Adjusting points (and ignition timing)

[J. Huber]

This is probably basic stuff for most of you but new territory for moi.

First off, manual is calling for lobes to be exactly on "block" so the gap is at its widest... I turn the engine by hand to get there? correct? And if so, how praytell. Automatic. Do I need a large socket to go on one of the fan belt pulleys? Help. Thanks

Note about this thread: It began as a basic how-to for adjusting the points but has gradually led to a discussion of setting the timing once the points are adjusted correctly...It made sense to keep the two together.
 
James

James
63 230SL

[George Des]

James--there is an easier way. What I do is loosen the distributor bolt and turn the whole distributor until the points rubbing block is on a high point of the cam. Then I set the points with a feeler guage and tighten. This should get you in the ballpark for an accurate dwell angle reading.  Now you need to check your dwell setting with a dwell meter and it is off, you can loosen the points just enough to allow slight adjustments with a flat bladed screw-driver against the two little pips on the points frame. You can now set the timing by rotating the whole distributor while aiming your timing light on the front timing marks. Regardless of what the points gap is, the dwell angle reading is much more important to smooth running.

George Des

[J. Huber]

Thanks George. That does sound easier. Unfortunately, I won't be taking Timing Light 101 until next semester... (don't even have one yet).

However, I did figure out I needed to buy a 27mm socket to turn the engine. I also picked up some feeler gauges and a file. And then the fun began. My dwell meter was reading 28 -- and when I looked at the gap it was kind of gappy (over 016). So I tightened the gap to about .012 -- re-read the dwell...it said about 37. Wow that was easy, I thought. So I took a drive, it ran really good. Then, like an idiot, I decided to fiddle some more hoping for 38. Realized that that first adjustment was really lucky...I must have redid the gap 10 times -- with it going from low 30's back to 40s -- but never near 38. I even tried a drive with it at 40+ to see if it was close enough. Major sputtering. I was smart enough to put all my tools in the car on the test drive -- so I pulled into a shady parking lot and tried again. Finally got it to 38. Closed everything up (fast). No more sputtering, so I am claiming victory! And do I get some kind of shade-tree mechanic badge?

Having adjusted these (ad nauseum) -- my next lesson will be putting a new set in. Is it straight-forward?

PS I noticed a "nib" on one of the contact points -- would I want to file this or leave it? Thanks.




James
63 230SL

[Ben]

quote:PS I noticed a "nib" on one of the contact points -- would I want to file this or leave it? Thanks

.........I normally file them flat as its hard to get an accurate gap if there is a slight "nib" there !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[al_lieffring]

quote:Originally posted by J. Huber

Thanks George. That does sound easier. Unfortunately, I won't be taking Timing Light 101 until next semester... (don't even have one yet).

However, I did figure out I needed to buy a 27mm socket to turn the engine. I also picked up some feeler gauges and a file. And then the fun began. My dwell meter was reading 28 -- and when I looked at the gap it was kind of gappy (over 016). So I tightened the gap to about .012 -- re-read the dwell...it said about 37. Wow that was easy, I thought. So I took a drive, it ran really good. Then, like an idiot, I decided to fiddle some more hoping for 38. Realized that that first adjustment was really lucky...I must have redid the gap 10 times -- with it going from low 30's back to 40s -- but never near 38. I even tried a drive with it at 40+ to see if it was close enough. Major sputtering. I was smart enough to put all my tools in the car on the test drive -- so I pulled into a shady parking lot and tried again. Finally got it to 38. Closed everything up (fast). No more sputtering, so I am claiming victory! And do I get some kind of shade-tree mechanic badge?

Having adjusted these (ad nauseum) -- my next lesson will be putting a new set in. Is it straight-forward?

PS I noticed a "nib" on one of the contact points -- would I want to file this or leave it? Thanks.




James
63 230SL

Back in the day when I was replacing the points in dozens of these cars every week, I would set the dwell as close to the low end of the dwell range as I could. Because as the fiber block that rubs on the cam wears down the dwell increases. So this way the points will stay in range for a longer time.

If your on the side of the road trying to get the car running file the pip of of the points, otherwise it is best to just replace them along with a new condensor.

FYI   a good side of the road point gap gauge is a match book cover. very close to .016

Al Lieffring
66 230Sl
Jones'n for a new gas tank

[TheEngineer]

IMHO the gap is obtained automatically when you set the dwell to the correct amount (38 deg) because the geometry of the cam and points determines it. It is sometimes difficult to accurately measure the gap and the points surface can be contaminated using a feeler gage. Don't ever use sandpaper to clean the points: Big time contamination. Best to get new new points when they are worn excessively. They should last years. It's also difficult to see the timing marks using a timing light unless you have your eyes on a stalk like a snail. It's easy when the hood (bonnet) is removed. There is no reason why the timing should change once you set it right.

