Recurve Duraspark

Hey fellas!

I'm taking a new Duraspark II that I just bought to Vintage Racing Motors in Redmond to get it recurved on their distributor tester. Here's the curve I'm going for and some specs for my `62. Probably way too much info but I figured it couldn't hurt. Just wanted your opinion on the curve specs. Anything else I should bring up when I talk to them? I'll have the car with me too.

Desired Curve:
• 750 rpm at idle (in gear)
• Ported vacuum advance at idle
• 12º btdc initial timing
• 24º mechanical advance
• 36º total advance all in at 3000 rpm

Engine block: 1968 200ci, specs unknown, likely stock

Cylinder head: 1982 200ci
• Oversized stainless steel valves (1.5" exhaust, 1.75" intake)
• Three-angle valve job (Top Cut: 30°, Valve Seat: 45°, Bottom Cut: 60°).
• Undercut intake valve 30° (not exhaust valves).
• Unshrouded valves
• Combustion chamber polished and equalized volumes
• Milled head .030 (57cc chambers, 8.1:1 CR)

Carburetor: Weber 32/36 DGV 2bbl progressive

Cam: Unknown, likely stock for 200ci w/hydr lifters:
• 252/256 (duration)
• 7 (int open)
• 65 (int close)
• 55 (exh open)
• 21 (exh close)
• 28 (overlap)
• 348 (valve lift)

Ignition control box: MSD 6A

Coil: MSD Blaster2, 45,000V

Exhaust: "Classic Inlines" Headers w/single 2" pipe

Transmission: C4 Automatic

1971 4-lug 8” Rearend (2.79:1): 2,350 rpm @ 50 mph, 2500 rpm @ 55 mph, 2,700 rpm @ 60 mph, 2,900 rpm @ 65 mph, 3,100 rpm @ 70 mph, 3,350 rpm @ 75 mph

Fuel: generally 87 octane regular

They may want your social security number and date of birth. And possibly your mother's maiden name. You've given them everything else.

:D

Honestly, if they need more than what you've listed (which is way more than I'd know about my motors unless I built them), they're the experts - and they should be asking it of you. The only thing I see missing is what year/model the distributor come from. Did you mention where you got it from and how much it was? Mine came from Pick-n-Pull and may be the cause of my current issues. I may be looking to swap it - maybe.

I still feel very uncomfortable about the work I did on mine considering the information on-line didn't match my experience when I got inside and started tweaking things. So I'll be watching this anxiously to see what you say and what they come up with.

Good thing you're taking the car..... They may need to know what kind of key fob you normally use and if the brake pedal pad is new or worn.

OK...quit razzin' me. I've got such a bad memory, I keep all this stuff in a Word doc anyway so it was just a cut/paste! You'd be surprised what they might want to know. When I took it in for an alignment they wanted to know how much I weighed. I guess they have a ballast system now so they can put weight in the driver's seat and get it more accurate...

I got the DSII from RockAuto. I went for the Autoline brand which is rebuilt in Canada. I think I went for the `81 Fairmont 200. It was $66.28 with shipping and included the cap and rotor (but no adaptor). There was a $3 core charge but Jeff's getting my old one for his upcoming build.

There are (of course) a lot of opinions on the curve characteristics on the Ford Six Forum and TFFN. Mine has always seemed to like 12 BTDC for initial timing and I figured 3,000 rpm was a good point to be all in considering I'm at 2,900 going 65 mph and 3,100 going 70. The mechanical being 24 at the crank seemed pretty middle of the road.

Hey kenny, thats just what they need to know, I use to set dist. on the old sun machine's years ago, my 327 chev was set at about 12 to 14 at idle and was full in by 2600, by changing the springs and adding to the weights or shaving some off to get what you want...I still have access to a dist.machine at transmission kellys,where I worked a few years ago, good luck, and how much do they want for this service??:rocker:

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Originally Posted by redfalken

There was a $3 core charge but Jeff's getting my old one for his upcoming build.

