[Healeys] Tapping SUs for air filters.

simon.lachlan at alexarevel.plus.com simon.lachlan at alexarevel.plus.com
Thu Nov 22 10:14:00 MST 2018

I don’t want to destroy anything. To suggest otherwise is absolutely fatuous. Anyhow, I’ve access to loads of them.

As to horsepower, my car started life with three HS4s. I was able to procure three HD6s for peanuts and took advice as to fitting them. I spoke to Denis Welch and John Chatham’s from where I’d bought the car; their separate opinions were that I would indeed get more power and that I’d maybe be surprised to see fuel consumption drop. I won’t name names, but various of our gurus on this list concurred. I fitted the HD6s. I got better performance and, particularly with higher octane, better mpg. However, I’m sure you know best………..



From: Healeys <healeys-bounces at autox.team.net> On Behalf Of josef-eckert at t-online.de
Sent: 22 November 2018 16:03
To: healeys at autox.team.net
Subject: [Healeys] Tapping SUs for air filters.


So you want to destroy three carburetter bodies???

What do you expect from the three HD6s?? More horsepower - nope!! More fuel consumation!!!






Betreff: [Healeys] Tapping SUs for air filters.

Datum: 2018-11-22T15:49:39+0100

Von: "simon.lachlan at alexarevel.plus.com <mailto:simon.lachlan at alexarevel.plus.com> " <simon.lachlan at alexarevel.plus.com <mailto:simon.lachlan at alexarevel.plus.com> >

An: "Healeys" <healeys at autox.team.net <mailto:healeys at autox.team.net> >




I’ll be removing my carbs soon in order to achieve clearance for raising (the front of) the engine. (Harmonic balancer installation).

So, it struck me that I may give my 3 HD6s another go. Swap them with the current setup.

Thinking it through and looking at the big box of bits, I recalled what a pain it is to get the nuts and two washers onto the bolts that hold on the air filters. I have French manufactured K&N lookalikes. The bolt starts inside the filter, goes through the carb and gets two washers and a nut. Very awkward to deal with those nuts and washers. PITA.

I thought that I might put in helicoils then I thought “Why not tap the holes?”

The holes on my HD6s are 11/32” or 8.8mm.

I am no engineer but it seems to me, from looking at tables on Google, that I could use a 25/64” drill bit and tap them out to 7/16”. I have both the drill and the tap but would like some expertise applied to the issue before I start drilling.

Any input would be much appreciated.



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