Fuel Tank Fit

[racaldwell]

I have seen others say that the fuel tank hits the firewall middle support, and guess what, mine does too. But I haven't seen if there is any resolution to this. What is the standard practice?

Just leave it as it is? and worry about chafing a hole in the tank? Or put a rubber strip in there? Or heat the tank corner to make a depression around the tube? Or squish the tube so there is 1/8" clearance to the tank?

The fit seems pretty good in the other places. I did have to remake the glareshield attach angles over again because I drilled them before fitting the tank and the tank pushed it up so I made wider angles to get good edge distance.

The tank sits on the firewall crosstie so I put a strip of UHMW on it to reduce chafing. I also had to drill out the center support rivets and install countersunk rivets so the heads wouldn't hit the tank.

Rick Caldwell
Xenos 0057

[Area 51%]

Your fit issues may not be limited to the items you listed. Have you checked the clearance between the filler neck of the tank and the bottom of the fill box on the upper firewall? Many have had to cut the bottom out of their fill box and extend it to miss the tank.

[racaldwell]

Randy, I am one of the lucky ones. The spout tunnel seems to fit OK. I have only fit the back strap and it fits as the tank is currently positioned. I have not yet fit the front strap. I'll check that over the weekend before I pull the tank out a drill for the oops fittings. I am not really sure why there is a front strap when the entire width of the tank is resting on the crosstie just inches from that strap location. That strap certainly cannot lift the tank off the crosstie since the tank is hard pressed up into the glareshield.

There is a pronounced upwards curve to the top of the tank where it meets the forward tank face. This is what really pushed the glareshield up and screwed up my previous placements of the attach angles.

Rick

[DCASonex]

Mine did same. Placed 1/8" thick plastic (Lexan) pads on angle on each side of the filler neck to raise the tank, then also made new housing around the neck that provided more clearance, and contact on broad surface under the neck instead of edge contact to the neck and incorporated a drip catch and drain.

Seems no two of the rotational molded tanks are exactly the same.

David A.

[bvolcko38]

I also had this same problem. I lowered the opening in the firewall by about 3/4" and used some ss sheet to accommodate the longer sides.

[racaldwell]

I checked the fit of the front strap and I lucked out. It fits right in line with the tank ribs.

Right now I am thinking to best option for the tank hitting the SQ tube on the firewall would be to flatten the tube about an 1/8" with the hydraulic press. Then I would not have the tank rubbing there where I cannot easily see it. Anybody done this or has the contact not been a chafe problem?

The neck seems to rest on the bottom of the firewall tunnel so the contact is spread over the complete filler spout. I may end up putting some UHMW chafe tape there, too.

Rick Caldwell
Xenos 0057

[DCASonex]

Rick, Before smashing the tube, try fitting a shim plate, plastic or ?? under the tank each side of filler neck, where it rests on the cross angle. Did that on mine and had no problem fitting the glare shield over it. Should be very easy to see if that solution will work for you.

David A.

[racaldwell]

David,
I'll try that tomorrow. The glareshield is already shoved up tight by the tank such that the unclecoed holes are pulled out of alignment. I used a couple of ground down AN3 bolts to pull the glareshield back into alignment and just barely got there but all the bolts & rivets are not in yet. I'm sure I can get some of the UHMW chafe tape under the spout but it is only about 0.032" thick. I doubt I can get the tank lifted up enough to get off the firewall tube but I'll find out tomorrow. And then on to installing the oops fittings with your tools. Thanks again.

Or maybe tighten up the front strap to lift up the tank front? Of course that will knock my firewall/glareshield angles out of alignment, again. Moral to this story is do not drill the glareshield angles until the fuel tank fit is finalized.

Rick Caldwell
Xenos 0057

[Bryan Cotton]

Do you guys worry about chafing on the front angle, the glareshield, or the straps? Or just the front square tube? My tank is jammed between all of those and I did not put anything to prevent chafing anywhere. Did I miss that in the plans?

[racaldwell]

Bryan, The fuel tank instructions say to use felt cloth on the straps to prevent chafing. There is not statement anywhere I could find that the tank is supposed to be hard pressed up on the firewall support tube. Since this contact is a small area, and the contact point is further away from fixed supports, I am more concerned about chafing there. I would rather have slight clearance but I may find some chafe preventing material. Maybe it is not a concern. I have not heard from anyone who has inspected this area after many hours of use to verify what happens there.

I am not concerned about the bottom of the spout or the top of the tank chafing as the area is large and the contacts are flat. But since I have UHMW chafe tape, I'll put some there just because. I also put it on the crosstie for the same reason.

Like you mentioned, I am thinking of using rubber on the steel straps instead of felt. My One Design had rubber on the steel straps holding in the aluminum tank and that worked well.

Rick Caldwell
Xenos 0057