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$3.00 :WHATTHE: - I'll have to raid the girl's piggybanks.;)

He's going to it for $60. I've got the springs and tried to do it with Jeff's dial back timing light but the MSD was causing some pretty funky readings.

After the timings down I can finally move on to tuning the Weber!

Kenny,

I would suggest have all the mechanical timing in a bit earlier. Shoot for 2500RPM.

Thanks Pat. So what's the thought process to figure that out? I've tried reading through threads on other forums to see what others have done but it seems to be all over the place.

Generally speaking, getting the advance in earlier will improve your throttle response and accelerate quicker. Getting it in too early will cause detention. Getting all of the mechanical advance in as early as possible without causing detonation is the goal. Mine is all in by 2200 RPM. Of course mine was set from the comfort of my sofa with a laptop.

Picked up the DS II today. Hopefully I can install it tomorrow and go for a spin...weather permitting. I peeked in through the holes on the base plate and noticed he had flipped it to the 13R slot and replaced both springs with the Mr. Gasket kit springs which are lighter. I've heard some say to only swap one of the springs We shall see!

Here are the specs he emailed:

Advance begins at 800 rpm
22 deg of mechanical @ 2300
14 deg of vacuum advance
36 deg of total all in at 2560 rpm

I did the "replace-only-one-spring" thing to mine, and I have to zing it pretty high, way more than 2500 rpm, I think, to get full advance. (Need to tee off the tach wire from the Street Fire box so I can use my test tach under the hood!) I really think I need install the other Mr. Gasket spring. My throttle response still sucks....

One thing I'm still a little vague on is how the vacuum advance works - or doesn't - when I converted to the DSII dizzy. I still have the stock carb on this thing and last night when I was debugging my run-time issues, I did watch the timing marks as I accelerated and it's not advancing 20+ degrees much less 30+ degrees. I didn't have RPM to watch, so I'm not sure what I got for that.

I shut it all down last night after only confirming I got the run issue resolved, so I have more investigations to go on this, but you both have vacuum options I don't have, I think. And I know the original distributor was for using the power valve port on the carb.

Any wisdom out there on this issue?

Is this the Load-o-Matic setup? If so, here's a link to a pretty good write up and I'll cut/paste the text on using this carb with a DS II. Basically, you can plug the spark control valve and run it off manifold vacuum, wherever you can find it.

http://www.classicinlines.com/Loadomatic.asp

Distributor Swaps
The "Load-O-Matic" distributor uses the "Spark Control Valve" (a spring and diaphragm mechanism), to determine the proper amount of vacuum advance, which is commonly a mixture of manifold vacuum (sensing load) and venturi vacuum (sensing rpm). On the other hand, a conventional distributor uses mechanical weights (speed) and manifold vacuum (load), to provide the proper amount of ignition advance for any given situation.

While you can use a Duraspark or DUI distributor with a stock Autolite 1100 carb, both of these distributors utilize a mechanical advance mechanism that was designed to operate with ported or manifold vacuum. As such they will not operate properly using the vacuum port on the stock Autolite 1100 carburetor. To correct this you need to plug the port on the carb, so you don't have a vacuum leak, and run the vacuum line from the Duraspark or DUI distributor to a manifold vacuum source. This can be accomplished using an existing vacuum source on the intake manifold, or the bottom of the carb adaptor. Or you can create a new source by drilling a hole in the intake manifold and installing a vacuum barb. However, you'd need to remove the cylinder head before drilling, to make sure the manifold is free of any debris that could work down into the cylinders and severely damage the motor.

So...what happens if you do try to use the vacuum port on the Autolite 1100 carb? At idle, the "Spark Control Valve" is open, sending manifold vacuum to the distributor. As such, the engine will idle just fine. However the "Spark Control Valve" will not provide the proper vacuum signal under load and/or speed. All engines need more advance when cruising, and less to none at wide open throttle. However since you are now using the carb (venturi vacuum advance) and the distributor (mechanical advance) to compensate for speed, the ignition system will receive to much advance at cruise and wide open throttle. As a result, the engine may chug and jerk from the over-advanced condition at cruise.

