440 ignition timing
#2970102
10/03/21 09:18 PM
10/03/21 09:18 PM
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Joined: Dec 2004
Posts: 733 Northern Virginia
Moparmaniacc
OP
super stock
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OP
super stock
Joined: Dec 2004
Posts: 733
Northern Virginia
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This is a newly rebuilt 440 Challenger with a mild roller cam, 4 seconds flat distributor, headers and 4 speed. I know you guys are going to tell me to use a timing light, but - I like to try and find the best seat of the pants performance just by moving the distributor in small steps around my "sweet spot". I've got a mark on my distributor and on my block.
So this is what what happens. If I keep advancing the timing past my sweet spot - the car will not ping at full throttle, but the idle gets rougher and the car bucks back and forth when I'm trying to cruise around at 30 or 40 mph in 2nd or 3rd. (Is this "surge" like in VCODE's recent Thermoquad post?)
So I'm trying to get my distributor sorted out before I start fooling around with my brand new Holley 750 vacuum secondary. My problem is, the car doesnt feel as strong as it should. Should I go back into the distributor and move the limiter plate to allow more advance? Should I really follow FBO's directions and plug the distributor into a constant vacuum source, which doesn't make sense to me?
thanks in advance! John
Last edited by Moparmaniacc; 10/03/21 09:20 PM.
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Re: 440 ignition timing
[Re: Ramrod39]
#2970114
10/03/21 10:03 PM
10/03/21 10:03 PM
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Joined: Aug 2006
Posts: 2,525 God's Country Maryland
GODSCOUNTRY340
master
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master
Joined: Aug 2006
Posts: 2,525
God's Country Maryland
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This is how I find my engine's sweet spot. Get the engine at normal operating temp, turn the carb idle screw until the engine is at 2500 RPMs, now start advancing your distributor until the engine just starts to slow down, back it off till it clears up. Sweet spot.
I love the smell of Deer guts in the morning, it smells like... VICTORY!
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Re: 440 ignition timing
[Re: Moparmaniacc]
#2970122
10/03/21 10:45 PM
10/03/21 10:45 PM
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Joined: Dec 2004
Posts: 10,555 Rittman Ohio
fourgearsavoy
I Live Here
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I Live Here
Joined: Dec 2004
Posts: 10,555
Rittman Ohio
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When you unplug the hose off the advance does it still "surge" at cruise speeds. I really don't get the "don't want to use a timing light thing" It's hard to give guidance when we don't know where your timing is. It's like the guy at the track complaining about his car running slower than expected and you ask him where the timing is set and he says "I've had it everywhere" Not a very intelligent response because timing is more important than ever with the crap fuels we have today. Set your total at 34* without vacuum and see how it runs Gus
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60
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Re: 440 ignition timing
[Re: Moparmaniacc]
#2970126
10/03/21 10:51 PM
10/03/21 10:51 PM
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Joined: Aug 2003
Posts: 43,230 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,230
Bend,OR USA
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I've race Mopars and won with them at NHRA races in stock and in the heads up 10.90 and 9.90 classes with BB, SB and 426 hemi. All the BB like between 34 and 36 total timing at the tracks we tested on, I weld up the stock advance slots and make them have around 16 degree mechanical advance so I can set the idle timing between 14 to 18 BTDC to get the total timing where I want it. I also use a set of real light advance springs from Mr. Gasket, part #95B I think. As far as the butt dyno, yours and mine probably are not calibrated the same Most butt dyno normally won't feel .030 to .009 ET and or from .3 to 1.5 MPH gain in the 1/4 mile The time slip will show those changes accurately Tune it to you like or love it and then read the real results with a good timing light
Last edited by Cab_Burge; 10/03/21 10:53 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 440 ignition timing
[Re: Cab_Burge]
#2970249
10/04/21 09:49 AM
10/04/21 09:49 AM
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Joined: Jan 2003
Posts: 15,434 Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,434
Omaha Ne
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The last two responses from Cab and 4 gear are spot on Your surging is likely the motor telling you it has too much advance Also, checking for pinging due to excess advance is best done from low RPM and speeds (20 MPH or so) in 3rd or 4th gear while putting the motor under a heavy load like climbing a hill, and then accelerating from both part throttle and again at WOT
Last edited by TJP; 10/04/21 10:00 AM.
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Re: 440 ignition timing
[Re: Moparmaniacc]
#2970258
10/04/21 10:27 AM
10/04/21 10:27 AM
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Joined: Jan 2003
Posts: 12,171 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,171
Benton, IL.
