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Re: Full advance [Re: B1MAXX] #2934594
06/18/21 02:42 PM
06/18/21 02:42 PM
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fredericksburg,va
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cudaman1969 Offline
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Originally Posted by B1MAXX
Originally Posted by cudaman1969
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.

Are you idling below 400 rpm? Just guessing on that rpm because when I check at 600 rpm it’s at 37 degrees and steady. Maybe we talking different springs?

Re: Full advance [Re: cudaman1969] #2934615
06/18/21 04:12 PM
06/18/21 04:12 PM
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Apollo, PA.
B1MAXX Offline
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Must be talking different springs. Most of the light springs I've messed with are full in around 1200rpm. So when you set the timing at say 23* at 900 idling in neutral then drop it in gear it takes timing away making it want to stall, at the timing is all over the place.I guess if your idling at or near 1200 in this case it would be a wash. So you are saying with light springs installed you have no curve? From 600 all the way up?

Last edited by B1MAXX; 06/18/21 04:12 PM.
Re: Full advance [Re: oldtimer5151] #2934628
06/18/21 05:07 PM
06/18/21 05:07 PM
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Aubrey, Texas
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My curve starts at 1700 @ 30*, and 3500 @ 40*total. I have a 400 with stock stroke. I’m afraid too much too fast @idle puts things in a bind . The idle and first gear idle seems better!

Re: Full advance [Re: B1MAXX] #2934635
06/18/21 05:32 PM
06/18/21 05:32 PM
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Originally Posted by B1MAXX
Must be talking different springs. Most of the light springs I've messed with are full in around 1200rpm. So when you set the timing at say 23* at 900 idling in neutral then drop it in gear it takes timing away making it want to stall, at the timing is all over the place.I guess if your idling at or near 1200 in this case it would be a wash. So you are saying with light springs installed you have no curve? From 600 all the way up?
all the light race springs i've ever used will bring the full centrifugal in at 1100-1200rpm using a 9 degree plate. so if you set the total centrifugal at 36 degrees there will be 36 degrees at 1100-1200rpm. naturally below that rpm advance will reduce. there is a point were the springs can be too light and not let the weights fully retard when the engine is shut off but that would only happen if someone tries to use only one of the race springs. i've found erratic timing to be other issues than springs.

Last edited by lewtot184; 06/18/21 05:33 PM.
Re: Full advance [Re: lewtot184] #2934657
06/18/21 06:56 PM
06/18/21 06:56 PM
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fredericksburg,va
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Spring was made for the Chevy dist, looked like the size of hair, almost to light to rotate it back to zero. Also no grease on those pivots or slots (center shaft too) dry lube only. We used one of those Sun machines to set it up but lost track of the dude, don’t know where him or machine moved to.

Last edited by cudaman1969; 06/18/21 07:05 PM.
Re: Full advance [Re: DaveRS23] #2934666
06/18/21 07:24 PM
06/18/21 07:24 PM
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Mt Morris Michigan
mopar dave Offline
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I do the same with my 511. Initial at 29* and all in 36*@2500rpm. I launch the car at 2500rpm foot brake. Runs very clean and reliable like this. I can let the car sit for hours and just hit the start button and it will fire and idle by itself. This is with a Indy T ram with 2 of Dom's 650's and did the same with a single 1100 Dominator. No hiccups bogs or stumbles. Works very nice like this.

Re: Full advance [Re: mopar dave] #2934668
06/18/21 07:45 PM
06/18/21 07:45 PM
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West Plains, MO
DrCharles Offline
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After sitting for hours, I can see it being able to start at 29 degrees. But will it start hot?
My 451 starts to buck at 26 hot.

The current setup I'm running to avoid the hot start problem is one light spring, one heavy spring with loop, and a 22/11 degree plate. This allows me to crank at 16 degrees, the light spring is all in at 27 degrees (the loop on the heavy spring holds it from going higher) as soon as it starts and idles at 1100-1200. The advance starts coming in around 1500 or so. I've measured 35 degrees at 4000 but I won't stand next to it and rev it any higher! whistling The plate will limit the advance at any speed to 38, less the inevitable retard in the ignition box, so that should be about 35-36 at high rpm.

Plus vacuum advance that does nothing at idle (8" Hg.) but is fully engaged at cruise (15" Hg.) Don't remember how many degrees. Haven't heard it ping yet on pump premium, 10.3:1, iron heads for now. 272@.050, .652 gross lift, .018 lash.

After reading this thread, I'm tempted to just put two light springs in so it's all-in at idle, and try it out... work

Re: Full advance [Re: DrCharles] #2934680
06/18/21 08:24 PM
06/18/21 08:24 PM
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Aubrey, Texas
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I think that the engine has a hard time with 38* anytime, except wide open. It just makes sense to take away timing when it isn’t wide open.

Re: Full advance [Re: oldtimer5151] #2934684
06/18/21 08:44 PM
06/18/21 08:44 PM
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West Plains, MO
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But - at partial throttle and low load, the lean, less-dense mixture requires MORE time to burn and reach maximum pressure at 15(?) ATDC. Sometimes much more time. That's why vacuum advance is so useful on an engine that doesn't run only at wide-open... light throttle cruise well into the 50's advance is not unusual.

