Does anybody have the specifications for checking mechanical advance on a Ser II distributor - that’s the one for US and Canada - the one without the vacuum canister. I thought this would be easy to find - I’ve got a half full library of manuals, and additionally access to various on line sources but this eludes me.
Some years ago I saved this from somewhere, possibly here on J-L. Title was “Advance Curve with factory spec static timing of 5° BTDC” Cannot swear it is accurate, but it is pretty:
I think you’re referring to 41207. That is what my S2 has. I tweaked the springs a bit and then overlaid the resulting curve with the curve lifted from the above chart (note, this graph ignores static advance which is still 5° BTDC:
I think (seat of pants) that is a peppier curve.
Thanks everybody - this is exactly what I need. Have a friend who just bought a '69 coupe with 14,000 original miles on it and he’s tuning it.
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Terry, the S2 curve is an early emission curve as you know. All wrong for performance. No torque. Although it peaks at 45 all in, its dead until 3k.
My advice is toss the dist. and get something you can work with to tune. Remember there’s no vacuum to add beyond the mechanical. A set of adjustable needles from Joe, and a lot more advance from idle to 3k will make it jump. I’ll post a chart that has Geroge’s as a start. Not sure an S2 needs that 3rd carb if everything else is optimised.
If you’re not caring about originality, might as well get a distributor with a vacuum advance. Once gasoline passed $1/gallon, the notion of a distributor without vacuum advance was recognized for the wasteful insanity it had always been.
Here you go Terry. A 69 should have a 41207. You can see from the chart why its get up and go is lacking.XKE-dist-compare-2-10-11.pdf (13.7 KB)
From what I have read here in other strings on this topic is that the Lucas 41060 from the earlier 4.2’s has the best curve of the period Lucas distributors. I finally found a decent looking used one that I am going to re-build and drop into my '68 to see how I like it compared to the original. I think at first at least I will not hook up the vacuum advance to see how I like it before going to the trouble of drilling and tapping into things for a vacuum source. I plan to swap over my Pertronix module into it that I have been running for several years with no problems. I have never dug into the guts of a Lucas distributor before. I have only played around much with Delco units. Any advice on what to check for ? This is on my to-do list over the next few months.
David
68 E-type FHC
They’re pretty simple devices, but need to be clean with light grease on the weight contacts and pivot points. 40 yr 50 yr old grease will be sticky. Springs can be weak, causing too much advance early.
More importantly the shaft bushing needs to be tight so the dwell doesn’t wander all over.
There’s a rebuilder somewhere (Midwest?) who has parts & knowledge, can’t remember his name. Perhaps someone else knows?
Marcel’s excellent spreadsheet gives applications and advance curves for all Lucas distributors:
Once you get the hang of the columns (RPMs and advance steps) it is pretty easy to compare alternatives.
Two biggest factors are the choice of springs (one fat, one skinny) and the number of degrees advance when the unit is ‘all in’. The latter will be stamped on the cam (in distributor degrees, double it for crank degrees):
Here’s a good tutorial on the subject of Lucas distributors:
As mentioned, springs can weaken (or have been replaced) so you will want to measure several points on the advance curve to see what you have. Moss (and others) sell an assortment of springs that allow for some experimentation. It helps to have a friend with one of these:
But the same result can be achieved on the engine with an advance-dial timing light.
I have spoken to the ‘rebuilder somewhere (Midwest?)’ but was not convinced he could do anything I couldn’t do myself (in one case I wanted a bearing replaced and he couldn’t or wouldn’t saying if a unit had excessive bearing play he just fits a Pertronix). He does polish the distributor body very nicely.
IMO - the distributor is worth digging into and understanding unless you are going with a system that eliminates its features altogether.
I’m comparing the Ser 2 distributor’s curve (the distributor without the vacuum canister) to older Ser 1 4.2l distributors with both vacuum and mechanical advance and find it has a more aggressive advance curve than the older ones. For example (all rpm and advance numbers are engine numbers as opposed to distributor machine numbers) at 1600 rpm the Ser II is 22-26 and the Ser I is 20-24, at 2900 rpm the Ser II is 29 -31 degrees, where as the older one is at 25-29. Maximum advance appears to be at 4400 rpm in the Ser II at 37- 41 degrees whereas the Ser I it occurs earlier at 3600 rpm at 27-31 degrees. (all numbers are out of the Jaguar manual and extrapolated in the case of the Ser I to engine speed).