Very interesting. The part that always cornfused me is the thought that vacuum advance actually advanced with acceleration. I'm sure it was a long-ago forgotten thing I learned in auto shop. I always did well in those classes, but I can't remember much from that time to know why. But that's another story for another time. :confused:

I have always thought that as engine speed increases, so does the advance, which of course is true with mechanical advance. But since manifold vacuum actual goes down with throttle plate opening, I always assumed (until today) that the reason you hooked the distributor to the carb was that they had a means of increasing vacuum with throttle opening. This is actually true, to a degree, with the old Load-o-matic distributor and carbs. This article, and a related link on vacuum advance, helped cure me of that assumption. Though this is true with this style carb, all distributors with mechanical advance, which the Load-o-matic distributors lacked, required manifold vaccum.

Bottom line is that vacuum advance is NIL off idle and during acceleration. It provides advance in lean-burn conditions, most common at idle and cruise. Lean mixtures need more burn-time (more advance) and rich mixtures require less advance. Mechanical advance is all RPM based and is the advance you have access to when you are accelerating, AKA "getting it on."

So, that being the case, the specs they provided you, Kenny, of:
Advance begins at 800 rpm (I assume all mechanical movement starts here)
22 deg of mechanical @ 2300
14 deg of vacuum advance (I assume they can check this below the 800 RPM)
36 deg of total all in at 2560 rpm
... would seem to imply that you add mechanical advance to the vacuum advance to get this total. Since they can apply vacuum at any point while on the test bench, this doesn't mean you will have 36 degrees of advance at 2560 RPM at wide open throttle (WOT) under load. So under WOT, I think your max advance may be closer to 22 deg. I can't see you getting another 14 deg out of another 260 RPM. So... how did they come up with this total?

On a side note, I stumbled onto a thread yesterday on the TFFN as I was looking around the Internet about what spark plugs people used when doing a DSII swap since I needed a set (this was on my phone - so it wasn't a serious search) and a guy did a bunch of elaborate mods to his 1100 carb to create "ported vacuum," which these guys on CI seriously denounced the use of. The guy on TFFN really thought this was a requirement to do a DSII swap.

Well...it made sense at one point...:confused:

I think maybe he meant 14 deg of "initial" advance and I should have corrected that but just did a cut/paste. So when your engine is at idle with the vacuum disconnected from the distributor and plugged, this is where you set the initial timing. As you begin to accelerate, the vacuum advances the timing until the mechanical part takes over and the vacuum from the manifold or carb port dies off.

Somebody way smarter than me can explain it better but here's a pretty good web page if you need some light reading:

http://www.angelfire.com/on/geebjen/timing.txt

I didn't get to install it yet but I have Friday off so I'll do it then for sure and report my findings.

Yeah, that link pretty much echo'd the CI document.

Initial advance is set by rotating the distributor in the hole, so they can't set it for you. They can recommend it and use that as a reference point to say what all the other values can be, but it still seems odd that they include vacuum advance. The best they could do is to indicate the maximum vacuum advance you can attain at idle (when the vacuum is greatest).

Essentially it is like this:

1) You set initial advance without any vacuum assist and at an idle speed below any introduction of mechanical advance. This setting, as seen in "the books" was all based upon compression ratios, fuels, octanes, etc... at that time. Though still a good place to start, the reason you may want to vary from this is because we are in a different day and age of fuels and you may not be running a completely stock setup anymore.

2) Mechanical advance is 100% rpm based. The old Load-o-matic distributors didn't have mechanical advance, so Ford actually did use vacuum (a mixture of manifold and venturi) to make a fake "mechanical" advance - which was needed (is always needed) during acceleration.

