Just been toying with the idea of a little nitrous to get our dragster into the low 7's. Anyone have any good resources to read up on it?

The current engine is a 605 bbc 14.5 compression. What kind of range of compression ratios work with nitrous or do I need new internals? Only looking to gain about .5 or .6 maybe

14.5 to 1 is fine, don't get too hung up on compression. Depending on your converter 200 to 300 hp should get you what you are looking for. Follow the tune recommendations of the system you get and remember too much timing and too much fuel can hurt the motor, be conservative with timing until you get a feel for your tune up and stay on the lean side at first, yes I said lean side!

If your converter is on the loose side now you may find yourself hitting the wall as you increase your HP levels with respect to performance.

OK, thanks for the information! Glad I dont have to change the bottom end of the engine.

Not many here use nitrous for whatever reason, so a bit hard to find someone to get real world advice from.

exactly what top38 said and your converter will be the limiting factor as to how much you can spray but 200hp for a few seconds should get you close.

Induction Solutions has nice stuff and good info on their website. Run your N2O on a timer from your delay box, retard timing some when the gas comes on, if you looking for .5 seconds to .6 seconds in the 1/8 mile you will need quite a bit of nitrous for that which will require a tighter converter to handle N2O power you'll be adding.

That's really the challenge for you, a good converter for NA will be too lose for any sort or real N2O use. If you spray 400 on a converter that's appropriately sized for your car and flashes to say 6600 RPM, more than likely it will run right through it and you'll just be wasting time and putting a ton of heat in the converter. The converter will need to be sized for the power level you want.

Now if you are talking .5 seconds in the quarter mile, that's a different story. 250 should get it done and may or may not run through the converter it all depends on how lose/tight the current converter is.

Your

Are you running gas or Alky? what heads?

When I first went fast bracket racing I took a conventional headed s/c 565 and bolted on an old tunnel ram with dual plates. 65/55 in each plate. Went from 7.77@171 to low 6.90s @ 195. Never hurt a thing. Pistons were allegedly incapable of taking any nitrous.

Later put nitrous pistons in and added a second stage in the runners and went 6.62@204.

If you only want to gain 0.5 in the 1/4 and your converter is on the tight side, you might get away with it. If you have a grid, the timing curve will help. Much more and you’ll want a dedicated nitrous converter.

Nitrous express twin Gemini plate. from 50 to 300hp gas or alky. Been doing it for may years. Spraying 200hp from the start for 2 seconds will get you .18 in et. Remember to pull 4 degrees per 100hp used.

Thanks for all the information! The hoped gain is .5 - .6 in the 1/4.

The engine is a 605 BBC with worked Dart 355 heads, (dont know how much, J.R. Baxter's old heads) The cam is 287* 306* @ .050 and lift is .824 on gas 14.5 compression and the ignition is crank trigger 7AL box. No real details on the converter other than it is a TCS 9 inch, have to look at video to see what the flash and fall back is, but 1.07 60' and 180 mph at the end.

Thanks for the note about induction solutions, I will have a look at their site.

quote:

Originally posted by TD6297:
Thanks for all the information! The hoped gain is .5 - .6 in the 1/4.

The engine is a 605 BBC with worked Dart 355 heads, (dont know how much, J.R. Baxter's old heads) The cam is 287* 306* @ .050 and lift is .824 on gas 14.5 compression and the ignition is crank trigger 7AL box. No real details on the converter other than it is a TCS 9 inch, have to look at video to see what the flash and fall back is, but 1.07 60' and 180 mph at the end.

Thanks for the note about induction solutions, I will have a look at their site.

NX is the best and easiest in my opinion. I have run them with ALKY, went 4.85 to 4.60 with 100 shot, 4.55 with a 150, 4.49 with a 200 all on ALKY.

On gas 4 degrees per hundred is good, on alky 1-1.5 per 100.

quote:

Originally posted by The Bozman:


On gas 4 degrees per hundred is good,

You mean pull 4 degrees timing per 100 HP on gas?

Sounds like 200 - 250 is the range I would need to gain the hoped ET

2 degrees per 50 HP is an old rule of thumb! Usually it's conservative but not always. Total timing on the sauce it was really matters! That is determined by tuning and watching the plugs however you can also get close to start with using 3 types of combustion chambers, slow burning, medium and fast. The slower the burn rate the less timing retard from NA timing is needed. An example of a slow burning chamber would be your typical BBC 454 with open chamber heads, with that CID and chamber size you need a huge dome to get any compression which gets in the way of combustion so more timing is needed. A fast burn deal would be 632 SR 20 BBC. You can get a good feel of what you have by home much timing your run NA. That old 454 deal would like 40 plus where the 632 SR20 only needs 30.

