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05-08-2017, 06:02 AM | #1 |
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Location: SoCal
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Automatic spark timing
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.
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05-08-2017, 06:35 AM | #2 |
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Location: Ontario,NY
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Re: Automatic spark timing
I have one on my Victoria. Works great. You'll wonder why you didn't install it sooner. Got mine from Snyder's.
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05-08-2017, 06:43 AM | #3 |
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Location: Eastern CT
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Re: Automatic spark timing
I had one in my roadster. It worked great in warm weather, but when it was cold and the oil was cold, it would not advance until I was going down the road a bit. I took it out.
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05-08-2017, 06:57 AM | #4 |
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Re: Automatic spark timing
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?
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05-08-2017, 11:11 AM | #5 |
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Re: Automatic spark timing
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. |
05-08-2017, 01:23 PM | #6 | |
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Re: Automatic spark timing
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05-08-2017, 01:29 PM | #7 | |
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Re: Automatic spark timing
Quote:
I will take pictures. Take a look at the video here http://www.nurex.com/automatic-spark...-advance-12176 |
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05-09-2017, 12:05 AM | #8 |
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Re: Automatic spark timing
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! |
05-09-2017, 12:22 AM | #9 |
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Re: Automatic spark timing
Thanks Mike, I didn't know that and will look to see if mine has any markings.
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05-09-2017, 03:00 PM | #10 |
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Re: Automatic spark timing
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?
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05-09-2017, 11:43 PM | #11 | |
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Re: Automatic spark timing
Quote:
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. |
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05-10-2017, 02:49 AM | #12 |
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Re: Automatic spark timing
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.
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05-10-2017, 08:50 AM | #13 |
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Re: Automatic spark timing
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05-10-2017, 01:43 PM | #14 |
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Re: Automatic spark timing
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.
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05-10-2017, 02:25 PM | #15 |
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Re: Automatic spark timing
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.
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05-10-2017, 05:08 PM | #16 | |
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Re: Automatic spark timing
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05-10-2017, 07:06 PM | #17 | |
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Re: Automatic spark timing
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Last edited by steve s; 05-10-2017 at 09:28 PM. |
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