Sub-topics included in this article -
The 009 distributor is a centrifugal-advance distributor. It has no vacuum advance component at all. It does not have the "load sensing" ability of the vacuum distributors that came as VW original equipment. But the 009 distributor is very popular because it is inexpensive (and unfortunately also "cheap," as in reduced quality). We personally prefer the vacuum distributors (Dave uses a Single-Vacuum Dual Advance distributor with which he is very pleased. For discussion of the distributor choices, please see John Connolly's (Aircooled.Net) excellent article on "Choosing the Right Distributor". But since so many Bugs on the road today are equipped with the 009 distributor, we must address the methods by which it is properly tuned.
First of all, make sure that the vacuum points on the carburetor are properly plugged or you'll be sucking air into the carburetor, making it impossible to tune.
The 009 distributor requires different static timing to the vacuum distributors. You should have about 5-7 degrees BTDC static timing with about 30 degrees maximum advance at high revs (about 3000 rpm or so). That's the short story. Here's how one person does it -
I start by setting the timing to about 7 degrees BTDC statically (see our Static Timing Procedure). Then attach the strobe timing light (see our Strobe Timing Procedure and rev the engine up until the distributor stops advancing. This should give a total maximum advance of about 28-32 degrees. Subtract the 7 degrees you added statically and you now know for sure what YOUR 009 distributor is doing.
Depending on where the quality of your 009 distributor, it may have a different amount of advance. The total advance for the example above is 21-25 degrees. The amount of total advance varies for each individual engine, what you intend to do with it, and the quality of the fuel your are using. Remember -- more advance makes more heat, so it's unwise to take the total advance to the extreme.
Rob's 009 Timing Procedure -
Note: Maximum advance is much more important than idle advance, and for the aircooled VW engine and 009 distributor, the maximum advance MUST be between 28 and 32 degrees at 3000+ rpm.
Note: The 009 distributor is usually set at 3000+ rpm because they produce their maximum advance at 26-2700rpm, and using 3000+ rpm ensures that it's all in.
So the spec 7.5 degrees BTDC MIGHT be right for some 009 distributors, but not necessarily for all. We have heard of 009 people with a maximum advance of 26 degrees; that would indicate that THAT 009 distributor should be set at around 10-12 degrees BTDC at idle so the maximum advance will be in the 28-32 degree range.
If the 009 distributor is set with more than 32 degree maximum advance, the engine is over-advanced in certain throttle/rpm conditions, and this can cause the engine to ping/detonate.
If it's set with less than 28 degrees, it will be under-advanced at high rpm and cause overheating. Overheating certainly puts an extra load on the head and it's components, especially the already very hot exhaust valves.
The 009 distributor sometimes causes an acceleration "flat spot" (hesitation), as it does not have the vacuum advance adjustment of the original distributor. These can usually be overcome by ensuring that the accelerator pump is adjusted for it's maximum stroke, and installing a richer main jet in the carburetor (one size up should do it).
This last point is particularly relevant if you live in an area which has a lot of MTBE or similar additives in the fuel (California, etc.). These additives cause carbureted engines to run a little lean, and VW engines prefer to run a touch rich.
Idle timing of 7.5 degrees BTDC is correct for most single-vacuum distributors on aircooled VW engines (some variation depending on the model year and the country -- emissions considerations and such).
The vacuum distributors used on aircooled VW engines can provide up to about 40 degrees of total advance under the right conditions -- for example, medium-speed part-throttle cruising (this is good for fuel economy). But the change in vacuum when you floor it reduces the advance to around 30 degrees or so until the increasing engine rpm catches up with the "new" throttle position.
It's actually an "airflow-through-the-carburetor vs amount of advance" thing, rather than actual rpm, but you get the idea. This ability of the vacuum distributors (which also provides a shot of advance off idle to help the engine spin up) is called "load sensing". The 009 distributor can't do this load sensing, so it must be limited to "worst case" of a little either side of 28-32 degrees maximum advanced.
Question -
My timing is set to 5 degrees advanced at idle; my points and valves are correct. Also I have a 009 distributor in case that matters.
Rob responded -
Yes -- having the 009 distributor matters big time. You HAVE to set this distributor using a timing light at 28-32 degrees at 3000rpm. They vary a lot from one to another (cheap build), and the maximum advance is more important than the idle advance -- so you set the maximum advance and let the idle timing fall where it may. Once the maximum advance is correctly set, you can then measure the idle advance and use THAT setting for statically timing THAT 009 distributor in the future.
Usually the idle timing (with the maximum advance correctly set) will be anywhere from about 5 to 10 degrees BTDC, but I have seen them up to 16 degrees BTDC to get the correct maximum advance -- so you can see how important the maximum advance is. The other thing is that you need to set the carburetor to run a little rich when using the 009 distributor, so checking the main jet size is important. Increasing the size of the main jet by one size (e.g., 127.5 to 130) will improve overall performance when using the 009 distributor.
Question -
I just finished building a 2275 cc. When it came to setting the timing I set it to 8 degrees BTDC. Do I use a timing light and set total advance between 26 and 32 degrees at 2500rpm? When I checked it was only about 20 degrees advanced. Can you set the 009 distributor with the test light method?
Response -
20 degrees total advance is WAAYYY too little. It's VERY important to set the 009 distributor to between 28 and 32 degrees at 3000+ rpm, and let the idle timing fall where it may.
The reasons are:
Note: The reason we use 3000+ rpm is that the 009 distributors provide maximum advance from about 2500-2600rpm, and you want to makes sure it's all there before setting it.
Any more than that and the engine will detonate (ping) when you floor the throttle.
Any less than that and it's under advanced at higher rpm and will run hot, and you don't want THAT on your high capacity engine.
Use as much of the 28-32 degrees advance as the engine can take without detonating (this gets is a fraction closer to the 40 degrees the vacuum units make and so improves mileage a fraction). If you can't stop it detonating at 28 degrees, then you need a higher octane fuel or (last resort) lower the compression ratio of the engine a little.
Show this to your mechanic and see what he says. Hopefully he'll agree with it and increase the maximum advance to at LEAST 28 degrees at 3000+ rpm, and he might then save himself the job of replacing a burned up (but untouched by owner) engine.
Disclaimer stuff: Rob and Dave have prepared this information from their own experiences. We have not assumed any specialised mechanical knowledge, but we DO assume that anyone using this information has at least some basic mechanical ability.
We hope you find this information useful, but we don't take any responsibility for anything which happens to you, other people, your VW or any other property or goods resulting from your use of this material.
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Last revised 4 May 2004.
