| Author | Message | ||
     Jeff Martin Experienced User Username: jeff_r_1 Post Number: 127 Registered: 07-2018 |
I'm in the process of installing some newer HD6 SU's on my MK VI Bentley, they are replacing the H6's. The problem is the HD6 carbs come with that external starting carburetor that requires the fuel being directly routed into the intake manifold. That would also involve drilling and tapping into the manifold to accommodate that system _ something I don't want to do. I was never a big fan of that set up anyway. I am planning to fit the air intake body from an R-Type, that has a choke flap that I plan on connecting manually for that purpose. The bolt pattern on both are the same for the different carbs (see #11 in the photo's). My question is, is the spacing on the air intake bodies (#7 and #9) the same, if they are, I would be good to go ? I've been told they are the same, but I would like to be sure. I've asked this guy at "The Luxury Junkyard", but he has not responded, and I don't think he will. The HD6 carbs are easier to balance and adjust the mixture on. Plus the shafts have a seal on them, where the H6's were never sealed, even rebuilt, there is a always a vacuum leak there.   | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 129 Registered: 07-2018 |
Or if someone with their R-Type could measure between the carb studs, that would allow me to compare, thanks.  | ||
| Christopher Carnley Unregistered guest Posted From: 5.62.43.234 |
I don,t have a stripped one, as they went to the scrap man, but the nearest that I can measure on a complete set is 15". (Message approved by david_gore) | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 130 Registered: 07-2018 |
Thanks, mine is 15 and 1/16th, so probably the same. Too bad you sent your spare bits the scrap man, I would of paid you money for them. I'm dealing with a guy from a place called "The Luxury Junkyard" I needed a servo cover and he got right on it, then nothing ??? I was waiting for a cost for shipping and a long time later his wife told me he was having dental problem, but by that time I found one locally for half the price. Now I'm trying again with the bits I need and it's been weeks, I'm totally getting ignored. I caught him on the phone and he complained that he gets 40 to 50 emails a day _ still though, what a way to do business. The guy needs to hire a small staff to deal with the emails and get stuff together, one for shipping too. The other place is in in California, Tony Handler, I'll call the other guy tomorrow. If someone has what I need, I'll offer 300.00 Canadian for the air intake body and auto choke mechanism. The 300.00 will leave room to negotiate. Thanks Chris ! | ||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 125 Registered: 09-2004 |
Tony Handler is long established, very professional, reliable, and stands behind what he sells. For this you may pay a little more, but when you are at a distance, you don't have much recourse when seller integrity is lacking. David Rogers, AKA Luxury Junkyard, often has problems like you describe. Years ago, I had a similar problem, when his business had a different name, and was located elsewhere. (Business name has changed several times, which I think says something about him.) I paid my money and it was months and several contact attempts before I got the merchandise. I actually believe he is honest and means well, my default assumption for people I don't know well, but his way of doing business and follow-through are missing a lot. He is now located a couple hundred miles from me, and if I really wanted what he had, I would drive there and deal face-to-face, with parts and cash on the table. That is the only way I would buy from him. | ||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 126 Registered: 09-2004 |
JEFF, I know this is outside what you asked, but why are you doing this? I understand potential for air leaks, but new throttle s Fujihafts for the H6 are available, and re-bushing the bidy for an exact fit is not difficult, or can be done by a reliable US based rebuilder, Joe Curto. When throttle shaft fit is very good, less than 0.001 clearance, air leakage is insignificant, even though, as you stated, is theoretically present. For that matter, there is no such thing as a "perfect" seal or a "perfect" anything. In my view, good enough is all that is needed. If difficulty of adjustment to achieve a smooth idle is what you seek, air leakage could be the cause, but not necessarily. Adjustment is difficult because the mixture leaving any carburetor is not homogenious and different cylinders get different mixture ratios. Manifold design is a factor, but there is no easy way to do much about that. This is one strong advantage of fuel injection, better control of mixture ratio for individual cylinders. So we adjust so that the mixture is rich enough for the weakest cylinder to fire reluably and weak enough for the richest cylinder to also fire reliably. With modern fuel that is a very narrow band, mush more difficult than 1950s fuel, and with temperature and atmospheric variations virtually impossible to achieve. I have seen cars idling with a very steady beat, as I am sure you have also. I dont think that means thos cars are perfect. Rather, it means for those, they are adjusted right for that particular situation. Change the weather or engine temperature, and they will be idling rough. The throttle bores of the HD6 and H6 used on Mk VI cars are identical, so there should be no performance difference if the carburetors are set up and adjusted correctly. I believe the HD6 was introduced to have an automatic choke feature, but it's unlikely that would matter much to an enthusiast. I personally prefer manual enrichment (in strict terms it's not a choke on the H6), and there's less to go wrong. I believe the the intake manifolds for the H6 and HD6 carburetors are identical, so the measurement you seek should be no different than that of the H6 intake, even though they are different parts. | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 132 Registered: 07-2018 |
