monty Posted July 8, 2007 Report Share Posted July 8, 2007 Hi All, Still struggling to get my carbs sorted (different needles/springs & retuning) & have just noticed that the vacuum advance hole/connection is presently not sealed off. Should it be or does it make no difference to things? It is not used as I am running K & N filters. Also I have the old brass screw topped damper assemblies on my HS6 carbs. Should they be the newer black plastic tops with I believe an air hole or does it not matter? The brass tops do look better! Regards, Monty. Quote Link to post Share on other sites
Rhodri Posted July 8, 2007 Report Share Posted July 8, 2007 By vacuum advance hole I take it you mean the little tube with the pipe to the distributor, but I fail to see what difference K and Ns would make to that? If you mean the large round holes where the filter bolts on then they should be left clear. Solid caps should only be used if the web on the neck of the chamber has been drilled. If there is no drilling then the plastic type of cap with a vent hole must be used. I suppose you could drill the brass cap ? What you must not end up with is a drilled cap AND a drilled web as this will give an air leak directly into the vacuum part of the carb. As you have things now, no drillings, it will be extremely difficult for the carb to work. The needle will not rise quickly enough giving you a very weak mixture on acceleration, nor will it drop quickly enough when coming off the throttle, both situations caused by no venting of the air . Quote Link to post Share on other sites
monty Posted July 8, 2007 Author Report Share Posted July 8, 2007 By vacuum advance hole I take it you mean the little tube with the pipe to the distributor, but I fail to see what difference K and Ns would make to that? If you mean the large round holes where the filter bolts on then they should be left clear. Solid caps should only be used if the web on the neck of the chamber has been drilled. If there is no drilling then the plastic type of cap with a vent hole must be used. I suppose you could drill the brass cap ? What you must not end up with is a drilled cap AND a drilled web as this will give an air leak directly into the vacuum part of the carb. As you have things now, no drillings, it will be extremely difficult for the carb to work. The needle will not rise quickly enough giving you a very weak mixture on acceleration, nor will it drop quickly enough when coming off the throttle, both situations caused by no venting of the air . Thanks Rhodri. Yes I mean the little tube which no longer has a pipe to distributor (converted to electronic ignition) but has just been left. I think I read somewhere that the tube if not now used should be blocked off? I cannot see any drilled webs so it would appear that the carbs have been run like this since restoration (solid brass caps/no drillings in web or caps) but they appear to work well except for one that runs rich, hence change of needles/springs. Acceleration appears good with a rolling road some time ago, at end of restoration, giving good results. Regards, Monty. Quote Link to post Share on other sites
monty Posted July 10, 2007 Author Report Share Posted July 10, 2007 Thanks Rhodri.Yes I mean the little tube which no longer has a pipe to distributor (converted to electronic ignition) but has just been left. I think I read somewhere that the tube if not now used should be blocked off? I cannot see any drilled webs so it would appear that the carbs have been run like this since restoration (solid brass caps/no drillings in web or caps) but they appear to work well except for one that runs rich, hence change of needles/springs. Acceleration appears good with a rolling road some time ago, at end of restoration, giving good results. Regards, Monty. On further investigation it appears I have dashpot covers with a drilling in the web (did not look closely enough) so that is ok with the brass caps. The reason for no vacuum advance to the dizzy is that I have a 'Rally spec. TR4' unit with no facility for vacuum advance, only mechanical. It has Aldon electronic ignition installed. Presumably the dizzy was fitted to match other mods such as cam etc. Any comments to the dizzy would be appreciated. Regards, Monty. Quote Link to post Share on other sites
TR 2100 Posted July 10, 2007 Report Share Posted July 10, 2007 The reason for no vacuum advance to the dizzy is that I have a 'Rally spec. TR4' unit with no facility for vacuum advance, only mechanical. It has Aldon electronic ignition installed. Presumably the dizzy was fitted to match other mods such as cam etc. Any comments to the dizzy would be appreciated. Hi Monty, It is normal and recommended to dispense with the vacuum advance/retard on the distributor for tuned engines. Depends to some extent on the degree of tuning, but desirable for fast road and required for rally/racing spec. The take-off from the inlet manifold should be blanked off although neglecting this would cause the mixture to be weaker, not more rich. AlanR Quote Link to post Share on other sites
67_gt6 Posted July 10, 2007 Report Share Posted July 10, 2007 Hi Would it not be the case that if you are using a tuned engine for normal road use a vacuum unit would be desirable because of the amount of partial throttle driving? Andy Quote Link to post Share on other sites
TR 2100 Posted July 10, 2007 Report Share Posted July 10, 2007 Hi Would it not be the case that if you are using a tuned engine for normal road use a vacuum unit would be desirable because of the amount of partial throttle driving? Andy Hi Andy, As I understand it, with a tuned engine for normal road use, the vacuum unit may well give benefit for the great majority of driving conditions, but the 'mechanical advance only' set-up serves to give protection for the odd occasion where you could do serious damage to the engine if you retained the vacuum advance/retard. Simliar principle with the fuel pump. I wanted to retain the original, both for appearance and reliability. TR Enterprises said absolutely no - if I was running a tuned engine at high revs for any period, I could run the float chambers dry and - big bang. I really can't imagine that my revs would ever reach 5.5-6K except going through the gears, but the principle is that you have to protect the engine by making sure the complete set-up is safe in all situations. AlanR Quote Link to post Share on other sites
TR 2100 Posted July 11, 2007 Report Share Posted July 11, 2007 After all that effort on your car, I should hope it gets past that through the gears . . . Every 4 or 6 pot Triumph I've ever owned has regularly been past 5.5K without protest, even the Pennant, and usually 6K+. I have a rev limiter (sitting in the front seat!)- you have Diana shouting "more, more . . . " I did once jam the needle of the late Stuart Jenkins ' red TR2 at the right hand end of the dial, but no ill effects. You mean the gauge wasn't broken?! AlanR Quote Link to post Share on other sites
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