Having a Distributor curve set at a speed shop
#3193943
11/28/23 04:10 PM
11/28/23 04:10 PM
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Joined: Apr 2006
Posts: 1,012 Central US
grancuda
OP
super stock
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OP
super stock
Joined: Apr 2006
Posts: 1,012
Central US
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Going to have a prestolite dual point tach drive set-up at the local speed shop but unsure what exactly I need. Normally I run aftermarket distributors that I can play around with springs & such so not sure what to tell them I am looking to get it set at. I am not sure how much advance that distributor has but probably just want it all in at 2800 or so.
I’m open to any advice & here’s the set-up: 3090lb ‘67 Barracuda 3600 stall w/3.55 gears & 26” tire 440 Edelbrock performer heads 850 DP Holley Weiand Single Plane Cam Grind Number: XS282S Advertised Duration: 282 int./290 exh. Duration at 050 inch Lift: 244 int./252 exh Lobe Separation (degrees): 110
Last edited by grancuda; 11/28/23 04:11 PM.
1967 Barracuda Formula S 383 1967 Chevy C10 Short Stepper 1980 Macho Power Wagon LWB 318 2021 Toyota Supra
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Re: Having a Distributor curve set at a speed shop
[Re: grancuda]
#3193955
11/28/23 04:42 PM
11/28/23 04:42 PM
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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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You really need to get the engine on a crank dyno where you can load the engine at a given RPM and hold it there. Then you move the timing up and down until it makes max power. Then you do it again. I usually start at 2500 and go up in 500 rpm increments until I get to 5000 then I go up in 1,000’s.
You can do it on a wheel dyno IF it’s not an inertia dyno. You need to be able to load the engine, steady state at WOT to develop your timing curve.
Otherwise you are just guessing. And my best guess is your engine will NOT want the full curve in by 2800. Plus you need to run vacuum advance if you can.
Last edited by madscientist; 11/29/23 05:15 PM.
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: Having a Distributor curve set at a speed shop
[Re: grancuda]
#3193957
11/28/23 04:43 PM
11/28/23 04:43 PM
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Joined: Dec 2013
Posts: 4,715 Wichita
GY3
master
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master
Joined: Dec 2013
Posts: 4,715
Wichita
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Going to have a prestolite dual point tach drive set-up at the local speed shop but unsure what exactly I need. Normally I run aftermarket distributors that I can play around with springs & such so not sure what to tell them I am looking to get it set at. I am not sure how much advance that distributor has but probably just want it all in at 2800 or so.
I’m open to any advice & here’s the set-up: 3090lb ‘67 Barracuda 3600 stall w/3.55 gears & 26” tire 440 Edelbrock performer heads 850 DP Holley Weiand Single Plane Cam Grind Number: XS282S Advertised Duration: 282 int./290 exh. Duration at 050 inch Lift: 244 int./252 exh Lobe Separation (degrees): 110
Getting it all in as quickly as possible has always worked for me. The lightest springs usually on function as a retard to make starting easier. Once the car is started all timing is in at idle.
'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: Having a Distributor curve set at a speed shop
[Re: madscientist]
#3193988
11/28/23 06:44 PM
11/28/23 06:44 PM
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Joined: May 2019
Posts: 714 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
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Lake Villa Il
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You can do it on a wheel dyno IF it’s not an inertia dyno. You need to be able to load the engine, steady state at WOT to develop your timing curve.
Disagree on that, can still get it close if not perfect on an inertia dyno as that's closer to it going down a track than zero rpm/sec acceleration. Even if it was eddy current, no way it can hold it steady state at WOT with an automatic and looser converter. (without lockup)
Last edited by INTMD8; 11/28/23 06:44 PM.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Having a Distributor curve set at a speed shop
[Re: GY3]
#3194005
11/28/23 08:24 PM
11/28/23 08:24 PM
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Joined: Dec 2005
Posts: 11,769 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,769
Fulton County, PA
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Getting it all in as quickly as possible has always worked for me. The lightest springs usually on function as a retard to make starting easier. Once the car is started all timing is in at idle.
iagree 25* initial and all in by 1,800 at the very least. So why not lock it out and be done with it?
If the results don't match the theory, change the theory.
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Re: Having a Distributor curve set at a speed shop
[Re: CMcAllister]
#3194019
11/28/23 09:05 PM
11/28/23 09:05 PM
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Joined: Jan 2003
Posts: 12,327 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,327
Benton, IL.
