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Timing adjustment

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bugedd

bugedd

Jedi Knight
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I just drove the bug yesterday after having it apart for a timing cover replace, spin on oil filter adaptor, and rebuilding the radiator, and was it great to drive her. Even better to see the major oil leak is gone, and none of my work leaked!
Now to tune the motor a bit, and get power! What kind of timing are you guys running to get the most out of these motors? Mine is a stock 1275 with header and Weber DGV.
 
7 degrees BTDC is stock.
 
How far advanced are people pushing these motors?
 
The stock value is a good place to start, but you'll have to experiment a bit and find what's best for your car. The fuels today are not like the ones in 1960.
the standard LBC trick is probably as good as any: tweak the advance a bit at a time until you get light knocking on acceleration, then back off until it goese away.
 
Given the sorry state of many distributor advance mechanisms, I think it best to tune for max mechanical advance of about 34 degrees. Remove the vac advance, run the revs up to about 3500 rpm and you should be at about 34 degrees. You can determine this by either measuring and making a mark on the flywheel at the right location, or by using a timing light with built in advance.
 
I don't have a vacuum advance, its mechanical if that makes any difference.
 
davester said:
Remove the vac advance, run the revs up to about 3500 rpm and you should be at about 34 degrees.
Click to expand...
This is essentially the advice Hap gave me for the motor he built for me.
 
When you say that you don't have a vacuum advance--does that mean that it's not connected, or that the distributor doesn't have the big, round thingy (pardon the technical terminology) where the vacuum tube connects?

If the former, you probably will want to hook it up to the vacuum port of the carbs, which is either plugged or is now sucking air at a disturbing rate.

If the latter, I just dunno--as far as I know, all BMC spridget engines had vacuum advance. I don't think there even exists a non-vacuum distributor that will fit. If I'm all wet on this point, someone please let me know.
 
I thought early 948 did not have vacuum advance.
 
The Lucas 23D4 did not have vacuum advance. It was used in the Cooper-S 1275 and I have seen people use it equally well in Spridgets. The casing of that distributor will be stamped 48019.

As above, 32 degrees (or so) at something over 3500 RPM. However, the 48019 distributor has VERY heavy centrifugal advance springs and will continue to advance a bit all the way up the RPM range. Test driving under load while listening for pinging and knocking is mandatory and the timing should be backed off a bit if any is heard.

Remember that this timing method is very dependant on the condition of your engine and the fuel you are using. If you change the grade of fuel you are using you should repeat your test drive under load.
 
I'm not trying to start an argument, but the 45D series had a vacuum advance like the 25D. The 43D distributor was built without a vacuum advance. The Aldon distributor in the Apfast link is a 45D that has had its vacuum advance removed and a cover plate added to the body. Aldon then installs a fixed breaker plate and different advance weights/springs to complete the conversion. Functionally, the unit shown in the picture is a well tuned 43D but it started life as a 45D.

The early 948s probably used the DM2 distributor. I am not very familiar with the DM2. There may well be a version of it that did not have vacuum advance.
 
Running without vacuum advance is fine for racing cars that operate largely at WOT, but for a street car will result in reduced gas mileage and drivability issues. I wasn't aware that the early sprites had no vacuum advance...a little surprising.
 
:iagree: It seems the only dizzy you can get for an old VW is the Bosch 009 with no vacuum. It really makes for a flat spot that almost requires a double pump of the go pedal to get moving. Of course I guess most of the Beetle drivers are at WOT most of the time anyway. :driving:
 
Lawson is correct, the motor is a 1275 with the distributor out of a Mini Cooper S. Perhaps the entire motor is out of that car. Regardless, its a mechanical advance which I think works on a centrifical mechanism. If I remember right, it is stamped 23D4, which is what I researched when I didn't know what the heck was in it. From what I was told, it has a more aggressive advance curve making it a little more performance oriented.
 
It doesn't really matter how "aggressive" the curve is, a purely mechanical advance is unable to respond to load conditions. A vacuum advance responds to throttle opening, providing a significant supplement to the rpm-based mechanical advance. Your car may run OK, but I'm sure it has gas mileage and performance that is subpar compared to the original mech + vac advance.
 
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