NOS, how big can i go(and a compresson question)

[Guest Anonymous]

ok, with forged pistons and a stock fuel pump on a mid 70's truck block(4-bolt main) what is the biggest shot of NOS i can use? it has a comp cams 268H cam, and edelbrock performer RPM intake, with a holley 4v(780cfm, 70jets in primary, 76's in secondary). also does anyone know the stock compression ratio on this motor and what compressin ratio should i go with if i'm gonna use NOS??

[Guest Anonymous]

What crank ya using? If you intend large doses of juice, it better be a strong one. I'd imagine the compression of a mid 70's small block will be on the low side, 8.5 - 9.0 to 1 as they were well into they're smog phase at that time, but thats speculation, depends on what heads and pistons are in it.

 

 

Lone

 

'Build it strong, or it won't last long...'

[MYRON]

I have heard that 1/3 of your actual hp is recomended for a stock engine. I have never

used the juice before so I cannot tell you what is best. This is just what I have heard

from other juicers....

[Guest nosz350]

HEY JUST WANTED TO TELL YOU ABOUT YOUR NOS TOPIC.THE STUFF IS SAFE AS LONG AS YOU CUT NO CORNERS.MAKE SURE YOU DON'T USE THE BIG BLUE BOTTLE KITS[N.O.S.]USE NITROUS EXPRESS [N. X.] BETTER QUAILTY STUFF 100%.I GET YOU IN TOUCH WITH A GUY IN SPRING TO SELL YOU THE STUFF IF YOU WANT.I'VE GOT A COUPLE OF QUESTION FOR YOU ON YOUR Z-CAR ,WHAT IS THE BEST REAREND FOR THE CARS. AND HAVE HEARD OF ANYBODY PUTTING A LS1 ENGINE IN ONE ?

[Guest Anonymous]

sorry i ain't been replying to this topic, nosz350, i've been told to use the r200 rearend in the z

[RickB]

With a stock fuel pump...DON'T USE MUCH NITROUS!!!

 

Usually when people hurt stuff on nitrous it's because they run the system lean.

 

In the past I have ran 200+ shots on a cast piston motor BUT...I had very good fuel delivery.

 

If you are going to run a stock fuel pump then keep around 125 or less.

 

 

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RickB

280V8

http://photos.yahoo.com/bornabov

[Guest Anonymous]

125?! dang i was thinking that 90 would be pushin the limit, so lets say a 100shot should do nicely.

[Scottie-GNZ]

RickB is dead on the money. This is not unlike tuning a turbo car. It is not the boost or NOS that kills engines, it is detonation. You must feed the engine all the fuel it needs and watch out for timing that is too far advanced in the upper RPM range.

 

A programmable engine management system might seem to have a high initial expense, but the flexibility you have in tuning fuel delivery and building timing curves, like retarding the timing when needed, pays for itself. The time and money spent in trial and error, tuning for maximum HP, will eventually equal or surpass the cost of the programmable system. The Motec does not count

 

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Scottie

71 240GN-Z

http://www.mindspring.com/~vscott911/gnz.html

[RickB]

I just ran over 90mph in the 1/8th mile this weekend with a very small shot (approx. 100 hp / 47 nitrous jet).

 

I have a very basic combo (350/small cam/Performer intake/Carter carb/blockhuggers) with a 6 PSI Carter electric pump...much more nitrous and I will upgrade the fuel delivery.

 

BTW Scottie...I've even had N20 on a turbo car!! WOW!

 

 

 

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RickB

280V8

http://photos.yahoo.com/bornabov

[Andrew Bayley]

The amount of "safe" N2O is more a factor of the extra fuel available. With carburated systems, things couldn't be any simpler. Make certain that the fuel line in the carb plate has at least 5 psi of CONSTANT fuel pressure. Personally, I run my setup at 7.5 psi. This allows me to run normal sized jets in the carb for street driving, and is also an added security.

 

As for "how much", jeesh the only suggestion I can say is to start small and work your way up. A good start would be a 125hp shot. Most healthy small blocks will accept this much "juice" fairly nicely, even with stock components (as long as the proper fuel PSI is supplied).

 

One key thing to consider is multi-stage systems. This is where a small(er) shot is sprayed intially, then a larger shot is sprayed at upper rpm's. The main reason a lot of people use multi stage systems is becuase N2O can be potentially deadly at low(er) rpm's. Once the cylinder velocity increase's, more N2O can be added. But at the low end, keep it easy. I am currently running a "modest" 125hp shot off the line and I am still breaking driveline components with drag radials.

 

As for fuel injection systems, I personally stay away from "dry" manifold setups. I was able to safely run a 150hp shot in an LT1, but it was a lot of work and EXTREMELY tempremental. The slightest change in temperature would send the system either way lean or way rich. Also, the NOS supplied in-line fuel pump crapped out after about 5000 miles. I'll agree that NOS sells some real "shady" equipment. However, I can't say that anything else I've seen is much better.

 

Good Luck

-Andy

 

[This message has been edited by Andrew Bayley (edited November 13, 2000).]

[John Scott]

Also a really good article on nitrous in the Chevy High Performance June 2000 issue. Pretty much covers all the previous disscussions and good safty tips.

JS

[RickB]

Andrews point of constant pressure at a minimum of 5 psi is right on for a carbed engine. I usually shoot for 6 psi. For match races you can choose to tickle the envelope

 

For additional safety you can install a Hobbs switch which will open your solenoids circuit if the fuel pressure drops below a preset minimum.

 

 

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RickB

280V8 http://photos.yahoo.com/bornabov

 

[This message has been edited by RickB (edited November 13, 2000).]