Miscellaneous Tune-Up Information

A couple of interesting snippets from the Aussie repair manual -

• The points should always be set BEFORE setting the ignition timing, as just a .004" alteration to the points gap makes a 3 degree change in the timing. (I'd knew it alters the timing but had forgotten it was that much).
• It is preferable to set the timing on a cold engine using the static timing method. Using a stobe timing light on a cold engine will result in alterations over the whole setting range. The engine CAN be set when warm, so long as the oil temp is below 50C/112F.

Can you tell me the procedure for adjusting the idle and timing on a '60 36hp motor?

These came with either a 28PCI or 28PICT carburettor (probably 28PCI, since the 28PICT first came with the 40hp 1200).

The later 30 series carbs, and the modern replacement H30/31 should also work on this engine - with suitable jetting. The last of the 30s - the 30PICT/3, plus the H30/31 have two adjusting screws, so the setting process is the "two adjusting screw" procedure (on our web site).

To my knowledge, timing is 10BTDC (if you have a vacuum distributor), set static (or at idle with the vacuum line removed and plugged on the carby - open on the distributor).

For a 009 distributor, you set the max advance at 28-32 degrees at 3000+rpm, and let the idle fall where it may (usually somewhere between about 5 and 10BTDC).

Idle rpm should be about 800-900rpm. You use the throttle arm screw on the rear (rear is rear of car) to set this (28 and early 30 series carbs - you DON'T use this screw on the 30PICT/3 or H30/31 for idle speed adjustment - that's what the second (larger) screw in the left side of these carbs is for).

For setting the carby (28s and early 30s), you can use the "one adjusting screw" procedure on our web site.

I've read a couple other places that the timing should be set at 7.5 BTDC. Are you sure about 10 BTDC?

10BTDC is used on the 1200cc engines which have lower compression (6:1 and 6.6:1). Low compression needs more advance than higher compression (relates to the larger proportional head volume on low compression engines, and the amount of residual burnt gases being mixed with the fresh stuff which lowers flame speed).

The 1300/1500/1600s engine all had compression of 7:1 or higher, and 7.5BTDC is normal for these.

I accidentally timed on the #3 cylinder -- is it possible to time on cylinder #3 as well as #1?

Timing on #1 is really "tradition" rather than "necessary," EXCEPT for cars with the in-shroud oil cooler, which heats up the #3 cylinder. These cars have the older style 3 degree-retard distributor (which prevents detonation in #3 cylinder), so the timing HAS to be on #1.

One good trick I use is (once you've sorted out the leads) to wrap each lead at each end with some thin copper or other wire, plug lead 1 gets wrapped one turn, plug lead 2 gets wrapped two turns etc. and then twist the ends to gently grip the plug lead (that's why I use copper it twists easily). Do it at each end of each plug lead. Then you don't have to 'follow' leads to work out which lead is going to each plug, and if you pull off all plug leads when you change plugs you don't end up trying to put No4 lead on to No3 plug etc.

The spark definitely happens when the points open -- the magnetic field in the primary of the coil collapses and sends a surge through the secondary to the plugs. Theoretically you COULD get a spark from the points connecting, but the magnetic field builds up more slowly than when it collapses as the points open, so that's when you get the best spark.

It's not idling cold at all well right now -- better when it warms up.

That could be as simple as rotating the choke canister a little to get an extra step on the stepped cam when cold. Or a tad more idle rpm on the big bypass screw.

The mechanic my son took the car to said it's "cold-blooded." Now THERE is a useful bit of technical data! :-/

On Saturday we're going to get it nice and warmed up and then I'm going to slap the instruments on it to see where things stand. It's always "liked" a somewhat higher idle speed, so maybe it's having trouble because the guy set it right on spec. We'll see.

Try looking at the choke before you start it up - just pull once on the throttle arm to see how "closed" it gets. Then do the rest with the engine warm.

