Re: Full advance
[Re: oldtimer5151]
#2934314
06/17/21 05:32 PM
06/17/21 05:32 PM
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Joined: Jan 2003
Posts: 2,915 A shed in England
Tig
master
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master
Joined: Jan 2003
Posts: 2,915
A shed in England
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For us it's idle quality and off idle response (footbraking). Just under .750" Roller T/R with2 1150 Dominators. Flash stall is around 5500. We also run a grid and crank trigger, so we can put any curve in we want. At the moment we are trying hi speed timing retards but we haven't had any really useful data yet.
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials. 9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge. RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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Re: Full advance
[Re: oldtimer5151]
#2934344
06/17/21 07:20 PM
06/17/21 07:20 PM
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Joined: Oct 2007
Posts: 4,206 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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Most common reasons mentioned: 1. one less thing to go wrong 2. eliminate a variable 3. useful RPM is above the end of the advance curve 4. don't understand what it does
Boffin Emeritus
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Re: Full advance
[Re: polyspheric]
#2934345
06/17/21 07:24 PM
06/17/21 07:24 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
master
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master
Joined: Jun 2008
Posts: 3,916
usa
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Most common reasons mentioned: 1. one less thing to go wrong 2. eliminate a variable 3. useful RPM is above the end of the advance curve 4. don't understand what it does 5. don't know how to set up a centrifugal curve,....lol!
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Re: Full advance
[Re: oldtimer5151]
#2934387
06/17/21 09:54 PM
06/17/21 09:54 PM
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Joined: Jun 2012
Posts: 1,899 MYRTLE BEACH SOUTH CAROLINA
ek3
top fuel
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top fuel
Joined: Jun 2012
Posts: 1,899
MYRTLE BEACH SOUTH CAROLINA
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What would be a good advance curve? Most common reasons mentioned: 1. one less thing to go wrong 2. eliminate a variable 3. useful RPM is above the end of the advance curve 4. don't understand what it does 16-18 initial. 35-6 all in by 2400 each engine will have its limits and needs with timing . if its racing, it never sees the low rpm's so no curve is needed. when locked out, it is one less issue to have to deal with and, it helps keep timing rock steady....
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Re: Full advance
[Re: oldtimer5151]
#2934388
06/17/21 10:18 PM
06/17/21 10:18 PM
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Joined: Jan 2003
Posts: 30,998 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 30,998
Oregon
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What is the purpose of locking out the distributor and advancing the distributor to full advance at idle? It is cheap and easy and it kinda works okay. It takes a bunch more money to build a sophisticated timing curve and the car probably won't go any faster. It will start easier and the plugs will stay cleaner with a fully developed timing curve but going down the track performance won't change much.
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Re: Full advance
[Re: Tig]
#2934393
06/17/21 10:37 PM
06/17/21 10:37 PM
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Joined: Jan 2003
Posts: 16,923 NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,923
NC
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For us it's idle quality and off idle response (footbraking). Just under .750" Roller T/R with2 1150 Dominators. Flash stall is around 5500. We also run a grid and crank trigger, so we can put any curve in we want. At the moment we are trying hi speed timing retards but we haven't had any really useful data yet. Lots of cam overlap (duration) can idle cleaner with more timing. From experience with footbraking, it helps to get full advance several hundred RPM below the staging (footbrake) RPM. If it is too close, it can be inconsistent off the line. I have seen a big difference in the response and sixty foot if the curve isn't all in. Say footbraking at 2000 rpm and the curve is all in at 2500.
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Re: Full advance
[Re: oldtimer5151]
#2934412
06/18/21 12:09 AM
06/18/21 12:09 AM
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Joined: Aug 2003
Posts: 43,127 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,127
Bend,OR USA
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Last edited by Cab_Burge; 06/18/21 11:23 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Full advance
[Re: Cab_Burge]
#2934417
06/18/21 12:35 AM
06/18/21 12:35 AM
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Joined: Dec 2005
Posts: 11,531 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,531
Fulton County, PA
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Usually with a big cam you have to make the thing idle so fast so it will run, that you are well up into the curve anyway. All in at 1500? When nothing happens below 3500? Or a curve that's 12 degrees from base to all in? Why bother?
Big roller, timing locked, idles in gear at 750. Nice and smooth. With the throttle plates set where they should be. Clean. Nice, sharp response.
Last edited by CMcAllister; 06/18/21 12:36 AM.
If the results don't match the theory, change the theory.