I never likes the H6's, they have a tendency to leak out the bottom where the main jet seals _ they are leaking now after replacement of those new seals from Burlen. Oddly enough they were not really leaking before, but I had them apart to install the missing lift pins, and now they leak with new seals. That's reason number 1 It's way easier to adjust the mixture from a screw down from the top rather then trying to turn the big clunky nut from below. Much easier to balance and set the idle with both butterfly valves right closed with the fine adjustment of the volume screw. I never liked the big clunky thing that RR came up with that connects the two carbs together, it's a very crude way to achieve a proper balance when compared to the volume screw. There are a few other reasons too to do with the return spring. And about the measurements, David wanted to sell me an air horn from an early S1, but it won't work, it's a little too long by about 1/4 of an inch. I didn't expect it to work, being that even on an early S1, I think it's a 4.9 litre, and that makes the whole block a little longer and wider. That in turn would change the length entirely of the intake manifold and all the rest that bolts to it, it has to come from an R-type with a 4.5 litre. I've also just discovered that setting the points at 20 makes it idle a little rough, setting them at 19 makes a big difference _ I'm going to try 18 and see what happens. Decreasing the gap increases the dwell and also increases the duration of the spark. I just received this fancy timing light that tells me the dwell and rpm's, I can also adjust the timing better because it has a variable timing feature on it. I think I will get in contact with Tony Handler, David is taking way to long to respond. I may have lost my lock and key to him, but I can't stand those leaky carbs. | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 321 Registered: 01-2014 |
Just FYI Jeff I have the SU piloted reamer for enlarging the shaft holes and have oversize shafts in stock. I also have a dial gauge balancing tool I made if you want to borrow it. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 133 Registered: 07-2018 |
Thanks Jim. The H6 Carbs had new bushings and shafts installed a while a ago now, I don't think they're going to get any better then they are now. Thanks for the offer on the tool, but I have a set from British Tools works. The dial gauges for balancing work well enough, but the rear carb with the return spring will not stabilize _ I have not been able to figure it out. If I zero the gauges and balance them they're OK, if I lift the piston on the front carb with the lift pin it goes back to where I set it, lets say 10 on the dial. The rear one though never returns to the same value, I end up doing an average, it's sometimes at 11 or 8 and sometimes it goes back to 10. I think it can't be balanced because the RR linkage is not very precise, it has these interlocking fingers that sort of move around and if the link is adjusted dead tight, then it binds when the engine is fully warmed up. So there's that... I also think the way the return spring is set up is it's tugging sideways on the butterfly shaft, so therefor causing a slight binding on the shaft which makes it impossible to stabilize the butterfly valve. These are all just theories, the piston is free and the needle is centered and not binding. The piston can be lifted once the air horn is removed and it raises freely and drops with the familiar metallic "clunk", so not a sticky piston. When I install the HD6's they will each have there own throttle return spring that mounts around the shaft so one doesn't get this sideways pull on it. The RR linkage will be gone and I'll use the proper SU coupling assembly, this will allow compensation of the spacing between the carbs when the engine is hot and cold. With all these improvements, I'm pretty sure that the balancing procedure will be much easier and more stable. This guy just lives in Victoria and does very good work, just as good as Joe, or even better. He's not as well known, because he has no YouTube videos. I've met him and been to his house and shop. https://www.sucarburetors.com/ | ||
| Norman Geeson Unregistered guest Posted From: 81.99.138.38 |
Jeff, With the absolute greatest of respect to you I am afraid you appear to have made a number of comments that appear in error and I have mentioned just three below viz. “The problem is the HD6 carbs come with that external starting carburettor that requires the fuel being directly routed into the intake manifold” S.U carburettors of the HD6 type do NOT come with an external starting carburettor by default, many have manual choke operations. In fact modification kits are available to convert starting carburettor types to manual chokes and vis versa. A HD6 with manual choke should be able to replace a H6 easily. “I am planning to fit the air intake body from an R-Type that has a choke flap that I plan on connecting manually for that purpose” That is an expensive and messy way to convert to a manual choke as the R Type parts you are chasing are in high demand for fitting twin S.U carburettors to Silver Dawn’s. Quite why you are not merely swapping your H6’s for manual choke HD6’s and leaving everything else in place I do not understand. You also lay great store on a local S.U specialists and I do not understand why he has not advised you about HD6’s accordingly. “I never liked the big clunky thing that RR came up with that connects the two carbs together, it's a very crude way to achieve a proper balance when compared to the volume screw” A volume control screw will not provide smooth throttle opening progression, which is one of the reasons for that torsional arrangement. Yet, that arrangement that you do not like, will provide a steady idle speed of max 450 rpm. In addition, on level road it will pull 1st gear, if not 2nd smoothly at idle. Trying that, and then attempt to pull away with your proposed arrangement will soon illustrate why the original RR throttle linkage is extremely “very precise” and effective. The H6 and HD6’s will perform equally well. The HD6 arrangement, if used with any auto choke or externally operated flap system is at a disadvantage and you will eventually find it awkward to adjust. A manual operated choke on a HD6 on the other hand is a different story to adjust and extends the time frame to the eventual jet housing leakage. I think you would find it helpful to conduct more research on aspects of the 4.25 / 4.5 ltr R-R engine’s and their installations that affect the carburettor settings. It is difficult to comment fully on the throttle linkage as a number of variations exist on MkVI engines and unless I have missed it, I cannot see a chassis number in your comments. (Message approved by david_gore) | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 135 Registered: 07-2018 |
Thanks Norman. I think the site is broken, I just now came across this post, there was no "new post" heading beside this ??? Yes, I am working on using this as a manual choke, much simpler. He did later advise me to use what is in the link. http://sucarb.co.uk/jet-housing-centre.html As far as using an R-Type choke flap, it's not happening, so far I have not been contacted by The Luxury Junk Yard, using the above solution defeats that that route anyway. We'll see about the rest... Works well enough on the Jag _ granted it's idle is at 600 rpm. My car number is B297LH. |
