Just curious if anyone has tried that ? I want to try a Holley 950 HP carb on my 63 but it does not have the vacuum nipple in the back like my 850 does that I use for my PCV vacuum line. So since I use a 1" open phenolic spacer I was thinking of drilling it and adding a vacuum nipple for my PCV system ? I don't see why it cant be drilled and tapped for the nipple ? Ron

I think just using a sharp bit in a drill press to control feed would be best, tapping, never done that before


https://www.alro.com/datapdf/plastics/plasticsmsds/msds_phenolicce.pdf

google it, seems dust is an issue

I've drilled them before. Best to drill a pilot hole first. Then a hole that is the ID of the tubing you want and then a final hole slightly larger than the tubing OD about 90% of the way through. This gives you a step that you can use when you epoxy the tube into the spacer. Never had luck trying to tap phenolic.

The resins vary but basically its no different than drilling fiberglass. I can't see drilling kicking up much dust to the point it would be an issue unless you're close enough to snort it. You want to start with a small pilot hole for sure. Keep in mind the layers are usually a cloth or canvas so use a sharp bit so it will cut clean.

Drill and tap just as you would anything else.
drill, Pipe tap, thread sealant and put your nipple in.

Machine shops all around the US use phenolic sheets as hold down fixtures, jigs, and tooling. For all sorts of stuff from one off fixtures to assembly tools, nothing special about working with it.

It's been my experience trying to drill and tap a phenolic carburetor spacer that the tap, because of the taper, will split the spacer at the hole. Now maybe I've had inferior spacers or dull taps but that's my experience.

Hey Ron, you know, if I remember right I think the 950 and 850 both have 1 and 3/4 butterflies in the baseplate.

Might be able to just swap the baseplate for the test and see how it goes?

Just a thought

Thanks for all the kind replies. I pulled the spacer off today and drilled and tapped it. I was very careful and took my time as I was worried it might crack but it worked out ok. So I finished up the mods on my 950 and plan to put it back on the car one day this week when I feel up to it. And I hope to try it at the track in April or May if I can make it to the track. Thanks again for the replies. Ron

Good thought and if it had not worked I might have checked it out. Thanks , Ron

I know you got it tapped, but if you have issues of the fitting coming loose you may be able to epoxy an fitting in the hole.

I was going to put some epoxy on the threads but it went in on the tight side so I don't think its coming loose. But I wil keep an eye on it. Ron

i know i'm late to the party [so what else is new ?], but when tapping plastics, a taper reamer for your desired pipe thread, makes things easier and prevents cracking.
glad you got it tapped ron. taking it easy and using sharp tooling was the key.