Timing

[Shaunb]

I know this has been covered a million times but I can't find an answer, I have just tried to time mine after fitting a new dizzy, however I have timed it to 30 degrees btbc at max advance with vac hose on, because when I remove it and plug it the engine won't run right coughs and cuts out. Took van out after timing it with vac hose on an runs fine so not sure why I can't do it with vac hose off and blocked.
Any ideas out there


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[Moseley]

Before anyone can help, what distributor is it?


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[Shaunb]

Sorry, was having problems with loss of power so have changed plugs and leads, set valve clearances and removed the electronic ignition dizzy and fitted a new svda accuspark dizzy to replace the one I thought had failed. I had engine at tdc and rotor at no1 on dizzy when I replaced dizzy . Started set timing at 7.5 btbc at idle, plug vac hose Rev engine to 3500rpm, splutters and stops, but if I leave vac hose on runs fine at 3500 rpm. Just thought I had to time it with hose off but I can't.


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[rlepecha]

You do time it with the. vac hose off. Something's not right there, does the timing advance as you rev the throttle without the vac?
Setting it with vac on probably means your idle setting is now well off.

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[Shaunb]

Have not noticed it advancing as it splutters and stops, checked my timing at idle and its now about 2 degrees btdc. One thing I omitted was I haven't got a Rev counter so I've got one ordered


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[Bluesnailman]

I had the same problem with the accuspark. Setting it at 7.5 didn't give me the right advance at 3500 rpm. setting it at 30deg at 3500 and it ran ok, but the idle was close to 0 deg advance (which does engine no good). I checked everything and decided the the distributor didn't give the full range it should have done. its now a spare.

If it is this (and once you've eliminated other probs), then my suggestion is send it back and buy a 123 dissy - its a lot better right from go - idle is rock solid and it advances all the way through the range nicely

 

[rlepecha]

Setting it at 7.5 degrees at idle is nearly never correct for a SVDA. Mines set at 30 degrees max and returns to about 5 degrees at idle.

You say 0 btdc advance is not good for the engine? But VW fitted some dizzys that would pull 5 degrees atdc for emissions purposes didn't they, on beetles they did anyway? So why would 0 be a problem.

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[matt-me]

you do need to know what dizzy it is, they're not all timed the same, info here :

http://www.oldvolkshome.com/ovhignbo.htm" onclick="window.open(this.href);return false;

 

[Bluesnailman]

Setting it at 7.5 degrees at idle is nearly never correct for a SVDA. Mines set at 30 degrees max and returns to about 5 degrees at idle.

You say 0 btdc advance is not good for the engine? But VW fitted some dizzys that would pull 5 degrees atdc for emissions purposes didn't they, on beetles they did anyway? So why would 0 be a problem.

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I think the dizzy with 5deg was a twin vacuum one, and you set it with both vacuums disconnected. connect them back up and the advance at idle changed. Running with not enough advance makes the spark happen to late in the engine cycle - the piston is on the down stroke already so you dont have the power you should have (and I think... it runs hot). too much advance, and your explosion happens before the piston has reached the top of its travel - again a bad thing, in this scenario the piston is pushed backwards - very damaging for the engine.

in your case i wouldn't worry about 2 deg off at idle - you need it right at 3000rpm as this is where you drive it. for this post however, somethings not right.....

 

[bluenose]

I still haven't heard a good reason for timing with vac hose disconnected, I just leave mine on. Maybe someone can explain.

Some dizzy a are meant to idle at 0 also. The single vac dizzy I run does. What carb u got?


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[Shaunb]

Ok update, seeing as I was having trouble just to get a steady idle as I would set it, then bring revs up, it would not return to 850 but sit around 1100 , turns out as bluesnailsman says accuspark dizzy is pants, just don't have the range and won't return to idle.... Spoke to mech friend and I'm going back to points so will update


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[Moseley]

At idle you will probably find that vac hose connected or not will give you the same advance. However, when revved and the timing is set to max advance, this must be done with the vac hose disconnected and plugged as the timing will change dependent on the load. The centrifugal advance is rev dependent only, not load. Timing your dizzy should always be done to max advance of about 30btdc, and then the idle timing should then fall between the allowable limits.

If it's any consolation, I tried an accuspark dizzy and once set, I found that every time I revved the engine up to max advance and let it drop back to idle, the advance readings kept fluctuating; almost as if the mechanism in the dizzy was sticking. Ended up sending it back for a full refund, and wouldn't buy one again - go for the 123 or the latest pertronix unit.


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[Bluesnailman]

shaunb - hope you've found the problem then, bit disappointing though isn't it.

bluenose - imo you're probably about 10deg out. With vacuum hose attached on an engine without load my advance at 3000rpm is about 40deg (and this is about right).

If you've got a few hours I'm sure the answer to this and many others can be found on the samba.....

 

[Moseley]

I still haven't heard a good reason for timing with vac hose disconnected, I just leave mine on. Maybe someone can explain.

Some dizzy a are meant to idle at 0 also. The single vac dizzy I run does. What carb u got?


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Is yours a single vac only, or SVDA? If single vac only, then you are timing it correctly I believe.

 

[Shaunb]

Thanks Moseley, I'm sending it back, just not happy with it, think that's what happening with mine, got it now that I can try and time it with vac hose off but it just won't return to idle, not reliable enough. Think I'm getting a used original Bosch dizzy and points and condenser, in future I may get a 123 , have read good things about it.


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