Davidw Posted July 12, 2013 Author Report Share Posted July 12, 2013 Hm. Glad you pointed out the issue re the plenum bracket. I guess the balance tubes would have to be checked too as a split would cause a similar problem. But I like idea of trialling it by temporarily jamming the throttles open, first. Quote Link to post Share on other sites
Peter Cobbold Posted July 12, 2013 Report Share Posted July 12, 2013 Hm. Glad you pointed out the issue re the plenum bracket. I guess the balance tubes would have to be checked too as a split would cause a similar problem. But I like idea of trialling it by temporarily jamming the throttles open, first. The 6 rubber rubber tubes will 'breathe' with the vacuum as you close the single throttle - that may hasten their uncoupling. Quote Link to post Share on other sites
kiwican Posted July 12, 2013 Report Share Posted July 12, 2013 (edited) The 6 rubber rubber tubes will 'breathe' with the vacuum as you close the single throttle - that may hasten their uncoupling. I am not sure if this would be a solution to the tubes "breathing" but when my original hoses started to split I replaced them with turbo charger coupling hoses. I assume they are a bit more rigid that the original rubber ones. Not that I am contemplating the single butterfly but just out of curiosity I would be interested to see if anyone else has done this on a PI system and what the results were. Simon Edited July 12, 2013 by kiwican Quote Link to post Share on other sites
Tony Millward Posted July 13, 2013 Report Share Posted July 13, 2013 Plenum security is vital though - as observed. Mine has 12 Jubilee clips and Tigerseal on the plenum side and I take great care that the supporting bracket is properly fitted. A solution not involving rubber tubes is on my to do list. Nick I would be very interested in your solution Nick, I too am wary about rubbers coming off. Cheers Tony Quote Link to post Share on other sites
Peter Cobbold Posted July 13, 2013 Report Share Posted July 13, 2013 (edited) re 'breathing'. I have about 1 inch gap between two blower transfer pipes that is bridged by silicone hose, 21/4" bore. On the over-run when driving it is pulled into the gap - looks to me as if there would be outward force from the hose ends. Double jubilees each end hold it. Edited July 13, 2013 by Peter Cobbold Quote Link to post Share on other sites
ijonsson Posted July 13, 2013 Report Share Posted July 13, 2013 I am not sure if this would be a solution to the tubes "breathing" but when my original hoses started to split I replaced them with turbo charger coupling hoses. I assume they are a bit more rigid that the original rubber ones. Not that I am contemplating the single butterfly but just out of curiosity I would be interested to see if anyone else has done this on a PI system and what the results were. Simon This guy in Finland has installed a single butterfly (and EFI) http://www.kolumbus.fi/triumph.tr6pi/earlier-work-sessions/work-session-20082009/ Quote Link to post Share on other sites
Tony Millward Posted July 13, 2013 Report Share Posted July 13, 2013 Hm. Glad you pointed out the issue re the plenum bracket. I guess the balance tubes would have to be checked too as a split would cause a similar problem. But I like idea of trialling it by temporarily jamming the throttles open, first. Hi David, It's a good idea to remove the balance tubes and block the holes, they are not needed with a single butterfly and can make idle setting difficult...when you do changeover to a single throttle body of course. Cheers Tony Quote Link to post Share on other sites
Davidw Posted July 14, 2013 Author Report Share Posted July 14, 2013 Hi Tony, bet it's warmer here at present that down under. Ijonnson above posted a link to a Finnish TR 6 who has done this mod ( and very tidily, I might add), However, I also think that Peter has a good point about the vacuum forcing the rubber hoses off. As I now have the clutch to worry about, I wlll think about his but probably not do anything for some time. I wlll post again if I carry out this mod. Quote Link to post Share on other sites
Peter Cobbold Posted July 14, 2013 Report Share Posted July 14, 2013 (edited) The Finnish jumpy throttle issue would be solved with a progressive throttle actuator so that more cable motion is needed to initially open the butterfly a bit. Like this: http://i278.photobucket.com/albums/kk91/woops1234/ThrottleActuator.jpg -often used with blowers where a single butterfly feeds the whole engine. He should take a look at those plenum support tubes on the over-run! - an engine destroyer if the plenum comes away. Edited July 14, 2013 by Peter Cobbold Quote Link to post Share on other sites
