Nitrous. Biggest shot for a 318

-
V

voodoo1

Well-Known Member
Joined
Jul 18, 2011
Messages
95
Reaction score
3
Location
Vancouver, wa
Just curious cause I might do it.
What is the biggest shot possible for a 318 roller motor. Totally stock motor, cam heads. Put a M1 intake or something similar and how big of a carb would you need for it. Would convertor matter and or help?
Car would be a 72 Dart.

I'm talking total drag car only.

Mike
 
So how disappointed will you be if you blow the motor one round short of finishing in the money?

A 150 shot should be fine if you keep the timing reasonable.
 
I see your point in what you're saying. I'm looking for experience from people who have done this. Just because it blows up doesn't mean failure. Junk yard motors are cheap. I'm certainly not talking about putting a maximum shot first time out either.

I just think it'd be a cool experiment.
 
150 is about as much as the slant guys ( on stock cast aluminum pistons) run for seasons and seasons. so being they are the same design thats where i would put it, maybe 175 or 200 and see what happens, just have to correct ring end gap.
 
805moparkid said:
150 is about as much as the slant guys ( on stock cast aluminum pistons) run for seasons and seasons. so being they are the same design thats where i would put it, maybe 175 or 200 and see what happens, just have to correct ring end gap.
Click to expand...


What plug?
 
150 is fine. If you want to make damn SURE it never leans out, run a completely separate fuel system for the nitrous. Pump, lines, filter and all. May seem like overkill, but they when you upgrade the fuel system will already be there.
 
RustyRatRod said:
150 is fine. If you want to make damn SURE it never leans out, run a completely separate fuel system for the nitrous. Pump, lines, filter and all. May seem like overkill, but they when you upgrade the fuel system will already be there.
Click to expand...

i agree unless he is running a 1/2" with return and a couple of pumps, then he could come off to another regulator and be ok. still safer your way!
 
I ran a 150 on a 318 for a few years. There comes a point where you physically can't cram anymore N2O/fuel mix into the engine. One of the car mags did an article that included this phenomena a few years ago (I think it was Car Craft). Basically, a cloud formed over the carburetor because the nitrous was not being pulled into the engine fast enough...it was pretty cool, but the motor went boom soon after.

Anyway, 150 shot with stock everything will work for a little while...not very well, but it will work. Not sure on the longevity either....what I can tell you is the stock 318 heads won't let much in. I swapped from my lightly ported J heads to a set of 302's....both I hit with the 150 shot (this was in Colorado at Bandimere...so the times are SLOW). If I recall correctly, the car ran 14.6 with the 302 heads and 13.9 with the "J" heads. The runs were 1 week apart, about the same bad air...which I found with a nitrous car in Colorado, my car would run the same no matter what as long as I had the same bottle pressure. The car ran high 15's NA....ah yes, those were the BAD old days...lol. :D
 
Yea! Car Craft or Hot Rod did that article. I remember that. Made me laugh a lot.
 
One of the car mags many years ago also did an article on a literal junkyard 360. They threw it in something....I think it was a dart. They got a base line then kept adding more and more nitrous to it TRYING to kill it. They never did.
 
Start with a 150 shot, back up the total timing, and a NGK plug, with a NON extended nose. Then you can start adding some timing, a little at a time, keeping an eye on the plugs, and the mph. You do not want to start detonating. After you get the best tune possible, then add one step bigger nitrous jet, and go through the same process. Then just keep going one jet size at a time larger. Keep the nitrous jet one or two sizes larger then the fuel jet (after you get the initial tune.) . I am basing this on a fuel pressure of 6 lbs (flowing), and 950 nitrous pressure.

Last time out with my Barracuda we had about a 195 shot, going 13.0's. If we don't get rained out, tonight, I will try one step larger at about 212 shot, looking for 12's. This is on a stock short block 170 slant six.
PS: I run C -12 fuel.
 
Charrlie_S said:
Start with a 150 shot, back up the total timing, and a NGK plug, with a NON extended nose. Then you can start adding some timing, a little at a time, keeping an eye on the plugs, and the mph. You do not want to start detonating. After you get the best tune possible, then add one step bigger nitrous jet, and go through the same process. Then just keep going one jet size at a time larger. Keep the nitrous jet one or two sizes larger then the fuel jet (after you get the initial tune.) . I am basing this on a fuel pressure of 6 lbs (flowing), and 950 nitrous pressure.

Last time out with my Barracuda we had about a 195 shot, going 13.0's. If we don't get rained out, tonight, I will try one step larger at about 212 shot, looking for 12's. This is on a stock short block 170 slant six.
PS: I run C -12 fuel.
Click to expand...


i'm liking this one a lot. Let us know how you do this weekend. Mike
 
My usual suggestion is go until it blows up, then back it off 50hp...