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Most of our big blocks like a similar timing set-up. So there is not really any need to experiment with timing schemes that are out of the ordinary. You have some good advice in this thread from guys that have a ton of experience.
Who chose to use a vacuum secondary 750 carb on a cammed 440 with a 4 speed?
Master, again and still
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Re: 440 ignition timing
[Re: DaveRS23]
#2970267
10/04/21 10:49 AM
10/04/21 10:49 AM
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Joined: Feb 2003
Posts: 10,220 Someplace you aren't
SomeCarGuy
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 10,220
Someplace you aren't
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The new engine masters tested mopar heads and timing and 34-36 was the ticket. I’ve had the best luck with smooth running at 34 with 906 heads. I gained .5 mpg by running 38, but the engine didn’t have that smooth feel like fuel injection running that much.
I want my fair share
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Re: 440 ignition timing
[Re: TJP]
#2970268
10/04/21 10:50 AM
10/04/21 10:50 AM
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Joined: Apr 2011
Posts: 1,520 West Palm Beach, Florida
Copper Dart
pro stock
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pro stock
Joined: Apr 2011
Posts: 1,520
West Palm Beach, Florida
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The last two responses from Cab and 4 gear are spot on Your surging is likely the motor telling you it has too much advance Also, checking for pinging due to excess advance is best done from low RPM and speeds (20 MPH or so) in 3rd or 4th gear while putting the motor under a heavy load like climbing a hill, and then accelerating from both part throttle and again at WOT Pinging is taking place long before a human ear is going to hear it especially from the drivers perspective and over the exhaust and road noises. If you can hear it, it has gone from a small hammer tapping on your valvetrain to a sledge hammer. Just sayin' Copper
Common sense, the least common of all the senses. Mom.
For fear of ridicule, society stifles creativity. Ricky Valdes
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Re: 440 ignition timing
[Re: BSB67]
#2970269
10/04/21 10:53 AM
10/04/21 10:53 AM
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Joined: Dec 2013
Posts: 4,689 Wichita
GY3
master
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master
Joined: Dec 2013
Posts: 4,689
Wichita
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x2. Anything else is just guessing. Did a dude with a timing light run off with your girlfriend? (trying to understand the reason for timing light aversion)
'63 Dodge 330 11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs. 10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: 440 ignition timing
[Re: GY3]
#2970315
10/04/21 12:12 PM
10/04/21 12:12 PM
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Joined: Sep 2003
Posts: 19,486 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,486
north of coder
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you can possibly get rid of the cruise [light throttle/high vacuum] bucking by using a 3/32" allen key into the advance can, and turning the can spring to a tad less vacuum advance at your cruise rpm. e-booger did an article for mopar muscle magazine on tuning the vacuum advance a while ago. look it up on their site. it's a well written piece, and should be tried before saying the heck with it, and just capping off the advance can. in some instances, it makes a world of difference on the performance of a vehicle no matter what engine you have under the hood. it has worked for me many, MANY times, while most just cap the can without even trying to tune it. i highly recommend reading that article and applying it to your combination !
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Re: 440 ignition timing
[Re: Moparmaniacc]
#2970576
10/04/21 09:28 PM
10/04/21 09:28 PM
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Joined: Aug 2005
Posts: 299 Hinckley, Ohio
KWF340
enthusiast
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enthusiast
Joined: Aug 2005
Posts: 299
Hinckley, Ohio
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Here's the link to the article. Link
1968 Charger R/T, 440 Auto, GG1; 1969 Super Bee, 383, 4-speed, T5; 1969.5 Road Runner, 440-6, 4-speed, 96; 1970 Duster 340, 4-speed, EV2; 1970 Charger R/T SE, 440 (496), Auto, EB3; 1970 Dart Swinger 340 (416), 4-speed, EV2; 1970 Corvette coupe, LS5, 4-speed, Daytona yellow; 2000 Corvette coupe, LS1, 6-speed, Twin Turbo, Torch red.
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Re: 440 ignition timing
[Re: Moparmaniacc]
#2970780
10/05/21 09:52 AM
10/05/21 09:52 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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Step one, buy a timing light. 2, unhook the vacuum advance, 3. start the car, 4. turn the idle up to 2300 rpm, 5. set full timing in at 36*, 6, back idle down to normal, 7. turn idle mixtures crews for best vacuum, 8. Go for a run. If you have a delay/bog you will need to mess with the spring in the "pod". You might also have to change the power valve.
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