Fuel cap for 7.5L only?

[1986F150Six]

E4TZ-9030-B - NOS

Why for 7.5L only?

https://www.ebay.com/itm/NOS-1984-Ford-Truck-E-F-V8-460-7-5L-Fuel-Gas-Vacuum-Cap/300269604069?epid=1158568441&hash=item45e9768ce5:g:c88AAMXQnXFRa8Ys

[Gary Lewis]

I grant that it says E4TZ 9030-B and "7.5L Only", but it isn't in the '94 version of the MPC.

[85lebaront2]

If you look though the 1980-86 parts list does show a different cap for the 460, the E4 PN was obviously replaced with a different PN (E7UZ) in 1987. I don't remember exactly what the difference is, but I do remember trying to find locking caps for Darth and they were not available except possibly from Ford.

[Gary Lewis]

I don't doubt you, Bill.  And I could probably prove it by climbing the microfiche tower, but I'll just take your word for it.  

[85lebaront2]

It may have to do with the evaporative system, the 460s even the 1996 systems are different from the smaller engines. They are not a closed system even then, there are still two vent hoses at the tanks, one goes into the evaporative system, the other is open with just a hose with a vent cap.

[Steve83]

I think it's due to the volume of gas &/or air that a big V8 can suck out of a tank, compared to the smaller engines.  The 5.8L uses the same venting you just described - look at the lower Left of this:



So I think the 7.5L-specific cap must have a larger vent to make sure the engine doesn't suck the tank flat (which I've seen pics of, though not by a 7.5L).

[85lebaront2]

You may be correct Steve, but I have seen 5.8L engines that get the same or worse mileage that I get with the 7.5L.

[kramttocs]

Little confused. What am I missing here?
So according to that screenshot, E7UZ-9030-B is applicable to 80-86 460's correct?

But looking at a photo of that cap taken from ebay:

 

It has two extra ears that look even with the normal retaining tabs. My filler necks (86 460) only have two slots so how would this work?

Update: I should have looked closer. The retaining tabs on the E7 aren't the same as the E4 like I thought. They do appear to be higher so I take it this gas cap would be a two step process. First the flat ears, rotate a little, then the retaining tabs, then rotate to close? Wonder why the change.

E4:

[85lebaront2]

It may be for when you are removing it so it can't be blown out by pressure. My front tank would actually dribble fuel in hot weather unless I used it first, the exhaust heat, even with the extra 35" between the exhaust and tank would expand the fuel enough to force it out the cap. The original evaporative system plumbing was a 3/16" line, the 1990 system used a 3/8" line to the dual canisters.

[kramttocs]

85lebaront2 wrote

It may be for when you are removing it so it can't be blown out by pressure

Gotta love the 460!

Does make sense. Thanks!

[Gary Lewis]

Yes, E7UZ 9030-B is for 80/86 F250/350 - - 8 cyl, 460.  (Notice that the MPC implies there was a 460 in years when there wasn't one.)

And I suspect Bill's right - the heat does cause the front tank to build up pressure.

[ArdWrknTrk]

And the U is for Bronco?

460's had no Cats, and therefore no 'unleaded fuel only' warning.
Maybe the filler neck is larger to accommodate the bigger nozzle?

(Ack! I'm dating myself again, aren't I?)

[Gary Lewis]

Yes, the "U" is for the Bronco.

Dunno about the neck.  Don't see anything specific to the 460, but maybe I'm missing something?

[ArdWrknTrk]

I didn't realize Bronco's came with the 460.

I thought the 460, 6.9 and H.O. were only found in 250-350 trucks.
And that 150's/U got the 300, 302 & 351.

I guess I was very wrong.

[kramttocs]

Even with the 'U' it will fit the 86 F250 right? Asking because I needed new ones as my gaskets were crumbling so I ordered some last night but cancel still if needed.

I'd briefly mentioned about the 'flapper' on some necks in the filler neck thread but thinking about it, the 3 86 460 trucks I've looked at had large mouths (not the main opening but the one a little further in) and none of them have that flapper. The other trucks (didn't pay attention to the motor but I know they weren't 460's) has the flapper and I think smaller mouths.

The size of the vent was mentioned above and you can see in the ebay photo the large cream colored part in the center of the cap underneath. The other caps I've looked at are all metal there except for something like a 1/8 hole.

[ArdWrknTrk]

U means it was originally designed for the Bronco.

I remember those little restrictor plates in the filler necks very well.
I used to pump gas 10-7 overnight, then get to high school by the 7:20 bell.

[kramttocs]

Just to followup, they fit the filler necks for my 86 460 fine although the whole 2 step twist process will get old really fast.

[Gary Lewis]

Interesting!  I'd heard about that cap, but don't guess I've ever seen one.  Maybe I don't care to?

[kramttocs]

I'd stick with the E4.
Good thing the 460 hardly ever needs filled up

[Gary Lewis]

Mine hasn't had gas added to it in a month, and probably won't for the next six months.