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blight 02-09-2012 10:03 PM

How big of a NOS shot can pump gas take?
On a sbc with aluminum heads, 10.5:1 compression, 700cfm carb, using nothing higher than 93 octane. How much (like a 100 shot 50 shot?)nos can one run without worry that every-time that button is pushed that a piston is going to crack? Please bare with me I know as much about nos as I do about having my manstrual-cycle sinking up with the other guys manstruals that I hang around.

whyholdback 02-10-2012 03:32 AM

With nitrous, octane becomes less important. Nitrous cools the charge enough to fight detonation. But it also accelerates the burn. This is why we pull timing as we add more nitrous. You don't want peak cylinder pressure before the piston gets to top dead center on the compression stroke.
For a typical stock 350 with cast pistons, a 125 shot is safe. I've done 200 with cheap hypereutectics and the Jacobs' Mastermind progressive controller, on 91-octane. I set it for 50% at 3000, ramping up linearly to 100% at 6000. Very safe, since it was also pulling out spark advance as it was adding nitrous and fuel. It has adjustment for that as well.

ethn_bert 02-10-2012 06:13 AM

NOS recommends premium fuel above a 50hp shot. Whyholdback offers some good advice. I also use a controller with much success. A wet system is much safer at higher levels. I would never use a dry shot system. I've sprayed 200hp with 94 octane, a wet system, and timing retard box for years with no issues. However, I run much lower compression and a camshaft for nitrous.

blight 02-10-2012 10:02 AM

So with a full forged rotating assemble (balanced) on 93 octane and the 10.5:1 what would be pretty safe then?
Could I run a 200 shot? Could you tell me more about these controllers?

Are there better ones than others?

As for the cam what does it need to be a nos cam a wider lsa? is a 110 enough then?

68NovaSS 02-10-2012 04:35 PM

While the bottom end is important at higher power levels, it's the pistons that will suffer from detonation first, forged, cast, hypers, they all melt.

Hotrod 80 02-12-2012 08:58 PM

Do you have a system now ? I also would only run a wet system . Are you looking at a plate or a Fogger style ? I have seen 250 sprayed on 93 with a fogger and a MSD box pulling correct timing and a properly flowed fuel system .

I had a 355 with forged flattops and a NOS cheater plate kit and sprayed 82 square jets on 92 with the timing pulled manually 2 degrees per 50 hp .

whyholdback 02-12-2012 09:24 PM

Here's what I've found success with:
Which has been replaced ( and updated ) with this:

ethn_bert 02-12-2012 09:50 PM

I run the mallory hyfire 6a box(685) w/ rpm switches and timing retard features. I have these boxes in both of my novas.

blight 02-13-2012 05:29 AM


Originally Posted by whyholdback
Here's what I've found success with:
Which has been replaced ( and updated ) with this:

Sweet I will look into it.

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