Does anyone have a guide to converting dhla40’s to throttle bodies preferably in a manner that can be reversed. I want to keep the external looking stick (for a classic car) so the ppc guide they did many moons ago is of no use (I have a copy of that article). The ones I have are the original (no letter) version. I was thinking of removing the chokes etc. and sleeving with some aluminium tube (40mm id with od turned down to a slide fit) and would like to retain the balance screws. What else would I need to blank off?

I'd be doing pretty much what you are proposing to do. I would be looking to incorporate an O ring arrangement at the butterfly end. This would give all the sealing necessary. If it were practical to have a tapered bore ending up at 40mm then I would do that to.

Thanks, do let me know how you get on.

I was thinking if I can get a slide fit then a healthy covering of blue hylomar would seal the sleeve in ok. Do you know if I leave the progression taps and the bleed screw in tact do I need to block anything inside I.e. main and idle jet screws?

If you can achieve a perfect seal at the butterfly end of the sleeve then no other mods should be necessary.

If I can machine the sleeve to be a good sliding fit, plus add a bit if hylomar and then leave it a half a mm proud at the inlet end then I can use the bolt on trumpet to tighten the sleeve against the butterfly shoulder hopefully creating a seal.

Have you found a suitable o ring yet. I think the outer diam would be about 45-46mm with a ring thickness of 2mm would do it, if you can find one.

Something like this? https://www.ebay.co.uk/itm/Metric-Nitrile-Rubber-O-Rings-2mm-Cross-Section-41-120mm-OD-Pack-of-10-30-50-100/222971081603?hash=item33ea1cb383:m:mBQD05r mZXrkjvUuvdk4pIQ

[Edited on 2/12/18 by Ugg10]

I'm not actually doing it, I'm saying how I would approach the job if I was. Your method should work if your injectors are downstream.