7A QB engine mount question

[Paul K]

OK, Van's builder support is closed and I would like to continue with the engine mount installation early tomorrow so here goes:

My firewall mounting holes line up really good, no pushing required, all four holes near center. The problem is that the QB firewall arrived with a fuel pump doubler and platenuts installed down near the lower crossbar by the front gear mount. One platenut is in the way of the engine mount and holds it about 1/8 of an inch away from the firewall. What to do? Options:

1. drill out the doubler and replace it with a new doubler without the platenuts?

2. just drill out the platenuts and fill the holes with firestop?

3. grind the platenut down and cover it with firestop?

4. something I haven't thought of yet?

I am not going to use these for a fuel pump so I don't think they serve any purpose.

Another thing I don't like is the 1 inch hole in the firewall to install the front gear bolt. Any ideas?

 

[LifeofReiley]

My 7A required a spacer in the lower center mounts to flush the engine mount... nothing touched the nut plates. Also, forget the 1" hole, put the bolt in the other direction. If you ever need to remove the bolt, it's not hard to do. You can always go the other direction if necessary. Use a reamer and oversize bolt of you're concerned about fit. Also, some have used taper fit bolts.

 

[Rick_A]

This is a common issue with the engine mount. If you don't plan on using the doubler for fuel pump you could really do any one of the 3 you suggested. If you remove the doubler, you may also consider where the throttle and mixture pass thru the firewall.

I used eyeball fitting that necessitated adding a shim next to the doubler. In other words, you may want to make the doubler larger or smaller depending on other holes you need in the firewall.

As far as the hole for the nose gear bolt, my suggestion is to do it per the plans. If you ever need to remove the bolt, you'll be glad you did it Van's way.

 

[Paul K]

7A engine mount

The size of the doubler is something I would never have thought of, Thanks.

Why would the bolt be difficult to remove if installed from the bottom? I don't see any obstructions top or bottom when I look at the plans, of course there is very little shown on the plans! For those of you who have done this, tell me why this would be so. I just have a problem with a one inch hole in the firewall.

 

[LifeofReiley]

First of all the 1" hole really is not big enough, also the bolt is a close tolerance bolt... tight fit. If you need to remove the bolt you will bend the *&#$ out of the firewall doing it. Most bend the firewall installing the bolt from the bottom. Really, it makes no sense. If the nut does come loose or strips out on the bolt, the bolt can come out. Then you really have a problem. There are many threads on this along with many opinions.

The size of the doubler is something I would never have thought of, Thanks.

Why would the bolt be difficult to remove if installed from the bottom? I don't see any obstructions top or bottom when I look at the plans, of course there is very little shown on the plans! For those of you who have done this, tell me why this would be so. I just have a problem with a one inch hole in the firewall.

 

[Fred.Stucklen]

Or you can put an indentation into the firewall where the front gear bolt nut will reside when the bolt is inserted from the top of the fitting (which is easily accessable..). To prevent a loose bolt from causing the bolt hole in the mount from becomming oblong (and requiring a "fix"), be sure to use locktight on the upper gear leg fitting when you insert the gear leg for the final assembly.

First of all the 1" hole really is not big enough, also the bolt is a close tolerance bolt... tight fit. If you need to remove the bolt you will bend the *&#$ out of the firewall doing it. Most bend the firewall installing the bolt from the bottom. Really, it makes no sense. If the nut does come loose or strips out on the bolt, the bolt can come out. Then you really have a problem. There are many threads on this along with many opinions.

 

[Bavafa]

I put a short bolt thru the nut plate and shaved the head of it off to the point that it was not interfering with the engine mount any more. The idea of the bolt was to cover the hole with metal and not just fireproofing material.

Mehrdad
RV7A