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Fuel pump, tight fit.

kjelle69

kjelle69

Active Member
The old fuel pump question...

Best solution? Shoot :)
 

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My memory could be wrong but as I recall the early RV4 fuel pumps were modified. like the center piece was turned so the fitting would not interfere with the firewall.
 
My old pump was re-indexed so that the overflow pipe went out the same direction as the inlet connection. However I would prefer not to re-index this new pump.

I have the special fitting from Vans but it still gets really close to the firewall when using it. The engine is out of the plane at the moment so it's easy to work with the fittings or the firewall if needed.

What is the minimum distance from anything on the engine to the firewall? Eg. from the Vans fitting to the closest point on the firewall?

Image from the other direction.
 

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kjelle69 said:
My old pump was re-indexed so that the overflow pipe went out the same direction as the inlet connection. However I would prefer not to re-index this new pump.

I have the special fitting from Vans but it still gets really close to the firewall when using it. The engine is out of the plane at the moment so it's easy to work with the fittings or the firewall if needed.

What is the minimum distance from anything on the engine to the firewall? Eg. from the Vans fitting to the closest point on the firewall?

Image from the other direction.
Click to expand...
When I built my 4, way back in the late 90's,, I re-indexed the overflow port (sort of). I actually drilled a new port in the ring and plugged/shaved the original

Fast-Forward to 2020,, decided to replace the fuel pump and I did not feel like pulling apart the pump so it's essentially the same distance (or lack thereof) as in your pic, and I am using Vans overflow fitting. Not much clearance but I have seen no evidence of firewall-to-pump contact. My guess is the forces are more "rotational", around the longitudinal axis, vs left-right on the vertical.
 
Thanks Mr.Aubuchon.- This is exactly what I needed/wanted/wished to hear :)
Did you trim anything at all?
I was thinking of shaving a tiny bit from the vans fitting in order to make the distance as big as possible.

N184DA said:
When I built my 4, way back in the late 90's,, I re-indexed the overflow port (sort of). I actually drilled a new port in the ring and plugged/shaved the original

Fast-Forward to 2020,, decided to replace the fuel pump and I did not feel like pulling apart the pump so it's essentially the same distance (or lack thereof) as in your pic, and I am using Vans overflow fitting. Not much clearance but I have seen no evidence of firewall-to-pump contact. My guess is the forces are more "rotational", around the longitudinal axis, vs left-right on the vertical.
Click to expand...
 
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I made a little cut out in the firewall

Way back when I built the -4 I trimmed the corner of the footwell back about 1/2 inch and maybe 3/4 wide. Then I riveted a little piece of stainless over the hole. It's still not much clearance, but it gets the job done.
 
I am thinking of doing something like this. Shaving off the flange on the pump and then tight it down deep.
 

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Engine movement

There is very minimal aft movement of the engine. That can be reduced further with aerobatic mount rubbers. You could also use as much as 3/32 steel shim washers on the lower mounts.
 
See photo

Not mine. The photo is Steve Sampson's RV-4; G-Ikon. If you google it the website comes up. Interesting solution to the problem we all have. Mine is very close to the SS firewall but no sign of contact after many years of flying. I'm using the fitting that Van's sells and I filled it down slightly.
 

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I just replaced the mechanical pump in my -4 about 8 months ago and had the exact same issue. As you proposed, I cut the threaded boss on the fuel pump housing down to gain the clearance needed. I cut nearly half of the boss off and it works just fine. I also trimmed the male-threaded portion of the fitting down as well so it would not engage as deeply into the fuel pump. this gave me a little additional clearance too. As a side note, the pump I removed was modified in the same manor by the original builder.
 
I have Steve Sampson’s mod. I think Aerosport Power has been doing this on their engines destined for -4’s. It can be done with the engine in place:
-Use a long drill bit to drill a 1/8 dia. hole in the bottom of the port.
-Plug the end of the port.
-Secure a length of 1/8 o.d. pipe in the hole with JB weld.
 
Brian Vickers said:
Not mine. The photo is Steve Sampson's RV-4; G-Ikon. If you google it the website comes up. Interesting solution to the problem we all have. Mine is very close to the SS firewall but no sign of contact after many years of flying. I'm using the fitting that Van's sells and I filled it down slightly.
Click to expand...

I bought my RV-4 flying with no overflow hose, (scary). I fixed mine like this one in the picture, loosened the bottom motor mounts and lifted the engine to get the pump away from the firewall, then drilled the side of the boss (long drill bit) and pressed in a 1/4" piece of stainless tubing with some sealer in the hole so it goes part way into the threaded area, then used a flush (Allen head) pipe plug threaded in so it jams the tube, further holding it in place. A 1/4" urethane fuel line slid on and safety wired to the stainless tube goes out the bottom of the cowling away from the exhaust.... Now I feel better about flying it. We lost a fellow RVator and Local airshow pilot when the fuel pump on his Rocket, without an overflow hose, blew the diaphragm and caught fire in flight. The fire was so intense it burned through the floor and got into the cockpit. He landed it, but died of the burns a month later... Yikes!

Mark Hannum
RV-4 bought flying
BD-4 restored, sold
Avid MK4 built, sold
 
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kjelle69 said:
I am thinking of doing something like this. Shaving off the flange on the pump and then tight it down deep.
Click to expand...

The cut depth of the (tapered) threads in the pump are what control how deep you can get the fitting to thread in.

To get it to go deeper you will have to re-cut the threads as well. Probably doable but pump should be disassembled to assure no contamination with-in the pump.
My point in mentioning is, are you working on a solution in search of a problem?
And in the process adding addition risk of other problems because of the additional work that you propose doing?

In engineering and problem resolution, data is king.
There has been at least a couple people post to this thread that they have stated they have used the special fitting sourced from Van's, that has also been used on hundreds of RV-4's for 35+ years in service.

Something to consider........
 
After installing Vans overflow pipe we still only have 3-4mm to the firewall so I think we will modify the firewall to make enough room to feel comfortable.
 
Had the same issue on my Rocket. Wish I had as much room as a RV4. Took pump apart considering clocking it but the port from the bottom would be plugged by doing so. I was not comfortable trying to drill new ports. So Drilled and indexed a solid pipe plug. Installed it in the boss then drilled and tapped into the boss and plug. Then filed off as much of the boss as possible. Still didn't fit so got a big hammer. Now it fits😆. Think I cried a little hitting my pretty polished firewall.
 
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