If your going to run a 250 shot you could be between 8 and 12 degrees of timing retard depending on your combo. Like I said it don't hurt to take too much timing out (within reason and stay on the lean side). Set your NOS fuel pressure with a fuel flow gauge, borrow one if you don't have one. If you don't have an NOS pressure gauge, measure the temp of the bottle, 84 degrees is 910 PSI,86 is 945 PIS, 91 is 995 PSI and 95 is 1050. Your NOS kit should give you both fuel pressure and bottle pressure for there jetting map.

On your first run, I'd recommend spraying if for a shorter duration (3 or so seconds with fresh plugs, set the gap at .030", then adjust as needed then increase the time you spray.

quote:

Originally posted by TD6297:
Thanks for all the information! The hoped gain is .5 - .6 in the 1/4.

The engine is a 605 BBC with worked Dart 355 heads, (dont know how much, J.R. Baxter's old heads) The cam is 287* 306* @ .050 and lift is .824 on gas 14.5 compression and the ignition is crank trigger 7AL box. No real details on the converter other than it is a TCS 9 inch, have to look at video to see what the flash and fall back is, but 1.07 60' and 180 mph at the end.

Thanks for the note about induction solutions, I will have a look at their site.

Anything more than about 150 for a few seconds will cause a converter to just not work. A converter that will stall at 63-6400 on the brake normally aspirated will only take 200 plus or minus in a 600 inch configuration.
You can only split the difference so much for a non dedicated converter.
A converter that stalled at 6650 on motor lost .02 lowering the stall to 6000.
A 6650 converter went sky high on a 200 shot, and the engine went rich, as there was no longer any load on it.
FTI has their 93B converter that works good on motor, and will take a 200 shot of gas. About .08 slower than a optimized unit.
A 600 inch with heads in the 355-375 range like a 1.8 rocker on a .475 lobe. Your .824 is only about .780 with lash and deflection.Been playing with 600" combinations for a few years and heads are the limiting factor. your 355..... are probably all done at 7000, but nitrous up there could boost the rpm some.

quote:

Originally posted by Bad News:

Anything more than about 150 for a few seconds will cause a converter to just not work. A converter that will stall at 63-6400 on the brake normally aspirated will only take 200 plus or minus in a 600 inch configuration.
You can only split the difference so much for a non dedicated converter.
A converter that stalled at 6650 on motor lost .02 lowering the stall to 6000.
A 6650 converter went sky high on a 200 shot, and the engine went rich, as there was no longer any load on it.
FTI has their 93B converter that works good on motor, and will take a 200 shot of gas. About .08 slower than a optimized unit.
A 600 inch with heads in the 355-375 range like a 1.8 rocker on a .475 lobe. Your .824 is only about .780 with lash and deflection.Been playing with 600" combinations for a few years and heads are the limiting factor. your 355..... are probably all done at 7000, but nitrous up there could boost the rpm some.[/QUOTE]

Not sure who's converter your talking about with that statement above but it's not true with mine and many others. You can easily spray 200 with a 600 cid plus motor that has an NA converter. We do it all the time. Sounds like your converter isn't up to the task.

quote:

On your first run, I'd recommend spraying if for a shorter duration (3 or so seconds with fresh plugs, set the gap at .030", then adjust as needed then increase the time you spray.

Thank you.I did finally see the PDF from Nitrous Express and they suggest 22 degrees of timing. With a 7AL is there any module that can be added to retard timing after the nitrous comes on or just have to run 22 from the hit?

The 7AL has plug in chips for retard, or you can get their dial module....works either way...


Attach a mother bottle to the car...Run a -16 hose from bottle to intake....install a 90* valve in driver's compartment....jet it on the rich side, and open valve! Nothing like a 1,000,000 shot off the line!!!!

quote:

Originally posted by TD6297:

quote:

On your first run, I'd recommend spraying if for a shorter duration (3 or so seconds with fresh plugs, set the gap at .030", then adjust as needed then increase the time you spray.

Thank you.I did finally see the PDF from Nitrous Express and they suggest 22 degrees of timing. With a 7AL is there any module that can be added to retard timing after the nitrous comes on or just have to run 22 from the hit?

If you have the older 7AL 2 then you need to get a timing module to retard the timing when the NOS is activated or like you said, set the timing to 22 and run it. If you are going to use the NOS for a portion of a run then get the retard module from MSD.

Ok thanks! I didnt know I could get a timing module for the older 7AL units. I had a quick look the other day and didnt see anything. I will have to look deeper into that.

Pretty sure the timing controller is the same or more $ for less functionality vs putting a grid in front of the 7al

I didnt know a grid could be used with a 7al. Are they legal for NHRA?