Pump Gas

[HITN94]

want some opinions for running nitrous on pumpgas on a built ltx

[proace4]

pull timing!!! lol just make sure yoiu are set up for it and have a good tune or a mallory hyfire(just what i use, msd and other retard boxes are fine) for timing. I only have 91 octane where i'm located and my car runs great on and off the bottle. so as long as your completely setup... spray and prey! lol

[HITN94]

i intend on retarding the timing, installing colder plugs, and a good tune up. i was thinking between 100 - 150 shot would be fine on pump gas with a little more timing pulled

[HITN94]

dont everyone speak at once. i know twisted z or tony shepherd or jakesz28 has got some opinions on my nitrous tune, what tune up would yall recommend to start, as far as plugs, fuel, timing, etc. oh and if wandering i have a 383 stock ported heads and intake, cam is on a 110lsa, its 410rwhp n/a. i think my timing is now 33 degrees. trying to decide what tune i want to start with on my setup.

[jakesz28]

I think the octane requirement is going to come down to total horsepower. If you have a mild combo lets say 425-450hp n/a I think a 150 shot on 93 is a safe goal. But you will want to run less timing and the compresion is going to have to be in the 11.5 range. I think this would be fairly easy to do but the cam will need some extra exhaust duration to get the heat out.

With any pump gas build it would pay to talk to some known cam grinders that have combo's that are doing what you want to do. The cam timing events can help bleed off some compression and work well with pump gas.

When my motor was built I kept the compresion at 12 to 1 so I could tun it on motor with pump gas. I have ran with pump gas in the motor and 112 in a stand alone fuel system for the nitrous. I ran about 175 hp shot this way. If I wanted to go any bigger then that I would have to have the timing way back. I need to start taking better notes on my tunes but with that gas setup I think I had about 17 or 18* timing in it. Any more nitrous and I would have had to pull a lot more timing out.

[jakesz28]

Another thing to add. I talked to a well known nitrous tuner about my combo and pump gas, when it was first built. He was saying that I could have ran 250-300 hp of nitrous with it but the timing would have had to go all the way back to single digits. Then there isn't much safety margin with the fuel quility that low. I still wouldn't mind doing something with a pump gas drags but I can't afford to kill it when I know I can keep it going running good fuel thru it. If I was going to do something in a pump gas deal I would look into a water injection system to help cool the cylinders (which would be plumb with dry nozzles in a direct port setup) and I would have to raise my quench from .040 to about .080.

[HITN94]

ok jake, i understand what your saying. my car is already built and is built for nitrous, i just have not put a kit on it yet. i have no problem running race gas i was just wandering how safe it would be on pump gas. my camshaft is 236/244@0.050, 574/586 lift on a 110lsa. i will probably have between a 100-150 shot on it. the absolute most i would put on it would be a 225, and i would definately have race gas in with that tune-up.

[HITN94]

oh and also my compression is 11:5 to 1. with 150 shot on pump gas how much timing would you recommend starting with and what heat range plugs? or the other way, if on race gas how much timing?

[jakesz28]

I would say when you start I would pull the timing back to 25* with a -8 non projected plug. Then look for a timing mark and fuel ring on the plug. Chances are you can run more timing I would just add it slowly while reading the plugs. With higher octane fuel you can play with more timing but I would rather add more nitrous and keep the timing safe.

If you haven't purchased a kit yet give Ray a call I'm sure he will point you in the right direction.

[Joker Z28]

Jake knows his stuff.

[HITN94]

ok thanks for all the input