With the DSII distributor and any post-1967 distrubutor, which has mechanical advance, this is the thing you are modifying with new springs. There are two weights inside that "fling out" with centrifugal force and these drive against a cam, of sorts, to rotate the breaker plate on Fords. Changing the weights effect how quickly the weights can move and how quickly the breaker plate rotates and how quickly you see advance.

Since there are two weights, you can, depending on how the springs are setup, have one weight move to allow for fast advance action and then the other comes into play later. At this point - both are in play together. If both spring are in play, their tension is summed. So, if you have one weak and one strong spring (as is the case with the suggested mod) and both are "under tension" all the time, you could actually have two equally sized springs as well - as long as the sum of two weaker springs are the same and one strong and one weak. If you have one spring slightly un-sprung (possibly the cause of them wanting you to bend a tab), then it might allow a quick advance - at first - and then when both are under tension it allows a slow and steady advance over the rest of the RPM range.

3) Vacuum advance. This only operates at idle and cruise, but highest vacuum is at idle. This is added to initial advance as soon as you set that and reinstall the vacuum line. So, in reality, this is what your "idle advance" is: initial plus vacuum.

That's the way I see it so far. Sorry for typing this all out and hijacking your thread Kenny, but hopefully it will come in handy. I'd still like to know whether they added vacuum advance to mechanical advance to give you total. Seems awfully coincidental that they just happen to add up.

Quote:

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Originally Posted by Luva65wagon

3) Vacuum advance. This only operates at idle and cruise, but highest vacuum is at idle. This is added to initial advance as soon as you set that and reinstall the vacuum line. So, in reality, this is what your "idle advance" is: initial plus vacuum.

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The vacuum advance is typically connected to a port that is just above the throttle blades. This is different than the old Load-o-Matic stuff. In this manner, there is little to no vacuum advance at idle. It's when the throttle just opens that the vacuum advance will be greatest and it will vary based on engine load. It is still best to set base timing with the vacuum capped off. Then reconnect the vacuum and go. The vacuum advance can is adjustable on Kenny's new dizzy. You can use a small allen wrench to adjust the amount of advance you get at a preset vacuum setting. The wrench adjusts the preload on a spring in the vacuum can.

This is contrary to the thread on Classic Inlines thread. They indicated this to be called "ported vacuum" which was used in the early smog emission days, but was not the way to go today. But they did indicate it was a "debated subject" and then proceeded to explain what each was. The Load-o-matic carbs only offered a load-sensing vacuum using the little diaphragm doodad on the carbs.

So, anyway, I guess it is still debatable. :D

I've spent all of 20 minutes so far looking into it. I only know that when doing a DSII swap when I have a 1100 carb - I only have manifold vacuum as a real source and should not be using the original feed from the 1100. I will continue to study the pros and cons, but I'm hooking it up to manifold vacuum tonight, for now.

This is the thread on ported versus manifold vacuum sources:

http://www.classicinlines.com/VacAdvance.asp

Quote:

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Originally Posted by pbrown

The vacuum advance can is adjustable on Kenny's new dizzy. You can use a small allen wrench to adjust the amount of advance you get at a preset vacuum setting. The wrench adjusts the preload on a spring in the vacuum can.

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I wish! I tried several sized allen wrenches and it is what it is. I think Crane and Standard make one for about $35-40.

When I get mine hooked up I'm going to compare ported vs. manifold. I borrowed Jeff's vacuum gauge so I can see what it's doing too. I've read plenty of forums where just as many people use one or the other and the consensus always seems to be "whatever works for you".

Well, first of all, you have to have the option. Perhaps your Weber offers the option, but the 1100 doesn't, really.

I've not done a lot of research yet, so for me the jury is still out, but tonight I added a manifold vacuum source and plugged off the Load-o-matic feed source on the carb. With initial timing sitting at 7 BTDC (I didn't try to adjust it to 6) I plugged in the vacuum advance and it jumped to 27 deg, or 20 deg added - at idle. With rev to about 2500-3000 it max'd at 41 degrees total advance. I do [now] have a spare vacuum source, so maybe I'll check vacuum reading too.

