Finalizing my nitrous setup

mrowe · 03-03-2021, 09:59 PM

I have ventured into the Nitrous realm this winter out of mere curiosity and of course the pursuit of faster times. I need some expert feedback on what I have done.

I'm a bracket racer and have a 219" Racecraft rail 468 BBC 2-bolt mains with a Powerglide. Never on the dyno but time slips and weight support something around 600-700 HP on the engine.

I'm running a single-stage plate wet system with NOS sniper solenoids. So far I have the following items added to my setup: All MSD electronics including 6AL ignition, crank trigger, billet distributor (locked out centrifugal advance) and a start and step retard control module. I also have a transbrake cutoff module activating the nitrous after the T-brake releases and only when the WOT switch is on.

As for the engine mods, I have TRW 50 cc domed pistons and H-beam rods. Brodix aluminum heads with 119 chambers. Head flow numbers supported a cam lift of around .650, which I have a .653/.660. I have the rings filed to .025 which were calculations I got off of some NOS website (4.31 bore times x) don't remember the site. Fel-pro head gaskets with .039 compressed thickness. Compression ratio is around 11:1 or 12:1. I didn't measure the deck clearance so I'm not entirely sure about the compression. I usually run the timing advance around 38 deg and will shoot to retard the step module to 31 deg.

So, is there anything I'm missing or absolutely need to change? How much Nitrous can I pour into this thing without destroying head gaskets, cooking pistons or shooting the mains out of the pan. I'm thinking anything over 250 is not recommended and I'm not sure this plate would pump anything over that HP rating anyway.

Sincerely,

"Nitrous Novice" Mike

Jeff Stout · 03-03-2021, 11:34 PM

I run 250 on a plate , but Im SBC. 12.5 compression. I feel you need more then 7 degrees timing out. Cold spark plug, maybe retard cam to reduce cylinder pressure. Plug reading is critical. I would start with 100 shot. That is pretty safe and find which cylinder der gives you leanest spark plug reading. All these things I do as my motor is aN/A motor and I have to be careful of torching head gasket in which I have done twice, but now comfortable with spraying 250. My gain is 1.1 second. It's a hoot to use.

Jeff Stout · 03-03-2021, 11:40 PM

Fuel pressure is critical as manufacture should have safe number to use. C16 for fuel.Converter becomes about 1000 rpms looser if it is a N/A converter yet gained the 1.1 seconds. Dont run motor cold as it will sneeze out the carb. Butterflies dont like that.

mrowe · 03-04-2021, 11:05 AM

Thanks for the responses, I forgot to mention that I have a separate regulator for the shot of fuel and I'm told 6PSI is a good location. I have also hear about the cold plugs and possibly a MSD cap-a-dapt to prevent misfires with the rotor phasing. Will definitely get colder plugs. We will see what happens opening day.

Jeff Stout · 03-04-2021, 02:18 PM

The large distributor cap is needed. I split the difference on phasing from the 2 different timing settings. 6psi is safe. When everything is happy you can get down to 5psi. You should monitor fuel psi or set with a flow tool. Flow tool is nothing more then a 73 jet and pressure gauge. Set regulator from the tool. If it's not watched or set and you dont have enough fuel pump it will go clean and be fast for about 2 seconds and then lots of smoke. It does help. I'm sure your plate has been flowed and jet sizes determined. Mine is pretty aggressive with 8 sizes bigger on nitrous over gas jet

mrowe · 03-06-2021, 08:28 PM

I have the larger dist. cap on the way. I have a very stout Product Engineering fuel pump so I don't think fuel pressure will be an issue after I test it. Thanks for all of the info!

