Best way to drill manifold for steam take off

Need fellow forum members assistance. I have a Edelbrock RPM Airgap intake manifold that I want to drill and tap for the steam take-off.

What is the best way to mark it up to drill? I am going to use a 1/8 npt to -3 adaptor, so I shouldn't need to get a mill to flatten the external part of the manifold.

All thoughts welcome, as I would like to try and get this done this weekend, assuming I don't need a mill of course....

Thanks

Brett
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
Hi Brett -

I've done these before and it's quite simple actually.
* Drill 1/8" pilot hole in my drill press
* Exchange bit for 1/2" bit
* Using the 1/8" pilot hole as a starting point use the 1/2" bit to lightly face the manifold
* Drill using Q or R size drill (not in my shop so I can't check my chart)
* Use 1/8 NPT tap

Hope that helps..
 

Ron Earp

Admin
I've done the same as Randy but with a hand drill. Worked fine. Start small on the bits, work up. I used a punch to locate the small bit, beat it good and make a good impression.
 
On a aluminum part you would get away with using a suitable size "wood" spade bit to give you a flat if you needed it. Just drill a suitable pilot hole first, than use the spade bit to make the 'flat' and then drill the final tapping hole size. This would be better done in a drill press to ensure the flat is square to the bore of the hole.

Cheers

Fred W b
 
Many years ago I had to have a hole drilled into a manifold and I found the best way was to take it to the local speed shop. Picked it up about an hour later and no worries or mistakes. Don't remember the cost, but it was pretty cheap. Good luck
 

Chris Duncan

Supporter
Pipe thread seals at the threads so you don't need a flat face.

to locate the drill hole look at the gasket and head on the other side and put it in the middle of that hole with the drill hole perpendicular to the gasket surface.
 

Howard Jones

Supporter
I did mine just like Kalun. Works fine, no problems. Go ahead and take the manifold off. It's just a set of gaskets. Easy pezi !
 

Malcolm

Supporter
Hi Brett

Do you need to drill? I have this manifold and have not modified it in any way and have no issues on cooling or air blocks.
 
Brett

I did my old GTD in situ with a hand drill, tapped the fitting and installed the pipework without an issue. If you manifold is on the car I have my edelbrock airgap manifold off at present so I could do the measuring for you, just let me know. Generally you only need to to this mod if the engine is slightly nose down in the chassis which traps air at the back of the heads/inlet manifold.

Regards Martin.
 

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