To spray or not to spray...please respond

[silver_pilate]

Well, I seem to be finding myself in a bit of a quandry. Here's the jist of it:

When I built my motor, I did so in a N/A approach with no future plans of using a power adder. However, now that I'm reaching the end of my chosen modding path, I'm once again bitten with the power bug.

My engine was built to be a reliable, well mannered, and quick street motor, and it has been just that. It's not the quickest car out there, but it is fun, and it will run with most things you run into everyday. I'm finally getting into that 13.7-13.5 range where as most LS1's at this altitude run 13.8's on street tires.

Anyway, when I built the motor, I used Keith Black hypereutectic pistons. They are very strong (my builder uses them in his 500 hp track cars), and they are lightweight and have great thermal expansion qualities allowing them to be run at a tighter clearance than forged pistons.

However, when we assembled the motor, we gapped the rings at .0065" which is where KB recommend for N/A cars. For nitrous / s/c applications, they recommend a .008" gap. I e-mailed KB, and they said the gap was too small for nitrous. Also, I'm running close to 10:1 compression.

I've been seriously considering a 75 hp shot which should put me into the 12's with this AOD car (at 3400 ft altitude). I was looking at Zex kits and I think with conservative tuning, it would be safe for occasional use. I've talked with others who think the same thing. However, I've also heard stories of blown off ring lands and such with these pistons. Also, my cam may not be the best setup for nitrous applications (although it works great for N/A ).

What do you guys think?

--nathan

[LX5liter]

I think you should be safe for a small shot. I definitely wouldn't go over a 100 shot though.

[PKRWUD]

How many miles are on it? Odds are that your ring gaps have grown a little. Not .0015", but some. The pistons, however, are hypers, which I've never liked, and which don't like nitrous. A 75 shot used sparingly will probably be okay, but it will take alot of self control. Only you know how well that aspect will go, and that is what should be the deciding factor, IMO.

Take care,
-Chris

[silver_pilate]

PKRWUD,

Well, the motor has about 20,000 after the rebuild. Maybe I should have used forged, but the price difference along with the weight savings and tighter tolerances peaked my interest on what I swore would always be a N/A car. Funny how things change over time.

The main thing I want the squeeze for is those very occasional track visits and the infrequent run on the street. Maybe also just to show off to a few friends . Ahh....but that's where we all get in trouble, isn't it?

I'm thinking with conservative timing and good gas with the reportedly very safe Zex kit, I would be ok for a squeeze every once in a blue moon. Not to mention that I really can't afford to be filling up a bottle all the time.

--nathan

[gtsr515]

Nitrous has always been my thing, been using for years, (got my first dry NOS system on my Taurus SHO now), here's what you need to do, you will need a very good fuel system for sure, and I ran hypertechtics too, lthough your at 10.0:1 compression, that doesn't necessarily mean you can't run nitrous, it is the chamber cc's that is key, also you will need colder plugs, and trust me that ring gap is not a problem, I suspect your engine builder is just covering his butt, as he should, you just need to be conservative with a small DRY shot of no more than 100.

Search the NET, there is TONS of stuff on nitrous.

[silver_pilate]

These Jr.'s are running 58cc...maybe just a tad bigger with the cleanup work.

I actually haven't talked to my builder about using nitrous, as he is a N/A guy all the way and doesn't really know the stuff. Plus I know what he'd say to try and cover his butt as you said.

Keith Black, who made the pistons, is the one who said the gap was too small. What kind of fuel setup would be needed? I'm about to order a new pump (as mine is dead), and I was thinking the 155 would be plenty.

--nathan

[PKRWUD]

Originally posted by silver_pilate
What kind of fuel setup would be needed? I'm about to order a new pump (as mine is dead), and I was thinking the 155 would be plenty.

--nathan

You also thought your car would always remain N/A. (LOL)


Honestly, for a 75 shot, the stock pump is sufficient, which means a 155, which is nearly twice that of the stock pump, would certainly be just fine. But, as I read in another thread, as long as the tank is out, you might as well go big. You know that bug is going to bite you again, and do you really want to have to drop the tank again?

155 is absolutely fine, but I think you should consider a 190.



Take care,
-Chris

[silver_pilate]

Haha....yeah, you're probably right there, PKRWUD.

We'll have to see how the checkbook holds out. I'm livin' off of loans right now, and will be for the next two years as my job serves only to pay gas, cell phone, and insurance. Cost isn't that much different, though, so maybe I can spring the extra $20.

--nathan

[PKRWUD]

Oh Nathan, you poor gearhead, you!

You're doomed. You'll love every minute of it, but you, my friend, are doomed.



Take care,
-Chris

[gtsr515]

OUCH! well. with 58cc's I would be VERY CAREFULL! with the giggle gas, and I would go with the 190 AND AN INLINE!, also i would go to 30 lb. injectors, as 24's are barely better than stock and the 30's will give you room to play, also an AFPR would really help tuneability!

I would run some killer gas too.

[Skyman]

Theres no problem running nitrous with compression. You just need to retard your timing like you always do with nitrous. Running anywhere from a 75-150 shot will be fine on your car. People w/ 94-95 GT's run 150shots and up with no problems on their hyper pistons. Look how much boost people push through cobra motors w/ the hyper pistons. If your going to change your fuel pump put in a 255, eventually you will wish you did. I went w/ a 190 and now Im having to swap again to a 255.

Drop 4 degree of timing w/ the 75shot from wherever you run it normally. Run good gas, and just listen to your motor. You will be fine.

Skyler

[LX XLR8R]

Originally posted by Skyman
Theres no problem running nitrous with compression. You just need to retard your timing like you always do with nitrous. Running anywhere from a 75-150 shot will be fine on your car. People w/ 94-95 GT's run 150shots and up with no problems on their hyper pistons. Look how much boost people push through cobra motors w/ the hyper pistons. If your going to change your fuel pump put in a 255, eventually you will wish you did. I went w/ a 190 and now Im having to swap again to a 255.

Drop 4 degree of timing w/ the 75shot from wherever you run it normally. Run good gas, and just listen to your motor. You will be fine.

Skyler

sky is correct..go read on NOS's website..although high compression has some affect on use of nitrous its not like running high boost with high compression