HoraceM Posted October 27, 2009 Share Posted October 27, 2009 Has anyone got an H6 SU carb? It will be 1 3/4" dia. with a single banjo at the bottom holding a 2 1/8" or 3" fuel float chamber on it with the airflow venturi horizontal and the float chamber vertical ( as opposed to being set at 15 or 20 degrees as some carbs were) I think I have at last figured out what is causing all of those explosions on my supercharger........ Further to the above, I have now been advised that it is an HD8 (2" dia) that will best suit my application and will still fit. This will have the float bowl held on by four bolts. Cheers All ATB H. Link to comment Share on other sites More sharing options...
John Loudon - Sponsorship Liaison Posted October 27, 2009 Share Posted October 27, 2009 Horace - what were they originall fitted to? Link to comment Share on other sites More sharing options...
John Fisher Posted October 27, 2009 Share Posted October 27, 2009 Horace, Does it have to be an H6 - as these are very old as opposed to an HS6 which is a newer (but still old) carb? If I remember correctly the HS6 was fitted to Rover 2000/2200SC & some Jags. The mounting flanges would be the same, but the main difference is the connection of the float chamber to the jet. Hope this helps a bit Fish Link to comment Share on other sites More sharing options...
stu999 Posted October 27, 2009 Share Posted October 27, 2009 Horace - dont worry about the float chamber angle on the HS6 - that can be 'set' anywhere you want it. If you unbolt the float chamber from the side of the carb, you will find that there is a little removable 'lug', that sets the angle of the chamber in reference to the carb. Either change the 'lug', or make/modify to adjust the float chamber so that it is level when the carb is mounted at the desired angle - jobs a goodun Link to comment Share on other sites More sharing options...
John Fisher Posted October 27, 2009 Share Posted October 27, 2009 Evenin Stu Is it only us old'uns that remember SU's Fish Link to comment Share on other sites More sharing options...
John Loudon - Sponsorship Liaison Posted October 27, 2009 Share Posted October 27, 2009 My old Dolly Sprint had them. They didn't give any trouble unlike the Webers on my old X Flow Link to comment Share on other sites More sharing options...
stu999 Posted October 27, 2009 Share Posted October 27, 2009 Evenin Stu Is it only us old'uns that remember SU's Fish Fabulous carbatooters The H6 is indeed an 'old example' of the breed, and a HS6 would be a worthwhile upgrade - unless there is a reason why a H6 *has* to be used... I'll have a rummage round. I might have either or neither. Watch this space... Link to comment Share on other sites More sharing options...
HoraceM Posted October 28, 2009 Author Share Posted October 28, 2009 Cheers all, I'm told by the very helpful guys at SU that as I need a 0.125" or 0.150" main jet it has to be an H6 (or an HD6) as the jet in the HS cannot be changed. On the HD6 these have the float assy held on by four bolts (in some sort of ring on the side, I presume) as opposed to the single banjo bolt underneath. I think the HS (the one I don't want) has the flexible fuel transfer pipe, as well as a 0.100" jet. A manual choke assy would help as well, but I'm sure I can get something sorted - vacuum or electric, just need the carb, eh? Whilst you're all having a shufty about, if you have a choice of carbs to send me, one with a brass piston would be a big advantage as well (it slows the response of the carb under supercharger suck!!) Don't suppose there'll be too many of those - I think some of these carbs may have been fitted to old Triumph TRs and some old Jags 3.8 and 4.2's - so almost brand new!! Thanks all, keep looking ATB H. Link to comment Share on other sites More sharing options...
stephenh Posted October 28, 2009 Share Posted October 28, 2009 Whilst you're all having a shufty about, if you have a choice of carbs to send me, one with a brass piston would be a big advantage as well (it slows the response of the carb under supercharger suck!!) Don't suppose there'll be too many of those It is many years since I played about with SU carbs, but dont you just change the piston spring to slow down the rate of change of the venturi? I never played with an engine with a blower, but I'd guess you would want a stiffer spring to stop the effect you refer to? Link to comment Share on other sites More sharing options...
HoraceM Posted October 28, 2009 Author Share Posted October 28, 2009 Yes, changing the spring pressure is the way things are done now, but only because the pistons are so much lighter than the brass ones as they are now alloy. (my rolling road man said I should take mine out and fill it full of solder!!! - I thought "No thanks, I'll leave it as you set it") ATB H Link to comment Share on other sites More sharing options...
stu999 Posted October 28, 2009 Share Posted October 28, 2009 Mmm. Dont want to argue with SU, and it is a long time since I have meddled with this particular type of carb, but I thought the HS jets *were* interchangable with others in the range (as you say, this is incorporated in the flexible fuel transfer pipe) - and that it would merely be a case of swapping the jet from a carb with the desired size. Unless there isnt one with the desired size of course! The other thing to consider is attacking a main jet with a drill, and drill it out to the size you need. Not as drastic as it sounds, and if you go too big, you can always solder it up and have another go (bearing in mind using a suitabkle heat sink so as not to melt the plastic bit). I'll have a rummage, nontheless P.s. - the rate of piston height change is governed by the thickness of the oil used in the dashpot, which effectively is the the accelerator pump mechanism on an SU, and to a lesser extent, the amount of holes in the floor of the piston - although this probably only affects HS carbs, as I think the 'H' carb only ever had one hole IIRC. The spring strength and piston weight decides just how far 'open' the piston is for a given rpm (once things have settled). The piston should ideally be *just* fully open at the point where maximum power is produced. I SU's! Link to comment Share on other sites More sharing options...
salexander Posted October 31, 2009 Share Posted October 31, 2009 I seem to recall using an HIF-6 on my autotest Mini's many years ago. flowed nearly as much as a pair of 1-1/4" carbs but cheaper and easier to setup. Maybe used on Allergro's and similar??? Link to comment Share on other sites More sharing options...
stu999 Posted October 31, 2009 Share Posted October 31, 2009 I seem to recall using an HIF-6 on my autotest Mini's many years ago. flowed nearly as much as a pair of 1-1/4" carbs but cheaper and easier to setup. Maybe used on Allergro's and similar??? Yup, best 'flowing' of all of the SU's. But not so good at mounting horizontally, as per first post... Link to comment Share on other sites More sharing options...
HoraceM Posted November 5, 2009 Author Share Posted November 5, 2009 I have an HIF6 at present - That's why I want to change. I have been told that a 2" would mount on the same bolt fixing I have so this is what I will now try and find, an HD8 (2" dia) - these have the float bowl held on by four bolts and will have the .125 or possibly a 0.150" main jet. Link to comment Share on other sites More sharing options...
Recommended Posts