I will say that if I had ported source and the thing was running at 6 BTDC, it runs pretty crappy that way.

I think I still have some carb issues though. It is running pretty rich and part throttle run is not real smooth, but WOT acceleration is very responsive under no load.

I was having trouble with that carb as well (I had a filter screwed right on the carb so I hopefully can't be blamed for the dirt)... but I was testing it when I had that bad resistor wire.

Have you swapped the one off your wagon for testing?

This is a pretty good article on ported versus manifold. Might also explain why, now, with manifold vacuum connected it seems to be running rich. If only it was easy to gain ported to try it.

http://www.lbfun.com/warehouse/tech_..._explained.pdf

Quote:

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Originally Posted by Jeff W

I was having trouble with that carb as well (I had a filter screwed right on the carb so I hopefully can't be blamed for the dirt)... but I was testing it when I had that bad resistor wire.

Have you swapped the one off your wagon for testing?

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Gene and I were staring at it tonight and this was floated. The answer is no, though. But it wouldn't be really hard to do. It's a slightly different carb though, so I'll hold off just until I give up trying other things here.

FWIW, with what was in it when I opened it, I can see why you would have had troubles. So no, the once rusty tank in the flarechero would be to blame.

A little more insight from my readings....

Basically manifold and ported vacuum are the same except at idle, where ported is OFF at idle and manifold is ON.

Initial advance is determined by whether you use or don't use one of these.

Still looking when I can, but nothing so far has helped me learn whether the recurve I did on mine, based upon the CI instructions, is doing what it was supposed to do.

:confused:

Not trying to beat this horse anymore than needed (OK, maybe I am), but I can really begin to see why there is no consensus out there on the subject of "which port to use." Even MSDtechsupport gets a basic idea of engine vacuum wrong, which I don't think is a debated subject. I was very surprised by this, but doesn't help clear the confusion out there:

Quote:

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We recommend that the vacuum advance cannister be connected to a ported vacuum source. This will provide vacuum at idle, part throttle, and cruzing speeds.

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This is not correct. It is very well established - reading 99.9% of the sites I've read (this would be the .1% that didn't agree) - that there is NO vacuum at idle from ported source because this port is above the throttle plates.

He then continues with:

Quote:

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Do not connect it to manifold vacuum because this will increase with RPM. With that, you would run the risk of having too much timing which can cause detonation.

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This too is wrong, partly. Manifold vacuum and ported vacuum have the exact same characteristics and provide the same readings off-idle. And do not increase with RPM at all. At cruise, say 3000 RPM +/- you will have all mechanical advance and a good portion (if not all, depending on the vacuum canister) of your vacuum advance, which will hopefully put you in the upper 40's, low 50's for advance. Total mechanical is hoped to me about 36-38 (initial plus mechanical) and adding vacuum to this, which is ~14 deg added, puts you at 52 degs at cruise. Too much advance, when you don't want it, or need it, or under the wrong conditions, can cause detonation. That part is true.

I think I can echo Kenny now when he said most people just say:

Quote:

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do what works best for you...

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...because there is nobody out there that is saying anything that is the same.

Most of those who are in agreement pretty much say it depends on the cam you use as to whether you might benefit from one source or the other. I will continue to play with it.

:rolleyes:

:doh:

I just got my dizzy back yesterday from the same shop Kenny went to (Thanks again Kenny for bringing mine with you). Ben confirmed what I always knew was true: too much mechanical advance although he reported much more than I thought was happening: 50 degrees! He got it reigned in to 18 degrees all in at 2800 RPM.

I dropped it in as soon as I got home yesterday morning (a process which still gets frustrating), and wow what a difference in throttle response. It had a real smooth slow rise in RPM from 700 to 2500 when I tested it in the driveway. Driving it around was much better as well, no more detonation on hills. The next step is to get the Vacuum advanced tuned in, it is still advancing too much on the ported vacuum but is much better than before.

