Converting non-SMOG to SMOG manifolds

[Steve Antonucci]

Re: Converting non-SMOG to SMOG manifolds

John,

Is this tap a standard? Possibly available from Snap-On or similar outlets?

Do you have any experience with the actual design of the port itself?

Steve

[Cary Lewis]

Re: Converting non-SMOG to SMOG manifolds

Steve I just solved the same problem on my '74 BB. I'm going back with A.I.R. and my right side exhaust manifold had been replaced with a non A.I.R. manifold. I considered the drill and tap method but found an exhaust expert in St. Petersburg, Fl. that has thousands of manifolds, he may be able to help, call him at 727-525-1558, his name is Neal Bridges. By the way, I'm told that the date on the back of those manifolds can't be seen even with a mirror. Good luck!
Cary Lewis

[Steve Antonucci]

Re: Converting non-SMOG to SMOG manifolds

Thanks Cary !

Unfortunately, I'm one of those people to whom the dates do matter.

I will contact him, but I still would like to consider surgery on my
existing manifolds.

Steve

[Steve Antonucci]

Converting non-SMOG to SMOG manifolds

This is a follow-up question for the research oriented members amongst us.

Can anyone suggest where I can locate a GM drawing showing the SMOG port
details ( depths, angles, tap, etc. )? I looked in Colvin's books. It shows
exhaust manifold 3872741 ( 66-68 small block ) and details the SMOG ports
accordingly. See page 210 ( figure 10-28 ) in the 65-69 "By The Numbers".
I don't know if small & big block ports are the same though. I could not find
any dimensional references for big block exhaust manifolds in either of Colvins
books.

By the way, that drawing does indeed call out a 1/4 - 18 NPSF thread and
not the 1/2 - 20 "straight pipe thread" mentioned earlier.

Any ideas?

Steve

[Joe L.]

Re: Tubes

Paul-----

These particular tubes are the SERVICE replacement for the 1979-ONLY application. The earlier tubes do not have the unusual end configuration.

[Paul L.]

Re: Tubes

Thanks Joe,
I was trying to helpful with the possibility that I was perhaps wrong. I appreciate being being corrected before I led anyone off in a misleading direction.

[John H.]

Re: Converting non-SMOG to SMOG manifolds

Steve -

My previous reference to 1/2"-20 was only to mention that functionally, a 1/2"-20 bolt will thread perfectly into a 1/2"-deep 1/4"-18 NPSF-threaded hole; it's only a coincidence that it works that way.

[Steve Antonucci]

Re: Converting non-SMOG to SMOG manifolds

Sorry John !

Didn't mean to shoot the messenger.

Steve