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Advance curve set Mr. Gasket 927G |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Feb/25/2017 at 12:50am |
I am lucky to have access to a distributor testing machine, an Allentest model. I took my D-R distributor and decided to run all of the various springs and weights. I will likely not use most of the settings, but I thought it would be nice to have such a chart for future reference. The aftermarket dissy users get nice charts to tell them what theirs do with various parts installed and I thought it would be good to have something similar. I have a 24 degree pole piece and a #159 center piece. I used the bronze bushing from the kit on the advance peg. This is what happened:
With stock advance weights: Springs total advance rpms ST/St 3400 ST/G 3200 G/G 3000 G/S 2700 S/S 2500 S/B 2200 B/B 2100 With Aftermarket advance weights Springs Total advance rpms ST/St 2900 ST/G 2600 G/G 2400 G/S 2200 S/S 1900 S/B 1600 B/B 1400 PS: ST mans stock springs, G=Gold, S=Silver and B=Black as per the colour coded springs in the kit.
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5903 |
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May I ask are posted RPM's Distributor RPM or Crank RPM ?
Is it possible to also post at what RPM the mechanical advance started ? Thanks for posting. |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Sorry, I was somewhat time limited on the use of the machine. Thursday before a long weekend, coming on for quitting time!
These are crank rpms. I did not note down the starting rpms, but generally they seem to start at around 1000 rpms or so. Another thing that I did not have time to map was the actual curve. For example, the heavier weights would tend to exert more rapid advance in the higher rpms, because centrifugal force increase exponentially. Lighter weights would have different values over the mid range of advance. Different pole pieces can affect this too. Lots of different things like this can come into play for those that are really into the finer details. With all of the different pole pieces and such there are a million combinations. I just wanted to give people some idea of what the max advance would be and where. That is probably the most critical and what people pay most attention to. Thanks! Chris
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348AMX
AMC Addicted Joined: Jul/03/2007 Location: Massachusetts Status: Offline Points: 4165 |
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Do you know what the total timing degrees were at the listed RPM's??
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5454 |
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I guess I've always paid more attention to what the shape of the advance curve looks like prior to about 2000 rpm, not just the total advance. I could be using the wrong approach though.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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348: 24 degrees. I have that center piece and that is probably the most popular amount of advance.
6pack: I also pay attention to those things, as much as possible. I am using a Mallory Group 19 dissy in my car right now, and it has a set up that allows me to have the first 20 degrees come on quickly and then slows down for the last 4. I found that useful for avoiding mid range detonation.
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Lyle
AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772 |
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Correct me if I'm wrong here but that 24° is a good number for mechanical advance but the total advance would be initial + mechanical. So 12° + 24° = 36° total timing which would be good depending on cam/compression ratio ...
Good to know the springs and mechanical advance numbers for given RPM for those using this distributor - thanks. |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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I use exactly the numbers you suggest. Anything from 34-38 total seems to be common and as much as 38-40 may be good too. 24 is probably the most common but there are a million ways to skin that cat! Pretty much up to the butt dyno and what works without detonation for your particular combination.
I hope it is useful to some here to know what a common advance kit and a stock type distributor actually is doing. Not everyone is able to access a dissy machine and using your car as a 400 hp distributor machine is both a nuisance and inaccurate. Chris
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