I'm going to try using NOS for the first time on my S/P car to run some local no prep races later this year. How much ET gain and how much MPH should I gain on my current combo running E 85 in my 2850 Lb. that has ran a best of 8.86 at 150.MPH in the 1/4 mile at Woodburn in late July several years ago N/A ?
How much more gain shooting 500 HP to it with a new FTI purpose built 10 inch converter?
Thanks in advance.
Cab

Assuming everything is optimized...

8.0 with 300 shot.

7.70's with 500 shot.

My WAG.

Thanks, I hope to try that this year depending on my Wifes health and treatments

Just my opinion, but I think that's close. Mine picks up about that on a 300 hit, but a lot has changed from it's best NA pass. It's slower NA than it used to be by a couple tenths. The nitrous will need a tighter converter and less gear.
At the 500 hp level I'd definitely be getting a nitrous specific camshaft. Seems like 300 hp is kind of the ballpark for needing a different cam. I'm still running the same cam in mine that I built it with in 2006. Not a "nitrous" cam, but it does pretty good.

No prep 1/8 mile or 1/4 mile. What size tire.

Mine is too, although I'm way slower than you. Used to run 11.20's pretty easily but now 11.30's - .40's.

I attribute it to the colder plugs, plate restricting flow and maybe the thicker VR1 20w50 I started using in conjunction with nitrous. Maybe the weight of the added hardware for nitrous as well? Freaked me out at first thinking it was having issues but the more I thought about why...

Mine lost it all in the 60' due to the converter being 1,000 rpm tighter and 3.54 gear versus the 4.10 I used to run.
My best NA pass ever (back in 2007) was 9.54 at 140.4 mph w/ a 1.32 sixty foot.
Now (w/ the nitrous setup) it has run 9.69 at 142.5 mph w/ a 1.43 sixty foot. It pulls hard up top w/ this setup, it just won't leave! For this pass I was on pump gas and had the hotter -8 plugs in it...just like I always ran for NA passes. When on the nitrous I use a -10 plug and Renegade Pro 120 nitrous fuel.
It also has a bigger intake manifold on it now which hurts the lowend.

Cab, cant stress this enough...and please listen to me. You have a (B1 heads) timing sensitive combination with nitrous. Make sure you take out extra timing for what your using .....Better to start out a little low on the timing and sneak up on it. Also if this is your initial experience, maybe start out with 200 and see how it effects your combination. B1 heads require a lot of chamber work to work well with a lot of nitrous. This doesnt mean you cant just use it...but if you end with 8-9* with the nitrous on ....so be it. Be careful about getting a lot of advice from a lot of people, because your going to get a lot of different answers !! Bad info or mismatched information will leave with some hurt parts for sure , what works on one particular engine may not work on yours

We gotta guy here running a '68 firebird, around 2800lbs all in with a 540BBC@8.80's NA, went 7.99 in a shootout with a single stage fogger 350hp tune, just for some info

This is extremely good advice. Go small, pull more timing than you think you need to, make SURE you have enough fuel pump for the motor and the nitrous

Some good advice on this post. As a previous nitrous user, you can't just plop 300hp kit on an N/A application and expect to get the same results of a nitrous set up. Your rings may be too tight. You may blow through your converter and if you have a lot of gear from N/A passes, you may run out of gear. For a smaller 100-150 shot, generally, you can get away with running it on top of an N/A set up motor.

Either way, with that much nitrous, YOU MUST back timing down considerably, run at good fuel (you didn't say what your current combo compression ratio is) and colder plugs.

Good luck and post your new times!

We spray my buddies BBC Cutlass from a 10:17 to an 8:24 on one Really Big kit on 275 D.R.'s.

I may use the 150 HP kit on my present bracket E85 motor with the single Dominator to see what effect it has on the car at our local track and go from there. It is a 400 block with aluminum main caps and ARP main studs (no girdle) stroked to 4.250(Molnar crank and 7.100 long BB Chevy type Molnar H beam rods and bore to 505 C.I. with a decent set of 440-1 heads with 1.55 ratio Jesel paired shaft rockers
I'm still waiting on the pistons, rings and debating on using a steel rod or ordering some new aluminum rods for the new B1 motor. This motor will be near or over 14.0 to 1 comp. ratio on E85 also in a new KB aluminum 4.500 bore wedge block with a KB old top full counterweighted 4.5 stroke crank with 2.375 rod journals
What do you guys think about switching to the BME aluminum rods?

Aluminum rod always a good choice with BBM , especially stock blocks making what you looking to make . Also as mentioned by some already, be generous with the ring gap

The ring gap on the E85 motor is from .022 to .025 on the top ring and from .024 to .028 on the second, hopefully that will work on the 150 shot
I'm thinking around .030 or larger gap on the top ring(4.500 bore size) for 500+ NOs and .035 and larger for the 2nd ring, is that good?
Thanks to al of you for the help. Cab

Total Seal wants 0.008" per inch on top and 2nd groove with heavy nitrous. That's worked for me so far at 4.500" bore. That'd put you at around 0.036" gap. Start small, watch the plugs and take LOTS of notes. As Tony said above, when in doubt, take timing OUT.