Bolt size for smog rail
11-02-2017, 08:41 PM
#1
Bolt size for smog rail
I recently put a brand new cylinder head on my 1992 4.9L inline 6. After getting it mostly back together, I noticed that the head I have has holes for that smog rail / air pump thingy. My truck doesn't have the rest of the system, so I'd like to plug those of with bolts. Anyone know the thread type / size I could use?
Thanks,
Rob
Thanks,
Rob
11-03-2017, 09:12 AM
#2
Senior Member
5/8-11
Ford actually sells plugs for them - I think they are called thermactor plugs.
Ford actually sells plugs for them - I think they are called thermactor plugs.
11-03-2017, 10:38 AM
#4
If anyone checks this later down the road, I ended up ordering from these guys (https://www.mustangsetc.com/). It was Ford part # C6AZ6052A.
------ Edit ------
Turns out those plugs are too small in diameter. Too bad because they looked great. I ended up using 9/16ths diameter bolts with 18 TPI. Length was on the short side, shorter the better. If I find the right plugs, I'll update this again.
------ Edit ------
Turns out those plugs are too small in diameter. Too bad because they looked great. I ended up using 9/16ths diameter bolts with 18 TPI. Length was on the short side, shorter the better. If I find the right plugs, I'll update this again.
Last edited by Rob Lisy; 11-09-2017 at 09:41 PM.
01-08-2024, 05:26 PM
#5
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Homemade Smog Rail Plug
I have a 1992 f150 with a 4.9L 300 I6 that I bought a remanufactured cylinder head to replace the old cracked one. I couldn’t get the smog rail off and decided to bypass the smog pump anyways. To plug the holes I used 1/4” pipe and it threaded right into it.