All of the threads I have read seem consistent with Pat's account of ported vacuum and the purpose of it is only for those times where more advance is needed at lower RPM (Such as climbing a hill).

I can see the pull arm off of the vacuum diaphragm and have confirmed that max ported vacuum seems to be around 1500 RPM for a very short window. The ported timing is correct, but the pull is too much. Pat is also correct on the hex screw adjustment on the diaphragm, however not all of them have it, mine included. I need to decide if my next step is to replace the diaphragm with an adjustable one or try to limit the vacuum line.

This is interesting and frustrating - because for every one thread I find suggesting the use of ported vacuum I find two or three saying to use manifold. And half of those proporting ported seem to describe its function as something it isn't, or manifold as something it isn't. I really wish someone would post some links to support why they believe one thing over the other. I'm sure I won't solve this mystery, but I'm not going to ignore simple physics, which is playing a big part in my continuing search.

There are are no differrces between manifold and ported except that at idle one supplies no vacuum (ported) and the other with full vacuum (manifold). Both produce the exact same same vacuum signal - as soon as you go off idle.

There is a purported "venturi vacuum", but there has been no indication I can find as to whether any Carb provides this port. The Load-o-matic Carb sort of made this and may be the reason of this example, but nobody "out there" draws the exact association.

The only change you will be making with the use of ported or manifold is how it is set up to run at idle - period. What initial advance you use and how you adjust idle and air/fuel to maintain idle. WOT or cruising operation is unaffected but the use of either - except as to how you set up initial advance, which will shift the entire advance curve, since mechanical and vacuum advance curves don't vary - off-idle - whether you use ported or manifold.

So Brian, what did you set your initial advance to? Kenny, what will you set yours to? What, if anything, were you advised to do in this regard? Factory settings? For what? A motor with or without ported vacuum source?

Unfortunately I don't have ported vacuum. This is simply a mission for me now (damn it all anyway... :doh:) :) ) This is how I learn stuff. Ported vacuum didn't even get thought up or introduced until the 70's to address emission control, so only smog carbs and aftermatket carbs offer it... to allow their use on cars with emmision controls. It wasn't introduced to aid in performance applications. I have found no source on-line to counter this. Even the other night, when I was looking at the instructions in Gene's new Edelbrock carb, they listed both source types and said to use ported with "emission controlled motors."

As for adjustable vacuum canisters, they allow adjustment of the tension of the spring behind the vacuum diaphragm. This allows a motor with a cam that can't produce a lot if vacuum to still operate a vacuum advance. It either shortens the curve (less tension) or lengthens it (more tension) for the same source - nothing more.

Anyway, sorry to be so emotional about this. :p Once I get into researching something, as you can see, it becomes a bit obsessive. I know, say it. Roger, get a life. :ROTFLMAO:

The new, recurved DSII is in and running really well. The hardest part was getting it to drop onto the oil pump rod and be on the correct tooth of the gear.

I have it set at 12 degrees right now and get a very tiny amount of that rattle can pinging when I have it under load. This is only on a really big hill a few blocks away and when I mash the pedal to the metal. Tomorrow I'll bring it down to 11 and see how that sounds.

I also will take a vacuum reading from the ported source and see how that looks. Brian was over and I hooked the vac gauge up to the manifold, just under the carb where I have the tranny modulator and PCV hoses attached. Warmed up at idle it was at 18. When you give the engine a quick goose it drops to near zero real quick and then comes back up to 18. If you accelerate slowly it will rise to about 20 but then comes back down again to 18.

Brian also noticed that the armature from the vac advance canister would pull when I accelerated off idle and stay there. He said his would pull at first but then come back to the resting position. And he says the canister diaphragm isn't torn either.

Now I've only ran it off ported vacuum so far but maybe tomorrow I'll try manifold. It did seem to idle better when warming up and I also noticed the lean spot I have when accelerating hard is less noticeable.