What does it take to set timing on my SC?

chrisp · 09-30-2002, 01:32 PM

I am running very hot and have upgraded my SC with a carrera cooler. I have not track tested it since the cooler install to see if the cooler is what I need (I have run 270 degrees at previous track days) but I have always suspected that my motor is running hot, hotter than usual, even when I had the trombone. I was always wondering and now want to check if my timing might be the culprit. I haven't done this before but I want to check timing. Is it pretty straighforward? I have Wayne's book (which may or may not cover this topic) and I have Haynes.

Any tips or advice? This will be my first engine project (outside of oil cooler work) but I have done all of the suspension work, interior work, etc myself so hopefully I have the talent to pull this off.

Chris

Superman · 09-30-2002, 01:39 PM

It's pretty easy to check timing. Follow the instructions for your particular car, most of which are on a label inside the deck lid. I doubt that your timing is the problem. In my mind, it is more likely a lean mixture, particularly if your engine is tuned to factory spec.

Unplug the O2 sensor if you have one. Get rid of the catalytic converter if you have one. Richen the mixture to about 3.5%.

emcon5 · emcon5's Garage

270º is scary hot.

You need a timing light and a wrench, connect the timing light hot connection to the engine fuse block, and the ground to the left rear motor mount bolt. Mark the Z1 notch with white model paint, or nail polish. SC timing specs per the Bentley manual are:

78-79, 5º ±2º BTDC@ 950 RPM, vacuume hose connected, with max advance 26º ±2º BTDC @6000rpm, vacuume hose disconnected

80-83. 5º ±2º BTDC@ 950 RPM, vacuume hose disconnected, with max advance 21º ±2º BTDC @6000rpm, vacuume hose disconnected

Tom

chrisp · 09-30-2002, 02:05 PM

Tom, I appreciate it very much. My car is an '83 so I will proceed accordingly. I am hoping it's incorrectly set and that adjusting it will give me some cooler temps. Hopefuly at least 10-20 degrees. And if on the track the carrera cooler can give me another 20-30 then that will put me in a very safe zone of 220-230.

dean · 09-30-2002, 06:16 PM

Are you sure your thermo is working and not stuck?

makaio · 09-30-2002, 06:40 PM

270 is way to F&%$#@ hot!

Superman · 09-30-2002, 08:51 PM

I thought that the earlier SCs were timed at 5 degrees AFTER TDC. I sure could be wrong, though.

Your '83 (and mine) are timed with the vacuum hose detached. Detach both if you want, but only one will change the idle. Adjust idle back to 950 with the idle adjust thumb screw at the rear of the throttle body. time to 5 degrees BTDC. Reattach vacuum hose, reset idle. You're done.

JW timed mine at full advance. 35 degrees of total advance. Said if it knocks, I should back it off. It did not. I measured it again when I got home and, using the same procedures as factory (950 idle with vacuum hose detached), it is now at about 12 degrees BTDC. And that is not too far advanced. No knocking. Spark plugs look great. So, I doubt if your advance is the problem. My mixture is richer than factory, which helps. If yours is lean (like the factory specifies), then this is contributing to your heat problems. I think factory HC spec for our cars is .7%. Mine is about 3.5%. So you see, factory spec is ridiculously lean.

And 270 degrees is WAY WAY too hot.

chrisp · 10-01-2002, 09:20 AM

Thanks for all of the info. How do I "set the mixture at 3%". I have seen this talked about before. Is this some sort of sniffer test? Is it a garage only procedure or can a DIY do it?

Chris

Superman · 10-01-2002, 09:35 AM

It's pretty much a garage procedure. Without a gas tester, you'd only be guessing. Still guessing is better than burning an engine. Examine your spark plug electrodes. If they have a hard white coating on them, or if they are burned or excessively worn, then replace them and richen your mixture just a tad. That's done with a 3mm allen tool about 5" long. Just a slight adjustment, clockwise. Very slight. Until your plugs get some tan coloring to them.

If you still have working catalytic converter, richening the mixture will heat up your cat, possibly destroying/plugging it. IN fact, it may already be partially plugged, causing some of these problems. If you richen your mixture, you will need to disconnect your O2 sensor. If it is plugged in, then your computer will be constantly trying to lean your mixture back to factory spec.

Also, check that the spark plugs look the same. If a cylinder's injector is not delivering proper volume, then that cylinder is running lean.