Ignition timing

[Derek UK]

Originally Posted by packers1712

https://photos.google.com/photo/AF1Q...xpv6UTBI9IHsuc

Try this link for the video!

Doug.

Link doesn't work for me.
Note that the dizzy has a light and a heavy spring. The light one controls the early part of the rev range and the heavier one takes over as the revs rise. This gives the ignition advance curve. Yes, wear will change this curve. Weights wear, the hole gets worn and maybe a little of the actual weight in the process, The posts that the springs fit on also wear which can give minor changes to the spring rate. Make sure the weights and springs are fitted in their correct positions. The correct weights and springs not easy to find new now days. These engines will tolerate quite a bit of dizzy wear. The shaft can wobble about quite a lot but that will affect the timing to each plug as the points gap varies. If your dizzy will take a Pertronix that will help counteract the wear a bit but it is still only a switch. For this reason, the advertised "improvements" you are supposed to get with electronic ignition of this type are usually in the mind rather than real. The fully mechanical B18B dizzy (no vacuum mechanism) is the best one to run with twin carbs and suitable cam. D cam can give a lumpy tick over apparently.

[packers1712]

Hi Derek,

Its a shame the link didn't work, but you might be able to see from the pictures of the CA assembly in the thread earlier that the two springs are indistinguishable and the entire set up isn't like all of the literature for Bosch distributor CA service and repair guides.

I already have the Petronix electronic ignition fitted so hopefully any shaft wear causes minimal upset, I'm at the point where I'm going to fit what I've got and retest and hope for the best, if it isn't successful then I may well opt for a123 distributor!

Thanks Doug.

[packers1712]

Just a quick update, the alternative distributor is back in my car and on first impressions appears to be performing correctly, idle timing check with a strobe is stable and I have plenty of advance available and have currently set it at 33 at 3500rpm a road test will establish if I can go more if I haven’t got any pinking.
I attempted to set the static timing so that I could rule out that I wasn’t experiencing any CA at idle but must have gone wrong somewhere as when I’d followed Ron’s tutorial then moved to the part where I start the engine and check idle timing with a strobe it was at 31 degrees and difficult to start!
I need to re-visit that test at some point also worth mentioning my cars settings regarding distributor position aren’t as per factory so I’ve improvised as per his alternative positioning section!

Doug.

[Derek UK]

Sounds like this "new" dizzy will be usable. The trick of twisting the dizzy to set the timing with the engine running can catch you out. This is where your 31 degrees might have come from. You twist the dizzy to get a faster tick over and that over advances the timing, hence the hard start. Although it is best to follow the written instructions you will be very close if you position the dizzy where it is shown in official Volvo photos. #1 plug wire is about 11 o'clock and the 4 wires are slightly rotated anti clockwise from centre. That will get the engine started and proper timing will only be a fraction off from there. Remember, 1 degree of dizzy turn is 2 degrees of timing so it is a very sensitive adjustment.

[Ron Kwas]

Doug;

If you've followed my Static Timing tutorial (which will also work with an electronic Dist or ign module installed) , you KNOW timing is wherever you set it, but then after starting, find Timing to be at 31Deg when checked with Timing Strobe, that suggest either CA is immeditely going to max (because it has zero spring-return force holding it at min at Idle), OR perhaps Timing Gear is loose on Cam, and is allowing relative motion (this is typically accompanied by noises which cannot be overlooked/ignored!) ...I mean, what else could it be?

Good Hunting

[packers1712]

Originally Posted by Ron Kwas

Doug;

If you've followed my Static Timing tutorial (which will also work with an electronic Dist or ign module installed) , you KNOW timing is wherever you set it, but then after starting, find Timing to be at 31Deg when checked with Timing Strobe, that suggest either CA is immeditely going to max (because it has zero spring-return force holding it at min at Idle), OR perhaps Timing Gear is loose on Cam, and is allowing relative motion (this is typically accompanied by noises which cannot be overlooked/ignored!) ...I mean, what else could it be?

Good Hunting

Hi Ron that was my fear that there is something else causing a problem but I’ll have another go at it when I get a chance just to confirm before I condemn it, at the start of tutorial you say set the engine to ignition point for number 1 cylinder is that 0 on the front crankshaft pulley or whatever angle the basic setting should be (eg 10 degree mark on the front pulley) ?

Doug.

[Ron Kwas]

Doug;

The ign point for static timing is the same as what you want it to be at idle (since CA will not have centrifugal force to have an effect yet at that low Dist rev), so whatever your engine calls for in the tune-up specs...but 10Deg will certainly allow starting...again, once the static timing has been performed, you should be able to confirm your static setting withing a degree or two with your timing strobe at idle, and if it is already 30Deg at idle (dynamically), either there is something wrong with your method of static timing (and if it turns out that my procedure is subject to misinterpretation, I will certainly improve it to make misinterpretation less likely, but I have had no feedback to suggest this until now)...or something else is amiss as I mentioned before, because there would seem to be no mechanical force holding the CA at Min...to check this, with Dist Cap removed, why don't you turn the Rotor CW from its rest position and see if: 1. you feel spring return force, and 2. if this force returns the Rotor to its starting position. That is a rudimentary check to establish free movement and return springforce.

I presume you've seen the info on CA here: http://www.sw-em.com/Volvo%20Ignitio...ugal%20Advance

Good Hunting!

[packers1712]

Further update on the ignition timing, I have revisited the static timing setting tutorial in Ron’s web page and executed it with success so thanks Ron!

Just trying to decide if I’m going to persist with the DCOE’s, if I’m doing some spirited driving they’re great but most of the time normal driving is better with SU’s, the brake servo isn’t as good on the DCOE’s either and it has this symptom where when turning sharply right it feels like one of the carbs stops working almost as if the float chamber has emptied but I’ve checked and it isn’t!

Doug.

[Ron Kwas]

Doug;

Congrats on getting it timed and Ign working as expected...and thanks for the kind words! If you can think back on what you were getting wrong before, when it wasn't functioning properly, I might add an emphasis to the Stat Tim Insts to avoid this, and improve the instructions...

Re carbs...If most of your driving will be normal, with only "Occasional Spirited Squirts", I suggest DCOEs are just more than needed given the amount of effort necessary to optimally tune and operate them (and if not yet installed, they would need to be paired with a free-flowing exhaust for you to really see full potential improvement)...it's just not worth it IMO! There is also value in being able to say you have a "factory stock setup" because the standard SUs (in good working order and tune) are quite good, including for those OSSs! If you're not racing...why would you do the expense and effort to yourself?...again, it's just not worth it IMO for only bragging rights when you open the hood! Having the DCOEs would likely also put you in a different class for those weekend hillclimbs...

As far as cutting out on hard rights, make certain it's not your Ign Sys (loose wires grounding out or somehow loosing connection etc. Tip: Connect up Timing Strobe and locate it where you can monitor the hopefully steady flash during cornering!)...short of a partially clogged Jet Supply Tube, or some Linkage issue, I can't really think of what might be direction or "G" dependent in the carbs...Good Hunting!

Cheers and Happy Christmas