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Getting it all in as quickly as possible has always worked for me. The lightest springs usually on function as a retard to make starting easier. Once the car is started all timing is in at idle.
iagree 25* initial and all in by 1,800 at the very least. So why not lock it out and be done with it? Mine won't start with 34* initial. 25* is the max. It will hit the starter when hot but will go ahead and tick over. 20* to 26* is typically the most initial that will allow a combo like the OP has to start on a hot day on pump gas. If his will start at full advance; COOL! Go for it. But most won't.
Master, again and still
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Re: Having a Distributor curve set at a speed shop
[Re: AndyF]
#3194067
11/29/23 12:38 AM
11/29/23 12:38 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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master
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Washington
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Good luck. It will cost a bunch of money to have a shop build you a custom curve. You'll actually have a hard time even finding a shop with a distributor machine much less someone who knows how to run it. We refuse to custom curve distributors anymore since it can take several hours to do it correctly. If you charge the customer $100 per hour for 4 hours of work they freak out, especially if they bought an old distributor for $50 at a swap meet. It is a lot less expensive to buy a digital distributor and program it with your laptop or cell phone. Fact. It takes a long time to sort out a timing curve. Then getting the distributor to do what the engine wants is another story. Most engines I see want a bunch of initial, almost no advance through peak torque and then a curve to peak hp. Quick curves and locking them out generally kills power at and around peak torque.
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: Having a Distributor curve set at a speed shop
[Re: madscientist]
#3194072
11/29/23 02:42 AM
11/29/23 02:42 AM
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Joined: May 2019
Posts: 714 Lake Villa Il
INTMD8
super stock
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super stock
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Lake Villa Il
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Fact. It takes a long time to sort out a timing curve. Then getting the distributor to do what the engine wants is another story.
Most engines I see want a bunch of initial, almost no advance through peak torque and then a curve to peak hp. Quick curves and locking them out generally kills power at and around peak torque.
Agreed. Once you find timing that makes max hp, you can pull several degrees at max torque without reducing output and then ramp low rpm up to max torque timing. Not happening with just centrifugal advance.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Having a Distributor curve set at a speed shop
[Re: grancuda]
#3194079
11/29/23 05:08 AM
11/29/23 05:08 AM
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Joined: Aug 2003
Posts: 43,352 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,352
Bend,OR USA
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I like to have between 14 up to 18 degrees advance before top dead center at idle below 1200 RPM and 34 to 36 degrees BTDC max at or above 2000 RPM If you take the advance plate out of that distributor and flip it over it may have the among of built in mechanical advance stamp on the plate, if it says 14 that means it has 28 crankshaft degrees due to the distributor spinning at half the speed the crankshaft does, if it is stamp 12 then it has 24 degrees. I measure the diameter of the advance studs on the advance weights and then measure the length of the slots on the advance plates and subtract the diameter of the studs and then due the math for how many thousands of an inch it takes for each degree of mechanical advance and then weld the slots up and then make them the length I want for the total amount of mechanical advance I want. Its been a long time since I did the last one I did so I can't remember now the exact amount of length and how much it takes for each degree of mechanical advance, SORRY
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Having a Distributor curve set at a speed shop
[Re: INTMD8]
#3194104
11/29/23 09:53 AM
11/29/23 09:53 AM
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Joined: Jan 2003
Posts: 12,327 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,327
Benton, IL.
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Fact. It takes a long time to sort out a timing curve. Then getting the distributor to do what the engine wants is another story.
Most engines I see want a bunch of initial, almost no advance through peak torque and then a curve to peak hp. Quick curves and locking them out generally kills power at and around peak torque.
Agreed. Once you find timing that makes max hp, you can pull several degrees at max torque without reducing output and then ramp low rpm up to max torque timing. Not happening with just centrifugal advance. While all that may be true, here's the reality: a warmed up (hot) 440 in a 3100lb car with a looser converter than stock and 3.55 gears will get along just fine without the timing curve set perfectly. The idle and off idle timing will be the most important areas to the driver. After that, the engine will pull basically the same where ever the curve is set. A dyno may show some slightly different numbers, but the OP's butt dyno will never tell the difference in curves. And if the driver is pushing the throttle hard, the converter will flash to 3,500RPM anyway. Unless the OP is running drag radials, the traction will already be compromised, so a little more torque from a perfect curve won't help anything. The cost to dial the curve in perfectly will not be worth the money in this combo. That money would be better spent somewhere else. If the OP starts with 25* +/-, we are talking about 8* or so through the curve. Not enough to kill power. It may loose some torque, but with an abundance at hand given this combo, it won't be noticed.
