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440 ignition timing #2970102
10/03/21 08:18 PM
10/03/21 08:18 PM
Joined: Dec 2004
Posts: 726
Northern Virginia
Moparmaniacc Offline OP
super stock
Moparmaniacc  Offline OP
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Posts: 726
Northern Virginia
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 08:20 PM.
Re: 440 ignition timing [Re: Moparmaniacc] #2970107
10/03/21 08:34 PM
10/03/21 08:34 PM
Joined: Feb 2005
Posts: 4,226
Prospect, PA
BSB67 Offline
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Prospect, PA
Use a timing light.

Re: 440 ignition timing [Re: BSB67] #2970111
10/03/21 08:53 PM
10/03/21 08:53 PM
Joined: Jan 2003
Posts: 8,798
Tucson, AZ
Ramrod39 Offline
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Tucson, AZ
Originally Posted by BSB67
Use a timing light.


haha

Re: 440 ignition timing [Re: Ramrod39] #2970114
10/03/21 09:03 PM
10/03/21 09:03 PM
Joined: Aug 2006
Posts: 2,262
God's Country Maryland
GODSCOUNTRY340 Offline
top fuel
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God's Country Maryland
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!
Re: 440 ignition timing [Re: Moparmaniacc] #2970122
10/03/21 09:45 PM
10/03/21 09:45 PM
Joined: Dec 2004
Posts: 10,152
Rittman Ohio
fourgearsavoy Offline
I Live Here
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Rittman Ohio
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 twocents

Gus beer


64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
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Re: 440 ignition timing [Re: Moparmaniacc] #2970126
10/03/21 09:51 PM
10/03/21 09:51 PM
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Posts: 38,131
Bend,OR USA
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Cab_Burge Offline
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Bend,OR USA
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 shruggy 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 shruggy twocents The time slip will show those changes accurately up scope
Tune it to you like or love it and then read the real results with a good timing light twocents scope

Last edited by Cab_Burge; 10/03/21 09:53 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 440 ignition timing [Re: Cab_Burge] #2970249
10/04/21 08:49 AM
10/04/21 08:49 AM
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Posts: 11,397
Omaha Ne
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TJP Offline
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Omaha Ne
The last two responses from Cab and 4 gear are spot on twocents
Your surging is likely the motor telling you it has too much advance whistling

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 wink

Last edited by TJP; 10/04/21 09:00 AM.
Re: 440 ignition timing [Re: Moparmaniacc] #2970258
10/04/21 09:27 AM
10/04/21 09:27 AM
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Benton, IL.
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DaveRS23 Offline
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Benton, IL.
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?


KOS
Re: 440 ignition timing [Re: DaveRS23] #2970267
10/04/21 09:49 AM
10/04/21 09:49 AM
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Posts: 9,073
Someplace you aren't
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SomeCarGuy Offline
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Someplace you aren't
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
Re: 440 ignition timing [Re: TJP] #2970268
10/04/21 09:50 AM
10/04/21 09:50 AM
Joined: Apr 2011
Posts: 1,504
West Palm Beach, Florida
Copper Dart Offline
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West Palm Beach, Florida
Originally Posted by TJP
The last two responses from Cab and 4 gear are spot on twocents
Your surging is likely the motor telling you it has too much advance whistling

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 wink


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. driveIf you can hear it, it has gone from a small hammer tapping on your valvetrain to a sledge hammer. hammer Just sayin'
Copper


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For fear of ridicule, society stifles creativity.
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Re: 440 ignition timing [Re: BSB67] #2970269
10/04/21 09:53 AM
10/04/21 09:53 AM
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Posts: 3,646
Wichita
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GY3 Offline
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Wichita
Originally Posted by BSB67
Use a timing light.


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.

Re: 440 ignition timing [Re: GY3] #2970315
10/04/21 11:12 AM
10/04/21 11:12 AM
Joined: Sep 2003
Posts: 15,113
north of coder
moparx Offline
"Butt Crack Bob"
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north of coder
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 ! up
beer

Re: 440 ignition timing [Re: moparx] #2970538
10/04/21 06:48 PM
10/04/21 06:48 PM
Joined: Dec 2004
Posts: 726
Northern Virginia
Moparmaniacc Offline OP
super stock
Moparmaniacc  Offline OP
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Posts: 726
Northern Virginia
Yes, I do recall that article and will check it out again. And I will cure my timing light aversion for everyone, thanks !

Re: 440 ignition timing [Re: Moparmaniacc] #2970576
10/04/21 08:28 PM
10/04/21 08:28 PM
Joined: Aug 2005
Posts: 289
Hinckley, Ohio
KWF340 Offline
enthusiast
KWF340  Offline
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Hinckley, Ohio
Here's the link to the article.

Link


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.
Re: 440 ignition timing [Re: Moparmaniacc] #2970780
10/05/21 08:52 AM
10/05/21 08:52 AM
Joined: Jan 2003
Posts: 24,555
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
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Posts: 24,555
Brookeville, Md
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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Re: 440 ignition timing [Re: Mr.Yuck] #2970925
10/05/21 12:19 PM
10/05/21 12:19 PM
Joined: Aug 2003
Posts: 38,131
Bend,OR USA
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Cab_Burge Offline
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Bend,OR USA
I have seen stock distributors have the big spring let the advance work up to over 5000 RPM shock scope
If the advance is all in by 3000 RPM make sure you rev the motor high enough to not have any more advance after that twocents scope wrench
To much advance can and will kill parts down


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)






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