My conclusion is that the Ser II distributor is actually better for performance than the Ser I. I’m ignoring vacuum advance on the Ser I because that is strictly for economy. Problem with the Ser II is that it’s idle setting is 5 degrees BTDC which will give you a rougher idle. The Ser I curve is very conservative, possibly because of it’s higher compression and for a legitimate fear of poor gasolene in the 50’s and 60’s. You can get better performance with the Ser I distributor by setting idle advance between 15 - 20 degrees BTDC - you’ll get a better idle, but starting becomes a problem. I would not recommend setting the Ser II distributor to earlier than 5 degrees as specified in the manual.
Remember that the critical point for advance is at the peak HP RPM. Jaguar eventually recognized this fact and specified that the V12 H.E. was to be timed at 3000 RPM. Hence, any variances in the advance curves would yield variations in idle timing, not timing at 3000.
Considering compression and octane availability, you’ll probably want to figure out how much advance you need at 3000 or so and work backward from there.
SII’s have a 9:1 CR (mine does) , I don’t believe SI’s, or any other " E’s", were above that.
Marco
All due respect Terry, but how do you define “aggressive advance”? More at 4K+? Then yes.
But it gives up the torque an S1 has from idle up to where the advance curves cross.
An 69 S2 has no urgency to accelerate until its screaming.
If you remember Dick Vandermeyden, he was JL’s Lucas distributor expert. Had one of those Sun machines George just showed us. He told me that the S2 41207 was great for a ported, cammed, high compression engine. That is, someone who didn’t really care what happened under 4000 rpm. I couldn’t find any softer Lucas springs to make changes but my S2 dist. was right on spec at every rpm.
If you agree the torque peak is @2800 rpm, there’s an 11 degree difference in advance between S2 & a Mallory at 2800. 6 deg versus a Pertronix, 5 less than an S-1.
That’s where the issue is.
Hi David My comment was “more” aggressive, and I didn’t mean anything overly significant with it…The Ser II dist. has greater advance at all RPM as compared to the Ser I 4.2l distributor, (which my manual describes as a 41060A) and quite a bit more at 3600 rpm plus, as you have noted. I can’t comment on acceleration of a Ser II - there may be other things that make it slower than the earlier cars - it was reported to be slower by contemporary road tests. The additional advance on the Ser II distributor at the lower rpm is not particularly significant IMO - in the upper rpm ranges it is.
We did a lot of dyno work on XK engines when I was racing. There is power to be made with ignition advance as the stock Jaguar curves are very timid. But you need to be really careful. In mid rpm ranges detonation under load is easily induced - something that hemi’s with their big combustion chambers are prone to.
Terry, An S2 41207 has less advance than the S1 until 4000, not more as you just stated.
Look- there are several reasons S2’s are slower, that ridiculous intake manifold, and one less carb. But the basic engine is the same: cams, pistons, compression, exhaust. It wants the same things as the S1. Hey, a lot of old Jags ran well on 2 carbs, right?
Jaguar was fumbling around in 68-69 trying to lower CO, HC & NOx. The S2 went thru at least 2, maybe 3 iterations. the 41207 was replaced after a short time with the vacuum retard distributor.
If your buddy has an unskimmed head and a good engine it’ll handle more advance, early. At least to S1 spec. And be more much responsive where he drives it. You can see the curve I’m running and my head been skimmed 10 thou. 8.7 and I run 89 octane. Adding the extra advance early knocked time off my 3rd gear uphill roll on ET. I haven’t touched the engine in a decade. I was going to buy a Vette until I replaced the distributor. Wiggy had been telling me.
I thought about adding the 5 or 10 all in timing as you said you found on the dyno. But it just runs so well, and its real hard to hear the ping at high rpm. FWIW
Geo and David thanks very much for the info. I will save it for when I start playing around with the 41060. I do like the way my car is running now but am always interested in ways to make it more responsive but still be able to take it back to original easily. Sadly most of my driving is in the city since I am miles away from open fun type roads.
David
68 E-type FHC