Interesting quote from Ohio Tom, Distributor Mod.

[67rustavenger]

[Glenn]

The 019 has 17° so ha I guess the idle at 12° yields a total of 29°.
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[evanfrucht]

Not positive but there might be a tab that can be bent to adjust the stop postion for where the advance starts?

I'm pretty sure there is a tab on 009's which can be bent to increase (or decrease) the amount of total advance. So without having one apart in front of me I gather there might be second tab to adjust the initial advance... speculating here.
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[AlteWagen]

Ive set tons of 009s to 30* total and they fall between 7-12 at idle. If really bad I just bend the tabs for the weight stops to dial in what the engine likes.

Ever wondered what that little oval plug is for? Popping it out gives you easy access so can adjust the weight stop without pulling the distributor!!!
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[Glenn]

The tabs can limit the advance, but not alter where it starts.
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[Vanapplebomb]

Unless running a 34 PICT, 34PDSIT, Bosch Djet or Ljet that really need the late timing to behave properly, I really like the 12 degrees of initial advance at idle. It makes for nice snappy response off idle.

As long as you can really choke off the amount of air flowing with the throttles fully closed, it works great.

This can be problematic for the crowd that over-carbs there engine, or FI with large throttle bodies because it can be tough to get the idle speed down with that much air bypass and that much initial advance. But with sane carburetion or FI throttle bodies, it’s awesome.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[74 Thing]

It is the stop tabs and spring perches. You can bend then to limit total advance and to have the timing come in faster or slower.

[beetlenut]

I asked Tom about that in a PM, and he told me about bending the spring perches in about 5 degrees. I just did that tonight, and am going to check my timing tomorrow before I adjust my carb and take a test ride.
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[raygreenwood]

[ccowx]

If you bend the tabs to limit the travel, it has the effect of shortening the advance curve. Since the distributor will have say, 18 degrees advance instead of 23 or so for a standard 009, you can set idle timing around 12-14 BTDC. Basically, the total timing is the initial plus the total advance. You want that number to land around 28-32, depending on many factors. If you make the dissy have less mechanical advance, you can set the initial higher without ending up at a huge number of total advance and destroying your engine.

Another thing to consider is that by bending the stop tabs, you are effectively cutting off the top bit of advance. This means that if you make the total mechanical advance stop at 18, you are probably achieving full advance at around 2400-2500 or so, instead of 2800-3000 like most 009's. Basically you are chopping around 20% of the travel, so it ends sooner. This might be a good thing, but just be aware of it.

Thanks!

Chris

[Zed999]

There is a disconnect for cammy engines. I see the power/torque graphs often posted here showing engines that "do" almost nothing under 3-4,000 rpm so these guys surely don't care about where the curve ends up as their engines operate at full advance, or they are idling?

Where that curve lies / revs had a huge effect on my stump pulling type engine that operates mostly somewhere on the curve. In fact unless I'm giving it all I'm always somewhere on that curve. Bending the advance stops then rotating the distributor for a higher idle advance messed it up. I would have liked to adjust at the start end but gave up hope of that and bought a programmable 123 which seemed the easiest way to get what I wanted. Not recommending them, I read they are pretty rubbish at higher revs... higher than I ever get to.

[Vanapplebomb]

If you want to stay mechanical advance, the VJU 4 BR 8 (019 with adjustable vacuum advance) from a 36hp bus should work well. They had about 16 degrees mechanical, so with 38 degrees all in mechanical advance, initial timing would fall back to around 12 degrees.

I plan on using one of these on my next 66x103mm T4 build. I have never used an old cast iron distributor on a T4 before, but it looks ideal for someone who wants to stay mechanical and be able to fix it on a trail 50 miles from the nearest road with nothing more than a flathead screw driver.

For more flexibility, the 123 Bluetooth fully programmable distributors are a really nice option.
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[Casting Timmy]

[raygreenwood]

[UK Luke 72]

I have adjusted my idle advance to pull the lowest manifold vacuum. It likes 17º best and I use another 5º when cold to keep my idle speed up. That's on my 2276 with an FK10.
I lose 10-12kPa if I time it to 8-10º
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[chrisflstf]

Pics or videos doing advance mods to distributors would be helpful

[beetlenut]

[j-dub]

I like Ray's point that the timing needs of the engine is very specific to application. I also like that the main point of this thread is that many of the common distributors we use do have some degree of adjust-ability if the user is willing to do some work and accept that it will be trial and error. I assume Tom's statement above was focusing on performance engines likely using dual carbs.

Some general rules regarding timing:
As RPM goes up the timing should go up, as load goes up the timing should come down.
More overlap and aggressive the cam, the sooner you can start to ramp in timing and often will want more initial timing.
The higher the cylinder pressure and high cylinder fill the less timing you need. This is why at a light cruise you can use 40-45 degrees(including the vacuum advance of an SVDA) but with a turbo on boost at wide open throttle you may only need 20-24 degrees.
Larger piston size needs more timing as the flame front has more distance to travel

Idle is a funny area where we are purposely NOT trying to maximize torque so we have torque in reserve as soon as we hit the throttle. If using carburetors it also needs to be set so that the butterflies are positioned right before the progression ports.
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[Ohio Tom]