along with a fuel pressure gauge and regulator for the nitrous enrichment.
A good ignition system is also mandatory... one that doesn't keep advancing
the timing to the moon as the engine revs. It should STOP at around 36
degrees total. (with the nitrous off) Check it!!!!!! Wild advance KILLS
nitroused engines... Factory distributors are really bad about this.

Mostly geared to a carb system, but applies to all.... Here Goes!!!
Now that we've got the juice, how do we have fun with it?

Well first off, you don't want to get anxious and hurt your engine... Once the
system is properly installed, check to be sure its fuel enrichment is working
properly. Turn the nitrous bottle off, arm the system, and with the revs around
3000 rpm, tap the button. The engine should fall on it's face. It should be
about like hitting a kill button.

Now that we know it works (the engine is getting enrichment fuel). Let's see
what other items are necessary...

-COLDER spark plugs! Do NOT use Split Fires! For the street, use the coldest
non racing plug you can find... especially if you might have to use the
system with pump gas.

-A bottle heater and pressure gauge! You MUST know what your bottle pressure
is to get consistent results! The gauge tells you the pressure, the heater
allows you to control it. Keep it around 900 psi for best performance.

-Fuel... Use the BEST you can find! Detonation on nitrous can lead to some VERY
un-pretty things! Straight pump gas should not be used on systems over 125hp
on a 302. These engines with their 10 7/16" head bolts are prime game for
blown head gaskets if everything isn't right. A little detonation goes a
loong way on these motors...

Make sure you have a good ignition system with good wires.

**** Now that you are set up, how is it tuned???????? ****

First is timing. The timing NEEDS to be retarded about 3 degrees for every
50hp of nitrous boost. If you don't, it's bye-bye head gaskets, or worse! You
need to go with the upper end of this scale when pump gas is used (even if you
add octane booster). Just DO IT!!!!! I use MSD's Multi-Step Retard to do this
automatically anytime the nitrous is engaged. If you are in the market for an
ignition system, The MSD Digital 6 Plus costs $279, has a timing retard, a two
step rev limiter, plus is adjusted by little dials. (instead of chips)

******** FUEL SYSTEM ********

To start, make SURE your fuel system is able to maintain full fuel pressure at
full throttle high rpm with the nitrous engaged! It's better to be safe than
sorry here. I've seen cars break into the 10's with a single Mallory 140 or
Holley Blue pump, but wouldn't really recommend it. I use two Mallory 140's on
my car. One for the engine, the other for the nitrous.

******** FUEL PRESSURE ********

If the fuel pressure is too high, the car will exhale a bunch of black smoke
out the exhaust, and will not run anywhere near its potential. It will feel
very lazy (well, for nitrous). We want to lean it out, just not toooo far.
My buddy's 2V 351C Mach I went from 9.00 to 8.50 in the 1/8, just from lowering
the fuel pressure!

Start with the smallest hp jets, with the fuel pressure turned up extra high.
This will ensure an extra margin of safety. With the tranny in neutral (park),
bring the revs up to 3000 and tap the button. The revs should jump up a bit.
Probably not super crisp or fast... just kind of a 'VROOOOM'. Do this with the
bottle pressure at its operating range. (850-950 psi)

If it hits EXTRA hard, like BAM! You are probably a bit lean, and need to
increase the fuel pressure.

We can now start to decrease the fuel pressure.... Do this with the car in
neutral. Starting with the pressure high, we are going to be tapping the
button at 3000 rpm as we gradually decrease the fuel pressure.

As the fuel pressure is lowered, the engine will start to respond with
increasing aggressiveness. The VROOOOOM will start to turn into a BANG! When it
BEGINS to get pretty crisp, it's time for a road test!

At full throttle around 3500 rpm, hit the button and hold it for 3-4 seconds.
The car should respond in a positive manner. :-) As you let off the button,
kill the engine, coast to a stop, and check the plugs. They should look clean,
but have NO specks on the porcelain. If they do, it's aluminum from the
pistons, and the fuel pressure needs to be increased. Chances are, at this
point it will still be a little rich, and you will find no specks.

Decrease the fuel pressure a little at a time while making the above test. As
soon as you begin to see ANY specks on the plugs, raise the fuel pressure a
half pound or so, and you should be close to optimum for that hp level. If you
want to try other jets, you need to go through this same testing procedure
again. Start rich, and work your way down.

You will be **AMAZED** at how much better a nitrous system works once the fuel
pressure has been optimized!

**** Other things that help optimize a nitrous equipped car ****

- A good exhaust. BIGGER is BETTER! 3" pipe and mandrel bends rule in nitrous
applications!

- Proper camshaft. A lobe separation around 110 deg is a good compromise on a
carbed street engine. Some extra exhaust duration is also a plus. 8-12 extra
degrees is good. To maximize nitrous performance, go to 112. 114 on an EFI car.

