C5 Scully

I have a forged 402 with Mahle coated pistons Manley H-Beam rods and Eagle steel crank. I am changing the heads to 235 TFS and a new cam with new Cometic multi layer gaskets as used befor. I have a 250hp Zex race kit on the Vette and run a 200hp shot last couple or three meetings.

Well I broke the starter and block trying to start it after two months!!!

Anti freeze in the drivers side front cylinder....

Question id what is the maximum amout that I could spray safely as I have timing retart box race gas and correct plug and no signs of detination or anything bad also have HPT Pro.

Four bolt heads with ARP bolt kit

Also need to know the minimum activation rpm as I have a tripple disc lock-up converter from Precision and the new cam is in the 240 - 246* range...

Thank you for your time and reply.

See may albums for picture of the set-up. Also installing 102 intake and t/b with new Zex 102 Nitrous ring instaed of the dual nozzel set-up I ran.


Not a progressive controlled system

corvette8189

anything over 250 and you really should consider a direct port then spray as much as u desire

C5 Scully

Thank you for the advice, so the MLS Cometic four bolt heads will be up to the job till 250hp if assembled correct and torqued down properly

LinearX

As stated before, a fogger is going to give better distribution than an EFI plate at the level. A friend and I ran 250 on a big bore 388 LS1 with Cometic gaskets, AFR heads, and ARP head studs. The only thing about Cometics is that you have to make certain the block and head surfaces are right or you may encounter leaks.

C5 Scully

Noted, thank you what was you minimum activation rpm??? if you don't mind me asking

corvette8189

hell yea i have a couple buddies spray 200 on stock engines. im sure you could probably do 300 if you wanted

jmuck

The amount you can spray is really dependent on the tune and parts.

How have you been determining the amount of timing you've been running? Are you relying on the AF gauge or KR in HP Tuners? If so, there's your problem. Read the plugs. Just b/c the sniffer shows it to be lean and or rich, the plugs will tell a different story, the real story.

As for the min. activation, spray it as soon as you can as long as traction isn't an issue. Aside from that, your converter is probably flashing to 3K at least? And I'd bet that with a Precision its a good 500 higher minimum than the rated stall speed. So the old theory of spraying below 3k is a non issue.

What plugs were you running? With a 200 or better shot, you should be running at least an BR7EF. That'll help you creep up on the correct tune. What gap are you running on them? Have any pics of the plugs you were using? Are you sure there wasn't any detonation? Did you ever cut the plugs to see for sure? If so, were you checking the plugs correctly? Cutting the engine off right after a full pass?

Also what fuel? I know you said race gas, but if your running a mix, say a few gallons of 91 with a couple gallons of race gas thrown in, that'll be tough to get the tune nailed down.

I'm not framilar with that Zex set up. What pills were you running? From past experiences, I know the jetting recommended by them is generally "fat". Rich will hurt parts long before a lean condition will. Fuel equals Fire.

Are you pulling from the fuel rail? If so, what's the rest of the fuel system?

Sorry if I'm coming across rude, just trying to help a fellow n2o junkie out.

Also what bottle psi are you running with? 950 will give you the most consistent results and make you faster.

On my T/A I was running a forged 347, stock head bolts, stock replacement Felpro h/gaskets and 91 octane. Hitting it with about 225 worth of spray on a WOT switch, I was also pulling from the rail. Had a 3600 Yank. Never torched a gasket or hurt it. Can't tell ya how many bottles I ran through that engine. I ran a smaller fuel jet for a 200 shot than most did with a 100-125shot. I was using a Nitrous Outlet Plate and had ZERO distribution issues through a LS6 intake. There have been tons of guys spray 300ish through a plate with out issue. Gotta be on top of the tune, but it is doable, though a fogger would be the way to go.

BLOWNBLUEZ06

The problem with telling someone to read plugs is that they have to understand how to properly read a plug. People look at the end of the plug and think they can tell something about fuel.

Here's a few basics about plug reading that you should know. There is a lot more to it than I'm about to say, but I don't have the time to go through it.

Widebands are tuning tools. EGT sensors are tuning tools. Knock sensors won't help with large shots of nitrous.

A person who's good at reading plugs can tell you how close you are on fueling AND timing.

In order to properly tell how close your fuel and timing is, you need to start with a proper plug. 200 shot, you should be able to get away with a NGK BR7EFS any more than that, step up to a B8EFS.
After you get proper plugs in, get your car close with the wideband and conservative on timing. Then make little, 1 gear hits with adequate timing pulled to verify your fueling is still on the rich side of close with your wideband.
Then make full pulls down the 1/8 or 1/4 mile track and pull over at the end of the track. You should change all of your plugs at the end of the track before pulling into the pits or get towed back and do it. Keep them according to cylinders. Either cut the threads off to look at how far down your fuel band is or use a good Otoscope.
You'll need magnification up to 10x.
See the band in this picture?


They say the plug is too cold, but that's not necessarily true. That band can move with timing. More timing and it'll move toward the body of the plug .Too close to the body and you had better stop adding timing because you're about to burn the tip off.

That's some basic info. I hope it helps. Spraying a 200 shot is no joke.

jmuck

Beat me to the last part Brett.

Reading plugs isn't rocket science, but it does take some time and studying to learn what's right and wrong.

If you aren't sure, check out YellowBullet.com, or better yet. Hit the local track and find the fast nitrous racers and pick their brains.

BLOWNBLUEZ06

So you admit you were holding out on the poor guy?

C5 Scully

Thank you for the full reply! Learning a lot just reading it...

I have a LS1 timing retard box from Thunder Racing and ZEX window switcher and a MSD launch control 2 step module.

I have used the Zex multi tip race plugs and my bottle pressure was 950 psi with a 43 psi fuel pressure from a stand alone fuel cell from nitro dave...



I am getting into the plug reading and will pay more attention to it in the future as it is a lot of work and money spent not to look at free info

Thanks again

See my albums in my profile for pictures of the set-up please