Technical Puzzled, Strange Timing Behavior, Advice?

[kkemerait]

On a 1978 124 Spider, my understanding is that correct timing is 0 BTDC. When I set my timing to that, it runs very rough and has very little power accelerating from stand still.

I had checked everything...timing belt, cams, carb, fuel pump, etc.

For lack of anything better to try the other day, I just blindly rotated the distributor and like magic the car idled very smoothly and accelerated from stand still like a jack rabbit.

When I got home, I put a timing light on to see what it was set to .. it was almost 15 or 20 degrees BTDC

Question...Why? Second Question: Should I leave it like that? Third: If not, what could be causing that behavior...what else should I look at or fix?

New plugs, new wires, new points already taken of.

 

[fingers99]

Best posted in the 124 section.

My guess is that TDC may be the place to check the cam timing. No engine will run properly with the ignition timing set to 0 degrees.

There are manuals -- even a link somewhere to the manual here -- online. Get it right or you may find yourself doing very expensive repairs.

 

[kkemerait]

Fingers99,

Haynes, Clymer and Shop Manual all say 0 degrees BTDC

 

[fingers99]

Then they're wrong. Think about it for a moment. If the static timing is 0 degrees, then the piston will be way past TDC when the spark occurs. Which is pretty pointless. All engines require static timing of x degrees BEFORE TDC. (And you've gone some of the way to proving that yourself!). I think I remember Guy Croft usung 24 degree btdc (that is, 24 degrees of ignition advance) on tweaked 2 litre twin cams (and no-one knows that engine better than Guy) so you're not that far out at 20.

As I say, the factory manual is on line somewhere, or you could join Guy Croft's elite forum and ask the man -- do read and follow the instructions: they're there to keep smammers and clowns out.

 

[spannerdude]

US Spec Spiders were fitted with dual points system. I believe this was for emissions purposes.
I believe that one set was used for starting and these were static timed to 0 degrees. The other set was for running on and these were set with some advance. I don't know what the dynamic timing setting is for the US spec motor, or whether you have an 1800 or 2 litre but a good benchmark figure would be 10 degrees BTDC @ 800 RPM. Try this as a starting point and let it back a bit if it pinks. Then find a manual that tells you what it should be for your car.

 

[GeorgeT]

US Spec Spiders were fitted with dual points system. I believe this was for emissions purposes.
I believe that one set was used for starting and these were static timed to 0 degrees. The other set was for running on and these were set with some advance.

Almost correct: only mid 70's ('75 & '76 I think) had dual points. One set was used until the engine warmed to a set point and then it switched to the second, more advanced, set.

 

[spannerdude]

Thanks for the clarification George,
my '77 1800 arrived from California with dual points. Which I promptly tore off and threw over the nearest hedge in favour of a European dizzy.

Was I right about the "starting" points being timed to 0 degrees? I still suspect this is likely to be the source of the confusion on the timing figures.

 

[Vintageant]

The Vehicle Emission Plate in the 1973 engine bay states 0° BTDC. Are even the manufacturers wrong?

 

[jackwhoo]

13 years since thread updated.

The text in picture you posted also states refer to workshop manual and "base" setting 0 degrees

 

[Vintageant]

Thanks jackwhoo! Just curious why many on this and other Fiat 124S sites state 10° BTDC for the early 124 engines. I believe post-1978 states 10° BTDC. Engine or fuel changes?

 

[jackwhoo]

Thanks jackwhoo! Just curious why many on this and other Fiat 124S sites state 10° BTDC for the early 124 engines. I believe post-1978 states 10° BTDC. Engine or fuel changes?

I have no idea but I wouldn't rely on an engine bay sticker to tell the whole story.