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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

85 f250 mystery part question

 
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Old 06-10-2019, 06:54 PM
Dillweed73
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85 f250 mystery part question

Hey guys,

Quick question for all you experts out there,

i have an '85 base model f250 2wd 4 speed granny low that originally had a 2bbl on it. Always sounded like I had an exhaust leak even after I put headers on and I noticed this broken pipe with air coming out of it that is the source of that sound. It's bolted to the back of each cylinder head and t's off in the middle. What does it do and is it needed? Can the now open ports (I removed the piece in question) be blocked off?

Thanks in advance for all the help!


 
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Old 06-10-2019, 08:46 PM
whisler
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That part connects the Thermactor system to the back of the heads. The holes in the back of the heads can be plugged with 5/8-11 bolts cut to 0.40 inches in length. Use a copper washer of the correct size to ensure proper sealing. Hope this helps.
 
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Old 06-10-2019, 09:42 PM
kr98664
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Please see post #20 here for an excellent description of the thermactor (air injection) system:

https://www.ford-trucks.com/forums/1...l#post18618032


Also see post #27 in that same thread for my experience, basically the same as yours.
 
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Old 06-11-2019, 01:18 PM
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Originally Posted by Dillweed73 View Post
Here's an example of the little darlin' .. 351W will be similar to 302.
 
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Old 06-11-2019, 04:43 PM
kh0432
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I had the same problem with my 86 F150 with 5.0L fuel injection. I've already deleted most of the emission controls. The holes in my head don"t appear to be threaded so I made a gasket out of asbestos gasket material to block off the hole. Would the 5.0 heads take the same 5/8 bolt?
 
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Old 06-12-2019, 07:21 AM
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Originally Posted by kr98664 View Post
Please see post #20 here for an excellent description of the thermactor (air injection) system:
That's an excellent write-up.

To the OP, be aware that removing the thermactor can be risky if your still running catalytic converters (as the linked write-up mentions in one of the last paragraphs).
 
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Old 06-13-2019, 07:11 AM
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Old 06-18-2019, 08:49 AM
Dillweed73
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Just want to thank all you guys for replying,

I ended going with what Whisler posted, cut some bolts down and plugged the holes and the exhaust leak sound went away completely. My trucks been stripped of all emissions equipment including the cats so that thermactor pipe was just sitting there broken with the rubber hose not connected to anything.

Again I want to thank all of you for the help!
 
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Old 06-23-2019, 12:13 PM
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I previously asked if the 5.0 L had the same size tread where the A.I.R. tube goes. It is a 5/8 18 like in the 351. I couldn't get the bolt started before because of all the carbon in the hole. I couldn't fit a tap between the firewall and head so I cut the tap down and ground the sides so iI could turn it with a short 7/16 wrench. Not easy to access but it is doable. Once the treads were cleaned out it was no trouble putting in the bolts. Laid a piece of plywood on top of the engine and radiator support to have something to lay on. A cut out tennis ball works pretty good to keep from getting jabbed from the hood catch. Other than the catalytic converter and oxygen sensor the are no other emission parts on my truck. Runs really well and is quiet now that all the exhaust leaks are plugged.
 
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Old 06-23-2019, 01:07 PM
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Originally Posted by kh0432 View Post
A cut out tennis ball works pretty good to keep from getting jabbed from the hood catch.
Oh sure, the simple 30 second solution that works perfectly...

Or if one prefers to overdo anything and everything:

https://www.ford-trucks.com/forums/1...ab-me-not.html
 

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