Fire Wall opening / hole?

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Fire Wall opening / hole?

FuzzFace2
I have a buddy with he thinks is a 83 or 84 F150 and that is about all we know of the truck.
He told me the motor, 302/auto, did not come in that truck based on the radiator sticker as is has 3.8L.
I think the support was replaced with a used one and why the sticker does not match.
Then again the oil pan is sitting on the cross member so who knows?

Any way a lot of wires have been cut & spliced for this 302 motor install but there is 1 hole in the fire wall with a bunch of cut wires hanging out of it. Sorry no picture(s)
It is an oval shape hole more to the center of the wall at the back of the motor.

Any clue what this hole & wires were for? I thought FI but I don't remember a large opening for the tank sending unit for a in tank pump or a return line. The truck has a flare side and no floor and why I side about the tank from what I remember seeing.

If the truck had a feed back system, 300 six or 302, would this be where the wires went thru?
I have never seen under hood of a feed back system to know where this system hangs out.
I did not think to look on the inside under dash to see what was there at the time.

His parts truck that could also be a 83 or 84, 1 is 1 and the other is the other he is not sure.
It has 300 six that looks factory and I did not see this opening / hole and if the year(s) are right would be a feed back system.
Thanks for any help you can give
Dave ----
Dave G.
81 F100 flare side 300 six/T18 project
http://cars.grantskingdom1.com/index.php/1980-Ford-F100?page=1
81 F100 style side 300 six/SROD parts truck -RIP
http://cars.grantskingdom1.com/index.php/1981-Ford-F100
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Re: Fire Wall opening / hole?

Angelo Voltura
85 was the first year for FI and I believe was only available as an option on the 302. The 300 would have had a feedback system with a Carter YFA 1bbl.

Here is the other thing, if that truck indeed had a 3.8, it would be in an F100 and not an F150. They were only offered in the 100s.

I've only seen one truck with the 3.8 in it and I do not remember there being a hole there. Feedback system stuff went through the firewall over by the master cylinder, in fact my fathers EEC is still in the firewall.

If you can supply pictures, that would be fantastic.

From the sounds of it, the truck is probably a hodge podge of pieces and parts.
1979 F150 "406M"
1985 F250 (Dads) 351W
1995 F150 (1985 clip swapped) 300
1997 F250 HD 351W
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Re: Fire Wall opening / hole?

Rembrant
In reply to this post by FuzzFace2
FuzzFace2 wrote
If the truck had a feed back system, 300 six or 302, would this be where the wires went thru?
Yes. My truck, an '84 (302, non-feedback) just has a rubber plug in this hole, and I have a spare oval plug I removed from an '86 F150 (300/6, non-feedback). See below.



On the '85 302 EFI truck that I had and junked, this is where the EFI wiring harness passes through the firewall, and the ECU is in the dash directly behind it. I removed this whole harness separately and sent it to another forum member.

The wiring harness for the Feedback carb trucks also passes through this oval hole, but I believe only in the later models? I'm not up on the feedback carbed truck details, but I've often heard people comment that if you're looking at a truck for sale online, that is the first clue that it is a feedback set-up...that wiring harness through the oval hole directly behind the engine (right next to where the throttle cable is and the ground lug on the firewall).

I'd rip it all out and get a blank plug from a Non-feedback DSII truck if possible.


1984 F150 4X2 Flareside. Mild 302 w/GT40 heads, BBK headers, Holley 4bbl, XE256H Comp Cam, M5R2 5spd swap, Magnaflow full duals. Fresh Medium Blue Metallic in August 2019.
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Re: Fire Wall opening / hole?

Rembrant
Dave,

Here's a screen grab from a 1986 with a feedback 300/6. You can see the oval hole in the firewall has a wire harness going through it. You can't see it well, but that's what it is.

1984 F150 4X2 Flareside. Mild 302 w/GT40 heads, BBK headers, Holley 4bbl, XE256H Comp Cam, M5R2 5spd swap, Magnaflow full duals. Fresh Medium Blue Metallic in August 2019.
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Re: Fire Wall opening / hole?

FuzzFace2
Thanks guys and yes "From the sounds of it, the truck is probably a hodge podge of pieces and parts." is an under statement from what I have seen!

Being the wires are cut right at the wall and he has no plans of going with that system he will have to find a plug for the hole. I wonder if the box is still there if he could get any thing for it?

I would like to know what motor came in the truck as I think it would help him some.
Feed back would be a 300 IIRC so the 302 oil pan sitting on the cross member may have the wrong frame mounts if the 300 mount could even be used with the 302? I do know that are different or bolted in a different place or both?

