denniskliesen
Well-known member
Has anybody here used the automatic spark timing system on their A engine? I have a 6:1 head with stock cam exhaust and intake. Thanks for everybodies opinion.
Automatic spark timing
- Thread starter denniskliesen
- Start date
denniskliesen
Well-known member
Maybe I should have asked this when I made my original post. Do you leave the mechanical linkage connected? Any starting problems? Is the Snyder's unit the same as Bratton's and all the other vendors?
RawhideKid
BANNED
Since I have not pulled the valve cover yet, I am told I have the Nurex advance and I love it.
As for starting and running, I turn the gas on, (when stone cold) pull the choke, turn the motor over, turn key on with about 1/3 throttle lever down, kick the starter button, varoom, starts right up, count to 10, set the throttle back to top, drive. It runs like it knows it is young and wants to play. I have removed the advance to distributor arm, really no need.
Needless to say, I am very happy with mine.
Now one drawback I have heard from others is, it is possible that when pulling the distributor the advance can raise enough to remove it from the drive.
So, when I pull the valve cover, I will also pull the advance and gear drive to install a set screw in the gear drive to hold the advance in the drive when the distributor is removed, removing the need to pull the valve cover to reinstall the distributor.
I am about to do this in the next few weeks. If you want to know, I'll post something when I do this.
As for starting and running, I turn the gas on, (when stone cold) pull the choke, turn the motor over, turn key on with about 1/3 throttle lever down, kick the starter button, varoom, starts right up, count to 10, set the throttle back to top, drive. It runs like it knows it is young and wants to play. I have removed the advance to distributor arm, really no need.
Needless to say, I am very happy with mine.
Now one drawback I have heard from others is, it is possible that when pulling the distributor the advance can raise enough to remove it from the drive.
So, when I pull the valve cover, I will also pull the advance and gear drive to install a set screw in the gear drive to hold the advance in the drive when the distributor is removed, removing the need to pull the valve cover to reinstall the distributor.
I am about to do this in the next few weeks. If you want to know, I'll post something when I do this.
denniskliesen
Well-known member
Yeah, I'd like to know when you do it. And a picture would be great. Looking at the picture of parts that Snyder's show, I was under the assumption that the half moon shaped spring would hold it in place. Last I looked the vendors did not have a .pdf showing installation instructions.
RawhideKid
BANNED
From what I know, the half moon spring does hold the gear drive in place, but the advance sits in the top of that drive just like the long shaft does. So the chance is there for the advance to want to come up with the short shaft, depending on which has the snuggest fit, the short shaft, or the advance.
I will take pictures.
Take a look at the video here http://www.nurex.com/automatic-spark-timing-system-mechanical-advance-12176
MikeK
Well-known member
The NuRex advance is actually a near-exact copy of a quite old period accessory made by Phillips and sold in parts stores. They originally sold for about three dollars.
There are three iterations of the NuRex centrifugal advances. The first run had a very small white "A" on the rotor, the second "B". I have installed, modified, and sold several. After a long time off the market by NuRex they now have run #3. I do not have one of the latest and do not know if the rotor, advance helix, spring tension, or other changes have been made.
The normal intermediate shaft is replaced by a special shaft that comes with the unit, and it has a single locator pin on the side. It is NOT slotted like the stock intermediate shaft. The fit is very close into the rotor assembly, and when soaked with oil, pulling it up from the rotor assembly when removing the distributor abruptly creates a suction that WILL uplift the rotor and drop it sideways into the valve chamber, requiring pulling the side cover to set it back in place.
There are several fixes that I tried. 1) Placing a locking set screw shaft collar on the special shaft to prevent it from being pulled up. 2) cross-drilling the rotor and shaft and pinning. Both work.
When you remove and examine it you will see there is a pin that rides a milled helical slot. Both the "A" and "B" versions of the NuRex copy of the Phillips advance mechanism have a very slight 'stick' or hangup at the beginning of travel in that slot. A little tweaking with a set of die sinkers files will correct this, giving improved initial response at idle speed.
The advance curve may or may not be to your liking. The "A" and "B" runs of the NuRex look like this compared to a 1932 Model B centrifugal advance:
If you are running a higher than stock compression head or hotter cam you may find the curve unacceptable. Changing the curve involves modifying the advance unit itself by changing its spring tension, mass, or travel limit (requires a distributor machine).
A simple approach to easily advance or retard the entire curve itself is to leave the advance lever connected to the dizzy and time it with the lever five clicks down as 'zero'. While running you can move the entire advance curve up or down by moving the advance lever slightly up or down from that position. This is not for the faint-of-heart or the absent minded!
There are three iterations of the NuRex centrifugal advances. The first run had a very small white "A" on the rotor, the second "B". I have installed, modified, and sold several. After a long time off the market by NuRex they now have run #3. I do not have one of the latest and do not know if the rotor, advance helix, spring tension, or other changes have been made.
The normal intermediate shaft is replaced by a special shaft that comes with the unit, and it has a single locator pin on the side. It is NOT slotted like the stock intermediate shaft. The fit is very close into the rotor assembly, and when soaked with oil, pulling it up from the rotor assembly when removing the distributor abruptly creates a suction that WILL uplift the rotor and drop it sideways into the valve chamber, requiring pulling the side cover to set it back in place.
