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It is known that VW engineers slightly retarded the timing to #3 cylinder
to help protect against this cylinder from running too hot and burning up exhaust valves. #3 was known to run hotter since it is cooled by air that had exited from and been warmed by the oil cooler which was directly in the air path from the fan shroud.Kent, you said in another thread that: “The retarding of the timing on the #3 cylinder on the 009 is done my slightly offsetting the location of the sparkplug wire on the distributor cap.” Since the distributor only distributes the spark to the correct cylinder, I don’t think that this is correct. Or, I don’t understand how that would work. (Of recent, it seems likely that I don’t understand.)
I don’t remember where I read it, but have always thought that it (the retarding of #3 compared to the other cylinders) was done by an asymmetrical grind of the distributor lobes, just under the rotor, that the points ride on.
I do not know which of the many VW distributors incorporated this feature. One could figure out if and how much retarded #3 is with a degreed pulley wheel by setting the timing on #1 and then moving the pickup to #3.
And, it seems that those who run Pertronix electrical pickups instead of points have defeated this protection of #3. I run Pertronix and like it, but have never really thought about whether my #3 is still retarded, until now. I have a ported, unknown cam, Holly Bugspray 2bbl, EMPI 4387 exhaust, 1600 non-doghouse engine and am concerned about #3. I have considered putting a #3 cy head temp gauge on, but you guys are already making fun of me with 5 gauges, not including speedo and tach.
Royal 2015-05-08 16:01:14 I’ve been doing a bit more research on this subject.
See: http://www.volkswebbin.net/topic/79132/distributors-and-number-3-cylinder-retard/
Seems that distributors manufactured with the doghouse (1971 and later) do not have this #3 retard feature since the oil cooler had been removed from the air path to #3 cylinder.
Royal2015-05-08 15:59:33
I’m certain I don’t have the doghouse cooler on the fan shroud, at least not like I’ve seen pictures of.
I don’t think the distributor lobe itself could be changed in a way to do this since it has only one high spot to open the contact points. EDIT: wrong! Sorry everyone. My thinking was way wrong on this, see my later reply. 4 lobes, 1 for each cylinder. Now I know how the #3 could be different!KentT’s explanation of offsetting the distributor cap #3 tower makes plenty of sense to me. Just that it wouldn’t coincide exactly with the points opening and closing, meaning some kind of change to spark power produced. Maybe…?LRH2015-05-08 23:50:27
Guys, I wouldn’t sweat the whole retarded #3 timing, either way. The amount that it was retarded was very slight – I seem to recall 3 degrees, but that may not be correct.
This was first done on the stationary engines that would sit and rn for hours at 3000 RPM plus. Then, they implemented it on the vehicles because of the problems with #3 cylinder that didn’t occur on the other cylinders. Burned exhaust valve (which would lead to dropped valve and busted piston if not found and fixed) and pulled head studs being the biggest issues.
If you’re keeping your valves adjusted, and not noticing the #3 exhaust valve tightening up (I.e. valve stem stretching) then you’re fine. I’d be more concerned about sealing the engine compartment to improve overall cooling than worrying about the specific issues of the #3 cylinder…
Early FF TDr on 69 VW pan
Slowly coming back from the ashes...Wow. Was I ever thinking wrong about the cam lobes inside the distributor. Finally realized these have 4 high spots, one for each cylinder, in a rounded square shape.Been soooo long since I’ve dealt with this stuff. So it’s like my ’69 Toyota 4 cylinder that I’ve forgotten all about! Silly really, that I could think a single lobe could work anyway. Dang. Can’t believe I haven’t seen a points distributor in some 20 years or so… and that was a 4 cylinder I/O boat motor.I’m going to do what I can to separate the fan shroud (front to back) and prevent hot air from getting to the fan intake. Right now there’s a considerable space between car shell and shroud, especially on left and right sides where all the heat is generated.In my own search for answers I found a message thread at http://www.thesamba.com/vw/forum/viewtopic.php?t=471555 showing a page from a service manual, says “4 crankshaft degrees” in it.
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