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I´ve got a stock bottom lt1 (400hp, TransAm) and have been using some nitrous on it.
At most I have been spraying 125hp. But I´m thinking of spraying >200hp and have read thats to much for stock bottom.
What are the weakest parts of the lt1 with nitrous? I´m thinking it´s the stock hypereutectic pistons?
Probably getting forged pistons instead.
Is this enough or do i need to change rods as well?
Something else I should think of?
The weak point of the LT1 is the 2 bolt mains the bottom end can only handle but so much horsepower. Boost, Spray, or even N/A you're going to have to reinforce it to make big power.
Like with any power adder on a stock bottom end. Ringlands will probably go before anything else. Watch your tune and you really shouldn't have any issues. Not a matter of if it will go, but when.
I've run up to 650 crank hp with a 100 shot on top of the NA power. Rebuilt bottom end, stock pistons and rods. Never any damage to the pistons from nitrous use. The motor eventually cracked a piston out of the lower (oil) ring groove from the tension loads at TDC spinning to 7100 rpm; nothing to do with cylinder pressure or detonation.
I'm assuming you're at 400 CRANK hp NA right now ? If so, it would handle a 200 shot with a VERY conservative timing curve on the nitrous tune. If it were mine, I'd limit it to a 150 shot and 6500 rpm, bringing in the nitrous no earlier than 3000 rpm, and you would still need a very careful tune to keep the stock pistons safe.
I built a 396 NA motor (ran it on a motor dyno so crank was 584hp) then put it on alcohol then nitrous and after I guess after around a 200 shot I burned up the rings due to a mechanical fuel injection pump failure.
50-150 didn't require much change to the motor, after that its plugs and timing if you mess that up its rings and pistons.
GM only rates the LT1 stock internals to 450 fw hp. After that you're on you are on your own. If you're going to build an engine build it the right way the first time and use the parts rated for what you want to do otherwise you'll eventually find yourself rebuilding your engine like everyone else that experiments pushing factory parts past their rating.
Engine malfunctions guys experience on stock parts would of held up better if they were components made from stronger materials "Cast Iron < Forged Steel/Aluminum". If you want to run big shots build a motor that can take them and you won't have to worry if your engine is going to grenade on you because you're pushing it past its limitations. If you're on a budget or down for experimenting then run a knock on wood build. If you want to build a motor that's going to last then build a motor to survive the stress you plan to put under it. That's how you build a race engine.
Personally I'm strongly against playing Russian roulette with stock internals. There's nothing fun about catastrophic engine failure. It's not worth it. You could be speeding down the track blow a rod or snap your crank, lose control of your car and end up slamming into the wall or worse the guy next to you. Sure that can happen even with the best of parts but it's better to play it safe than sorry that's' why you do the upgrades in the first place.
Last edited by Heatmaker; Sep 21, 2017 at 11:06 AM.
How do you know how much HP you spray if the same amount of nitrous and gas gives different HP depending who you ask.
NOS says 125hp and Nitrous calculator says 180hp.
Maybe I should post this in the ”Nitrous Oxide” instead?
That NOS chart is wrong.
A 62 nitrous jet is generally considered a 150 shot (@ 950-1000 psi bottle pressure).
So a 65 jet giving 180 hp is about right.
It depends on the engine setup and tune also. For instance, a 52 jet should give about 100 hp; however it gave mine about 120 hp at the crank (100 at the wheels).
Factory Mahle pistons are not really designed for a lot of n20 but i have seen 175 and 200 shots work successfully.
The factory ring gap is a little tight for this amount of n20
The factory fuel system is not adequate for this kind of setting for sure.
Definitely, pull at least 6° of timing
The factory crank and block have seen NORTH of 1000 go on turbo builds.
I have built a motor for a mild shot that's about 400 whp, stock crank, stock rods with ARP bolts, Mahle forged pistons, ARP studs in the mains, MSD 6AL. I am planning to run just a 75 hp shot for a total of less than 500 whp. Still, that's nearly 575 at the crank so I can't say I'm not a little concerned.
I have built a motor for a mild shot that's about 400 whp, stock crank, stock rods with ARP bolts, Mahle forged pistons, ARP studs in the mains, MSD 6AL. I am planning to run just a 75 hp shot for a total of less than 500 whp. Still, that's nearly 575 at the crank so I can't say I'm not a little concerned.
No reason for concern on that build. Keep the revs under 6800 and with a reasonable nitrous tune, and it will live a long life.
I am actually more concerned about the clutch and rear than the engine at this point. Still has the 10 bolt so I'm thinking a 8.8 hybrid is in my future.
Lt1 nitrous weakness? 
Still has the 10 bolt so I'm thinking a 8.8 hybrid is in my future. 
