Raggylad Posted August 29, 2012 Share Posted August 29, 2012 I'm about to replace the knackered Stromberg carbs on my 110 V8 with a new pair of SU HIF44s (acquired on ebay for considerably less than Burlen sell them for). A couple of questions: - There are currently 2 vacuum pipes running from the distributor vaccum advance unit to the near side Stromberg: The pipe on the left side in the photos runs to the top of the carb on the inlet manifold side (there is an equivalent connection on the SU carb): The other runs from the right to a connection under the carb on the air inlet side: On the SU carbs there is no apparent connection for this second pipe (what is its function, anyway, if the first pipe is the advance - being after the throttle ?). So, do I: - Leave the right hand (in the photos) connection on the vaccuum advance open to atmosphere ? - Block it off ? - Tap a connection into the air inlet manifold ? Second question: - What are these toothed spacers (?) that go with the carb mounting insulation blocks for: Many thanks. Nick Quote Link to comment Share on other sites More sharing options...
western Posted August 29, 2012 Share Posted August 29, 2012 IIRC those toothed plates are restrictors, these http://www.brit-car....php?xProd=99717 & I believe you can leave them out of the carb to manifold joint. can't help with the vacuum hoses. Quote Link to comment Share on other sites More sharing options...
Spearos Posted August 30, 2012 Share Posted August 30, 2012 I'm sure I read somewhere that those plates are to create a tubulent airflow, which helps the petrol mix.... I'm sure someone will confirm this... or shoot me down! As for the vacuum hoses, I have no idea! The Dirty Bus' V8 has SUs and has just the one hose. Perhaps an option is to tee both vacuum hoses into one hose and connect that to the SU? Quote Link to comment Share on other sites More sharing options...
tacr2man Posted August 30, 2012 Share Posted August 30, 2012 They are not restrictors ,(they have 4 small holes in them) as mentioned they are a snake oil economiser/emissions idea HTSH do the two vac pipes run to either side of the advance retard diaphragm ? Quote Link to comment Share on other sites More sharing options...
western Posted August 30, 2012 Share Posted August 30, 2012 I didn't remember correctly then. Quote Link to comment Share on other sites More sharing options...
Raggylad Posted August 30, 2012 Author Share Posted August 30, 2012 Thanks for the answers on the deflectors. I'll leave them out. The vacuum pipes do run from either side of the advance/retard diaphragm. The left hand (in photos) one definitely advances the distributor when you suck on it - which makes sense as it goes to the inlet manifold side of the carb and hence the vacuum it delivers will vary with the size of throttle opening. That's the easy one. The right hand one runs from the other (retard ?) side of the diaphragm, through a trap of some sort (you can see it in my first pic) to the underside of the carb on the air inlet side. If I understand my sidedraft carb theory correctly, that should mean that is delivers a pretty constant vacuum unaffected by throttle opening or closing ? If you suck on the tube, there's no visible effect on the distributor - which sort of makes sense if I am right about the constant vacuum ? So what happens with SU carbs which have no connection for this second tube ? I've chase this question around through google and come up with the 3 conflicting pieces of advice/options I listed in my original question. Any ideas ? Nick Quote Link to comment Share on other sites More sharing options...
Scooby Jim Posted August 31, 2012 Share Posted August 31, 2012 Going from the Rover 3500 V8 SD1 Haynes manual. The Ignition advance is controlled by a mechanical and vacuum operated system. The mechanical governor mechanism comprises two weights which move out under centrifugal force from the central distributor shaft as the engine speed rises. As they move outwards they rotate the cams relative to the distributor shaft, and so advance the spark. The movement of the weights is governed by the two springs, and it is the tension of the springs which is largely responsible for the correct spark advancement.The Vacuum control comprises of a diaphragm in a sealed casing, one side of which is connected via a small bore tube, to a carburettor and the other side a moving plate. Depression on the inlet manifold causes the diaphragm to move, so moving the plate. This advances or retards the spark. A fine degree of control is achieved by a spring in the vacuum assembly. It also says Ignition timing Static 6 degrees BTDC. Dynamic (with distributor vacuum pipe removed) 10Degrees BTDC at 1200rpm 17Degrees BTDC at 1800rpm 22Degrees BTDC at 2600rpm Quote Link to comment Share on other sites More sharing options...
Julian Posted August 31, 2012 Share Posted August 31, 2012 Thanks for the answers on the deflectors. I'll leave them out. Any ideas ? Nick I might be tempted to leave them in. They look like an attempt to get the petrol mixed with the air. V8 inlet manifolds (is it dual plane or plenum?) are bsuggers for the fuel dropping out of suspension and adhering to the manifold walls during warm-up. It's a way of 'un-blueprinting' (if you understand my made up word?) the assembly. Julian. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted August 31, 2012 Share Posted August 31, 2012 I'd agree with Julian, turbulent air is much better for keeping fuel aerosolised that a clean stream. Quote Link to comment Share on other sites More sharing options...
welshsurferdude Posted August 31, 2012 Share Posted August 31, 2012 I have a box of V8 carbs and bits, I think they are SU, with a few bits u can have for say £50 plus postage? Quote Link to comment Share on other sites More sharing options...
