IowaTom Posted February 16, 2022 Share Posted February 16, 2022 Guys - My '85 F150's old head was beyond repair and the machine shop had a very good replacement 240 head for my 300 c.i. I notice threaded holes just above the manifold, opposite the spark plug side of the head and believe them to be for fuel injectors. Since my truck is carb'ed, I'm thinking I should plug them, right? If so, what size plugs do I need? As always, thank you!! Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2022 Share Posted February 16, 2022 Tom - If I understand which holes you mean I don't think that the threaded holes, circled in red, are for injectors. I don't know what they are for, but I suspect they are blind, meaning that they go nowhere. But you can check that out by turning the head up and filling those holes with brake cleaner or somesuch. However, the hole circled in green might be for an injector. As far as I know, gasoline injectors are not screwed in but go into a recess, like the one in green, using o-rings to seal them. But you can check that to see if that hole goes into an intake passage, and if there are 5 more of them just like that one into intake passages. If they are for injectors you can seal them with brass cups. I don't know the size, but I ran Big Blue's engine for over a year with those holes plugged with brass cups. So I'm sure we can find out what size they are. I put them in with a smear of non-hardening sealer and it worked fine. Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 16, 2022 Share Posted February 16, 2022 Those may go into the exhaust ports and would be for the smoke grinder (Thermactor system) if they are threaded. If not threaded do as Gary recommends. If your truck does not have that, they can be plugged. They should be a 7/16-20 thread, but could be 3/8-24. Which ever they are get six headless Allen screws (set screws are good due to the point) and put them in tightly. Link to comment Share on other sites More sharing options...
IowaTom Posted February 16, 2022 Author Share Posted February 16, 2022 Those may go into the exhaust ports and would be for the smoke grinder (Thermactor system) if they are threaded. If not threaded do as Gary recommends. If your truck does not have that, they can be plugged. They should be a 7/16-20 thread, but could be 3/8-24. Which ever they are get six headless Allen screws (set screws are good due to the point) and put them in tightly. Thank you, Guys! It's the one circled in green...and that's slick how you can do that, Gary. :-) All six holes are threaded, so I'll use my taps to figure out which size then get those plugs. Sure can't wait to get this baby running again! Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2022 Share Posted February 16, 2022 Thank you, Guys! It's the one circled in green...and that's slick how you can do that, Gary. :-) All six holes are threaded, so I'll use my taps to figure out which size then get those plugs. Sure can't wait to get this baby running again! I think Bill is right, the green one is probably for the AIR (air injection/reaction) thermactor system to inject air into the exhaust. If so, and if it is threaded, you can plug it with a set screw, although I'd use anti-seize on the threads to seal them. But check to see where that hole goes. Link to comment Share on other sites More sharing options...
Rembrant Posted February 16, 2022 Share Posted February 16, 2022 That would be a 300 EFI cylinder head, not a 240. I don't think there was any air injection happening when the 240 was still in production, was there? Here's a picture of what the air injection pipe looked like on the 300 EFI. It had little drop down pipes that fit into each of those holes with threaded fittings. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2022 Share Posted February 16, 2022 That would be a 300 EFI cylinder head, not a 240. I don't think there was any air injection happening when the 240 was still in production, was there? Here's a picture of what the air injection pipe looked like on the 300 EFI. It had little drop down pipes that fit into each of those holes with threaded fittings. I think you are right, Cory. I was sure there wasn't any EFI, but couldn't find anything on the thermactor. But your pic is spot-on. Link to comment Share on other sites More sharing options...
mat in tn Posted February 16, 2022 Share Posted February 16, 2022 I think you are right, Cory. I was sure there wasn't any EFI, but couldn't find anything on the thermactor. But your pic is spot-on. so, the real question here is. is it a 240 head? Link to comment Share on other sites More sharing options...
mat in tn Posted February 16, 2022 Share Posted February 16, 2022 so, the real question here is. is it a 240 head? the threaded holes on the gasket surface are the ones needed to mount the manifolds. the un threaded look to be for injectors as I do see a taper, yet I do not see threads Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2022 Share Posted February 16, 2022 so, the real question here is. is it a 240 head? If we had a casting # I might be able to tell. Link to comment Share on other sites More sharing options...
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