Firewall Fuel Line Passthru

I've studied the OP-XX drawing which shows the hole spacing for the doubler plate to be fabricated for the firewall fuel line passthru (Horizontal Induction IO-360). I'm not sure I understand it though. One hole in the doubler is supposed to be matched with one of the rivets that is just underneath and right of the starter solenoid. However, if that doubler is supposed to be on the cabin side of the firewall, I don't see how it could be since a stiffener is located in the same place. I also remember reading about some builders recommending moving the hole an inch or two inboard to space it a little farther away from the starter solenoid. Does anyone have any measurements or pictures? Thanks!

Trevor

If you have your engine mount on hand do a temp install. You'll find that the proposed hole has clearance issues with the mount.
Some have placed this hole a little north of the plan spec.
Regards

Lorne is spot-on ...

I didn't know that at the time, but came out OK only thru an incredible stroke of luck. My fuel line misses the engine mount at that spot by 1/8"

Engine Side

The doubler plate goes on the engine side of the firewall so there is no interference with the rib. However, plan ahead because after I installed mine I had to drill it out and trim the upper left corner a bit to avoid a starter contactor mounting bolt. There is also a potential interference with the throttle cable pass-thru on the lower right corner of the doubler depending on your engine and carb/fuel injection configuration and if you choose to use an eyeball pass-thru. Sorry I can't be more definitive but it depends on your configuration.

John

New Product

Perhaps this is a good time to introduce a new product that we are working on. This fitting is courtesy of Aircraft Artist Dave Howe in CA. They come in two sizes, one has 1/4" female NPT threads on both sides (not modeled in photo below), the other has 1/8" female NPT threads in both sides. This allows for any pipe fitting to be used in either side making for some amazing combinations of readily available fittings going through the firewall in restricted spaces. The 1/4"NPT model is 1" long and uses a 7/8" firewall hole. The 1/8"NPT model is 3/4" long and uses a 5/8" hole. The 1/4" version is off the machine and waiting to be anodized, the other we will start next week. I am thinking they will retail in the $20 area.

Looks like a neat idea. Are they Steel for use on the firewall?

I'm not looking at any drawings for measurements but here is a picture of what I did. I think I did move the hole a little for better clearance on other's recommendations. I also ended up using a steel 90 instead of the aluminum one shown.

Maybe no help as mine is a 7A.

I had to lower mine about 1/2" from the plans to clear the contactor.



You can see here how it is oriented versus the engine mount with plenty of clearance.

Hmmm... seems like with all the comments here and elsewhere about engine mount clearance issues, one should not drill any holes into the firewall until they have the engine mount on hand and test fitted.

grayforge said:

Hmmm... seems like with all the comments here and elsewhere about engine mount clearance issues, one should not drill any holes into the firewall until they have the engine mount on hand and test fitted.

Click to expand...

Engine mount definitely yes. Having the engine mount will help you decide where to put the electrical pass throughs that are really up to you.

There are a number of engine combinations and fuel controller/carb positions that affect the pass throughs. I found the documentation for Vans IO-360-M1B to be quite good. I did not use the stock master and starter solenoid (mounted slightly differently) so I did not run into the fuel pass through clearance issue noted in this thread even though I drilled the position per plans.