I have done my research and just want to make sure I have this right-
I am (at least temporarily) pulling off the A.I.R. system from my '83 305 engine. Part of the system is rusted apart, so off it comes.

I need to plug manifold holes with 5/16" inverted flare plugs? Are these brass? This seems to be the right size for late 80's models, just want to make sure it's the same for 1983.

Thanks much!

 

Don't know the differences 80's to 90's but on my 91 305 I used these brass LFA-737 from Home Depot 1/4 male MIP pipe plugs ....maybe the 80's are different sized ???????

 

the inverted flare plugs seat to the flare you'll see at the bottom of the threads on the manifold once the AIR is removed. you may be able to seal fine with standard plugs though. expect to need some heat to remove the old fittings. good time to replace the lower manifold studs at the same time.

 

They are ALL 5/16" inverted flare. Year doesn't matter.

Sure, you can jam pipe plugs in there, and with enough Teflon tape, they'll be fine; but if you want to do it RIGHT, like, finger loose until they seat and then TORQUE EM, and when you want to remove em you break em loose with a line wrench and then back em out with your fingers, they're 5/16" inverted flare.

 

I plugged mine with 1/2" grade 8 bolts from ace hardware... And for the AIR tube coming off the cat was plugged with a 3/8" plug and exhaust sealant. Has been silent so far, but an AIR fitting broke the threaded nut in half in the manifold. Couldn't drive a bolt in that hole and requires removal.