Master, again and still
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Re: Having a Distributor curve set at a speed shop
[Re: DaveRS23]
#3194133
11/29/23 11:31 AM
11/29/23 11:31 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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Fact. It takes a long time to sort out a timing curve. Then getting the distributor to do what the engine wants is another story.
Most engines I see want a bunch of initial, almost no advance through peak torque and then a curve to peak hp. Quick curves and locking them out generally kills power at and around peak torque.
Agreed. Once you find timing that makes max hp, you can pull several degrees at max torque without reducing output and then ramp low rpm up to max torque timing. Not happening with just centrifugal advance. While all that may be true, here's the reality: a warmed up (hot) 440 in a 3100lb car with a looser converter than stock and 3.55 gears will get along just fine without the timing curve set perfectly. The idle and off idle timing will be the most important areas to the driver. After that, the engine will pull basically the same where ever the curve is set. A dyno may show some slightly different numbers, but the OP's butt dyno will never tell the difference in curves. And if the driver is pushing the throttle hard, the converter will flash to 3,500RPM anyway. Unless the OP is running drag radials, the traction will already be compromised, so a little more torque from a perfect curve won't help anything. The cost to dial the curve in perfectly will not be worth the money in this combo. That money would be better spent somewhere else. If the OP starts with 25* +/-, we are talking about 8* or so through the curve. Not enough to kill power. It may loose some torque, but with an abundance at hand given this combo, it won't be noticed. I regularly find 30-40 for pounds at peak torque and 20-30 at peak hp. Giving that up isn’t “getting along fine” even with a loose converter. I don’t understand how guys can’t figure out the engine is pissed off without the correct timing curve. It makes zero sense to not sort it out.
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: Having a Distributor curve set at a speed shop
[Re: Cab_Burge]
#3194223
11/29/23 06:21 PM
11/29/23 06:21 PM
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Joined: Feb 2008
Posts: 717 Central TEXAS!!!!
sr4440
super stock
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Central TEXAS!!!!
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Thats a lot of money for it Not when you don't have to buy, mount and wire an MSD box and distributor. Just one distributor and 2 wires to a coil and a hot. I have set up 5 or 6 of them on the dyno, and they are impressive. Joe
Without Data, you’re just another guy with an opinion.
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Re: Having a Distributor curve set at a speed shop
[Re: sr4440]
#3194233
11/29/23 06:55 PM
11/29/23 06:55 PM
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Joined: Apr 2006
Posts: 1,012 Central US
grancuda
OP
super stock
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OP
super stock
Joined: Apr 2006
Posts: 1,012
Central US
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Lots of good info & stuff I hadn’t considered. I was kicking around locking this distributor out & getting the newest MSD offering that has timing control, it’s now only around $400, The MSD 6AL Ultra Plus, I can load maps to it set the curve based off RPM & vacuum. By using my dual point distributor, I can still run a tach drive tachometer & leave the factory wiring intact, just disconnect it & if the MSD unit goes out I can hook it back stock & get it back home on the points & not be stranded. https://www.holley.com/products/ignition/ignition_boxes/street/parts/6523
1967 Barracuda Formula S 383 1967 Chevy C10 Short Stepper 1980 Macho Power Wagon LWB 318 2021 Toyota Supra
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Re: Having a Distributor curve set at a speed shop
[Re: sr4440]
#3194236
11/29/23 07:12 PM
11/29/23 07:12 PM
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Joined: Dec 2005
Posts: 11,769 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,769
Fulton County, PA
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Thats a lot of money for it Not when you don't have to buy, mount and wire an MSD box and distributor. Just one distributor and 2 wires to a coil and a hot. I have set up 5 or 6 of them on the dyno, and they are impressive. Joe First I've seen them. Pretty cool if it works and lives. Poor man's Grid. Wonder where it's made, ETA I see designed and assembled in the USA.
Last edited by CMcAllister; 11/29/23 07:14 PM.
If the results don't match the theory, change the theory.
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