YOUNG GUN: Putting Nitrous on 318!!!

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318DSTR

318DSTR

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Hey Guys,
I've decided to put nitrous on my Duster. I figured its cheap horsepower and it can be alot of fun and fairly safe if used correctly. I've been doing alot of research and I'm pretty sure I've covered all my bases. But I figured I would post my setup and let you guess let me know what you think. I'm really just trying to get as much helpful information as possible, because even though I have the knowledge, I lack the experience that you all have.

Here's what I'm running:
74' 318, standard bore, 70k miles,
Stock heads rebuilt with mild machine work (gasket match, valve seats, valve job, bowls cleaned up etc.).
CARTER 625 CARB,
EDELBROCK PERFORMER INTAKE,
HUGHES WHIPLASH CAM .485" INTAKE, .518" EXHAUST; DURATION 213/226@.050.
Headers 1 7/8", to 3" exhaust,
2500 stall, 3.55 suregrip.
Carter hi flow fuel pump (120gph).
Champion factory style spark plugs.
Initial timing @ 12* total 34* all in at 2000.
Compression ratio (calculated) 8.5-8.8:1.
Nitrous Express Mainline kit (100hp).
Standard Mopar electronic ignition with black control box.

My main concerns at this point is what I should set my timing at, I know they say retard 2* for 50 hp, but just wanted to see what people have experienced. I checked my plugs and it looks like I might be a little too advanced. I also want to make sure that my fuel pump is going to be able to keep up because it is only rated at 6.5 psi even though its (120gph). I've also heard some recommend running colder plugs, but I just inspected my plugs and that actually look like they might be too cold as is (heat transfer is only to 1-2 threads at most). Anyways I just really want to make sure there's nothing I'm leaving out or forgetting because I want this to be a good fun learning experience and not a regret later down the road. Any and all advise is greatly appreciated!!!!
 
28-30 total advance on the spray, run some NGK8's or something in that ballpark and let it eat!! I'm spraying 300 on a fogger and use 5psi. I feed both the carbs and nitrous with one pump.
 
If you have an A/F meter, tuning it is really easy. Get the A/F to where it likes to run N/A, either changing fuel jet or fuel pressure, MPH/plugs can be your guide here too... then start dialing timing back in 1 degree at a time, watching MPH and spark plugs.

I don't know what fuel pressure the NX kit wants as a baseline. Some want some fairly high settings. 6.5 is usually an acceptable/usable pressure. If your pump pressure is lower than the kit requires, you may want to put a slightly larger fuel jet in the kit than the jetting recommendation suggest. It's all a dance.

I'd take 6 degrees out to start. Better to take too much out and sneak up on the tune up than not enough.

My 2 cents, get more initial, 16-20, on it if it will start OK when warm. Limit total to your current 34*. That cam has a bit of overlap and the engine will probably run cleaner at idle with snappier response. It takes some work, but, the way it will run off idle and cruising will be much better.
 
Well I drove the car last night with the nitrous hooked up. I ran the 100 hp jets. I backed the base timing down to 10*. The car seemed to run pretty good. I think I could advance the timing a little more, I also think it could handle the 150 shot as well put i dont wanna get too greedy yet. I was wondering how I can advance the base timing without advancing the total timing. Don't the two go hand in hand? If the base timing increases doesnt the total timing increase as well? Also my kickdown linkage wont clear my air cleaner base because i had to put a drop base on to allow it to clear the hood. Any ideas for modifying the kickdown?, Right now i just have it strapped all the way back so I have full line pressure all the time and I'm shifting it manually.
 
So you only took 2 degrees out, 12 to 10? And yes the total number and your base go hand in hand at this point. So you went from 34 to 32 total, not near enough of a beginning safety margin IMO. If you want more initial you need to reduce the mechanical advance in your distributor to keep the 12 you started with and back it down to 28 which is a good starting point for total on nitrous. I'd live with the idle now and concentrate on taking enough timing out, then tailor it once you get the tune up figured out.