There are several fixes that I tried. 1) Placing a locking set screw shaft collar on the special shaft to prevent it from being pulled up. 2) cross-drilling the rotor and shaft and pinning. Both work.
When you remove and examine it you will see there is a pin that rides a milled helical slot. Both the "A" and "B" versions of the NuRex copy of the Phillips advance mechanism have a very slight 'stick' or hangup at the beginning of travel in that slot. A little tweaking with a set of die sinkers files will correct this, giving improved initial response at idle speed.
The advance curve may or may not be to your liking. The "A" and "B" runs of the NuRex look like this compared to a 1932 Model B centrifugal advance:
If you are running a higher than stock compression head or hotter cam you may find the curve unacceptable. Changing the curve involves modifying the advance unit itself by changing its spring tension, mass, or travel limit (requires a distributor machine).
A simple approach to easily advance or retard the entire curve itself is to leave the advance lever connected to the dizzy and time it with the lever five clicks down as 'zero'. While running you can move the entire advance curve up or down by moving the advance lever slightly up or down from that position. This is not for the faint-of-heart or the absent minded!
RawhideKid
BANNED
Thanks Mike, I didn't know that and will look to see if mine has any markings.
denniskliesen
Well-known member
Good information regarding the higher compression and hotter cam. Now how about the mechanical linkage type that advances with throttle movement. Anybody try that setup?
MikeK
Well-known member
I have not tried one, but did help someone remove one a few years ago. NuRex came out with this contraption sometime after the end of the second run of the Phillips type advances. Word was they could not find an acceptable machine shop to produce the units. Their replacement was this mechanical throttle position linkage setup now sold by some of the vendors.
Primary problem: It works OK only if you are always light on the throttle and the manifold vacuum never falls below about 10" Hg while accelerating through the gears. If you accelerate at wide open throttle from a low rpm you will be about 20 degrees over advanced. The engine will buck and pound itself internally.
Advance should relate mostly to rpm and somewhat to vacuum. This is why later dizzys had both centrifugal and vacuum advance mechanisms. The unit in question works with NO relation to rpm. In addition, it actually responds the wrong way to engine vacuum by advancing when the vac drops instead of retarding when the throttle is opened to accelerate.
You will note they only recommend it for a stock 4.22 compression head and a stock cam. That setup can tolerate a lot of 'wrong' timing excursions without too much feedback to the driver. That doesn't mean no damage, it only means you won't easily sense it. As you increase compression ratio and change valve timing (cam) the acceptable advance range at any given rpm becomes much narrower.
Second (third?) problem is the wierd linkage bracket that requires you to drain the water, remove the second head bolt from the firewall on the right side, and retourque. For some, no problem. For others, this is opening Pandora's box and creating a head gasket leak. The instructions say "drain the water" for a reason.
denniskliesen
Well-known member
Mike, thanks for all that information. I'm going to keep my original setup and forget about doing any modification to the timing. I've gotten used to the mechanical advance and found it doesn't need to be full advance with my 6:1 head going 40-50 mph. Maybe being at sea level has something to do with the performance, doesn't ping or buck at low RPM taking off from a stop. I use Les Andrews method of timing with a test light on the points.
MikeK
Well-known member
MAG
Well-known member
http://www.ginsphotos.com/alaska.html
This is a travel log of 2 Model A's on a trip from Texas to Alaska, May to July 2013. One of the cars was equipped with a automatic timing device. It failed and was replaced with another one. Unfortunately the car was driven several days with the failed automatic timing device locking the distributor timing in "high time" resulting babbit failure.
The travel log is very long but also very interesting. If you go to the site, click on the picture of the Cabriolet to begin viewing the daily logs.
This is a travel log of 2 Model A's on a trip from Texas to Alaska, May to July 2013. One of the cars was equipped with a automatic timing device. It failed and was replaced with another one. Unfortunately the car was driven several days with the failed automatic timing device locking the distributor timing in "high time" resulting babbit failure.
The travel log is very long but also very interesting. If you go to the site, click on the picture of the Cabriolet to begin viewing the daily logs.
I have found the stock Model B dizzy to be ideal for use with a high compression head, and with a reasonably original appearance retained. With the prevalence of high compression heads in use these days I have to wonder why nobody has yet produced a suitable facsimile of the Model B distributor with a centrifugal advance appropriate for use with a Model A timing cover? The technology is fairly simple.
steve s
Well-known member
I'm the guy who first complained about the pulling-the-distributor problem, and I would be very interested in seeing your fix. Removing the valve cover is even more of an aggravation when you've got the full-flow oil filter adapter machined into it. Otherwise, mine was from Nurex (before they lost their ace machinist) and works great. I installed a little block to clamp on the advance "plate" to prevent over-advance (which can be bad) yet allow a few clicks of extra retard when pulling a hill in between gears. I set the timing TDC with the lever against the stop block. I've got a Brumfield 5.9 head, and mysteriously always take one or two gallons less gas to fill up on fuel stops than any other Model A's on our club tours.
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