Tony Millward Posted July 14, 2013 Report Share Posted July 14, 2013 David, I understand what is being said about the rubber connectors but bear in mind that each one has a pair of hose clips on. I couldn't pull mine off if I tried...I agree that the plenum support is essential though. I saw Martti Ojanen's installation a couple of years back and have been in communication with him regarding EFI. At the moment, I am considering the value of changing to individual butterflies (I have a complete set of manifolds in good condition), but there are a lot of factors to consider.. Peter, that is exactly what's needed for a progressive throttle control and should work well. Cheers Tony Quote Link to post Share on other sites
Davidw Posted July 15, 2013 Author Report Share Posted July 15, 2013 Playing hookey again, chaps. Peter, your remarks raise the issue in my mind that even the standard plenum mounting bracket (made of crimped steel tube and easily bent by hand) might be insufficient to keep the hoses in place under sudden deceleration. Perhaps the starting point shoul be a solid plenum mounting bracket possibly from welded flat aluminium? One would need something pretty strong anyway to ensure the single throttle does not come off the end of the plenum tube. With a TR5 I could probably manage if it fell off but as you said above, if you have a steering lock, the choice of either lunching the engine and maintaining steering or saving the engine and losing control is not a palatable one. So, straight away I can see that a rev limiter and/or an instant ignition kill switch is the first thing to fit. Only then should one start to muck about with a single throttle body. Back to the clutch! Quote Link to post Share on other sites
Peter Cobbold Posted July 15, 2013 Report Share Posted July 15, 2013 Playing hookey again, chaps. Peter, your remarks raise the issue in my mind that even the standard plenum mounting bracket (made of crimped steel tube and easily bent by hand) might be insufficient to keep the hoses in place under sudden deceleration. Perhaps the starting point shoul be a solid plenum mounting bracket possibly from welded flat aluminium? One would need something pretty strong anyway to ensure the single throttle does not come off the end of the plenum tube. With a TR5 I could probably manage if it fell off but as you said above, if you have a steering lock, the choice of either lunching the engine and maintaining steering or saving the engine and losing control is not a palatable one. So, straight away I can see that a rev limiter and/or an instant ignition kill switch is the first thing to fit. Only then should one start to muck about with a single throttle body. Back to the clutch! Hi David, Backfires are another possible dislodger. I wouldn't be put off a single TB by the plenum. A couple of tie rods, one end anchored into the old balance pipe hole and the other to eyes welded to the plenum should keep the plenum tight onto the rubbers. Put one underneath the plenum too for belt and braces. Peter Quote Link to post Share on other sites
Davidw Posted July 15, 2013 Author Report Share Posted July 15, 2013 Hi David, Backfires are another possible dislodger. I wouldn't be put off a single TB by the plenum. A couple of tie rods, one end anchored into the old balance pipe hole and the other to eyes welded to the plenum should keep the plenum tight onto the rubbers. Put one underneath the plenum too for belt and braces. Peter Good thinking, Peter. Will save this thread and might revive it in a few months, time and money permitting...... Quote Link to post Share on other sites
Peter Cobbold Posted July 15, 2013 Report Share Posted July 15, 2013 Good thinking, Peter. Will save this thread and might revive it in a few months, time and money permitting......David, Suggest you multiply time by ten when fitting non standard bits!Peter Quote Link to post Share on other sites
Davidw Posted July 15, 2013 Author Report Share Posted July 15, 2013 Thanks, Peter. As always, sound advice for which I am most grateful. Quote Link to post Share on other sites
Tony Millward Posted July 16, 2013 Report Share Posted July 16, 2013 It occurred to me that on EFI installations, there is a device called a Throttle Position Sensor, this is used to measure the amount of fuel injected for a given throttle position. If the plenum became dislodged the engine would merely gulp in lots of air. This would either stop the engine or cause it to run extremely badly. Cheers Tony Quote Link to post Share on other sites
Andy Moltu Posted July 16, 2013 Report Share Posted July 16, 2013 Checking the plugs when the car has idled will tend to reveal 5&6 appearing to run rich for 1 or both of 2 reasons. (even on a perfectly set up car). 1) The air bleed valve feeds the front manifold so cylinders 5&6 get whatever air is left. 2) At low throttle openings the air in the plenum chamber heats up (it's above the exhaust after all) becoming less dense. The air that gets to the the rear cylinders gets warmed most and thus will be less dense. perhaps more important on early 5s with no bleed valve) The key thing to do is a plug chop - drive for a while, cut the engine and coast to a stop & see what the plugs look like then. If the rears are still sooty then your throttles are probably out of balance. Quote Link to post Share on other sites
