james christie Posted January 31, 2016 Report Share Posted January 31, 2016 I'm not supposed to be in here as I'm a sidescreen man At the suggestion of Lebro on the Tr2/3 forum here's a question for you Winding Window folk: I have just acquired a siamesed ported inlet manifold with a view to looking for a bit more torque than the standard 3A high port one. Does anybody know if there is a difference in performance (or anything else) between 305547 with the pcv boss on the top of the balance tube and 307455 with the adaptor fitted to one side behind the balance tube? James Quote Link to post Share on other sites
TR 2100 Posted January 31, 2016 Report Share Posted January 31, 2016 Jim, By "siamese ported" manifold, do you mean the late 4A type? These are reputeded to give the best gas flow/ torque but you need to take account of the extra length - you may need HS carbs with shorter body, depending on your air filter arrangement. I can't see there being any noticeable difference between difference balance pipe arangements. AlanR Quote Link to post Share on other sites
terry Posted February 1, 2016 Report Share Posted February 1, 2016 hi James ... I have 4 manifolds with me at the moment but not one with the numbers you give,....one is the genuine tr4a manifold {cant see the number} and the other 3 have the number 305744 cast into them,...there is a difference on the balance pipe as regards the cast in bumps and lumps sticking out,..two are the same with the mounts sticking out at a backwards angle but the other one has a vertical rounded piece cast in alongside. looking at them all I agree with AlanR, I cant see there being any difference in air flow between them,....the tr3 manifold here with me now is a different kettle of fish. cheers Terry Quote Link to post Share on other sites
terry Posted February 1, 2016 Report Share Posted February 1, 2016 hi James, here are 3 photos to show what I mean. cheers, .Terry Quote Link to post Share on other sites
terry Posted February 1, 2016 Report Share Posted February 1, 2016 got one photo duplicated in last post,....here is the tr3 manifold Quote Link to post Share on other sites
Lebro Posted February 1, 2016 Report Share Posted February 1, 2016 (edited) None of the photos above are of the 307455, the triangular lump should not be there, instead there is a tapped boss at the rear end of the balance tube, pointing directly towards the cylinder head. As far as I can see the inlet tracts are the same shape though. Also note the two small lugs sticking upwards on top of balance tube - these are locations for throttle return springs. (I did not use these) Bob. Edited February 1, 2016 by Lebro Quote Link to post Share on other sites
McMuttley Posted February 1, 2016 Report Share Posted February 1, 2016 Like this Ignore everything else that is wrong with them ! Quote Link to post Share on other sites
Alec Pringle Posted February 1, 2016 Report Share Posted February 1, 2016 Hi James, 305547 is the later 3A fitment, H6 carbs, straight tube, successor to the original high port head 302119. 305744 the earlier 4 curved tube unit, as in HS6 or 175 carbs, and 307455 the later 4A version, again HS6/175. The efficiency, in particular mid range torque, improved with each evolution of curved tube - there is little practical difference between the 3A manifolds though, other than the boss take-off on the later type. Cheers Alec . Quote Link to post Share on other sites
james christie Posted February 1, 2016 Author Report Share Posted February 1, 2016 Lots of good info here, thanks everybody. Alan, that beer together in Hong Kong some 32 years ago has lasted a long time. Long time no see! I'm lucky to have HS carbs already fitted - bought from Pete W for £20 in 1975. According to my measurements the siamese ported manifold is 36mm deeper. It'll be a tight fit..... Terry Mine is the other version with the tapped boss at the back. The cast part number 307455 is in the same place - see McMuutley's photo Bob Good to know I won't die ignorant of the use of the two bosses, my (eternal) thanks McMuttley Is that an oil drain plug in the tapped boss, if yes, anybody got one to spare? Hard to find in metric land here James Quote Link to post Share on other sites
terry Posted February 1, 2016 Report Share Posted February 1, 2016 (edited) is this what you are looking for when you ask about the drain plug,...if so it is for the engine breather. I cant help you with the plug though Edited February 1, 2016 by terry Quote Link to post Share on other sites
McMuttley Posted February 1, 2016 Report Share Posted February 1, 2016 Silly question, but doesn't venting the rocker into the carbs just make smokey ? I have too much oily smokey already ! Quote Link to post Share on other sites
terry Posted February 1, 2016 Report Share Posted February 1, 2016 when i am running the 4a on strombergs there is no smoke and the engine runs fine,...a few years back I fitted new piston rings when I had the engine down for a overall...no smoke at all,......when running with the webers fitted its a different matter and rocker box is vented to atmosphere but yes no smoke. Quote Link to post Share on other sites
james christie Posted February 1, 2016 Author Report Share Posted February 1, 2016 We polluters aka Sidescreen Owners don't have the Positive Crankcase Ventilation arrangement so I need to block off the 'ole. I have been ferretting around in my box of treasures this afternoon and found an old crankcase plug which is of course tapered and I find is is too big (only just). I think the thread on the manifold boss may be a 5/8 unf thread - can anybody confirm?? james Quote Link to post Share on other sites
Lebro Posted February 1, 2016 Report Share Posted February 1, 2016 I think it is a BSP parallel thread ¼" from memory. I used a standard plumbing end plug (not tapered) with a fibre washer. Bob. Quote Link to post Share on other sites
james christie Posted February 1, 2016 Author Report Share Posted February 1, 2016 Hum. 1/4" That's a bit small isn't it? But it is certainly a parallel thread. The current fitting is about 625 thou measured, which I think is 5/8" As to the thread....... James Quote Link to post Share on other sites
Motorsport Mickey Posted February 1, 2016 Report Share Posted February 1, 2016 Hum. 1/4" That's a bit small isn't it? Not when it's BSP - try this http://www.bspt.co.uk/ Mick Richards Quote Link to post Share on other sites
terry Posted February 2, 2016 Report Share Posted February 2, 2016 its more confusing than I thought it was cheers for that info mickey.....Terry. Quote Link to post Share on other sites
Lebro Posted February 2, 2016 Report Share Posted February 2, 2016 They seem to have missed out 1/8" BSP commonly used on pressure gauges. Bob. Quote Link to post Share on other sites
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