Soon to be my first experience installing/using nitrous. 75 vette, 4 bolt main 350, cast crank, hypereuteric pistons. I ordered a 125 wet shot.
here are my questions,
last dyno run I observed an air fuel ratio of 10.5 at 3500rpm and it would linearly rise to 13.5 at 5500. I think buying one size smaller metering rods(edelbrock carb) should fix the slight lean out at 5000ish rpm. My understanding is for nitrous, being less than 12.5 is safe.
I seen on other posts that a rule of thumb is 1.5 degrees retarded for every 50 shot. So this would be about 3 degrees dialed back. Is this just for dry shots? Or is the fact that it’s a wet shot, with ideally a touch rich ratio make it so the timing doesn’t need to be dialed back?
I would appreciate some feedback from people more experienced than me.

 

what is your fuel source? Are you running this off the mechanical pump or did you install an electric? What plugs are you using? For timing I always do 2 degrees per 50 ho shot. What jets are you running in the nitrous plate? I wouldn’t adjust the carb for fueling I would change jets in the plate.

I should also add, you have to be real careful spraying on hyper pistons. They have a small window to get it right or you melt a piston.

 

Thanks for the feedback, Here I was thinking hyper would be more resilient than cast lol
the kit I ordered has the jet size for both fuel and NOS corresponding to 125. You have the option to buy different sizes for 50,75,150 shots and so on. Im
not sure of the actual sizing.
It’s supposed to tie into the mechanical fuel pump, I’m running one that’s rated 7.5-9psi at 40gph. Should be sufficient to supply the fuel jet.
plugs are champion RC12YC gapped at .46
sounds like I should drop the timing probably 4-5 degrees

 

fuel starvation is the last thing you want at w o t strongly suggest a separate fuel pump and line to deliver fuel to the plate with a regulator it's imperative that you keep it wet and Rich enough to avoid lean out especially with those hypers a forged piston would give you a lot better peace of mind. hypers may be better than cast but they have their weaknesses so I recommend a very strong ignition signal a very reliable fuel delivery for the nitrous plate and watch those air fuel readings ....nice to have someone in the passenger seat keeping an eye on things while you do your tune I would lean towards 11 and 1/2 to 1 and then read your plugs look for particles of aluminum on your plug ceramics ... I recommend a safety switch after your regulator to shut off your nitrous if you fuel pressure drops below threshold..... lastly Teflon lined stainless braided fuel line with a and fittings will make for a much better install than rubber lined stainless steel lines if you're not going to use hard lines make sure you do a return line if you can so you don't deadhead the pump so much to read on the subject I'm sure you'll find plenty of opinions and suggestions keep reading and reading...... sorry about the run on sentences

 

I ended up talking to a Holley tech, they recommended .1gph per hp at 6psi, so I need a fuel pump at least 47gph at pressure, most are rated free flow. I found a carter that’s 120gph free flow, should be sufficient.
it was also recommended to retard the timing 2 degrees per 50 shot, so 5 degrees, then do an additional 2. Make a pass, check your plugs for lean condition/predetonation, then advance it by 1-2 degrees if desired.
I really like the idea of a fuel pressure shut off switch, I should be able to add that in easily enough.
thanks y’all

 

Just to update y’all.
I ran a carter street super fuel pump, with a holly regulator, got the nos system all installed easily enough, used a push button on the steering wheel. I used smaller metering rods in my edelbrock carb to get on the rich side of stoichiometric ratio. I pulled 5 degrees timing out, from 12 degree to 7 degrees.
and tbe NOS system worked great, huge fan. Highly recommended.