Ignition problems/smoke

[andreic]

Hello fellow 914-ers,

For the past three years I've been enjoying a 1975 Porsche 914, with the 1.8L engine. At some point in its past someone converted it to a single Weber carburetor instead of the fuel injection system.

I've had it for about 3 years. Apart from running rough when cold, and some minor oil leaks, it's been running very well. It has about 95k on the frame. The guy I bought it from said the engine was rebuilt in the past 20k miles, but I have no proof of this fact.

In the past couple of weeks I noticed a couple of things that are not right. One happened while cruising at about 55mph. I stepped on the gas really hard (floored the pedal), the engine made the loud growling noise it always does, but on top of that there was a metallic clicking noise (which I have come to think of as the timing not being quite right; but I am not sure of this) and when I looked behind the car there was this thick cloud of whitish smoke that had come from the exhaust. I tried this again a couple of times, and every time the same thing happens. When riding the car at normal power settings (even very high speeds/RPM's) there is no smoke out of the exhaust.

The other thing that bothers me is that when I cut the ignition off after a longer drive (so the engine is warmed up) the engine keeps sputtering a couple of seconds, as if it is self-igniting.

Any suggestions as to what may be causing these problems?

Thanks,
Andrei.

[beatnavy]

Sounds like your car is "dieseling" where it continues to fire even after ignition is off. There could be several issues going on here, but the easiest thing to check/remedy is timing. Please check your dwell and timing and let us know how it goes:

Timing
Timing with Carbs

Also, single carb is considered the least desirable fuel delivery system on a 914. If you can, look into replacing the FI or going to dual carbs.

[porschetub]

You must correct these issues before you continue driving,otherwise you will damage your engine......seriously.

[andreic]

There is something that puzzles me about the advance/timing issue. The car runs fine (I would even say great) at all RPM's. No "clicking" or smoke. Doesn't this mean that the timing is properly set? It only misbehaves when I push the throttle to the floor.

Today I did a longer drive (150 miles), and before doing it I checked the oil level. To my surprise it was a quart low. Any idea where it might have gone? The oil leak may be responsible for a small fraction of this, but certainly not all. The exhaust gases have an unpleasant smell, but there is nothing visible coming out the tailpipe, so I don't think the car is burning oil (except as above when I stepped hard on the gas).

Andrei.

[andreic]

I forgot to say that the distributor that I have does not appear to have vacuum advance, I think it is purely centrifugal. Could it be that it simply can not keep up at high power settings? If I were to get a vacuum advance distributor, which one is the recommended one?

Thanks.

[Dave at Pelican Parts]

Originally Posted by andreic

The car runs fine (I would even say great) at all RPM's. No "clicking" or smoke. Doesn't this mean that the timing is properly set?

No. And, in fact, it does not run fine at all RPMs and throttle settings, you have demonstrated that. And engines can run OK and still have their timing off by a pretty surprising amount.

One thing you should find out is which distributor you have. Look for part numbers on the side of it. The Bosch numbers would start with something like "0 280 ...", while VW or Porsche part numbers would start with a three-number group denoting the model. (Like 039 for a 2.0 distributor, or 113 for a Bug distributor, etc.)

The "009" distributor is a popular choice because it is cheap--but it doesn't have a good advance curve for our engines; it was originally designed for stationary engines like generators. It is often paired with the single-carb setup because both are cheap. And both have that as their sole good point, at least on our engines.

You can fiddle with the timing to try to get a setup that allows a good idle but won't start detonating at high loads. It may not be possible without re-curving the distributor, but it is worth a try. The best place to do this would be on a dyno, where they can apply a given load to the engine and keep the RPMs constant at that load. But dynos aren't cheap.

I would recommend finding a better distributor (Mallory Unilite has lots of fans and is relatively easily adjustable) and going to decent dual carbs if you want to improve the way your car runs.

The disappearing oil is probably a mixture of leaking and burning. You can burn oil without making visible smoke, if you're burning small enough amounts of it. Smoke is also harder to see in your mirror at high speeds, so you could be smoking without noticing it.

--DD