'69 280SL,Signal Red,Automatic,retired engineer, West-Seattle,WA

[J. Huber]

Good stuff guys, keep it coming! I a total neophyte -- so any little bit is huge. But a few questions in response to your input:

Engineer -- How can you set the dwell without doing the gap first? The way I am doing it is: guestimate a gap (I knew 012 to 016 was close, so I used 012) then close everything up, start car, put dwell meter on...Repeat if nec. (several!)

Ben -- do you take the points out to file them? My "pip" is so obvious that I placed feeler away from it. The idea is there is a corresponding hole on the other side? Not really sure since I did not take them out.

Al -- by low end of dwell would you mean around 35?

Anybody -- if I take old points out and put new ones in, is it just a matter of some screws? Then reset gap? Or will new ones "require" adjusting timing -- if timing is good now? Because like I said, have no idea about timing yet... Thanks.

Oh, and when I am actually adjusting the gap, I am loosening the screw near the contacts and sliding the stationary bracket away from the pivot arm, fiinding a gap, the n tightening that screw. Is this correct? The manual shows another screw #2 but I don't see it.


James
63 230SL

[TheEngineer]

1.don't touch nothin. 2. hook up dwell meter. 3.start engine & look at dwell meter: If dwell is more than 38 deg: stop engine, increase gap by a very small amount and recheck. With a little practice you can eyeball the correct gap. That's it !

[J. Huber]

Thanks Engineer -- I think I see what you mean. That's pretty much how I started the process but was using the feelers to get an idea of the gap. My ultimate goal was the 38 -- the gap was secondary.

The parts that slowed me down a lot was A. Having to turn the engine each time to hit the lobe and B. I stink at guessing the gap...

James
63 230SL

[George Des]

As I said in my post, the dwell reading is so much more important than the gap because it will take into account any wearing of the points, cam or the cam block. There is an inverse relationship between the dwell angle reading and gap. Easier way to remember this is "bigger gap-smaller dwell" and "smaller gap--bigger dwell". This may help you remember which way to adjust the gap after you take a dwell reading. Also, there is some relationship between the dwell angle and the timing, so the points should be set first. After doing this many times, you can just about make the timing adjustmment by sound and feel rather than by using the timing light. Many even find that the factory timing specs do not give the optimum running. Hope this helps.

George Des

[graphic66]

The dwell angle is the number of degrees the points remain closed on each lobe, in relation to the distributor rotating 360 degrees. I like to set the dwell first by removing the cap and rotor, don't forget to take the rotor off! Then while using a screwdriver in the adjusting slot with the points just tight enough so they slide with the screwdriver have an assistant turn the car over with the starter while you read the dwell and adjust the points to your setting. Then tighten the points and assemble the distributor and recheck. If you find the dwell has changed you then do the adjustment again, while adding or subtracting the running reading from you starter reading. So, if your starter turning over read 38 degrees and when running it reads 44 degrees, set it while turning over with the starter at 32 degrees and recheck. Just remember to remove the rotor or when you have the screwdriver in the adjusting slot and the car turns over you will break your rotor against your screwdriver. This has been my method for many cars and works pretty good most of the time. Just don't overheat your starter or overwork your assistant.

[TheEngineer]

Graphic66: Now there is a good idea! I never thought that I could check dwell with just cranking it. On this li'l red car of mine, I usually just pull the connector on a relay, insert a wire & touch it to the pos. battery. It's the same as energizing the lead to the thermo switch. That way, it doesn't energize the fuel pump or the ignition circuit.

[J. Huber]

So, Graphic, are you saying you can read the dwell with the cap and rotor off? and turn the car over with things apart?

And what is this adjusting slot you speak of...is it that little oval hole near the second screw? I've been pushing the bracket to move the gap.

George -- thanks for the "bigger gap -- smaller dwell" mantra. That explains why when I had the initial 28 dwell -- the gap was gaping. But is it more common for the dwell to go out of whack higher than 38? As I have heard the concept of the "points closing" as the cause for really crappy performance.