The Bug is running great except for it's "cold-bloodedness" in the morning. We drove it out to work the other day and then, when it was hot upon our return, I slapped the dwell/tach and timing light on it. I was rather astounded at what I found, given that the mechanic my son took it to adjusted the dwell and timing. I found that the idle was at about 1200 rpm, the dwell at 30 degrees (!), and the timing at about 10 degrees BTDC. I'm amazed that it's running so well!

Hmmm - certainly not very close to the mark. Dwell should be 50-52 of course. The slight advance on the timing might just be the result of the rubbing block wearing which would ALSO cause the reduced dwell. Try adjusting the points and see it that fixes both, before you touch the timing.

The dwell, timing and idle are all interrelated, and I'm never sure which to adjust first.

Points gap (dwell) first, then timing if it needs it (the timing will probably be MORE advanced after the dwell is set).

Narrowing the point gap to produce a dwell of 50 degrees will surely affect the timing, which (if I remember correctly without my books) should be 7.5 degrees BTDC with about 30 degrees of advance at 3000 rpm.

7.5BTDC - yes. The upper end will probably be over 30, since that's the centrifugal amount only - the vacuum adds about 8 to that as needed. So if you time it at 7.5 then get it up to 3000+ rpm then blip the throttle about, you should see it jump about from roughly 30 to 40 degrees as the vacuum cycles. A little over 40 is fine.

But first, while the car is cold, I'm going to take the nice new air cleaner off :-) and check out the choke, per your advice. If the butterfly is opening too quickly, that could account for the "cold-bloodedness," right?

Yes - the choke opening before the engine is really warm. Probably partly related to the aftermarket air filter you had which doesn't have the warm air induction paper tube - that gets warm as soon as the heads do, and helps vapourise the fuel until the engine and heat riser are fully warmed up. (I presume that the inlet warm air tube is not connected?

Speaking of the air cleaner -- the mechanic didn't attach the vacuum line to the port on the intake manifold -- it was just tucked up under the clip on the air cleaner. The new air cleaner seems to have solved the problem with oil blow-back, though.

That's the vacuum switch tube for the warm-air inlet you mean? (I presume he did have the distributor advance line connected to the left port on the carby).

If that warm-air vacuum tube was left open from under the carby, it would be causing a massive air leak - lean mixture. If it's not used, that manifold port has to be plugged. (Lean running means HOT - could that be the cause???)

First thing I removed the air cleaner, and with the engine stone cold found the choke butterfly wide open, standing straight up!

Oh, boy -- who gave that guy a mechanic's licence!

The inlet warm air tube is not connected. That was one of the things I wanted my son's mechanic to be sure to do when he installed the new air cleaner, but it didn't happen.

Our new stock air cleaner has a vacuum line that runs down to the port on the intake manifold, right below the carburetor. I had assumed this was to provide vacuum in the air cleaner to assure that air/oil was sucked from the crankcase, thus preventing blow-back through the crankcase vent behind the pulley. I thought this might be the source of the oil on the engine tin, since the aftermarket air cleaner didn't provide for this.

That under-carby vaccum line should be connected to a temp sensor switch built into the standard air cleaner. That switch has TWO vacuum line connections - the first one up from the inlet manifold, and the other to the flap in the air cleaner inlet. So when the temp sensor is cold - the vacuum switch is open and the air cleaner flap gets vacuum and moves so that warm air is pulled up from the cylinder head area. As the air inside the air cleaner warms up, the temp sensor closes (or partly closes) the vacuum line switch so the flap moves over for cold (or mixed) air. This means the carby is breathing air at a near constant temp, making it easier to set the carby for just the right mixture, since they don't have to worry about air density so much. Aftermarket air cleaners usually miss out on all that stuff.

The other connection to the standard air cleaner is the breather from the oil filler neck, and this is a much larger pipe than the vacuum line.