- Compression. Low compression makes tuning a lot more forgiving. Make the
same mistake with both a high and low compression engine, and your chances
of living through it are MUCH better with the lower compression.

If an engine is a little low on compression anyway, (5.0 with a cam for
example) nitrous can bring in a SERIOUS wake-up call!

The weak link with 289/302's is the fact that they only have 10 measly 7/16"
head bolts.

351W's have 10 beefy 1/2" bolts, so they hold very tightly. SBC's have
seventeen 7/16" bolts.

If you plan on very much nitrous at all, you'll need to be sure the engine
has top quality gaskets and ARP bolts or studs. It will also need to have
good fuel and the timing will have to be kept in check, or you'll be changing
head gaskets.

To be safe, I wouldn't be using more than 100hp without all the above. Any
above that, and you'd better have race gas in the tank as well.

Many people get away with more, but their systems are running extra rich and
aren't tuned to make max power.

The safest bet is to use two pumps. A high performance mechanical can be used
to feed the engine, then an electric one can be used for the nitrous
enrichment. I like the Mallory 140, but it's fairly expensive now. A holley
blue should also work.

The billet distributer is an EXCELLENT investment. It will keep that wild
advance under control. It comes with really heavy springs installed from the
factory, so those will have to be changed to the lighter one for about any
application.

I like the new Edelbrock kits. They are very good quality. 100hp is a good
limit to stick with. That 100hp will feel really strong. You won't feel that
much difference stepping it up to 150 from there. Don't forget to pull 3
degrees out for every 50hp. You'll want to start around 36 degrees total (with
the engine revved up) then retard it to 30 with a 100hp shot.

Nitrous follows the rule of diminishing returns... You get a LOT more out of
that first 100hp than the next 100. Don't get greedy... unless you enjoy
changing head gaskets.

When using an electric fuel pump for the nitrous enrichment, it's a good idea
to wire it up to the 'arming' switch. This way, anytime the system is armed,
the fuel pump gets turned on automatically. (forgetting to turn the pump on is
a bad thing.

You can take the distributer apart and make a 'stop' that will keep it from
advancing past a certain point, but a MSD distributer @ around $160 is a really
good buy. A good fuel system is a good investment as well. Messing with the
stock unit involves a lot of trial and error...

I would recommend using your nitrous money to buy these items, get the engine
tuned in and running well... then invest in a nitrous system. Haste makes
waste. Do it right the first time, or you'll just end up having to do it again.

You might get by with a 50-75hp shot as it sits (except for at least a high
performance fuel pump teed off to the nitrous solonoid) but my advice is to
wait and do it right. You NEED to be able to control the fuel pressure and
timing. If you do go forward anyway, be sure to retard the timing by turning
the distributer before any nitrous blasts.

It weighs in at 3300lbs w/driver, has owner ported 289 heads, factory cast
crank, factory 289 rods, TRW pistons... and runs on 93 octane pump gas. The
trans is a stone stock toploader, and the car still rides on it's stock
suspension. The front has had it's sway bar removed, but still has the stock V8
springs. The rear consists of leaf springs and slapper bars.

You could point the car anywhere you wanted, and drive it there no problem. In
this state of tune, it's been driven 100 miles each way in 90+ degree heat to
cruise ins.

The secret is building the car for nitrous use. Nitrous doesn't need much
compression ratio, so the car can be built to run on 93 octane. It runs great
on the street, but come race time... replace the pump fuel with race gas, turn
the bottle on... and it turns into an animal. It's no slouch without the
bottle. Set up for nitrous, but not using it, it's still run 7.48 @ 92 in the
1/8, and 11.91 @ 113 in the 1/4. (It never got run much at the 1/4 off the
bottle... just a few runs) I don't get to the track much, and that's usually
1/8 mile.

The stick shift also helps streetablilty. To get the most out of my car with
an autotragic, it would need an 8" converter. This would be a major pain in the
butt on the street... and the street is where this car gets its most use. It
sees the road every weekend when the weather is good.

It's down right now, awaiting a new engine. The 289 headed unit lasted many
years, but finally wore out. (I had to pick the nitrous up from 150 to 200 a
few years ago to 'adjust' for wear) The new bullet should be a little hotter,
and will hopefully run just as good or better than the old one. It's taking
longer than I'd like... Weird obstacles, along with three kids age 5 and under
and tightened finances tend to slow things down a bit...

Lower compression + nitrous + stickshift = one extremely fun street car.

Hey, I admit it's not a 'daily driver', but if it was... it wouldn't be my
'toy'. It's just the ultimate 3" exhausted, nitroused, stickshift stress
reliever. Backing it out of the garage for a blast around the local roads
makes me feel all better and relaxed every time.