[malstrom]

Hi Friends

I have been searching for months on my garage queen for a bad lifter sound or exhaust leak. SHop vacs tests, soapy water sprays and finally the only thing that worked was a good old Oven MITT on a cold start engine. I was throttling header pipe surfaces with the mitt when ........

I can believe what i found, So help me understand !

I have a hole that was used to mount my Transmission tube. Its was plugged which never amounts teh tube flange because its too big for the tube flange hole. So I could never find the right adapter, So i got lazy and left this off ..It just a mounting point. right ! WRONG ! I cant get my eyes back there and when probing I find the large hole is pumping out air on a idling engine. WTF! these are not smog heads so why is this hole open?

I have been struggling with 10 MPG prb;ems, Ive changed carbs, just finished a valve lash adjust and ..........can this really cause 10 MPG..loss, The push is gentile garden hose strong but i can seal it with my finger no problem.

the smaller threaded hole below the freeze plug is burned but not pumping air.

What is this !

 

[EmbergloConvertible66]

You have heads that used thermactor air injection in their original configuration. Use plugs from Silver Seal # 6556. You'll need a quantity of 2.

Silver Seal Products Category

Silver Seal Products categories page

shop.silver-seal.com

 

[Maxum96]

You have heads that used thermactor air injection in their original configuration. Use plugs from Silver Seal # 6556. You'll need a quantity of 2.

Silver Seal Products Category

Silver Seal Products categories page

shop.silver-seal.com

Yup. The transmission dipstick tube does not mount to that. It goes on one of the transmission bellhousing bolts.

 

[my289]

I used these to block the holes in the GT40 heads I had, wish I would have known about the ones Emberglo pointed out:
.

Trick Flow Specialties TFS-51400265 Trick Flow® Small Block Ford Thermactor Inserts | Summit Racing

Free Shipping - Trick Flow® Small Block Ford Thermactor Inserts with qualifying orders of $99. Shop Plug Fittings at Summit Racing.

www.summitracing.com

.
But looks like its a just 5/8-11in bolt. See if you can find a bolt and plug it up be alot cheaper.

 

[richardsimon52]

Congratulations...as frustrating as this may have been, it's always satisfying to find the problem.

 

[malstrom]

You have heads that used thermactor air injection in their original configuration. Use plugs from Silver Seal # 6556. You'll need a quantity of 2.

Silver Seal Products Category

Silver Seal Products categories page

shop.silver-seal.com

Thanks Emberglo SOOOO much ! I am still a bit perplexed. I has a pressure coming out the hole .. why is that... Im fearing my heads are cracked?

 

[Anangryford]

I used short bolts to plug those.

 

[stroker393]

Persistence is a learned behaviour on classics. Well done.

 

[rusty1161]

Thanks Emberglo SOOOO much ! I am still a bit perplexed. I has a pressure coming out the hole .. why is that... Im fearing my heads are cracked?

Those are open to the exhaust ports on an emission control engine. Get those plugs and you will fix the issue.

 

[malstrom]

Those are open to the exhaust ports on an emission control engine. Get those plugs and you will fix the issue.

Thanks Rusty ........okay So I thought I had 65 heads on my 66. The engine stamp on the block is '5'. So okay 66 heads on the engine. But they are not smog heads. I have a set of those with hole inputs each cylinder. Still confused.

 

[malstrom]

I used short bolts to plug those. View attachment 825989

Mr Angry
you also have holes below the freeze plugs . Are yours producing air Cuz I cant get back there to know. I dont feel air out of them. And wonder why mine are burned.

 

[Anangryford]

Mr Angry
you also have holes below the freeze plugs . Are yours producing air Cuz I cant get back there to know. I dont feel air out of them. And wonder why mine are burned.

I connected the engine ground to the passenger side below the freeze plug. Nothing on the drivers side. I had no exhaust leaks.

 

[Woodchuck]

Thanks Rusty ........okay So I thought I had 65 heads on my 66. The engine stamp on the block is '5'. So okay 66 heads on the engine. But they are not smog heads. I have a set of those with hole inputs each cylinder. Still confused.

There were 2 different styles of Thermactor used. The more common ones are "internal" with the holes on the ends of the heads. The "external" version used a "spider-like" manifold, like GM used on its engines with individual holes next to the exhaust ports. IIRC, the "internal" versions were cast at Windsor foundry and the "external" ones at Cleveland, or vice-versa. BOTH types are "smog" heads.

 

[malstrom]

There were 2 different styles of Thermactor used. The more common ones are "internal" with the holes on the ends of the heads. The "external" version used a "spider-like" manifold, like GM used on its engines with individual holes next to the exhaust ports. IIRC, the "internal" versions were cast at Windsor foundry and the "external" ones at Cleveland, or vice-versa. BOTH types are "smog" heads.

Thanks Bart

I ve only known the External type .............So I guess the thermactor holes exit air into a tube for a smog system to re burn gases?

 

[5R07K252388]

I ve only known the External type .............So I guess the thermactor holes exit air into a tube for a smog system to re burn gases?

No, "re burning" would describe a later type of emission system, aka the EGR.
Thermactor was a short-lived (1966 - approx '69) pumped air injection system called an AIR (air injection reactor) that just provided extra air directly into the exhaust port downstream from the exhaust valve:

:

 

[Flade]

No, "re burning" would describe a later type of emission system, aka the EGR.
Thermactor was a short-lived (1966 - approx '69) pumped air injection system called an AIR (air injection reactor) that just provided extra air directly into the exhaust port downstream from the exhaust valve:

View attachment 826881

:

That’s the External style head.

 

[KD Blue]

I used these to block the holes in the GT40 heads I had, wish I would have known about the ones Emberglo pointed out:
.

Trick Flow Specialties TFS-51400265 Trick Flow® Small Block Ford Thermactor Inserts | Summit Racing

Free Shipping - Trick Flow® Small Block Ford Thermactor Inserts with qualifying orders of $99. Shop Plug Fittings at Summit Racing.

www.summitracing.com

.
But looks like its a just 5/8-11in bolt. See if you can find a bolt and plug it up be alot cheaper.

Should be a standard pipe-thread hole.
Any local hardware store should have something U can thread in there, using some sealer compound.
Just don't drive some long threaded shaft in there and puncture something. Use something that is just deep enough to fill the hole depth.

 

[Woodchuck]

Should be a standard pipe-thread hole.
Any local hardware store should have something U can thread in there, using some sealer compound.
Just don't drive some long threaded shaft in there and puncture something. Use something that is just deep enough to fill the hole depth.

No, the Thermactor holes on the ends of the heads are 5/8-11.