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Changed jets and now sending raw fuel through the tail?
#368028
07/06/09 12:40 PM
07/06/09 12:40 PM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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Howdy,
I'm running a Magnum 380hp crate with a Demon 650 double pumper and was having lots of problems fouling out plugs and running very rich. I changed the primary jets from 70's to 67's and the car ran much better but still fouled out the plugs. After some research and a vacuum test I found that the power valve (6.5) was much to large for the amount of vacuum I was pulling at idle. It has a pretty healthy cam and only pulling 8hg in drive and warm. I was told to put a rating around half that of the reading on the gage so I put a (3.5) in. Because I thought I found the problem, I placed 69 jets back in the primary for fear of being to lean. Well... I took it for a ride and I'm still running to rich and now sending raw unburned fuel through the tail pipe! So... Here's my question. Should I put the 67 jets back in and hope for the best or tweak my timing? My timing was dead on with the 67's and larger powervalve and it should still be dead on. Not sure why it would change? When you ease into the gas it run's fine, but when you give a little more throttle, it spits, farts, and act's like it's getting a ton of fuel.
Any help is appreaciated!
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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Re: Changed jets and now sending raw fuel through the tail?
[Re: Mr.Yuck]
#368030
07/06/09 01:57 PM
07/06/09 01:57 PM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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I thought of that to and they were actually lower than what they should be. They're both at the bottom of the site glass when the motor is shut off.
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368031
07/06/09 02:06 PM
07/06/09 02:06 PM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
I thought of that to and they were actually lower than what they should be. They're both at the bottom of the site glass when the motor is shut off.
that should be fine. Are you sure your 2ndaries are closed all the way??? If they hang ever so slightly it can cause issues. You can adjust them on the pass side of the carb.
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Re: Changed jets and now sending raw fuel through the tail?
[Re: Mr.Yuck]
#368032
07/06/09 04:00 PM
07/06/09 04:00 PM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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I think I have them open as much as I do the primaries. I thought the book said to make adjustments between them equally but I could be wrong. I'll make sure they're shut and try that tonight.
Thanks!
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368033
07/06/09 04:13 PM
07/06/09 04:13 PM
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Joined: Jan 2003
Posts: 9,826
las vegas
70AARcuda
master
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master
Joined: Jan 2003
Posts: 9,826
las vegas
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went you changed the power valve did make sure you got the gasket centered under it...
Tony
70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368036
07/07/09 08:25 AM
07/07/09 08:25 AM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
I think I have them open as much as I do the primaries. I thought the book said to make adjustments between them equally but I could be wrong. I'll make sure they're shut and try that tonight.
Thanks!
No I mean when you are at idle the rear doors need to be closed 100%. If they hang open a tad it will cause problems.
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Re: Changed jets and now sending raw fuel through the tail?
[Re: mark7171]
#368037
07/08/09 09:36 AM
07/08/09 09:36 AM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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I have a curved distributor and I'm set a 35 total at 3K rpm. I think my initial was at 15. I'm not running any vacuum advance.
Does that make sense?
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368039
07/24/09 11:11 AM
07/24/09 11:11 AM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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Help! My car is worse! It's still backfiring out the tail pipes and really missing bad. I try to set the initial timing at 18deg. but it won't even run at that. It's still running extremely rich. When I turn the distributor to around 25 deg advanced at idle it runs better for a second and then starts to stumble. I can't get it to idle at all! If I pull it up to 1500rpm is runs good for a second and then starts to miss and stumble. I checked the following:
-Put the timing light on each wire and check to ensure each were firing and they are
-Check the cap and rotor
-tried a different coil
-Tried a different ECU
-Pulled carb and ensured everything was set properly for base line. (Transfer slots etc...)
-Check the rockers arms and all seem tight on driver side so I assumed passenger side is good
-Plugs are carboned up pretty bad but not wet. the #8 was a bit wet but I wiped it off and it was just carboned up after that.
I have a show tomorrow and really want to get it running.
Any help is appreaciated!
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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Re: Changed jets and now sending raw fuel through the t
[Re: gkellycuda]
#368040
07/24/09 11:21 AM
07/24/09 11:21 AM
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Joined: Jan 2003
Posts: 5,443
Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,443
Indiana
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With the car idling and with the air cleaner removed, look down the carb to see if there is any fuel flowing from the squirters or boosters. It sure sounds like the carb is flooding the motor.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368041
07/24/09 11:22 AM
07/24/09 11:22 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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#1 get your float levels right, take out the sight plugs(even if you have the see thru types) & get it just at the bottom edge, and your timing back where it was doing Ok. That'll get you started.
live every 24 hour block of time like it's your last day on earth
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368042
07/24/09 11:30 AM
07/24/09 11:30 AM
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Joined: Apr 2004
Posts: 1,396
Mass
dgc333
pro stock
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pro stock
Joined: Apr 2004
Posts: 1,396
Mass
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Quote:
I have a curved distributor and I'm set a 35 total at 3K rpm. I think my initial was at 15. I'm not running any vacuum advance.
Does that make sense?
Very likely not enough initial timing based on the amount of vacuum you have. You have to get the timing sorted out for your combo before you can start to dial in the carb.
To determine the initial timing the engine wants you keep adding timing in 1 or 2 degree increments while maintaining a constant idle rpm. The point you reach make manifold vacuum is what the engine wants. Don't be surprised if it's over 20 and you will need to limit the advance in the distributor to maintain your 35 total.
Once the timing is sorted out then you can start getting the carb dialed in. I would start with the carb back at the factory settings.
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Re: Changed jets and now sending raw fuel through the tail?
