engine block

[mightymopar]

Hi Guys, I have a 67 Coronet 500 with apparently a 76-79 318 in it and not the original exhaust manifolds. My question is underneath each port is a small unthreaded hole that goes up into the port opening and when changing exhaust man. gaskets I cant seem be able to get a gasket that will cover these holes and stop the frigging leaks, and exhaust leaks really suck. Does anyone have a solution. I though about self tapping SS screws in there, whatya think? Thanks, Dave

 

[Mopar To Ya]

I can't remember if the late model manifolds dump into the same spot as the late 60's ones. I am guessing you are using the old style manifolds. I think lots of people have sealed these by tapping for set srews with hardening threadlocker. All hail the smog head.

 

[Meep-Meep]

Those are for air injection and those heads require a matching exhaust manifold that connects those holes to the air injection manifold. You can surely tap and plug them with set screws but I think a 1/8-27 pipe plug will require drilling the hole bigger. If I recall you might be able to get away with a 5/16-18 thread size.

 

[Cranky]

Tap them with a 1/4 x 20 tap and install allen socket set screws. Just use the 'second' tap and don't go very deep....and cast iron doesn't need any tapping compound so don't bother making that mess and don't buy a China made tap unless you like digging out broken taps.

 

[mightymopar]

Thanks Guys, all of you have been really helpful. Dave

 

[mightymopar]

Hey Cranky, not sure what you mean by the "second" tap

 

[Cranky]

Generally, taps come in a set of 3...a starter tap or taper tap, an intermediate or second tap and a bottom tap which is usually called a bottom tap Cast iron is tough on taps so a good quality one should be used. Cast iron is gritty and using a lube won't do much of anything except be messy. Once you get all the holes done, fire it up to blow out any grit then plug em.

 

[mightymopar]

Thanks man, Dave