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Re: Full advance
[Re: 440Jim]
#2934433
06/18/21 05:47 AM
06/18/21 05:47 AM
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Joined: Jan 2003
Posts: 2,915 A shed in England
Tig
master
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master
Joined: Jan 2003
Posts: 2,915
A shed in England
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For us it's idle quality and off idle response (footbraking). Just under .750" Roller T/R with2 1150 Dominators. Flash stall is around 5500. We also run a grid and crank trigger, so we can put any curve in we want. At the moment we are trying hi speed timing retards but we haven't had any really useful data yet. Lots of cam overlap (duration) can idle cleaner with more timing. From experience with footbraking, it helps to get full advance several hundred RPM below the staging (footbrake) RPM. If it is too close, it can be inconsistent off the line. I have seen a big difference in the response and sixty foot if the curve isn't all in. Say footbraking at 2000 rpm and the curve is all in at 2500. Yep, way back when I was even less experienced, I can remember chasing an off the line hesitation with squirters and cams at a test and tune day. An old timer came over and after a short discussion told me to put some lighter springs in the distributer. That cured it.
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials. 9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge. RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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Re: Full advance
[Re: oldtimer5151]
#2934472
06/18/21 10:10 AM
06/18/21 10:10 AM
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Joined: Jan 2003
Posts: 12,036 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,036
Benton, IL.
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Track only experiences may be different, but on the street, our big blocks respond dramatically to rapid early timing advance. In my experience, as soon as a cam has enough overlap to be heard at idle, the engine will want more initial. And total as quick as it will take it. I always put as much initial as the engine will take without hitting the starter at hot start. Or maybe even hitting the starter some. It really improves the idle quality. Off idle response, too. I've had good results with 20* to 28*initial with pump gas.
Then, shorten the slots and install springs to get the advance in as soon as the engine will take it. On mine, it's usually all in by 2,000. Sometimes, 1,500. Although it would be much easier, I have not had an engine that would start with the distributor locked. Starting a street engine hot with 32* +/- initial timing is not going to happen. Well, not for my combos. Again, track experiences may be different.
Master, again and still
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Re: Full advance
[Re: cudaman1969]
#2934556
06/18/21 01:04 PM
06/18/21 01:04 PM
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Joined: May 2005
Posts: 1,966 Apollo, PA.
B1MAXX
top fuel
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top fuel
Joined: May 2005
Posts: 1,966
Apollo, PA.
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I used one light spring to make it close on start up, then bang it’s wide open. Didn’t need a spring with points because friction on the rubbing block would pull it back, electronic needs the spring. Never bothered with the slots, just the stock dist in every race car. Trying to set idle with light spring is tough. In my experience they will move your idle timing around, causing erratic idle rpm.
Last edited by B1MAXX; 06/18/21 01:04 PM.
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Re: Full advance
[Re: DaveRS23]
#2934571
06/18/21 01:31 PM
06/18/21 01:31 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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Track only experiences may be different, but on the street, our big blocks respond dramatically to rapid early timing advance. In my experience, as soon as a cam has enough overlap to be heard at idle, the engine will want more initial. And total as quick as it will take it. I always put as much initial as the engine will take without hitting the starter at hot start. Or maybe even hitting the starter some. It really improves the idle quality. Off idle response, too. I've had good results with 20* to 28*initial with pump gas.
Then, shorten the slots and install springs to get the advance in as soon as the engine will take it. On mine, it's usually all in by 2,000. Sometimes, 1,500. Although it would be much easier, I have not had an engine that would start with the distributor locked. Starting a street engine hot with 32* +/- initial timing is not going to happen. Well, not for my combos. Again, track experiences may be different.
Would your(street) recommendations change when running vacuum advance? and a four-speed? My cam likes to idle around 1100-1200. thanks.
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Re: Full advance
[Re: DrCharles]
#2934583
06/18/21 02:19 PM
06/18/21 02:19 PM
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Joined: Jan 2003
Posts: 12,036 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,036
Benton, IL.
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Haven't had the opportunity to mess with as many 4 speed cars as automatic cars. The reasons behind the recommendations on the initial timing would be the same but then obviously bringing the timing in that soon could reap less benefits with the stick.
As for chasing the timing at idle, with the initial as high as the engine likes, the additional advance that comes in and out with RPM changes has less impact. The farther the initial is from what the engine wants, then the more the engine responds when it changes. The closer the initial timing is, the less impact timing changes have.
As an example, I have about 28* initial and all in to 34* around 1,600 on my current combo. In and out of gear means a change of a couple of degrees in advance. Since the engine is already pretty happy with the timing, that additional timing doesn't have a big impact. Some of course, but not enough to hardly notice. It does hit the starter when hot. But not too bad.
Master, again and still
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Re: Full advance
[Re: DrCharles]
#2934587
06/18/21 02:27 PM
06/18/21 02:27 PM
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Joined: Jan 2003
Posts: 12,036 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,036
Benton, IL.
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Vacuum advance is a different thing in and of itself. So, in my humble opinion, it has no impact on any of this. Set each of these timing events to the way that the engine likes it. On my cars, the timing is all in before 2,000 and I usually cruise above 2,000, so each system can be set to it's own preference. Tall rear gears would be the only curve ball here and that would be on how early the total could be in when in the higher gears.
Master, again and still
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