[Re: dgc333]
#368043
07/24/09 12:37 PM
07/24/09 12:37 PM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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I do know the nozzles aren't flowing during idle. I've never heard of initial timing over 20deg though. This thing won't run decent till it's over 30 and you'd think it would spark nock at that. I have a curved and welded distributor from FBO and set to 18 initial and 35 at 3Krpm. I think it's the carb because before I tried to lean it out it ran good. Could it be I'm not letting it get warm enough to set the timing? She's cold blooded for sure. An earlier post said to set the floats below the sight glass but it ran fine with them at half. It's a 650 Demon double pumper w/ mechanical secondaries. It came from the factory with 72 front jets, 6.5 powervalve, and transfers slots set to .020. To try to lead it out at idle I took a vacuum reading in drive at idle and had 8.5hg. So.. I pulled the 6.5 powervalve out and placed a 3.5 in it, cranked the idle mixture screws in 1/4 turn from 1-1/2 out and changed the front jets to 67's. it seemed to run to lean so I then pulled the 67's out and put 69's in and a 4.5 power valve. I'm not sure what to do now. You can't even make it idle to set the initial timing. Would a vacuum leak cause this?
Someone told me that I may have jumped a tooth on the chain but it's a dual roller and I doubt it.
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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Re: Changed jets and now sending raw fuel through the t
[Re: gkellycuda]
#368044
07/24/09 12:45 PM
07/24/09 12:45 PM
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Joined: Jan 2003
Posts: 5,443
Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,443
Indiana
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Check the IAB's to see if they are open. Demon's have a reputation for crud in the passages. If one or more of the IAB's had something in them, this would richen the idle circuit.
Which Demon? (Speed or Mighty)
Note: I had a 650 DP Speed Demon on my mild 340 and the stock jetting of 70/78's gave very good plug color. Best idle was with all four corners out 3/4 turn each.
Last edited by YO7_A66; 07/24/09 12:53 PM.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368045
07/24/09 12:49 PM
07/24/09 12:49 PM
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Joined: Oct 2005
Posts: 4,946
WI
Dcuda69
master
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master
Joined: Oct 2005
Posts: 4,946
WI
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Quote:
Help! My car is worse! It's still backfiring out the tail pipes and really missing bad. I try to set the initial timing at 18deg. but it won't even run at that. It's still running extremely rich. When I turn the distributor to around 25 deg advanced at idle it runs better for a second and then starts to stumble. I can't get it to idle at all! If I pull it up to 1500rpm is runs good for a second and then starts to miss and stumble. I checked the following:
-Put the timing light on each wire and check to ensure each were firing and they are
-Check the cap and rotor
-tried a different coil
-Tried a different ECU
-Pulled carb and ensured everything was set properly for base line. (Transfer slots etc...)
-Check the rockers arms and all seem tight on driver side so I assumed passenger side is good
-Plugs are carboned up pretty bad but not wet. the #8 was a bit wet but I wiped it off and it was just carboned up after that.
I have a show tomorrow and really want to get it running.
Any help is appreaciated!
What kind of plugs? If they are Champions and they are black....they are junk!I would screw a set of NEW plugs in it and start over. 
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Re: Changed jets and now sending raw fuel through the tail?
[Re: gkellycuda]
#368046
07/24/09 12:54 PM
07/24/09 12:54 PM
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Joined: Apr 2007
Posts: 2,826
NY usa
540challenger
master
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master
Joined: Apr 2007
Posts: 2,826
NY usa
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Quote:
I do know the nozzles aren't flowing during idle. I've never heard of initial timing over 20deg though. This thing won't run decent till it's over 30 and you'd think it would spark nock at that. I have a curved and welded distributor from FBO and set to 18 initial and 35 at 3Krpm. I think it's the carb because before I tried to lean it out it ran good. Could it be I'm not letting it get warm enough to set the timing? She's cold blooded for sure. An earlier post said to set the floats below the sight glass but it ran fine with them at half. It's a 650 Demon double pumper w/ mechanical secondaries. It came from the factory with 72 front jets, 6.5 powervalve, and transfers slots set to .020. To try to lead it out at idle I took a vacuum reading in drive at idle and had 8.5hg. So.. I pulled the 6.5 powervalve out and placed a 3.5 in it, cranked the idle mixture screws in 1/4 turn from 1-1/2 out and changed the front jets to 67's. it seemed to run to lean so I then pulled the 67's out and put 69's in and a 4.5 power valve. I'm not sure what to do now. You can't even make it idle to set the initial timing. Would a vacuum leak cause this?
Someone told me that I may have jumped a tooth on the chain but it's a dual roller and I doubt it.
First thing too do it pull the carb off and take it complety apart.
Demons are know for poor quality control.
My demon carb was doing the samething found lots of metal shavings in the new carb.
Which demon are you running speed, road etc... ?
Demons you set the floats a little different then a holley the clear sight plugs has 3 lines around them each is a different level for the float to be adjusted to try the bottom line.
Also what kind of fuel pump and pressure are you running to high of a fuel pressure could do this.
Also do you have or know someone with another carb to swap out and try to see if you can get it to run.
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Re: Changed jets and now sending raw fuel through the t
[Re: YO7_A66]
#368047
07/24/09 01:24 PM
07/24/09 01:24 PM
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Joined: Jan 2005
Posts: 373
South Western Michigan
gkellycuda
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 373
South Western Michigan
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I've had the carb for some time actually. I pulled the carb completely apart this last winter and cleaned it. I will try the setting you just mentioned. Thanks!
1999 Dodge 3/4ton Cummins 24 Valve, 4x4
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