He is going to have fun with this build LOL
Just hope he does not give up on it like the Chevy Luv with a 350/350 sitting in the garage has.
Then again he is more of a Ford guy with a 66 Mustang and late 60's pick up.
Dave ----
Dave G.
81 F100 flare side 300 six/T18 project
http://cars.grantskingdom1.com/index.php/1980-Ford-F100?page=1
81 F100 style side 300 six/SROD parts truck -RIP
http://cars.grantskingdom1.com/index.php/1981-Ford-F100
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Re: Fire Wall opening / hole?

Frank Wyatt
Not that it helps but my 1985 F250 had a 302/AOD with feedback carb and it's MCU was under the seat on the passenger side. It works well when everything is working correctly but if not a non feedback carb and DS II distributor is the way to go.
1981 F 150 Custom 300 ci Carter YFA T-18 3.25 9" rear 2WD
all emissions intact except thermactor pump and cat
dual gas tanks
1990 Lincoln Town Car 5.0 AOD
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Re: Fire Wall opening / hole?

Frank Wyatt
Also the frame perches and oil pan may not be correct for the engine. IIRC pre 1980 302 trucks had a front sump pan and maybe the previous owner was unaware of the change from the front to rear sump change.
1981 F 150 Custom 300 ci Carter YFA T-18 3.25 9" rear 2WD
all emissions intact except thermactor pump and cat
dual gas tanks
1990 Lincoln Town Car 5.0 AOD
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Re: Fire Wall opening / hole?

LARIAT 85
In reply to this post by Frank Wyatt
Frank Wyatt wrote
Not that it helps but my 1985 F250 had a 302/AOD with feedback carb and it's MCU was under the seat on the passenger side. It works well when everything is working correctly but if not a non feedback carb and DS II distributor is the way to go.

That's interesting, as my 1985 F150 that also has a 302/AOD *had* a feedback carburetor and it's computer was located under the dashboard, right about where that firewall plug is located.  The wires that fed the computer ran through that firewall plug.  When I did the DSII conversion on my truck, I also got a blank plug to fill the hole, like the one in Rembrandt's post.

I agree in that the feedback carburetor is a good system, provided everything is present and in working order.  Unfortunately, mine came to me second hand and missing many vital parts.  

Lucille:  1985 Ford F150 XLT Lariat

*Colors:  Dark Canyon Red exterior, Canyon Red interior
*Engine: 5.0, CompCams 31-230-3, "Thumper" E7 heads, Edelbrock Performer intake, Autolite 4100 carburetor, DuraSpark II ignition, Thorley Tri-Y headers, Flowmaster dual exhaust, H-pipe.
*Drivetrain:  AOD transmission, 3.55 gears, 2wd.



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Re: Fire Wall opening / hole?

Frank Wyatt
Feedback system malfunctions weren't as easy to diagnose as EFI so more often than not it was not working correctly. I changed mine out soon after getting it as well and installed a non feedback carb.
1981 F 150 Custom 300 ci Carter YFA T-18 3.25 9" rear 2WD
all emissions intact except thermactor pump and cat
dual gas tanks
1990 Lincoln Town Car 5.0 AOD
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Re: Fire Wall opening / hole?

85lebaront2
Administrator
In reply to this post by LARIAT 85
The firewall oval hole was on all the 1985/86 trucks I have seen, whether it had and FBC, EFI or none of the above. Darth has a large oval plug there and I had considered using that to run my EFI wiring through. The 460 is big enough to require the wires to bend upward after passing through, and a bad motor mount would probably break or cut them. The EGR pipe runs very close to that area also.

I went with the later location, in the left kick panel area with the 104 pin connector underhood.
Bill Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 1994 Taurus LX Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Fire Wall opening / hole?

Angelo Voltura
Wow I didnt even realize it was there on my dads truck, I just looked at a picture lol.

I didnt realize it was that hole.

1979 F150 "406M"
1985 F250 (Dads) 351W
1995 F150 (1985 clip swapped) 300
1997 F250 HD 351W
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Re: Fire Wall opening / hole?

FuzzFace2
In reply to this post by 85lebaront2
Thanks guys I looked at the truck again and it does look to be a  hole for the feedback system and the computer was mounted to the lower edge of the dash.

As for the oil pan hitting the cross member I think the truck should be running a rear sump pan but that's me.

I tried to get VINs but that is a no go till the trucks are pulled apart more so we can see the dash numbers or the titles. Guess we don't really need them but I would like to know what the trucks started as as it should help down the road.
Thanks again
Dave ----
Dave G.
81 F100 flare side 300 six/T18 project
http://cars.grantskingdom1.com/index.php/1980-Ford-F100?page=1
81 F100 style side 300 six/SROD parts truck -RIP
http://cars.grantskingdom1.com/index.php/1981-Ford-F100