James
63 230SL

[TheEngineer]

Just came out of the garage: My dwell meter doesn't read with the ignition off and so I just started the engine. It reads 42 degrees and doesn't change much with increase in RPM's. So, I consulted the BBB: Interesting, it says: (for my '69 with regular ignition) set points, when installing new points, at 40º and don't touch them anymore. When reading the dwell on used points it should be between 34º and 41º. When the reading reaches the lower limit, replace points.
I can't remember when I installed new points. It was a long time ago.

[Naj ✝︎]

For me, the easiest way to set or change the points is to pull the distributor out.
But first, turn the engine to #1 on TDC on the firing stroke. The rotor notch on the shaft should line up with the mark on the timing mark on the distributor body (See picture. Also note, points about to open when shaft rotates clockwise - firing point!).

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Do the business and reinstall at the same spot. Now, get out the strobe and fine tune....

naj

68 280SL

[George Des]

Naj,

You're basically doing it the same way I do i.e rotating the cam without having to turn the engine over. I just dont't pull the distributor out although I have in the past done it that way once or twice. This beats the heck out of trying to do it with a remote starter, helper, or big wrench on the front crank and you can be absolutely sure you get it dead on the cam high point when you do it this way.

George Des

[enochbell]

Just my 2 cents:

I always did my first setup on new points by setting the gap with feeler guage, then cranking the engine with the dist. cap off (and protected from possible arcing) to get a reading on the dwell.  Then I adjust the gap to get it closer to 39 degrees, then replace the cap and start the car to get a good reading, then adjust as necessary.  Usually meant only having to r&r the cap once for adjusting.

But I also used to set the gap on my '67 VW with a matchbook cover (a very handy and inexpensive feeler guage) and the timing by ear, so what do I know.

g  



'64 230sl, fully sorted out...ooops, spoke too soon

[J. Huber]

Thanks again folks. I am starting to think that knowing how to use a strobe light is part and parcel of getting the points done quickly and easily...

And Naj -- I borrowed your pic for this:

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PS does arcing mean I run a risk of being toasted. Final request -- bury me in my Guzzi...

James
63 230SL

[Benz Dr.]

I like to set the dwell around 40 degrees. The points are closed a bit more but if you have any real wear inside of the distrbutor this will help to keep the points from bouncing at higher RPM's.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[enochbell]

James,

You can't lose by buying the best strobe light you can afford.  I am sure a really experienced mechanic can set the timing by feel, but for us mortals there is no way to get it right without the strobe.  It also will let you learn something about the health of your advance mechanism by telling you when and how much advance you get.  I would start by cleaning and painting the timing marks on the harmonic balancer, that will let you see what is going on much better, as you have a tough angle to shoot the light and see the marks.

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[Naj ✝︎]

James,

Look at the two 'pips' below the adjusting screw in the picture. There should also be a 'cut out' in the base plate of the points.
You can use a flat bladed screw driver between the pips and the slot to make minute adjustments to the points gap with the screw slightly loosened.

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quote:Thanks again folks. I am starting to think that knowing how to use a strobe light is part and parcel of getting the points done quickly and easily...

Any time you tinker with points is going to change the timing, so a strobe is worth having. You can also check the centrifugal and vacuum systems as stated by enochbell.

naj

[waqas]

Greg,
You say that one should get the "best strobe light you can afford"... are there differences between strobe lights? (besides durability)

Is there one you'd recommend?

WAQAS in Austin, Texas

[enochbell]

I am not an expert, but I have a Sun light that is superb, and I have had it for 25 years.  They have probably made a few improvements since then   but I just remember that there were cheaper ones that were not nearly as bright (I found that out the hard way by buying a cheap one and returning it) so that is why I offered the comment.  Perhaps there is a more current opinion from the board?

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[Ben]

The method George Des describes is my method, by far the quickest and most accurate.

To simplify, the "gap" is only created to provide the correct dwell, which is vital. So the gap setting is a rough approximation given so that folk without a dwell meter can set things up pretty accurately.

The thing is that the points gap generally closes up over time, through wear on the plastic block/heel and through the transfer of material from one side of the points to the other.

The result is that your dwell gets bigger, your spark is possibly not as good in theory and your timing retards.

However Dan makes the point that a smaller gap/bigger dwell will make a worn dizzie perform better, and he would know, but the scret here would be of course to still have correct timing !

Also when you set these things and tighten, the start the motor and recheck..........things will always have shifted. Each car is slightly different so playing around with things can make a small but worthwhile difference.................or none at all !! :oops:



Regards,
Ben in Ireland.
'64 230SL 4sp.

[hands_aus]

Hey Naj,

Is that a 230sl distributor?

I am confused as the points and vacuum unit on my 250 were pointed the other way.

Are they different on a 230sl?

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto