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Need help tuning mild 440
#146710
11/06/08 11:14 PM
11/06/08 11:14 PM
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Joined: Aug 2003
Posts: 848
Avondale AZ
Prodart440
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 848
Avondale AZ
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Ok. I am lost. I have a 71 cuda with a mild 440. 750 holley, mopar dual plane intake, 1 inch spacer, tti 1 7/8 headers with 3" exhaust, 484-282 pulple shaft cam, 3000 stall 727. I cannot get it lean enough at idle. It will pull 9.5in of vacuum in neutral, but drops to between 5-7 in gear. I have a 6.5 power valve. What can I do to get it leaner?? Oh, timing is at about 12 BTD. Thanks!!!
Aaron
68 Roadrunner 383/AT
69 Dart GT Conv. 383/AT
05 Dodge Ram 4x4 Cummins
06 GoManGo R/T Daytona #757
68 Coronet 440
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Re: Need help tuning mild 440
[Re: Prodart440]
#146712
11/06/08 11:24 PM
11/06/08 11:24 PM
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Joined: Jan 2003
Posts: 3,136
Palm Coast, FL (near Daytona B...
Blown_Hemi
master
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master
Joined: Jan 2003
Posts: 3,136
Palm Coast, FL (near Daytona B...
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Bump the inital timing up to 16º to 18º and have the total timing at 36º to 38º all in by 2500 RPM's. That shoul help your vacuum. Then adjust your carb from there. Always get your timing straightened out first then tune your carb.
Ask me my opinion of Frank Mitchell....... A Mopar crook!
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Re: Need help tuning mild 440
[Re: Blown_Hemi]
#146713
11/06/08 11:28 PM
11/06/08 11:28 PM
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Joined: Aug 2003
Posts: 848
Avondale AZ
Prodart440
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 848
Avondale AZ
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I would bump the timing, but it pings if I do. I need to get a timing light to see when the total timing comes in.
The idle screws are very sensitive. 1/8 turn either way and it doesn't like it.
On another note, what kind of vacuum should the vacuum advance port have??
Thanks!!
Aaron
68 Roadrunner 383/AT
69 Dart GT Conv. 383/AT
05 Dodge Ram 4x4 Cummins
06 GoManGo R/T Daytona #757
68 Coronet 440
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Re: Need help tuning mild 440
[Re: Prodart440]
#146715
11/06/08 11:57 PM
11/06/08 11:57 PM
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Joined: Jan 2003
Posts: 292
Atlanta
DartGTX
enthusiast
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enthusiast
Joined: Jan 2003
Posts: 292
Atlanta
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Are the throttle blades closed past the transfer slots on the carb? My setup is very similar and I replaced the std. hyd lifters with crane "fast bleed" lifters. I went from 11" of vacuum @ idle to 13.5...... Total timing to 34 all in by 2500 rpm. Good luck  Good luck
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Re: Need help tuning mild 440
[Re: thedriver]
#146717
11/07/08 10:13 AM
11/07/08 10:13 AM
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Joined: Jul 2007
Posts: 531
Virginia
JimG
mopar
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mopar
Joined: Jul 2007
Posts: 531
Virginia
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A power valve opening at idle will not cause rich idle.
I'm with 1 Wild R/T in that you need to check t-slot/throttle plate relationship. Drill holes in the throttle plates only as a last resort, after you're sure the timing is where you want it, etc.
Do a search for 68Bullit's post entitled "Holley Rich Idle" or something similar. He had a situation similar to yours and the transfer slot thing is discussed in detail.
What is this carb - a 3310, double pumper...?
Jim
Last edited by JimG; 11/07/08 10:33 AM.
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Re: Need help tuning mild 440
[Re: JimG]
#146718
11/07/08 10:38 AM
11/07/08 10:38 AM
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Joined: Aug 2003
Posts: 848
Avondale AZ
Prodart440
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 848
Avondale AZ
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The carb is a double pumper. The throttle blades are not open too far. I am thinking the powervalve is the issue.
