Well, thanks to the help of the people on Turbobricks, the car is back on the road. After all that, it turned out that it was the ignition timing that was the culprit. (edit: nope, it wasn’t – see this post)
The plus side is that the newly rebuilt cylinder head is a major improvement. The engine revs smoothly and has noticeably more power (most likely due to the increased compression ratio and possibly the change in ignition timing).
In other news, I’ve picked up some nice bits and pieces for the 242: a non-A/C power steering bracket, so I can get rid of the A/C system, a new seatbelt for the passengers side, a tachometer, an uncracked dash, etc. etc. So I am slowly getting the car ‘back to stock’ as it were – basically, I’m just trying to make sure everything works.
Finally, I’ve compiled my timing instructions for setting the base timing on a K-Jet 240 (i.e. a car with breakerless, non-computerized ignition.) These instructions apply to 1976-82 N/A 240s and 1981-85 240 Turbos:
Setting the Ignition Timing on a K-Jet 240
1) Get a timing light. You can probably borrow one from a friend to save some money.
2) Hook it up, with red clamp on + battery post, black clamp on a ground screw on the car body (not the neg. battery post). Put the inductive sensor clamp around the #1 cylinder spark plug wire (spark plug closest to the engine cooling fan).
3) Disconnect the vacuum lines from the distributor
4) Get a white-out pen or a glitter pen or a paint pen and mark the crank pulley (bottom pulley) at the little notch that’s in the pulley.
5) Start up the car, aim the timing light at the marks on the black plastic timing cover. You should see your mark go whizzing by with the strobe light effect thing going on. Refer to your timing light manual for more info, but basically, you’re going to move the reading on your timing light until the mark on the pulley is at “0″ on the timing cover. Whatever number you get from the timing light display when the mark is at ’0′ is your ignition timing.
6) Check your timing. Consult the ignition greenbook (TP30432-2, page 41) for the proper spec’s (see the greenbooks section).
If the base timing is off, you can adjust it by rotating the distributor.
1) Soak the bottom of the distributor in WD-40 or penetrating oil. The area you want to hit is where the silver aluminum-ish body of the distributor meets the red/rusty iron block. This is at the very bottom of the distributor, basically.
2) If your car has A/C, you’ll probably have to disconnect the power steering pump and move it out of the way. The hoses are long enough that you can get it out of the way w/o disconnecting them. You’ll also have to remove the intercooler piping and spark plug wires etc. Basically, anything in the way of getting a pair of channel lock pliers (or similar large pliers) around the bottom of the distributor, just above where it meets the block.
3) Get a socket on a long extension (12 or 13mm I think) and loosen the bolt at the back of the distributor. You can see that the distributor has a channel in it and can be turned back and forth, and that the bolt is what clamps it down. The engineering behind this is very similar to the way the power steering pump belt adjustment or the alternator belt adjustment works – a bolt in a sliding channel.
4) Once that bolt is loose (no need to remove it completely), you can get out your channel locks and turn the distributor. Clockwise increases the degrees of timing, counter clockwise decreases the degrees of timing. These can be a pain to break loose, but if you started out with WD-40 or penetrating oil, it shouldn’t be too bad.
5) The next part is guess and check. Move the dist. Tighten down the bolt so it can’t move. Make sure everything is out of the way to start the car – watch the belts – and fire it up. Check the timing. If it’s good, put it back together. If it’s not, move the dist. again in the appropriate direction. Don’t forget to check the timing at both RPM levels – this will tell you if your centrifugal advance is working or not.