Firewall glands

[Doug]

Why shouldn't I bundle a 1/8" copper tube for Manifold Pressure along with electrical wires through the same firewall gland?
I cannot figure a problem with this and will save me another hole on the firewall.
Doug Gray

[flion]

In principle I don't see a problem with it, but I prefer Van's method: flex line from engine to a bulkhead fitting on the firewall; tube after that. I've never been comfortable with a solid line 'twixt engine and firewall, even with loops.

That said, I believe that the standard for not bundling wires and plumbing together was to prevent the wires from being saturated should a fluid line break. I'm not sure how messy a MP line would be but I think you could risk it. In my not-so-educated opinion, wires forward the firewall are at risk of an oil coating anyway.

[f1rocket]

No problem. I ran mine that way. No need for another bulkhead fitting, nuts, weight,complexity, etc for just the MP line. I have pictures of the install on my web site if interested.

[Doug]

Thanks, I will bundle the MP with the electrical...
Doug Gray

[Greg Arehart]

So flion's comments leaves me wondering whether there would be an issue with work hardening (and possible breakage) in either a copper or steel (or aluminum - I know not a good idea FF but I am wondering about fundamentals here) tubing due to engine shake?

greg

[flion]

From what I've seen on spam cans, it's not a huge risk. Just an inspection item. Then again, the rule is that connections to the engine must be flexible and I just prefer a hose to a loop. Before I noticed that my FWF kit had Van's hose and bulkhead connector, I was playing the the tubing supplied by Klaus for the Lightspeed ignitions but was worried about the heat issue. f1rocket mentioned the complexity issue for the hose to bulkhead to tubing scheme but, since I had complexity (connection to two ignition boxes and the BMA engine pod) built in, it was a no-brainer for me.

[f1rocket]

These comments caused me to clarify my response. For the manifold pressure line, I have a flexible hose fitting from the cylinder to the firewall manifold. From there, I ran a copper line in through the firewall with a bundle of wires. No shaking of the copper line is involved, it is fixed and firm. The hose handles any shaking.

Just wanted to clarify. For those of you old enough to remember Tony Bingelis (sp?), his book Firewall Forward showed copper lines running from the engine to insturments without a fitting as long as you coiled it several times to take up the vibration. I wouldn't do it that way but Tony B. thought it was acceptable and the way it was done on early airplanes.

[Greg Arehart]

Randy, what type of hose are you using FF? Something with regular AN fittings on it (i.e., similar to fuel or brake lines), or just slip-fit/hose clamp type hose?

thanks,
greg

[f1rocket]

I used a regular -4 hose with standard hose fittings. It is probably overkill, but all my firewall foreward hoses are stainless, braided hoses with integral firesleeve. My MP line is not firesleeved.