Jode Posted September 1, 2012 Share Posted September 1, 2012 1. The WSM indicates that the toothed spacer is a deflector, and must be installed with the teeth facing the inlet manifold (joint washer at manifold, toothed deflector, joint washer, insulator, joint washer, carb). 2. The second pipe may have something to do with emissions contrrol, as the device that is inserted in-line of the hose looks like an oil catcher. Could this hose therefore be a form of breather hose? (Our V8 had SUs, so I can't help much with the Strombergs.) Quote Link to comment Share on other sites More sharing options...
Julian Posted September 1, 2012 Share Posted September 1, 2012 2. The second pipe may have something to do with emissions contrrol, as the device that is inserted in-line of the hose looks like an oil catcher. Could this hose therefore be a form of breather hose? (Our V8 had SUs, so I can't help much with the Strombergs.) My memory is very sketchy here as I was never really a Rover V8 man but in the installation with two pipes (to either side of the dizzy vacuum capsule) you have are vacuum advance and a vacuum retard - depending on the source of vacuum. (manifold or adjacent to carb butterfly) There's maybe going to be a different set up on the dizzy as they differed internally depending on the carbs used. This question needs addressing properly as there's a chance that the dizzy will need to be modified to suit the new plumbing arrangement that you will be forced to use c/o the carb swap. I'd ask on a rover V8 forum if nobody here has the definitive exact answer. Julian. Quote Link to comment Share on other sites More sharing options...
Raggylad Posted September 1, 2012 Author Share Posted September 1, 2012 Thanks for the thoughts above. - So I'll fit the deflectors, after all. - I've asked the question about the vaccum advance/retard connections over on the V8 Owners' Forum. I'll report back here on any useful answers. - I fear that the answer may well be to change the distributor (expensive !) or the vacuum advance unit (less so) for one with a single vacuum advance connection. Nick Quote Link to comment Share on other sites More sharing options...
Julian Posted September 2, 2012 Share Posted September 2, 2012 Thanks for the thoughts above. - I've asked the question about the vaccum advance/retard connections over on the V8 Owners' Forum. I'll report back here on any useful answers. Nick Please do, I'm curious to find out if I was on the right track here. Either way it'll be a good thing to get sorted as you don't want to compromise performance or economy by having to run the ignition more retarded to stop pinking if a better set-up is available and more suited. Julian. Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 2, 2012 Share Posted September 2, 2012 I left the second pipe off and havn't seen any loss. On my 1991 Pinto engined ford transit that second hose is way more important. There it is cold running ignition-advance with a thermal air valve in the top hose. Small hoses go all directions to plastic 'things'. It couldn't be replicated with one in-tube devise which looks supicously like a flame trap? I bet it is a flame trap as the carb fuel could be exposed to the electrics via a worn advance rod? So my vote is for a; diaphram breather pipe. Quote Link to comment Share on other sites More sharing options...
Julian Posted September 2, 2012 Share Posted September 2, 2012 one in-tube devise which looks supicously like a flame trap? I bet it is a flame trap That 'in-tube' devise is to be found on just about any Leyland car from Moggy-Minor onwards, actually just about any 'A' or 'B' series engine. It's always mounted vertically and is (as I understand it) to stop the possibility of any raw fuel from the inlet getting onto the rubber diaphragm on the carb and bsolloxing it. Julian. Quote Link to comment Share on other sites More sharing options...
Raggylad Posted September 20, 2012 Author Share Posted September 20, 2012 Well, after letting it soak on the V8 Owners' Forum for a few weeks, I'm really none the wiser - only one reply ! It looks as though the lack of a vacuum pipe to the inlet side of the SUs should be OK - the question remains as to whether to leave the connection on the vacuum advance unit ope or plugged. I'll just have to do it by trial & error. Nick Quote Link to comment Share on other sites More sharing options...
Landrovernuts Posted September 20, 2012 Share Posted September 20, 2012 Only just noticed this and I am on the V8 forum! From what i remember from my 3.5 V8 in my 90 that had SU carbs, the pipe fitting closest to the dizzy on the advance capsule is left open as it needs to breath to let the advance and retard casule move (blocking it will stop it). Mine was open and that is how it was from the factory. The big but is there are different advance capsules from what I recall (for 3.5, 3.9, 4.2 and for carbs and injection) as yours started as a carb version, I think you are pretty safe to leave it as is (but leave the dizzy side connection open) providing if you give it a good suck that it visably advances the dizzy (works!). I am now converted to injection and have to be honest have left my advance capsule disconnected and adjusted my timing to give my dynamic advance without using the advance which is prone to sticking seizing anyway. Toby Quote Link to comment Share on other sites More sharing options...
Raggylad Posted September 21, 2012 Author Share Posted September 21, 2012 Thanks Toby - that confirms my intention to start with the fitting left open. I've done the suck test & the advance capsule seems to be working fine - I've never (touch wood !) had a problem with timing. Nick Quote Link to comment Share on other sites More sharing options...
mikec Posted September 23, 2012 Share Posted September 23, 2012 I did this conversion, I just left the other dizzy pipe lose, it has a one way valve mid pipe? I Quote Link to comment Share on other sites More sharing options...
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