Please stop before this turns into a nitrous blew up my engine thread.

You really need to take enough timing out first and get the fuel jetting side done. Contrary to popular internet belief, a fat tune up is worse than a lean one with nitrous. A fat tune up will continue to run and break stuff, lean usually quits running. Get that sorted out, then worry about dialing timing back in. Once you have that figured out the distributor can be worked over.

I don't know how versed you are at running nitrous, but, learn to read plugs REALLY well as they will tell you a bunch. If the electrode strap is getting burned off that's usually too much total timing, so pay attention to that.
 
Hemirunner said:
28-30 total advance on the spray, run some NGK8's or something in that ballpark and let it eat!! I'm spraying 300 on a fogger and use 5psi. I feed both the carbs and nitrous with one pump.
Click to expand...

You like flirting with disaster. Do you have a low pressure cut off.
 
Well about a week before I hooked up the nitrous I bumped the timing up to 14 initial and 36 total just to see how the car reacted and it ran good. So I figured backing it down to 10 (4* change, 2 per 50hp) would be sufficient with the nitrous. Like I said I pulled the plugs before I ran the nitrous to read them and get an idea of what was goin on in there. Didn't appear to be too rich or lean, the plug temp appeared to be a little cold, and the timing line was just past the 90* point on the ground strap so maybe just a lil too far advanced. Gonna run it a few more times and pull em out again. I'm definitely being cautious cuz me of all people don't want this to be another " I blew my motor up with nitrous" threads.
 
You could probably shoot a bottle rocket into the air and have a 90% chance of finding a free running 318 where it lands.
If you can weld, you can close up the advance slot in the dizzy and have the total and initial timing you desire. Or even braze it up with a propane torch
 
i just got rid of 1 of my dizzy that was locked out (welded) i think i have another :D i have been working in garner at night come on by with the duster lol ...hay bob 318dstr is the guy i was telling you about maybe we can get tog. and get someting to eat are drink lol and talk mopars ...now i just have to get off work long enough mike you could come down 1 friday night and we go to the local drag strip and help out some ...:glasses7:
 
First, you really have to work to blow it with a 50hp shot and a mild 8:1 318. You can break it, but it's not that easy.
1. I'd say consult NX because you;re probably running too high a pressure to the plate, which can cause overrich, which is actually worse than lean with a mild system.
2. Timing was fine where it was. If the engine is in good mechanical shape 50hp is nothing to it. In fact 100hp is barely past something and it's pretty bulletproof.
3. cooler plugs are a good idea. It means they may show rich more than not, but you're not really looing for color. you;re looking for the burn mark, and for specks of aluminum on the porcelain. Flecks are a problem. Burn mark just helps tune.
4. Running on full kickdown pressure and manually shifting is not a solution. It's wearing the trans almost as fast as not running kickdonw at all. Get the right kickdown linkage, clearance the air cleaner, whatever you need to do but get that back working before you really fry the tranny. You'll do that long before the engine gets hurt at 50hp.
 
On my 318 efi magnum I was running 11 lbs of boost and a 75 shot with no problems, must have made 100 passes with it. Thats the motor thats going in my dart. Heads were stock with scce head gaskets and arp head studs. I agree with the above a 50 shot is nothing 100 shot do a little home work.
 
Lots of scattered advice here... sheesh... so I guess I'll give you some more....

It's not about timing pulled... stop thinking this way. It's about total timing. 36 might be fine on a 50 shot but it'll nuke stuff with anything more. Get conservative when playin with sprayin where timing is concerned. The way to get it setup right is to put in a good ignition box with a nitrous activated timing retard. I run a programmable digital 7 MSD. Lock out the dizzy advance. Set it at the total amount of advance that you'll run NA and then set up the timing retard. Get rid of any vac advance. That's playing with fire on a nitrous car.

Fuel-Get a regulator or two. One for the carbs and one for the spray so you can adjust them independently.

Get a wide band and learn to read plugs....

Good luck!
 
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