Having a Distributor curve set at a speed shop

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

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.

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.

25* initial and all in by 1,800 at the very least.

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)

So why not lock it out and be done with it?

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.

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.

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.

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

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.

First, what is the distributor number you're using. That will tell what mechanical advance max is. Normally they have pretty light springs unless your using an older 300 type. If it is one of the race types your probably getting 16 or so mechanical at the crank. 8 deg distributor.

Programmable box with locked distributor. What happens to your curve the next big change?

Progressive ignition for the win:

https://progressionignition.com/products/ols/products/chrysler-413440-v8-small-cap-distributor

Their stuff solves your problem with some added features. I don't have personal experience with their stuff yet but have seen some good input on a number of forums and on Facebook groups as well. There is one in my future once I get mine back together this summer.

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

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

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.

What I heard from my customers is the feature they really like is being able to disable it when they walk away from their car. No way in h&ll to "hot wire" it.

A distributor that has 2 wires to make it run & you can’t hot wire it?

LOL, it's disabled/re-enable via your smartphone (Bluetooth), same way you tune it. Once you disable it, you need to log back in and re-enable it before it will ever fire.

Joe

Either way, it’s still much more difficult to set up a curve without being on the dyno. The programmable stuff is great. But you still need to know what key strokes to make.

I recently worked with Joe White at Joe's Distributor Restoration and was very happy with his service and pricing.

You can check out his work on Facebook; or call him at 330-843-0335.

He restores distributors primarily but, has a distributor machine and does custom curving.

I've personally experienced big gains more than once when messing with custom timing curves.

The first time, I picked up 1.5 tenths going from a distributor that I knew was not curved correctly, to one that FBO spec'd for me.

This last time, I switched from the FBO distributor to a NOS Mopar Performance Distributor from the 80's that Joe curved for me and picked up 3 tenths and 2.5 MPH. Disclaimer, I made other changes at the same time but, none I really felt on the butt dyno; I really feel that most came from the distributor. Did a bunch of street testing with all changes 1 by 1 and most were "meh, maybe that did something". Did testing with the distributor and was blown away with the difference I felt. So, did the distributor account for all the found time, MPH? Probably not but, I bet that it was most of it.

Went ahead & picked up a MSD 6AL Ultra Plus so I can just do the timing curve, have full control & adjustability of it. Going to lock out the Prestolite & see how this thing works out.

Yep, digital work around for analog problem!

All you need is a Progression Ignition distributor and a Carb Cheater with a couple smartphones to help tune your car.

Gus

No need for the carb cheater, I’ve had an O2 in the car for years, they work great for dialing in the carb.

Performance Trends engine program will calculate a timing curve for whatever fuel and engine combo you have. I have used it a bunch and it is always close.

If you have a timing light just get a buddy to help you, get a piece of paper have your buddy rev the engine at 250 rpm increments record the timing on the paper plot your advance curve. Distributor machine is faster but few of them are left around.

Have you had a chance to install the MSD and play with it yet? I am considering getting one and was wondering if you can update the timing curve on the fly while driving or dyno tuning without having to shut it down and restarting? I called and talked to a tech at Holley. It didn’t seem like they had a complete grasp on everything it did yet. I saw in the features that it said up to 35 degrees max retard and in the installation manual it said 30 degrees. They seemed to think you could get the 5 extra degrees only by doing the nitrous retard. I’m not sure which to believe.

I have not yet, I got a new, to me, winter 4x4 & I have been going thru doing maintenance to that before I get that MSD unit hooked up. Hopefully the week of Christmas I can get it in & see how it works. My understanding is the nitrous retard is not going to be adding to the 30 total because the point when you would hit the nitrous switch, you wouldn’t be near the max retard, you would be somewhere in the middle of the timing.

Is that a "race only" system? By that, I mean, it doesn't appear to have an engine load setting I.E. a vacuum advance. I never had one in my hands and there is no mention of any kind of light load (cursing) setting
.


Joe

It does have a vacuum/boost port to connect to for advancing/retarding timing, see below pic.

I don't know how I missed that. thanks, looks like a good system.