Re: Race timing
[Re: RustyM]
#2742148
02/12/20 12:44 AM
02/12/20 12:44 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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So, Cm and all: If im reading correctly: Can lock it out, we do have ignition on its own switch, so thats not a problem and, locked out we will lose timing with rpm. Anyone know at what rpm the reduction starts taking place ? Is it actually pulling out the right amount etc? Does it not pull out rpm if your not locked out?
If its 1 degree every thousand rpm above say 2500, that would pull us back to 30 degrees from 34 by 6500 rpm. But if it starts pulling out at 1500, that would have us at 29 degrees at 6500.
Interesting to think on.
It depends on the box. I've got a Chrylser gold box form the early 1980's that doesn't back up until about 8000 and between 8000-12,000 it stays the same. It loses one degree at 8 k and nothing else to 12k.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Race timing
[Re: Thumperdart]
#2742353
02/12/20 04:30 PM
02/12/20 04:30 PM
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Joined: Jan 2003
Posts: 2,926 A shed in England
Tig
master
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master
Joined: Jan 2003
Posts: 2,926
A shed in England
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Yep called slew rate and mine looses about 1 degree every 1000 rpm's towards max........... Any one ever done back to back testing, slew v's a flat hi rpm curve? Interested to know if it works and dead easy to do with a grid.
'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: Race timing
[Re: dvw]
#2742356
02/12/20 04:45 PM
02/12/20 04:45 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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If you don't have a separate starter switch to spin the motor over before turning on the ignition or a ECIU that won't allow the coil to fire until the crankshaft has spun over several times before firing the plugs good luck on getting any motor started that has a lock out distributor with more than 24 degrees total timing Mine starts at 34 degrees no issue, 15-1, ignition on. Actually starts better with ignition on. 1 revolution and it's running. No crank, crank, crank. My 10.4:1 (iron head) 451 with 272@.050 begins to fight the starter at more than 24 degrees (when hot). Since it's mostly street driven I am not sure about using the super-light springs so it's at full advance as soon as it fires. Running vac advance can instead.
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Re: Race timing
[Re: Tig]
#2742403
02/12/20 07:45 PM
02/12/20 07:45 PM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Any one ever done back to back testing, slew v's a flat hi rpm curve? Interested to know if it works and dead easy to do with a grid. Coworker of mine tested it, although at the time he didn't know it. Replaced the heavy secondary spring with all sorts of quicker springs and they were losing time (E.T) which in stock class racing is a problem! I think Bill Baldwin who has tested it, and not accidently. https://board.moparts.org/ubbthread...ry-unilite-timing-issue.html#Post2488599https://www.facebook.com/baldwinperformancecarbs/videos/529140844222174/Bill Jones has tested the retard. https://www.speed-talk.com/forum/viewtopic.php?p=201470Apparently back when electronic ignitions were new to racing, some smart folks scratched their heads when the cars ran faster with dual points. Guys like Yunick and Jenkins. The mechanical advance compensates for the retard in the electronics to provide a flat static total or continue to advance all the way through the RPM range, however the engine likes it and you set it up.
This is a technique I have used for distributor curves since the 60's, though I didn't come to understand the reasoning behind it until the early 70's when I replaced a points ignition that did not retard as RPM climbed with an electronic ignition that, like all electronic ignitions, has slew-rate retard, and the car slowed down.
A-B-A-B it was faster with the GM dual-points distributor, even though the spark energy was higher with the electronic, a GM Magna-Pulse, and the electronic had the same “curve” except for the retard after the “total” was reached at 2500. Jenkins book “The Small Block Chevrolet Racing Engine” details the high-RPM curve and explains his reasoning.. Snipped from RFS Forum
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Re: Race timing
[Re: JACK1440]
#2742411
02/12/20 08:08 PM
02/12/20 08:08 PM
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Joined: Oct 2005
Posts: 1,646 Ringtown, Pa.
Dartsport540
top fuel
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top fuel
Joined: Oct 2005
Posts: 1,646
Ringtown, Pa.
