Exhaust Manifold Smog Holes ??

[John Brown]

Did several searches and came up empty. I seem to remember someone asking who machines non smog manifolds to accept the smog stuff. I have a friend that need it done to his big block manifolds. Any help would be appreciated. Thanks.....

[Chevy454]

How about I just swap him a set *with* the holes?

[John Brown]

Thanks Rob, but.... he wants his done cause they're date coded to his car?? Already tried that but it was a "no go".

[Chevy454]

Bummer...he posseses the hardest ones to find, then!

[nuch_ss396]

Hi John,

If it's the one I'm thinking about, I was the one that
started that thread some time ago. Here's the link.
Let us know how you make out here.

Steve

SMOG port machining topic

[SS427]

Most any reputable engine machine shop will do these for you. I brought my manifolds to my engine builder along with the tubes so that he could use them for measurements. $100 and one day later they were done.
Rick

[John Brown]

Steve,

Thanks for the link. I didn't think it was that long ago so I didn't look that far back. That was the thread I was looking for. I'll pass the info along. Thanks again.

[Unreal]

Could you talk your friend into installing replacements, and keeping the originals unscathed? I'm pretty sure you can't undrill a hole.

[k92]

Jerry Mcneish currently has my ls6's exhaust manifolds.He said that he does not have the ability to drill the smog holes so when I get them back I am having a local machine shop drill the holes. One of my manifolds is the original so it has the smog holes, the other I had to buy off of ebay and it needs the holes drilled.

[427king]

Rick while its true any machine shop can drill the holes not too many can or know to drill the "step" so that the smog pipe will slide in and fit properly,its not just simply drill a hole and your done.The tubes have an angle so they seal and its also a special tap. If you look at the hole from the backside of the manifold it is smaller than in the front. Ive actually had all the machining and tools made up and can have these done to perfection for 80.00 a pair for members only. Not trying to make a buck off this post, but ive seen so many done improperly just so as the pipes would fit,yet there was no angled lip for the short inner pipe to seal against. I guess you can just drill and tap a hole if your not using the inner pieces and that will work,but it really isnt correct or complete. The other issue is alot of times ive seen redrilled manifolds have the holes off center, and also have seen some where the pipes actually didnt fit because the holes[angle] were off just enough. thats a big problem on a set of 1500.00 manifolds