150 shot

.058N, .052F, 6psi, 900 bottle pull at least 8 degrees timing.

That's where I would start. Here's a couple decent places to get a baseline tune up.
http://www.robietherobot.com/NitrousJetCalculator.htm
http://www.dynotunenitrous.com/store/Scripts/Jet_calculator/nitrousjetcalc.asp

If you start with a N jet for a certain HP and step up the N jet, that increases the potential hp.

Approximate sizing of N jet for an HP.
75 = .041
100 = .047
125 = .053
150 = .058

I go the other way, take fuel away until the car car slows down, then back up one jet size. Then start dialing timing back in until it slows, back out one degree. Watch the plugs for speckling/detonation.

If you aren't familiar with juice, I would start with a 75ish shot and tune it. Step up once you get the procedure down. It's harder to hurt your stuff with a 75 shot. If you run it real rich, that's as bad as lean.

Run decent fuel, race gas at that level isn't required, just get good premium level fuel, 93 or 94 is better than our pump swill.

If you have an A/F meter even better! That will tell you if it's fat or lean.
 
crackedback said:
My usual suggestion is go until it blows up, then back it off 50hp...

150 shot

.058N, .052F, 6psi, 900 bottle pull at least 8 degrees timing.

That's where I would start. Here's a couple decent places to get a baseline tune up.
http://www.robietherobot.com/NitrousJetCalculator.htm
http://www.dynotunenitrous.com/store/Scripts/Jet_calculator/nitrousjetcalc.asp

If you start with a N jet for a certain HP and step up the N jet, that increases the potential hp.

Approximate sizing of N jet for an HP.
75 = .041
100 = .047
125 = .053
150 = .058

I go the other way, take fuel away until the car car slows down, then back up one jet size. Then start dialing timing back in until it slows, back out one degree. Watch the plugs for speckling/detonation.

If you aren't familiar with juice, I would start with a 75ish shot and tune it. Step up once you get the procedure down. It's harder to hurt your stuff with a 75 shot. If you run it real rich, that's as bad as lean.

Run decent fuel, race gas at that level isn't required, just get good premium level fuel, 93 or 94 is better than our pump swill.

If you have an A/F meter even better! That will tell you if it's fat or lean.
Click to expand...

That system works well also, and I concur about not running too rich either. That is where I had problems, when I started. I thought I was running lean and hurting parts, when I was actually too rich. I use the "robietherobot" site to get my hp numbers. I didn't suggest jet sizes, as I have a fogger system.
We got rained out last night, so will see what next Tue brings.

PS: I now have 28 n jets, 27 f jets, Fuel pressure is 6.0, starting nitrous pressure is 950-1,000 and drops to about 900 at the end of the run. Timing is fixed at 17 degrees. Car weighs 3250
 
Did you guys see where the editor Friburger of hotrod bought that cuda with a 360 and poured a **** ton of nitrous in it and had to drive it 1000 miles, race it and drive back? They were running 12.2's on a 150 shot they hooked up at a junkyard shop. I thought it was entertaining and amazing how well that sucker held up after all that abuse.
 
Charrlie_S said:
That system works well also, and I concur about not running too rich either. That is where I had problems, when I started. I thought I was running lean and hurting parts, when I was actually too rich. I use the "robietherobot" site to get my hp numbers. I didn't suggest jet sizes, as I have a fogger system.
We got rained out last night, so will see what next Tue brings.

PS: I now have 28 n jets, 27 f jets, Fuel pressure is 6.0, starting nitrous pressure is 950-1,000 and drops to about 900 at the end of the run. Timing is fixed at 17 degrees. Car weighs 3250
Click to expand...

Sounds cool, have fun when the rain lets up.

Fogger is a whole different jet package as you know. They are "fun"!!! I had a car with two plates and a fogger with three manual activation buttons...talk about fun to work all that stuff and still drive. That was back when we didn't really know much about how to cure issues, we just threw more fuel at it, up the fuel pressure. :)

I agree, the old, "rich is safe" thing is a dangerous slippery slope to step on to. It lets the engine run and beat the snot out of parts. If running rich is bad when NA, it sure isn't good when running juice. I've had discussions with one particular nitrous guy and he always suggest running a f jet 10, yes 10 sizes, smaller than the N jet to start on a plate system. I've seen plate kits with a 200-250 kit end up with F jet 14-16 smaller than the N jet, where the instructions say to run equal or ~6 smaller. That's a big swing to get it in range.

Usually when I see plug straps are burning off, it's most likely too much timing/detonation. Feeding more fuel to it may mask the issue, but, that puts the engine into the rich, detonation, ring land killer territory. I'd rather pull a ton of timing and be safe, sneaking up on the right timing setting, than the opposite.

Lots of ways to tune the stuff, hopefully everyone gets to the right spot.
 
You must log in or register to reply here.
-

Back
Top