Timing a single vacuum advance distributor for a beginner

[Moseley]

Been doing a lot of reading on timing, as finally wanted to get around to checking that all is well on our bus. Maybe I have now done too much reading as I'm a little confused at the results!

So I'm pretty sure I have a single vacuum advance with electronic ignition. With the vac line connected, I'm getting what looks to be about 11 or 12 degrees of advance at idle. Setting the gun to 30 degrees, as the revs increase, the TDC mark comes very quickly into view and lines up - but seems to advance well before 3000rpm. It doesn't move from this point as revs increase though, so hopefully this is a good thing.

Just wanted some pointers really, slightly concerned by the high advance at idle, when I'd assume it shouldn't be advancing at all at this point. I don't have a rev counter, so I guess the issue could be that it is idling a little too high.

Really shouldn't have started tinkering before MOT day tomorrow!

 

[Bluesnailman]

1 you need to disconnect the vacuum connection, and plug the carb suction point
2 at idle, you should have about 7 to 8 deg of advance
so set the distributer there, mark with a dot of tippex on the bottom of the distributor where it meets the base plate - let it dry and score through it with a knife as a marker point. that's your setting/ref point for the future
3 as a check, at 3000 or above rpm you should have around 30deg advance. - you shouldn't need to turn your distributor to get this reading if its advancing properly. You don't really need a rev counter for this as there gets a point where there is no more advance - so just take the engine speed to that point and you should be reading about 30
4 reconnect vacuum connection and tighten you bolt on the dissy base plate

with the vacuum connection in place you will have a greater range in advance, but because its load dependent you can't check it while it sits stationary. Sounds like yours is working though.

From my experience you might not have the full range (eg. you might go from 7 to 27 - if so, set it at 7.5 deg at idle), (if you find you have 7 to 33, then set it at 3000rpm and 30 deg).

 

[Moseley]

Thanks for your reply! I've just tried plugging / unplugging the connection to the carb and the advance is sitting at about 14 degrees - it makes no difference either way. But at idle, should the vac connection be doing anything to the timing anyway?

I tried rotating the distributor to 7.5 degrees, but the engine then runs noticeably lumpier, and the timing marks begin to jump about a bit. When plugging the vac connection back in and revving it up - it advances to about 24 and that's it.

I'm slightly stumped as to why I can't seem to get the base settings without the engine sounding as though it's misfiring.

 

[Bluesnailman]

Are you saying, that with the vac disconnected and timing set at 3000rpm at 30deg advance, when you check the advance at idle you have about 14deg? If you try and drive it, I suspect it will be terrible as its far to far advanced and the spark/explosion will be pushing the piston down long before it reaches the top of its stroke - very bad for the engine.

If this is what you're saying then i suspect your distributor isn't working right..... in which case set it for 7 or 8 deg at idle and take it for mot - at least it will run, and buy a new distributor

must be some other opinions out there - so please remember this is just my experience

Its worth remembering that valve clearance, spark plug gaps etc all need to be spot on before you set the timing, as it could be something else that's making it lumpy. In my case the distributor wasn't advancing properly AND the idle jet in the carb was blocked. Fiddling with the distributor could overcome (not solve, it just seemed to help the engine run o (on what must have been the wrong air/fuel mixture) the carb problem until i went to drive it.......

 

[Moseley]

Nope, I'm saying that with the vac connected, I rev it up and I get 30deg max advance (timing light set to 30deg advance, TDC notch lines up with crankcase join). Following this, at idle, with or without vac connected, it's sitting at about 14 degrees advanced.

If I then try to retard idle timing to 7.5deg, the engine runs lumpy and the timing notches become erratic. I can only get about 24deg max advance at this setting.

I've just driven it briefly set at 30deg max advance and it seems to be running well and pulling nicely. Just doesn't sound too healthy at idle - there's a noticeable ticking that wasn't there before.

I guess what confuses me is that regardless of other settings being off (carb, plug gaps, etc) I should still be able to get the base line distributor setting at idle and max advance when revved up. It seems currently that it is one or the other, and neither are sounding too great.

 

[Bluesnailman]

well, I'm hoping someone else can help, but I think your distributor doesn't have the full range of advance it should have.

In fact, it seems you have a very similar problem to the one i had with my accuspark. I bought a 123 and it works much better

any other thoughts out there?

 

[Moseley]

I think I'd agree - looks like I might need to do a bit more research into the best to swap it for. Have heard SVDA's seem to be the best way to go. Have seen Accuspark ones on eBay, not sure if there are better options out there.