The reason for having variable centrifugal advance is that at low rpm there is already more time for the mixture to burn so less total advance is needed. As the rpm climbs, so does the need for advance - up to a point... that point is usually 34-36 degrees for most big-blocks, maybe a few degrees more for small-blocks. Depends on the combustion chamber design, of course. You're right that 38 may be too much at low rpm and wide-open throttle. Except that my cam has a lot of overlap so it needs more low-speed advance...

My engine won't see 38 degrees. Every ignition box has some retard, because a finite amount of time is required to read the trigger signal and fire the coil. At higher RPM the crank turns more degrees in that same time interval. Somewhere I saw (maybe on FABO) a test of several boxes and many were retarding 1 degree per 1000 rpm, or even more shock

Re: Full advance [Re: oldtimer5151] #2934692
06/18/21 09:09 PM
06/18/21 09:09 PM
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Aubrey, Texas
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Thanks for the reply’s! I might try some your timing curves.

Re: Full advance [Re: DrCharles] #2934693
06/18/21 09:13 PM
06/18/21 09:13 PM
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Apollo, PA.
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What ever works is best, we all have preferences. All my race stuff is locked out up Even my 14 to 1 good engine, a little tough on the start. but it works.

Re: Full advance [Re: DrCharles] #2934716
06/18/21 10:32 PM
06/18/21 10:32 PM
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Mt Morris Michigan
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Yes, will start and idle hot or warm. cold, 1 pump of the throttle and fires up and idles without being too rich once warmed up. Idles at 13.5-14:1 AFR once up to temp. I think alot has to do with the Dragon fuel i use. Good stuff. I think i used 1 blue and 1 silver spring and a large bushing from Don at FBO.

Re: Full advance [Re: mopar dave] #2934749
06/19/21 01:32 AM
06/19/21 01:32 AM
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Washington
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All ignition boxes retard with RPM. If you lock out a distributor you haven’t a clue where the timing is once the box starts retarding. And it WILL retard.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Full advance [Re: madscientist] #2934771
06/19/21 08:41 AM
06/19/21 08:41 AM
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i think the only way to properly set up a locked ignition is with a start retard box. at least with a start retard box there's less of a chance of breaking the snout off a starter.

Re: Full advance [Re: madscientist] #2934778
06/19/21 09:30 AM
06/19/21 09:30 AM
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Mt Morris Michigan
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Yes, they will and i am using the Ice Ignition box which has 10* start retard.

Re: Full advance [Re: mopar dave] #2934799
06/19/21 10:47 AM
06/19/21 10:47 AM
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Apollo, PA.
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I know and work on engines that acquaintances race and all are locked ( usually crank trigger). Some are mid 600 cube at close to 16-1 and no-one uses start retards. I have never heard one of these engines kick back. Heck they wing around with ease, but they have good well planned starting circuits/parts (even 16v on some). Go to a racetrack and ask. I think the most common answer is no on retards. I personally have never seen a broken starter nose from a hard to turn over engine. If your car is kicking back turn off your start retard has always been the consensus around here. Again I am not saying, one that works for someone else is no good. I'm just giving what my experience has been. The only reason I responded to this is because , I got the impression some are saying locked out timing, is a intolerable condition (broken parts/ won't work). up

Re: Full advance [Re: B1MAXX] #2934807
06/19/21 11:24 AM
06/19/21 11:24 AM
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Mt Morris Michigan
mopar dave Offline
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Crank trigger is the way to go. I ran one on my 408 Indy headed small block and never had a kick back and no loss of timing. Rock steady timing. I do not have a crank trigger on the 511 BB, just didn't want the expense, but i will say again i think it is the way to go. What i noticed with my current set up, Ice Ignition box and billet MSD dist. is when i try to run it locked out, the timing will retard as i increase the rpm of the engine. I was losing 3 or 4* by 3-4000rpm and had problems with kick back hot locked at 35*. The retard may have had something to do with that as there was a post i read about that awhile back. When i run a curve as i do now 29*/36* it's almost like having it locked out as far as performance that i have seen. No timing loss with rpm and no kick back at all. Thats why i use a curve for now.

Re: Full advance [Re: B1MAXX] #2935204
06/21/21 08:23 AM
06/21/21 08:23 AM
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Marion, South Carolina [><]
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Big cams always idle better w/ full timing in my experience. The only thing I wouldn't lock out is a near stock build. twocents

Like some others have said, we don't use a start retard on anything.


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Re: Full advance [Re: an8sec70cuda] #2936336
06/24/21 09:37 AM
06/24/21 09:37 AM
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Plymouth, MI
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Based on this thread I bought the Mr. Gasket 925B spring kit and put it in my .590 cammed 440. The distributor had one heavier spring in it already but changing it out was a noticeable improvement in idle quality and off idle response, definitely snappier/crisper now and the idle speed picked up by a couple hundred rpm with no other changes. My drive idle is just below full advance so it still might lead to some hunting but I'll live with it.


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