ADVICE:Baseline carb jetting/engine timing/spark plugs

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dustoff440

dustoff440

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Almost ready to fire up my 360 MAG since rebuild
Need advice on starting points for jetting / timing/plugs

Heres the specs:

92 360 Magnum
bone stock block/ rods/pistons/ crank/ std bore
stock heads
crosswind air gap intake
mopar performance distributor
msd6al/blaster coil
out of the box Holley 650 double pumper
cam 512 exhaust 496 intake 220@50 ( 276/286 advertised) lsa 113.5
hughes single valve springs/retainers/locks
3.91 sure grip
street fighter converter advertised 3500 stall
150 shot of nitrous
car is 3200 lbs
early 340 exhaust manifolds

im at a total loss for jetting
was considering 33 total degrees all in by 2500 for the dizzy
not sure about initial advance
totally clueless on plugs
 
Try the 650,out of the box. I would run,the Autolite version of the Champion plug,(3924 comes to mind.) MSD's love Autolites.Similar cam.Crower 284 advertised,224@.050,.491 lift/1.6 ratio.Had 21 inches of vacuum@ 800 in drive.Went 34@3000.Worked out,to 16 initial ,at idle .Mind you,the distributor was already "curved". This is a necessary detail.I would curve it,before starting it. My cam idled,like a stock 340.800@idle,slight rump.
 
Abodybomber said:
Try the 650,out of the box. I would run,the Autolite version of the Champion plug,(3924 comes to mind.) MSD's love Autolites.Similar cam.Crower 284 advertised,224@.050,.491 lift/1.6 ratio.Had 21 inches of vacuum@ 800 in drive.Went 34@3000.Worked out,to 16 initial ,at idle .Mind you,the distributor was already "curved". This is a necessary detail.I would curve it,before starting it. My cam idled,like a stock 340.800@idle,slight rump.
Click to expand...

Great, what you accomplished is exactly what I want a "sleeper"---a slight rump, high vacuum, and goes like a bat out of hell when I step on it. I was pleased that you recommended the Autolites I have had great success with them in the past.
 
Go get it!(lol). Love Autolites,no spray. Automatically go NGK/Accel ,with the bottle.
In my limited experiences ,these seem to do better.
 
A 650 on all that motor? I think with nitrous it will run lean. Something you DON'T want. I could be wrong, but I think you have more motor than just a 650.
 
My apologies, Robert. I included,N20 on my future endeavors. I normally run a 4779 double minimum,on anything with a healthy cam. He might need a bigger intake/carb combo later. I ramped up ,the cam timing,and airflow.Jumped to the actual Eddy manifold.
 
RustyRatRod said:
A 650 on all that motor? I think with nitrous it will run lean. Something you DON'T want. I could be wrong, but I think you have more motor than just a 650.
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Please explain how you come to this conclusion? What does the size of the carb have to do with if it runs lean on nitrous?
 
CPMotorworks said:
Please explain how you come to this conclusion? What does the size of the carb have to do with if it runs lean on nitrous?
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Not necessarily just for nitrous. IMO a 650 is a little small for his combo. For the motor as a whole. I said I might be wrong. Did you flunk English?
 
RustyRatRod said:
Not necessarily just for nitrous. IMO a 650 is a little small for his combo. For the motor as a whole. I said I might be wrong. Did you flunk English?
Click to expand...

I asked for an explanation of your statement, not if the carb was too small for his combo.
My Engrish is fine, but your physics isn't even close.
 
CPMotorworks said:
I asked for an explanation of your statement, not if the carb was too small for his combo.
My Engrish is fine, but your physics isn't even close.
Click to expand...

Ok well help me out, Mr expert man. I'm all about learnin.
 
RustyRatRod said:
Ok well help me out, Mr expert man. I'm all about learnin.
Click to expand...

Plenty of factual info to be found with a little reading on how a carb functions, how A/F ratios are calculated, etc. I'm not here to hold your hand, I asked for an explanation based on your statement and facts.
But instead I get insults like we are in 3rd grade. You stomp your feet when you don't get your way?
Its as simple as two separate systems, you don't tune the carb based on the nitrous use.
 
Johnny Dart said:
So how bout them Dodgers !
Click to expand...

Yup, they are doing great this year!!! LOL

By the way, I was going down HWY 285 on the way to Denver and passed this sweet looking 65/66 Bright Red Dart with a white convertable top on a trailer. NICE!!! Wonder if he's a member here?

Back to the subject!
 
dustoff440 said:
Almost ready to fire up my 360 MAG since rebuild
Need advice on starting points for jetting / timing/plugs

Heres the specs:

92 360 Magnum
bone stock block/ rods/pistons/ crank/ std bore
stock heads
crosswind air gap intake
mopar performance distributor
msd6al/blaster coil
out of the box Holley 650 double pumper
cam 512 exhaust 496 intake 220@50 ( 276/286 advertised) lsa 113.5
hughes single valve springs/retainers/locks
3.91 sure grip
street fighter converter advertised 3500 stall
150 shot of nitrous
car is 3200 lbs
early 340 exhaust manifolds

im at a total loss for jetting
was considering 33 total degrees all in by 2500 for the dizzy
not sure about initial advance
totally clueless on plugs
Click to expand...

Carb jetting will be based on what the plugs look like and mph at the track. Start with the standard jetting for that carb, nobody will be able to tell you what is optimal for your setup but the engine itself.
Start with the stock plugs, Autolite or I prefer the NGK's myself.
Timing will be same as jetting, start with your proposed 33 and go up or down from there, again based on how the plugs look and the cars responds.
Nitrous tuning will be at the plate itself with jets, and fine tune with fuel pressure, but I would only do that after making sure the engine tune is good.
It does need to be done in order though-
Timing first
Jetting Second
fine tune both from there once your close.
 
Find the point where the engine kicks back on your starter.

Set up the distributor so you have some room to advance it without opening it up.

You find the starter kicks back at 20* initial. So you set your initial limit at 18. If you want to start at 33 total and range up to 38, set the distributor with 20* mechanical, 38-18, and initial at 13*. Then you can start feeding timing in up to your 18* kickback limit.

You may have to reset your idle speed as you dial in more initial timing.

Once you find the right total number, subtract 18 from it and you have your mechanical advance number.

That's one way to do it.

Timing first as mentioned

IMO, carb is small. If you decided to go up in sizing, grab a proform style mainbody. Make it about an 830.
 
18 initial/34 total should be a pretty safe starting point. That's what mine set at and it runs on 87 octane, so if you're running 91/93 fuel there should be some room to play around with it. Personally, I found very little gain running 93 n/a, even after adding timing and tweeking the fuel, so I just run 87 all the time to save a little money.

I run NGK FR6 (v power) plugs also. These are stock heat range for the later magnum engines. Personally I think that the NGK plugs are easier to read (timing, not fuel). For nitrous you may want to consider an FR7 or 8.

Run the carb you have for now. While I do agree there is something to gain with a larger carb, that doesn't mean it won't run well without it. Looks to me like it should do better than 12.50 in the 1/4 n/a.
 
Thanks guys...I'm starting with the 650 cause it's what I have on hand
I have an 850 Thermoquad that I will eventually put on
 
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