The two types of connection have nothing to do with each other - the vacuum line does not create any vacuum inside the air cleaner - it just attaches to the sensor switch which looks at the air temp inside the cleaner.

The "vacuum inside the air cleaner" you mention (for scavenging the crank case) is provided only by the carby pulling air through the cleaner.

The distributor advance line is connected properly to the left port on the carburetor.

OK -- so at least the distributor will be advancing normally.

The vacuum port on the intake manifold was plugged. Now I have a line attached to it running up to the air cleaner (as per the original design, I think).

OK. It can stay plugged and unused but that would result in cold air to the carby inlet all the time (OK for warmer climates but would be a large part of the "cold blooded" problem.) In this case, the vac line to the air cleaner sensor can be completly removed and the port in the inlet manifold plugged at the manifold.

I have the older wire-pull system on my cars (attaches to the right side cooling flaps), and on Bradley that wire is missing, so I have "continuos cool" to the carby. Works OK in Adelaide, but I have a little wire hook on the inlet flap I can use to shut in manually (for full warm intake) on really cold days - haven't needed it yet. This older method gives only hot or cold (the flaps are only open or shut so the pull wire is in or out) - not mixed like the vacuum operated system can.

I continued to work with the engine cold. First I got out the handy-dandy little points setting kit that I've had ever since my '65 Bug. It has a sleeve that fits down over the shaft that the rotor sits on ...

I've never heard of a device like that - sounds very useful.

Anyway, the point gap was way too wide, which the dwell of 30 degrees indicated. And the guy had tightened the adjusting screw so tightly I could hardly get it loose - finally succeeded, but I'm going to have to replace that screw - it's pretty buggered up. I reset the points, then statically timed it at exactly 7.5 degrees BTDC.

Why do people overtorque stuff all the time - it just doesn't make sense. That's a small screw, and has only light spring pressure on the plate it has to hold, so only needs a few ft-lbs to hold it still.

The next thing I found was that the little screw on the top of the throttle lever was backed off from the cam about an eighth on an inch! Where this guy got his mechanic's credentials I sure don't know.

We are both on the same wavelength there - I think your son should find a new mechanic if he is ever takes the Bug back to college!

So I fixed that per the procedure, then started it up. Ran great, except still "cold-blooded." So I turned the choke element counter-clockwise another eighth of an inch or so, and that, plus a tweak to the volume screw, did it! It's running like a new car - better than it EVER has. I'm delighted!

Isn't that a great feeling - I just love it when I've worked through a frustration and it WORKS :-)

The only problem we had I hope you can give me some insight on. I had a problem with my glasses - the right lens fell out and smashed on the floor while we were at the Post Office, so my son and I beetled over to my optometrist. There my son parked in a spot that was sloped, the engine end down. When we came out the car wouldn't start - acted for all the world like it was flooded. So we pushed it around facing the other way, and after a couple more tries it started right up. I'm hard pressed to understand why the carburetor would flood under those circumstances - even if the gas would tend to drain toward the low end, it couldn't get past the fuel pump, could it? Is there maybe something wrong inside the carburetor (float, perhaps?) What would cause this problem?

Two possibilities come to mind, the needle valve in the carby and (faint possibility) the idle shut-off not shutting off properly.

In the early days before the idle shut-off, flooding carbs from facing up hill were not uncommon. The top of the fuel tank is about level with the top of the carby so it' doesn't take a lot of uphill to put some of the tank above the carby.

Yes - fuel will "leak" through the fuel pump, since the two one-way valves inside allow fuel flow in that one direction - it doesn't matter where the pressure comes from - you could pressurise the tank with compressed air and fuel would flow through the pump too.

Just to give you a feel for the rest of our weekend - after I got the Bug running properly I pulled it into the driveway and washed it. Poor little thing has been sorely neglected over the past year - it was sure glad to be back to Daddy! :-)

So it's a happy and clean bug now. I bet it feels like it's "home".