03-03-2021, 09:59 PM	#1
mrowe Junior Member Join Date: Jul 2018 Posts: 5 Likes: 0 Liked 0 Times in 0 Posts	Finalizing my nitrous setup I have ventured into the Nitrous realm this winter out of mere curiosity and of course the pursuit of faster times. I need some expert feedback on what I have done. I'm a bracket racer and have a 219" Racecraft rail 468 BBC 2-bolt mains with a Powerglide. Never on the dyno but time slips and weight support something around 600-700 HP on the engine. I'm running a single-stage plate wet system with NOS sniper solenoids. So far I have the following items added to my setup: All MSD electronics including 6AL ignition, crank trigger, billet distributor (locked out centrifugal advance) and a start and step retard control module. I also have a transbrake cutoff module activating the nitrous after the T-brake releases and only when the WOT switch is on. As for the engine mods, I have TRW 50 cc domed pistons and H-beam rods. Brodix aluminum heads with 119 chambers. Head flow numbers supported a cam lift of around .650, which I have a .653/.660. I have the rings filed to .025 which were calculations I got off of some NOS website (4.31 bore times x) don't remember the site. Fel-pro head gaskets with .039 compressed thickness. Compression ratio is around 11:1 or 12:1. I didn't measure the deck clearance so I'm not entirely sure about the compression. I usually run the timing advance around 38 deg and will shoot to retard the step module to 31 deg. So, is there anything I'm missing or absolutely need to change? How much Nitrous can I pour into this thing without destroying head gaskets, cooking pistons or shooting the mains out of the pan. I'm thinking anything over 250 is not recommended and I'm not sure this plate would pump anything over that HP rating anyway. Sincerely, "Nitrous Novice" Mike

03-03-2021, 11:34 PM	#2
Jeff Stout VIP Member Join Date: Dec 2001 Location: phoenix Posts: 1,466 Likes: 59 Liked 703 Times in 280 Posts	Re: Finalizing my nitrous setup I run 250 on a plate , but Im SBC. 12.5 compression. I feel you need more then 7 degrees timing out. Cold spark plug, maybe retard cam to reduce cylinder pressure. Plug reading is critical. I would start with 100 shot. That is pretty safe and find which cylinder der gives you leanest spark plug reading. All these things I do as my motor is aN/A motor and I have to be careful of torching head gasket in which I have done twice, but now comfortable with spraying 250. My gain is 1.1 second. It's a hoot to use.

03-03-2021, 11:40 PM	#3
Jeff Stout VIP Member Join Date: Dec 2001 Location: phoenix Posts: 1,466 Likes: 59 Liked 703 Times in 280 Posts	Re: Finalizing my nitrous setup Fuel pressure is critical as manufacture should have safe number to use. C16 for fuel.Converter becomes about 1000 rpms looser if it is a N/A converter yet gained the 1.1 seconds. Dont run motor cold as it will sneeze out the carb. Butterflies dont like that. Last edited by Jeff Stout; 03-03-2021 at 11:42 PM. Reason: More

03-04-2021, 11:05 AM	#4
mrowe Junior Member Join Date: Jul 2018 Posts: 5 Likes: 0 Liked 0 Times in 0 Posts	Re: Finalizing my nitrous setup Thanks for the responses, I forgot to mention that I have a separate regulator for the shot of fuel and I'm told 6PSI is a good location. I have also hear about the cold plugs and possibly a MSD cap-a-dapt to prevent misfires with the rotor phasing. Will definitely get colder plugs. We will see what happens opening day.

03-04-2021, 02:18 PM	#5
Jeff Stout VIP Member Join Date: Dec 2001 Location: phoenix Posts: 1,466 Likes: 59 Liked 703 Times in 280 Posts	Re: Finalizing my nitrous setup The large distributor cap is needed. I split the difference on phasing from the 2 different timing settings. 6psi is safe. When everything is happy you can get down to 5psi. You should monitor fuel psi or set with a flow tool. Flow tool is nothing more then a 73 jet and pressure gauge. Set regulator from the tool. If it's not watched or set and you dont have enough fuel pump it will go clean and be fast for about 2 seconds and then lots of smoke. It does help. I'm sure your plate has been flowed and jet sizes determined. Mine is pretty aggressive with 8 sizes bigger on nitrous over gas jet Last edited by Jeff Stout; 03-04-2021 at 02:23 PM. Reason: More

03-06-2021, 08:28 PM	#6
mrowe Junior Member Join Date: Jul 2018 Posts: 5 Likes: 0 Liked 0 Times in 0 Posts	Re: Finalizing my nitrous setup I have the larger dist. cap on the way. I have a very stout Product Engineering fuel pump so I don't think fuel pressure will be an issue after I test it. Thanks for all of the info!