Davidw Posted July 16, 2013 Author Report Share Posted July 16, 2013 Thanks for the suggestion, Andy, but I think I have sorted the problem insofar as I can with worn throttle spindles. But I had previously cured the same problem a couple of years ago by fitting an extra bleed valve on the rearmost pair. This was before the throttles went out of balance (again!). Quote Link to post Share on other sites
Peter Cobbold Posted July 16, 2013 Report Share Posted July 16, 2013 It occurred to me that on EFI installations, there is a device called a Throttle Position Sensor, this is used to measure the amount of fuel injected for a given throttle position. If the plenum became dislodged the engine would merely gulp in lots of air. This would either stop the engine or cause it to run extremely badly. Cheers Tony TonyGood point. Difficult to implement on Lucas PI I think. Killing the fuel pump with a microswitch when the throttle is shut would cover the plenum falling off, but would be terrible for normal running - the lean spike in a gear change would be even worse! Peter Quote Link to post Share on other sites
Tony Millward Posted July 16, 2013 Report Share Posted July 16, 2013 I'm a tadd confused Peter, are you saying that there would be an open throttle if the plenum came off with a PI car?. I was referring to the EFI system with a throttle position sensor...everyone that has EFI has such a sensor. The plenum coming off a PI car wouldn't make any difference. Cheers Tony Quote Link to post Share on other sites
Peter Cobbold Posted July 16, 2013 Report Share Posted July 16, 2013 The plenum coming off a PI car wouldn't make any difference. Cheers Tony Tony,I was still thinking about Davidw's idea of Lucas PI with single TB on the plenum, to get around worn Lucas butterflies. I agree the standard PI is not affected by the plenum dropping off - had it happen several times! bit noisy though. cheers Peter Quote Link to post Share on other sites
johnmac Posted July 30, 2013 Report Share Posted July 30, 2013 Hi All, just a quick comment regarding the PI air bleed valve. Following reading various articles by Michael Bingley with gas valves and all sorts to cure this problem on the rear cyclinders, I was moved to simply drill a suitable size hole in the fitting in the blank in the front(?) throttle body then moved it to the middle throttle body and having soldered the air bleed valve into it. Plugged the original air bleed valve hole and moved the brake vacuum to the front throttle body. This allows the air bleed to be much better balanced to all the cyclinders and looks quite original. Plugs usually very well balanced over many years. I currently have the head off because No4 exhaust needs attention. I have run Redex Lead replacement on unleaded fuel with standard valves & seats & MU. Deciding whether to go for hard seats just because the head is off, but reluctant at present. FYI, still working well on original MU after 130k miles though I have stripped it myself twice over the years. Also rebuilt my own injectors and set up with an air line and pressure gauge. I made myself a concentric allen key device to adjust the injector pop-off point. I have very good torque & power from stage 2 head, 6 branch manifold (3 into 2 all the way to the standard type s/s tranverse rear box) with a lightened and balanced flywheel. reggards, John Quote Link to post Share on other sites
johnmac Posted July 30, 2013 Report Share Posted July 30, 2013 Hi All, PS to last post. My TR6 is late 1972 with 150hp engine with the later close ratio gearbox with earlier 3 speed overdrive, so is one of the rare changeover cars. The point is it has the earlier throttle linkage which is underslung but each link rod has locking nut adjustment to get the throttles balanced before any of the expensive after market kits were available. I take it this was how all earlier cars were. Anyhow, there does not seem to be too much problem synchronising all six throttles if it is not all worn out. Possibly the thottle spindles are causing problems? I will still be interested to see the single body outcome though because always interesting. Being a control engineer, many years ago I toyed with fitting some kind of stepper motor to the MU instead of the vacuum unit then using electronics to control it but just too busy to get around to it. Should be considerably easier now with the power of microprocessors at such low cos, PIC chips, Rasberry Pi, etc. One day maybe unless anyone else has any thoughts to add. regards, John Quote Link to post Share on other sites
Davidw Posted July 31, 2013 Author Report Share Posted July 31, 2013 John is there any chance of a photo of your air valve mod? I am having difficulty imagining it. Quote Link to post Share on other sites
johnmac Posted August 13, 2013 Report Share Posted August 13, 2013 Hi David, sorry for delay, I will take photo and post when i have worked out how to include in post! How do I include a pic? regards, John Quote Link to post Share on other sites
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