qim Posted July 13, 2017 Report Share Posted July 13, 2017 Hi Should there be something where I marked with a red circle? Thanks Quote Link to post Share on other sites
Fireman049 Posted July 13, 2017 Report Share Posted July 13, 2017 Hi qim ~ Your carbs. seem to be non-standard for a TR3. I would guess that this is the take-off for the vacuum advance for the distributor? Tom. Quote Link to post Share on other sites
qim Posted July 13, 2017 Author Report Share Posted July 13, 2017 (edited) I have a TR3A (1959) and understabd that I have HS6 carbs, which may, or may not be original, They may have been factory fitted in later TR3As or added during the first reconstruction in the 70s before I bought it. Maybe this pic shows better I'm in the UK now, far away from the car that is not too happy about the English drizzle! Camilo Edited July 13, 2017 by qim Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 13, 2017 Report Share Posted July 13, 2017 (edited) This image clearly shews the closed circuit breathing of a sealed crankcase on a Spitfire 1500. (yes I know Spit has HS4 carbs, but the inlet tube you refer to is the same deal.) As can be seen the blanked port on your car is used on this Spitfire engine to suck the oil mist from the engine into the combustion area. https://www.bing.com/images/search?view=detailV2&ccid=WvaoNdup&id=4D26EC0CCF5B710A1E15F8B2C940FAC002FCD0B6&thid=OIP.WvaoNdupsHmB4SAEnKxi5AEsDh&q=Engine+Spitfire+1500&simid=608008731794015230&selectedIndex=6&ajaxhist=0 Keep the port blanked. I too (like many other TR3-4 owners) have that design of carb, HS6 fitted. Mine have run fine since fitting in 1975. They were sold as pairs for fitment to cars with worn out H type carbs - (£12.50 a set a believe) I still have the fitting instructions we wrote to provide with every set. I would guess too that they have spring loaded needles that are SM - Special commission manufacture by Peter Cox. Peter W Edited July 13, 2017 by BlueTR3A-5EKT Quote Link to post Share on other sites
ianc Posted July 13, 2017 Report Share Posted July 13, 2017 (edited) This is the take-off for the distributor's vacuum advance. However, on modified engines, vacuum advance is often (usually) not used, so the port at the carburettor must be sealed (as in photo). At the distributor end, the connection to the diaphragm will be closed in similar fashion (but might only be a piece of insulating tape, as it's not critical). Ian Cornish Peter W and Peter Cobbold are correct - my mistake. Edited July 13, 2017 by ianc Quote Link to post Share on other sites
Peter Cobbold Posted July 13, 2017 Report Share Posted July 13, 2017 The tube enters the choke-tube where the depression is a mere 0.25psi or thereabouts. TR7s use that tube to scavenge blow by form the sealed crankcase as PeteW says above. The disy vac adv take-off is here: http://0.tqn.com/w/experts/MG-Car-Repair-3786/2010/07/SU-HIF44-Carb.jpg When the butterlfy is open at cruise the air flow over it is sonic and creates a vary large depression locally under that take-off. It pulls the diaphragm in the vac adv capsule agaisnt its spring. At wider butterfly openings the air velocity drops at the port so the depression reduces and the va capsule no longer advances the sparks. On earlier TRs the butterfly swings the opposite way and the vac take off is on the bottom of the carb. Peter Quote Link to post Share on other sites
Don H. Posted July 13, 2017 Report Share Posted July 13, 2017 I have a TR3A (1959) and understabd that I have HS6 carbs, which may, or may not be original, They may have been factory fitted in later TR3As or added during the first reconstruction in the 70s before I bought it... HS6 carburettors were never original equipment, Camilo. Those are 100% later replacements. Quote Link to post Share on other sites
ianc Posted July 13, 2017 Report Share Posted July 13, 2017 In the early 1970s, Cox & Buckles were selling a pair of brand new HS6 carburettors to members of the New Spares Fund for a bargain £25 total! Of course, I was one of those who grabbed the opportunity and, 20 years later, they were fitted to my TR4 to replace the knackered H6s. Ian Cornish Quote Link to post Share on other sites
Lebro Posted July 13, 2017 Report Share Posted July 13, 2017 Yes, I purchased a pair back then too. They are still on the car, & still working well. The AD number suggests they were originally for the "Allegro sport" For decades I kept those "extra" unions blanked off, but have found out that they were for breather use, I now have a 4A rocker box cover, & a simple "Y" connection to link it all up. No reduction in performance or MPG, & it makes for a neat installation without the bother of a PCV valve. Bob. Quote Link to post Share on other sites
Ian Vincent Posted July 14, 2017 Report Share Posted July 14, 2017 I have what I thought was a TR4a rocker cover but it's not the same as yours Bob. I have a brass threaded plug in the centre of the cover between the retaining stud holes. Does anyone know what sort of fitting went in there, presumably to allow a connection to the manifold? Rgds Ian Quote Link to post Share on other sites
Lebro Posted July 14, 2017 Report Share Posted July 14, 2017 The more observant will have noticed, in my photo above, the bicycle brake adjuster on the end of my choke cable. This is very useful for fine tuning the choke action, i.e. getting the desired amount of choke / throttle advance with each "click" of the choke knob. Bob. Quote Link to post Share on other sites
qim Posted October 16, 2017 Author Report Share Posted October 16, 2017 (edited) Ignore post. Sorry! Edited October 16, 2017 by qim Quote Link to post Share on other sites
Drewmotty Posted October 16, 2017 Report Share Posted October 16, 2017 I have what I thought was a TR4a rocker cover but it's not the same as yours Bob. I have a brass threaded plug in the centre of the cover between the retaining stud holes. Does anyone know what sort of fitting went in there, presumably to allow a connection to the manifold? Rgds Ian My TR4 has a similar cover Ian I've wondered what the blanked port was used for too. Quote Link to post Share on other sites
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