Sock filters on fire. Looks like I better hook up those chokes after all...

[grimlynsan]

Winter is here! How do I know? My car caught fire :-(

 

 

 

[d3c0y]

[gav240z]

Socks to be you!

 

At least you didn't have a bigger problem. I've not seen that before, but I guess I won't be using sock filters on my Z.

 

By the way I heard this is the reason pod filters are not permitted in Australia? Because of fire hazards like this?

[nizm0zed]

Pod filters are legal, they just have to be secure.

Ideally you want them boxed off and fed cool air too, so if you design it right you can tick all the boxes and it'll work as a proper performance part.

[grimlynsan]

Ha ha ok, I guess I better expand a little, even if only for future generations... I did a few searches on filter socks catching on fire and the results were scarce and inconclusive, so here is my contribution to the knowledge base. Please contradict and correct me as I mostly don't know what I'm talking about 

 

The situation (lunchtime):

Car was cool. It had been started that morning to get to work. I drove 5 minutes round the block to grab some lunch. Pulled over for 10 minutes. Drove back to work. As I pull into the car park and turn off the engine, I see a whisp of smoke come out the vent. I open the bonnet to see the smouldering remains of two filters. Another still on fire. Luckily it was a small flame and I just blew it out. The OP pic was taken a few seconds later.

 

Drove it home that arvo and it was not happy! In retrospect, this was probably the sound of filter sludge being broken down as it was atomised in the engine 

 

Ordered some replacement filters the next day (after a walk to work!) and they arrived the following day (thanks Daniel at Weber Parts!).

 

Everything cleaned up pretty good, took me two evenings to get it clean:

 

 

 

 

 

So how did this happen?

 

When I put on the triple webers, the mechanic asked me what I wanted to do about hooking up the chokes as the stock 77 260z 2+2 choke cable is split into two and of course there are now three carbs.

 

It is complicated by the fact that the weber choke mechanism means you need to pull the lever towards the front of the car, so the factory choke wont adapt to the task happily as it wants to go over the engine and pull upwards.

 

As I live in QLD and had just spent a load of cash on a new engine, I was happy to keep the extra fabrication cost in my pocket and just leave the chokes disconnected.

 

That was in summer. And I have had just under 5000km of worry free, exhilarating motoring since then.

 

But now it is a good 10 degrees cooler, and this is my daily driver - I can't warm her up for 10 minutes every morning.

 

And I don't know how to tune webers. I paid a 'weber doctor' a good sum of money in summer, which will return soon, to get it right; so I would be hesitant to mess with them even if I did know! Anyway, I have digressed.

 

Even on a cold day, the car starts very easily with no chokes however before it has warmed up, with no choke, on a cold day, I get a tick tick sound from one of the cylinders (it's the 3rd one from the firewall by the way).

 

This 'front firing' as I like to call it, is the sound of fuel being squirted out the front of the carb and into the sock filter.

 

Flames come out sometimes too. Most exciting when I was testing it WITHOUT the filters on.

 

This is because a sock filter is like a sponge. A fire retardant sponge. But it doesn't matter how fire retardant something is if it has been saturated in petrol and is having flames shot at it.

 

And this is the cause of my engine fire to my understanding. If someone knows more about the physics of it I would be interested to hear why it spits it back out on a cold day (I assume something to do with the cold air having more oxygen?).

 

And now it's back together

I drove it this morning with much nervousness as it was front firing more than it ever has (freezing this morning!) but I had to drop the Mrs in town so had no choice.

 

When I got home I rushed to open the bonnet, fire blanket in hand. Pleased to report all looked good. But the paranoia will continue for some time I suspect.

 

Lesson learned

Don't be a cheap bastard. If you're going to spend the best part of a year's disposable income on a new race engine, and want to drive it regularly, spend a bit more on getting the chokes hooked up (even if it's warm where you live) cause the temperature changes and that can cause a misfire as the mixture will be lean.

Another lesson is that it may be pertinent to carry a fire extinguisher in case of emergency.

[dat2kman]

The tick tick at no 3 may be a bigger than required valve lash adjustment.

The timing is incorrect to allow that much backfiring through carbs, and camshaft duration is probably too high.

"race spec" camshaft ??

If your carby "tuner" left it like that for you, i'd suggest someone else be used.

Your comment "on the cheap" does not go with "triple carbs" and "race engine"

 

If the chokes are not hooked up, they need to be wired in the open position, as they can jiggle with vibration to open up the internal passages to then allow excess fuel.

 

They require a longer single cable, try a bicycle shop for inner/outer cable, and have all three linked, make sure all choke assy's have effective return springs, if not, make up small L brackets fit external springs.

 

Often had these dramas with overcarbed webers on rally cars.

[grimlynsan]

The tick tick at no 3 may be a bigger than required valve lash adjustment.

The timing is incorrect to allow that much backfiring through carbs, and camshaft duration is probably too high.

"race spec" camshaft ??

If your carby "tuner" left it like that for you, i'd suggest someone else be used.

Your comment "on the cheap" does not go with "triple carbs" and "race engine"

 

If the chokes are not hooked up, they need to be wired in the open position, as they can jiggle with vibration to open up the internal passages to then allow excess fuel.

 

They require a longer single cable, try a bicycle shop for inner/outer cable, and have all three linked, make sure all choke assy's have effective return springs, if not, make up small L brackets fit external springs.

 

Often had these dramas with overcarbed webers on rally cars.

 

I knew you would have the answers!!!

 

It has run like a dream since I had it at the carb doctor. It has a ridiculous cam (can't remember and don't understand the specs myself) but when I picked it up I could not believe it could run so smoothly and reliably (until recent drastic temperature change).

 

And yea, I know 'on the cheap' is incompatible all to well; I would have money if I didn't have that car!

 

As for your advice re the bicycle cable, great idea! Do you run it around the front of the engine and pull the one long length of cable through all three? I was looking at it last night for a while and I'm almost tempted to try it myself.

 

Thanks for the advice!

[gav240z]

As for your advice re the bicycle cable, great idea! Do you run it around the front of the engine and pull the one long length of cable through all three? I was looking at it last night for a while and I'm almost tempted to try it myself.

 

Thanks for the advice!

 

Nothing like giving it a go yourself and coming up with a solution, you'll feel better for giving it a go.