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I'm having a lot of issue with kick back. Dyno'd it at 34deg but, in the car hot it wants to fight us starting. I actually knocked 3 teeth off a new convertor. Currently I have it at 30 and it starts great. Dist. is locked. I'm running an old msd7C box. I have a new msd 7al with a starter saver box ready to go in. I hope this fixes my problem. 572 in 15:1 Hello, my name is Paul, from Ringtown , Pa. I have a 540 cu.in. in my car. A little over 14.6 to 1 compression. MSD distributor, with MSD 7AL2 ignition, NO crank trigger. Last spring, I locked out my distributor. Then sometimes it would kick back . I broke 1 flex plate, and 3 starters. 2 starters had a billet front piece. I tried everything. MSD Starter Saver didn't help. Ended up being Rotor Phasing. MSD makes a phase able or adjustable rotor. Rotor tip was out 16*.. Spark would sometimes jump to next terminal on distributor cap, causing motor to kick back. I sent you a PM. It is easier to talk to you than typing it out.. Thanks, Paul
Last edited by Dartsport540; 02/13/20 05:12 PM.
548 cu. in., Bill Mitchell Aluminum Block, CRT 727 auto trans, Alston Chassis. 8.981et at 149.46 mph. 1.204et - 60 foot, So Far....
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Re: Race timing
[Re: Dartsport540]
#2742498
02/13/20 06:23 AM
02/13/20 06:23 AM
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Joined: Mar 2006
Posts: 9,852 MI, usa
dvw
master
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master
Joined: Mar 2006
Posts: 9,852
MI, usa
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If the rotor is correct they start fine. Mine is crank trigger. The rotor is phased. I never start it by cranking and then hitting the ignition. Same starter (stock) 7 years . Never hurt a converter tooth. 630 passes and counting. Doug
Last edited by dvw; 02/13/20 06:24 AM.
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Re: Race timing
[Re: Border-shadow]
#2744919
02/20/20 12:36 PM
02/20/20 12:36 PM
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Joined: Dec 2005
Posts: 1,495 Shelby mi.
JAKE68
pro stock
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pro stock
Joined: Dec 2005
Posts: 1,495
Shelby mi.
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I had a odd problem one time. I tried to lock dist on my hemi car and it was hard to start. kept kicking back. So I put the curve back in it. Latter I put a crank trigger in it and same total timing as before when locked out and no more kicking back. Since then all the motors I have done with crank trigger never kick back. Jake
JAKES AUTOMOTIVE
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Re: Race timing
[Re: JAKE68]
#2744934
02/20/20 01:55 PM
02/20/20 01:55 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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If you’re worried about the electronics retarding the timing at high rpm...... just check the timing at high rpm and see if it’s happening or not.
A lot of times it ends up being the cam walking, which changes the timing. That’s a good reason to run a crank trigger.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Race timing
[Re: fast68plymouth]
#2745468
02/22/20 12:51 PM
02/22/20 12:51 PM
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Joined: Dec 2007
Posts: 12,588 Great Neck,LI,new york
hemi-itis
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 12,588
Great Neck,LI,new york
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I have tried to discuss this in the past. I have the 6al programmable that allows me to put the timing anywhere I want like every 500 RPM.Starts at 24* and is up to 30* by 800 RPM for idle. Depending on the boost level I am running I start taking timing out at 2500 RPM. I could also use the boost retard to take timing out and leave the timing curve at 30* for street driving. So I ask the guys in the know,,,when should I start pulling timing,,,,and how much total.I can take it gradual as it is totally programmable with a laptop,
HEMI-ITIS has no cure. My condition is fully BLOWN!!
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Re: Race timing
[Re: Belvedere1]
#2745499
02/22/20 02:22 PM
02/22/20 02:22 PM
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Joined: Aug 2003
Posts: 43,228 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,228
Bend,OR USA
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It sounds like your going to have to find out on yours Please let us know what you find out I would put the thinnest one in first and see what you get I've never seen one of those distributors, can you limit the mechanical advance also? If so I would shoot for 15 to 18 crankshaft degrees max advance in the distributor and then set the initial timing around 14 to 18 BTDC and make sure to not exceed 34 to 36 degree max advance when revved up
Last edited by Cab_Burge; 02/22/20 02:26 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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