BBC Ign Timing..n20 question...
02-06-2008, 09:17 PM
#1
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BBC Ign Timing..n20 question... I'm looking for some advice on the amount of timeing i should pull to start with testing the n20 on my car. The motor is 13.5:1,572ci bbc,solid roller,afr 357's,1250cfm dominator, msd crank trigger-pro billet dist-and digital 6 ign.Currently running autolite 3933's and c16 fuel. My builder has timeing locked out and set at 35 degrees,and the car has ran great on the motor so far although a little on the rich side. I made a couple test passes last wknd w/the big shot plate w/225hp jets but didn't realize when I set flowing fuel press,and locked down the regulator I bumped it up from 6 to 9psi
I pulled 8 degrees first pass,6 degrees the second and it ran rich (naturally ) both times and really ran like ****
. I have reset fuel press and plan to go back to the track sunday,but would like to know how much retard you guys would start with for the same n20 jetting? We never dynoed the motor so we went a little consevative with the timeing. Thanks in advance.
I pulled 8 degrees first pass,6 degrees the second and it ran rich (naturally ) both times and really ran like ****. I have reset fuel press and plan to go back to the track sunday,but would like to know how much retard you guys would start with for the same n20 jetting? We never dynoed the motor so we went a little consevative with the timeing. Thanks in advance. 
02-06-2008, 09:31 PM
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well i had a small block in mind but on motor i ran 40 degrees of timing and when i sprayed 250 i only took out 6 degrees and that was on c16 fuel and i had 12.0:1 motor so i would say on yours maybe 4 degrees or u just might be fine where ur at and i cant say about my bigblock yet i should have it running by march or april i hope
02-07-2008, 12:39 AM
#3
When I got my car is was jetted to 275 or 300 (not much of a difference regardless) and it had an 8 degree pill in it. This is with 110 race gas and 10.1 compression. This seemed to work pretty good and was kept that way for a while. So I think 8 degrees for you is way to much.
Id start taking out a degree per run and check the plugs per run.
How safe are you jetting it? That plays a factor in things also.
Id start taking out a degree per run and check the plugs per run.
How safe are you jetting it? That plays a factor in things also.
02-08-2008, 06:16 PM
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Just useing the nos recomended jets for that hp rating (82 n2o/91 fuel).I guess i'll start out pulling 4degrees and go from there. I'm eventually going to spray 350+,but i'm going to try and tune it in and work my way up to there.
02-10-2008, 09:30 PM
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Went to the track tonight. Only made two passes,1 on motor and one on n20.
Motor pass was crappy,because the plugs were shot from last weekend,shut it down at the 1/8th but still ran 6.11@113mph w/1.37 60'. After changing plugs,I pulled 4degrees on the n20 and managed a full pass.Ran 5.98@120mph 1/8th w/a spinning 1.47 60' en route to a 9.27@149mph. Still had just a little bit of pop on the big end but i'm headed in the right direction
Motor pass was crappy,because the plugs were shot from last weekend,shut it down at the 1/8th but still ran 6.11@113mph w/1.37 60'. After changing plugs,I pulled 4degrees on the n20 and managed a full pass.Ran 5.98@120mph 1/8th w/a spinning 1.47 60' en route to a 9.27@149mph. Still had just a little bit of pop on the big end but i'm headed in the right direction
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03-10-2008, 11:42 PM
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Hey Stress.
Any fuel on the window after making a pass??
If you can get the crappy 60' down, you are about to hit an 8. Any timers or auto retards in that car??
Oh yea, don't turn your back on AZ. He wants that car.
.
Hey Stress.
Any fuel on the window after making a pass??
If you can get the crappy 60' down, you are about to hit an 8. Any timers or auto retards in that car??
Oh yea, don't turn your back on AZ. He wants that car.
.
03-11-2008, 06:27 PM
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Thanks for the comments guys. I have not noticed if there is any on the windshield or not
Right now i have a msd dig6 ign that i'm running,useing that to pull timeing(activates retard with 12v) . Next time out i'm going to bump up the initial from 35 and try and get it dialed in on motor,then pull from there with the msd for the n20.I think my 60' problem is due to a short burnout,gonna really heat em up next trip
Here's a few int pics.They aren't very good,i'll try and get some better ones.
Right now i have a msd dig6 ign that i'm running,useing that to pull timeing(activates retard with 12v) . Next time out i'm going to bump up the initial from 35 and try and get it dialed in on motor,then pull from there with the msd for the n20.I think my 60' problem is due to a short burnout,gonna really heat em up next tripHere's a few int pics.They aren't very good,i'll try and get some better ones.
03-11-2008, 09:09 PM
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This is a slip from the last time i went to the track,(still w/ 225 shot jets) Pulled 2degrees,initial still at 35. It definately is getting better with every degree i add.Still acting up a lil on the big end.
03-12-2008, 07:15 PM
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how are you flowing the system? how much bottle pressure? start at 5.75 flowing through a .073 jet about 900-950 psi of bottle pressure square the system up run an .082n .082f pull 6 deg and you'll be suprised i promise.
Last edited by 68maro; 03-12-2008 at 07:22 PM.
03-14-2008, 01:26 AM
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26 to 28 degrees will work,are you going with factory nos jetting?if so you need to bring your nos jet within 2 of your fuel jet and start there.i would set flowing pressue threw a flow tool at 5.5 and start at 26 degrees as your basline,and set your bottle pressure at 950 as you willhave less fall off down the track then 1000 or more psi.Also make sure you heat the bottle evenly.then let the car tell you what it wants.
03-14-2008, 07:01 PM
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I pull 8 out of a 36 total but that's on a smallblock.
How are the plugs looking after a full pass? That popping has to be doing something to the plug. Fat or lean? Where's the timing mark? It has to be at the ragged edge of timing for a 225 hit if not past the edge.
03-14-2008, 07:48 PM
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This guy gets it! YB.com in the house. I pull 8 out of a 36 total but that's on a smallblock.
How are the plugs looking after a full pass? That popping has to be doing something to the plug. Fat or lean? Where's the timing mark? It has to be at the ragged edge of timing for a 225 hit if not past the edge.
I pull 8 out of a 36 total but that's on a smallblock.How are the plugs looking after a full pass? That popping has to be doing something to the plug. Fat or lean? Where's the timing mark? It has to be at the ragged edge of timing for a 225 hit if not past the edge.
03-15-2008, 05:01 AM
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if you were running just the 8th mile i would tell you to keep the 34* in it and run the nitrous..... just make sure you dont unload the tires or..... POP....
that last 8th mile is hard on motors.......
yb.com..... bitch.....
that last 8th mile is hard on motors.......
yb.com..... bitch.....