I've tried looking up the part number on mine on the oldvolkshome site - strangely it's not listed so I can't get a factory setting point for it.

For reference it is 0 231 137 037, VW part number 211 905 205P.

 

[Bluesnailman]

http://www.paruzzi.com/webstore/?zoektrefwoord=2246&" onclick="window.open(this.href);return false;

works well, expensive, but cheeper than other places

 

[Moseley]

Wow, that really isn't cheap!

I'm tempted to try one of the ebay ones such as the Powerspark SVDA just to see if that sorts the advancing issue. I have lots of other things that I want to spend my money on currently!

 

[aogrady]

Hi

I've just got a new timing gun where you can dial in the setting, so in theory, once I find proper tdc via pencil down the spark plug on number one, then the mark the pulley to match the notch on the engine case, dial in 7.5 degrees on my gun, point and adjust till white mark is in the center of the engine case, and in theory job's a gud un....

Though need to check tappet gaps first...

Maybe your timing gun is the same?

Cheers

Alistair

 

[aogrady]

Though saying that, as mentioned, 30 degrees is about the max, so if your dizzy gets to 30 max, but drops off much above 7 at idle it propably would be rough to drive? Dunno, I'm in a similar position, my dizzy clamp is crap, and my timing drifts out, now with a new gun, and a spare new dizzy, I can have a faff about with it.

Cheers

Alistair

 

[Moseley]

Yes my timing gun is the same - although I nearly got caught out as the advance knob is very very loose. I took the van for it's MOT yesterday and it drove fine, started fine etc, so I am a little confused about what is going on.

The only thing I haven't checked is spark plugs, and that TDC is where the pulley says it is - just waiting for the right size socket to come through the post.

Having a little read on other websites to try and find similar scenarios, I came across an article that talked about the springs that sit in the distributor to control the rate of advance. It went on to describe what happens if the stronger of the 2 springs fails, and effectively means the engine sits at higher advance at idle, but also hits max advance too soon in the rev range. This sounds just like what I'm experiencing, so will be interesting to see what I find when I strip it down.

 

[Moseley]

Just to update on this, I've just pulled the plugs and checked TDC - all good and lines up with the notch on the pulley. So next step, distributor out and started to strip it down. The vacuum side is working fine, but I've found that once the spring and vac can have been removed, the mechanism is a little tight, and isn't returning under the spring tension alone. So effectively under zero advance conditions, the dizzy is being held in a slightly advanced position. Guess that proves what is going on with the high idle advance reading.

I've begun stripping the dizzy to see if I can clean it out and get it working again, but I can't get the drive tooth off the bottom of the spindle. It seems there is a roll pin that just won't budge. Any tips to anyone who has successfully removed one?!

 

[bluenose]

what carb you got?

 

[Moseley]

It's a 34 Pict 3, albeit a Bocar one rather than a Solex.

Got roll pin out earlier, cleaned everything, re-lubed the spindle and have put the dizzy back together. Straight away the mechanism is much smoother, and it returns to the zero advance (or at least closer to it) than it was pre-clean. i cant get the vacuum can to hold in the fully advanced position, so it may be on it's way out, but I'll get it back on the van tomorrow and see what results it brings.

Fingers crossed!

 

[bluenose]

That's wrong carb for vac only dizzy, u need svda one


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[Moseley]

That's wrong carb for vac only dizzy, u need svda one


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Every day's a school day!

How do you know this though? I've tried searching for some info on this dizzy, and the only reference I can find is on a table listed on thesamba - which states it is for a 1969 1600 bus. As mine is a 1970, I figured it could be original to it. The engine is a 1600 TP, but again, I'm not sure what it came with originally.

Just trying to unpick the PO's changes and figure out what has been done!

 

[67westy]

That's wrong carb for vac only dizzy, u need svda one


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From the earlier description it sounds like an SVDA to me as when revved with vacuum plugged it advances to 24 degrees. Suggests there is a mechanical advance as well

 

[Moseley]

That's wrong carb for vac only dizzy, u need svda one


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From the earlier description it sounds like an SVDA to me as when revved with vacuum plugged it advances to 24 degrees. Suggests there is a mechanical advance as well

Sorry - descriptions earlier in the thread probably weren't clear enough. It is vac advance only, the canister had to be plumbed to the carb to get it to advance when revved.

 

[67westy]

Sorry - descriptions earlier in the thread probably weren't clear enough. It is vac advance only, the canister had to be plumbed to the carb to get it to advance when revved.

Ahh my bad, probably not the best distributor for the carb then.