81 timing mark question

[Bart]

Hey guys, great forum here, much appreciate the wealth of knowledge. I have a quick question:

I have a 81 with FI and I just replaced my distributor due to a leak at the seal and a mag pickup that was way past it. I reinstalled and I am setting my timing. I have it up and running and all seems normal but before I pack away my timing gun I wanted to double confirm my assumption.

I know I'm looking for 10btdc and my crank has three arrows to line up tdc. Does the long one indicate tdc the the next 2 are 5deg and 10deg? I just set cylinder 4 to the 3rd arrow, 10btdc?

Are my assumptions correct? When timing is at the larger mark the idle slows and it speeds up when I rotate to the 3rd arrow mark and seems happier (both actually feel better than before the dizzy change) Anything further either way is obviously not happy. Thanks for the advice in advance.

Bart
81' 124

[18Fiatsandcounting]

I'm not very familiar with an '81, but if it's similar to earlier years, yes, the longer mark is 0 degrees (TDC), the first mark is then 5 degrees BTDC and the second mark is 10 degrees BTDC. Sounds like you have it timed right.

In general, since the engine runs clockwise when looking at it from the front, advancing the timing (BTDC) would move the mark "backwards in time" that is, counterclockwise against the engine rotation direction. Retarding the timing (towards ATDC) would move the mark in the same rotational direction as the engine. Hope that makes sense, as it's much easier to describe in person than here on a blog...

I will say, at least on the earlier model years where the timing marks were hard to see and difficult to set accurately, I just used them for getting the timing in the general ballpark and then adjusted the timing slightly in either direction until the car seemed to run best. On my cars, this usually ended up being between 10 and 15 degrees BTDC at idle, as best I could tell.

-Bryan

[Daddio]

Bryan has it right; another way to explain it would be that the last mark to go past the pointer is TDC, the other marks are BTDC, by 5 and 10 degrees. There are no marks ATDC.

Jeff

[18Fiatsandcounting]

Jeff, thanks for clarifying about the lack of marks for ATDC. I didn't mean to imply that there were ATDC marks, but I can see how what I wrote might lead one to look for these non-existent marks.

-Bryan

[Bart]

Huge thanks guys. This forum is a big help getting my 124 back to glory.
Bart

[tima01864]

Question that has come up, Does using #1 plug wire or #4 plug wire with the timing light make a difference?

[Daddio]

It will work on either one, just be careful to be on the compression stroke if you've had the engine apart.

[18Fiatsandcounting]

As Daddio notes, you can use either #1 or #4 for the timing light, but I prefer #4 as it allows you to look at the camshaft timing holes relative to the two marks on the camshaft housings and, if your timing cover is not present, the approximate location of the similar timing hole in the auxiliary shaft (it should be roughly 40 degrees clockwise from vertical looking from the front). Be careful with fingers, hair, clothes, timing light wires, etc. around the pulleys and spinning timing belt of course.

-Bryan

[tima01864]

The newer models, With the battery in the trunk, Need a work around hooking up the timing light. I opted to buy a battery operated one seems a safer route.

[18Fiatsandcounting]

A battery operated timing light should be fine, although I've never had one. In the past, when I had spiders with the battery in the trunk, I just connected my timing light to any old spare car battery that was close by. The power source for the timing light just needs to be about 12 volts, and it doesn't have to be the battery of the car you're working on.

-Bryan

[wetminkey]

I REALLY like my battery powered timing light! With a single conductive lead, it is terribly easy to use on my cars and trucks, works on my tractor's 6V system, and even works on my other tractor's magneto system (no battery). Just as bright as my regular 12V timing light, too.
It's also a lot easier to keep that single lead out of the fan blades and from melting on the exhaust manifold,...
Todd.

[RRoller123]

I wish I had bought a battery powered one long ago, but I had one already, with the clips, so I rigged in a connector that I can just plug it into, near the coolant bottle. Works fine, keeps the wires out of the way. The hot side is well shrouded, I tuck it down into the wire bundle when not using it.

[18Fiatsandcounting]

I wish I had bought a battery powered one long ago, but I had one already, with the clips, so I rigged in a connector that I can just plug it into, near the coolant bottle. Works fine, keeps the wires out of the way. The hot side is well shrouded, I tuck it down into the wire bundle when not using it.

Very nice, Roller, and I really like that you used the more exposed connector pin for the ground (the white wire), as believe me, I know people who would have done it the other way with predictable results...!

-Bryan

[dinghyguy]

nice solution, but what i did is use the cigarette lighter socket for the 12V. seems to work for me and i can use the light on both cars.

dinghyguy

[RRoller123]

Good idea! Long wires though.