Aaron
68 Roadrunner 383/AT
69 Dart GT Conv. 383/AT
05 Dodge Ram 4x4 Cummins
06 GoManGo R/T Daytona #757
68 Coronet 440
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Re: Need help tuning mild 440
[Re: Prodart440]
#146723
11/07/08 12:25 PM
11/07/08 12:25 PM
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Joined: Apr 2007
Posts: 1,261
ILL
mark7171
pro stock
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pro stock
Joined: Apr 2007
Posts: 1,261
ILL
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you want more timming at idle, so i'd connect it to full vacuum instead of ported.
i dont know what your build "should make" , vacuum wise. with the correct timing more than 9.
the vacuum advance goes away when you give it gas. it wont be the cause of pinging on normal throttling situations. the clowns that hammer it may have some problems...with their "brain".
your mechanical curve will be the culprit of causal throttle pinging.
700 rpms ? thats a big cam in there.
Last edited by mark7171; 11/07/08 12:29 PM.
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Re: Need help tuning mild 440
[Re: Prodart440]
#146724
11/07/08 12:26 PM
11/07/08 12:26 PM
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Joined: Jul 2007
Posts: 531
Virginia
JimG
mopar
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mopar
Joined: Jul 2007
Posts: 531
Virginia
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Quote:
If I move the idle mixture screws in at all, the engine wants to die. I think they are set perfect. After reading your link, I am thinking I need more initial timiing. I can put more timing in, but then it pings. I think I need to re-curve the distributor and work on that angle first. I read the article on the distributor slots and am leaning that way.
Hi Aaron:
I'm a little perplexed by the idle mixture screw situation. If you turn the screws in (lean) to the point the engine stumbles, are you still getting the rich condition? That's what's confusing. Sitting here trying to visualize where additional fuel is coming from still makes me suspect the throttle plates are open too far at idle, causing the mains to operate. But you said that's OK, so I'm still confused.
How far open are the secondary blades? Did you look at those when you looked at the primarys? The same thing can happen back there too, and people sometimes overlook it.
You can try dropping your float level some and see how it responds, although that usually affects part throttle more than anything.
Other than that, I dunno...
I agree with checking the timing, certainly, and getting that dialed in, but (again) retarded initial timing usually results in the throttle plates being open too far at idle and...well, we know the rest!
I ran an almost identical engine in my car before I built the current one. 446", piston tops flush with the deck, same cam as you, home-ported 452's, DP4B intake, and a Holley 3310. I was running 16-18* initial timing, 38* total, and it worked well with no pinging. I had to drill 1/8" holes in my primary throttle plates, for what it's worth.
Jim
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Re: Need help tuning mild 440
[Re: JimG]
#146726
11/07/08 12:43 PM
11/07/08 12:43 PM
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Joined: Aug 2003
Posts: 848
Avondale AZ
Prodart440
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 848
Avondale AZ
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I guess I should get the timing figured out before I even decide to play with the carb. I will see what it like on the initial, and figure total from there. So 36* all in by 2500??
Aaron
68 Roadrunner 383/AT
69 Dart GT Conv. 383/AT
05 Dodge Ram 4x4 Cummins
06 GoManGo R/T Daytona #757
68 Coronet 440
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Re: Need help tuning mild 440
[Re: Prodart440]
#146728
11/07/08 12:47 PM
11/07/08 12:47 PM
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Joined: Jul 2007
Posts: 531
Virginia
JimG
mopar
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mopar
Joined: Jul 2007
Posts: 531
Virginia
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Quote:
I guess I should get the timing figured out before I even decide to play with the carb.
That should always be the plan as long as the carb isn't so far off as to prevent you from messing with the timing!
Quote:
I will see what it like on the initial, and figure total from there. So 36* all in by 2500??
With stock iron heads, 38* is the mostly agreed upon number.
Jim
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Re: Need help tuning mild 440
[Re: JimG]
#146729
11/07/08 01:27 PM
11/07/08 01:27 PM
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Joined: Aug 2003
Posts: 848
Avondale AZ
Prodart440
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 848
Avondale AZ
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They are mildly ported iron heads. Just the bowl area. Still 38*???
Aaron
68 Roadrunner 383/AT
69 Dart GT Conv. 383/AT
05 Dodge Ram 4x4 Cummins
06 GoManGo R/T Daytona #757
68 Coronet 440
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