The Official 356Talk Forum

Saw that you posted on another thread.... glad to have you back so soon. Everything going well?

I hope the recovery is moving right along!

Hi Ron.
Hope you are recovering and well
See that you are taking it easy and only working the computer keys. Get well soon, give us an update! We all care.
Kind regards Jay

THX to all of you.
Better, but that really doesn't mean a lot. Tech tip: If you're going to get injured, do it when you're young; when getting help putting on your pants is an opportunity!
Two orders out the door today; (left) one-handed packing is SLOW!

Glad to hear you are in the mend, Ron. Yep, we bounced back sooner when we were younger. My guess is you will get good at one-handed tasks but it is frustrating. Been there.

All the best,

Mike

Hi Ron,
Hope you are recovering at a decent speed.
I have a question regarding one of your products, the Solex Knecht air filter adapter for Weber carbs.
I bought a pair of these adapters from Mainely by Design before you acquired their lineup, and I'm just now getting ready to use them on a car that had a Weber carb fire back in 2007.
I may also need to buy a second set of adapters for my other C coupe that's being repaired from Weber carb fire damage that occurred last November.
I have original Knecht rock catcher wire mesh filters that I want to use.
On your current web page, you mention that a slight alteration to the Knecht filters is required.
I'm guessing it involves enlarging the hole in the bottom center of the filter to accommodate the Weber jet stacks. Mainely gave no instructions on this.
I would appreciate it if you could enlighten me on what to do.
Thanks much,
Dave

Dave,
The wording of your post makes it sound like Webers catch fire a lot. My experience is that air cleaners catch fire. If you were to run without air cleaners, any spark should get sucked down into the cylinder. All the Weber air cleaners that I know about use foam of some sort as the filter material. This foam can get saturated with gas from even small backfires and ignite. Besides the stock looks, this is another reason why Ron's Knecht/Weber air filter adapters are so useful. Knechts may only catch small birds, but at least they don't BBQ them too.

Craig Richter wrote: ↑Mon Jun 07, 2021 6:36 pm Dave,
The wording of your post makes it sound like Webers catch fire a lot. My experience is that air cleaners catch fire. If you were to run without air cleaners, any spark should get sucked down into the cylinder. All the Weber air cleaners that I know about use foam of some sort as the filter material. This foam can get saturated with gas from even small backfires and ignite. Besides the stock looks, this is another reason why Ron's Knecht/Weber air filter adapters are so useful. Knechts may only catch small birds, but at least they don't BBQ them too.

I'm not sure what the frequency is, but I have now had 2 bad experiences with the stand-off in the K&N filter on a Weber IDF40 catching fire, one fire in each of my 2 C coupes, one in 2007, and one in 2020.
The K&Ns have a pleated fabric as the main filtering element, as I'm sure you know. In each case where the fabric caught fire, I never heard the backfire. The symptom was that the engine balked not long after startup and would not take throttle. This was followed by the car leaving a smoke trail, shortly followed by me jumping out with a Halon extinguisher to snuff the flames.
I don't really know how many 356 drivers use Webers. My 65C coupe had them on it when I bought it in 2000. I know Webers are used on some (all?) 912s, but the air filter there is contained within a metal can with an elongated "snout". I'm sure this prevents the type of problem I've had, but I don't think these 912 metal assemblies can be adapted to 356s, although maybe you could drastically shorten that snout. In the wings, I have a set of Zeniths and their standard metal-housed air filters that came off my 64C coupe, but I've never worked on Zeniths.
I guess I could blame Harry Pellow for persuading me to go with Webers, but I liked Harry, and he was a good guy overall.
So, I think I'll stay with the Knechts/Webers.

The 912 always had Solexes, very slightly tweaked from the SC version.
Craig or others, how about those foam outer sleeves for the Knechts? Do they put the fire hazard back? And worthwhile improvement in filtering? In a normal city environment I have always thought the air filter was not likely to extend engine life very much, quite unlike my beliefs about oil filtration.

In theory the foam outer sleeves even if they could catch fire should not cause a fire inside the Knecht because flame arrestors work on the theory that a flame will not survive the transition through a metal filter because it will cool down and extinguish itself by the time it would have reached the inside of the filter. The K&N filter if it gets wetted by gasoline will allow a mixing of gasoline vapors and oxygen to be present inside the air filter and a backfire caused by a weak mixture will ignite those vapors and the back burn will ignite the fuel in the filter itself if it reaches it's ignition temp. I think the problem Dave experienced may have arisen as a result of fuel boiling/evaporating off a hot carb bowl and then recondensing on the colder K&N filter and subsequently on a hot start with a lean mixture ignited the whole kit and caboodle. Just my theory but yours may differ.

Dave Wildrick wrote: ↑Mon Jun 07, 2021 4:24 pm Hi Ron,
Hope you are recovering at a decent speed.

Better than expected, worse than hoped for.

Dave Wildrick wrote: ↑Mon Jun 07, 2021 4:24 pmOn your current web page, you mention that a slight alteration to the Knecht filters is required.
I'm guessing it involves enlarging the hole in the bottom center of the filter to accommodate the Weber jet stacks. Mainely gave no instructions on this.
I would appreciate it if you could enlighten me on what to do.
Thanks much,
Dave

Correct:

Martin, Your assessment of air filters and oil filters is right on!

I have air filters on my race car. I have dyno tested and the filters do no harm to the power. On the other hand poor ring seal does definitely hurt power and every little grain of sand ingested through your open stacks makes a scratch that erodes your ring seal. That is a certainty.

About air filter fires... It boils down to engine tuning. If you are getting a lot of fuel on top of your carbs and/or into your filters then a fire could easily happen. Fix the source of the fuel. It shouldn't be there. Do a correct tune-up and make sure that the float level and jetting are correct. Any car could have a fire but it is extremely unlikely if it is properly maintained. I am always more worried about fuel line leaks than carb fires.

My closest brush with a car fire was around 1982 when I did mechanical work on the side at my house. The garage was under our bedroom. I had a 1972 Oldsmobile Cutlass Convertible in the garage with the front up on jack stands. I can't remember what I was fixing but a wrench dropped down around the starter and grounded out the positive battery cable. Then the accumulated grease by the starter caught fire! YIKES!!!! This happened quickly, very quickly. I did get the cable disconnected in record time but then I had to put out the grease fire. I got it done but it was very scary. Since then I always disconnect the battery if I will be anywhere near the positive battery cable.

Cliff, you race with a black fan shroud? Doesn’t that cost some power?

Martin Benade wrote: ↑Tue Jun 08, 2021 3:02 pm Cliff, you race with a black fan shroud? Doesn’t that cost some power?

You might be right. One 356 engine builder paints his shrouds baby blue.... not that there's anything wrong with that.