Grinnal Posted May 28, 2014 Report Share Posted May 28, 2014 Hi, I have a TR6 which we are going to fit HS6 SU's onto. The manifold has a through pipe that would normally be connected to the exit on top of the water pump and then the pipe that runs from the back of the water pump and connects into the pipe that go to the heater. What I want to know is, if I blank off the exit at the top of the water pump and then change the pipe that runs from the back of the water pump through to the heater pipe and simply blank of the pipe that runs through the manifold will this cause issues? Thanks Mike Quote Link to post Share on other sites
Peter Cobbold Posted May 28, 2014 Report Share Posted May 28, 2014 Mike, A hot spot in the manifold only matters if you do a lot of cold weather, stop/start driving. For performance its a disadvantage: the colder in the manifold the better. You do want to connect the heater return to the pump, though. Make sure you have the correct manifold for the head ! Peter Quote Link to post Share on other sites
Grinnal Posted May 28, 2014 Author Report Share Posted May 28, 2014 Thanks Peter I will continue with my plan to blank the through pipe on the manifold off. I have checked the manifold matches the head Thanks again Mike Quote Link to post Share on other sites
Peter Cobbold Posted May 28, 2014 Report Share Posted May 28, 2014 Mike, Heat is the enemy - a cold air intake for the SUs would be good. Peter Quote Link to post Share on other sites
RonA Posted May 28, 2014 Report Share Posted May 28, 2014 Hi Mike I ran for years with the pipe connected until a couple of years ago when it started to look a bit corroded, I bypassed it then and have run that way since, can't say I've noticed any difference, it certainly hasn't caused any problems that I'm aware of. RonA Quote Link to post Share on other sites
Grinnal Posted May 28, 2014 Author Report Share Posted May 28, 2014 Hi Ron, Thanks for the advise, I am going to run without the pipe connected Cheers Mike Quote Link to post Share on other sites
johnny250 Posted May 29, 2014 Report Share Posted May 29, 2014 I bypassed mine last year, with no difference noticed. No need to blank off the water pipe in the manifold, but may cut it off flush now. john Quote Link to post Share on other sites
Grinnal Posted May 29, 2014 Author Report Share Posted May 29, 2014 Thanks John Quote Link to post Share on other sites
PaulAA Posted May 29, 2014 Report Share Posted May 29, 2014 Mike, A hot spot in the manifold only matters if you do a lot of cold weather, stop/start driving. For performance its a disadvantage: the colder in the manifold the better. You do want to connect the heater return to the pump, though. Make sure you have the correct manifold for the head ! Peter Hi Peter Would it be correct to make the extrapolation that warm air reduces density and therefore weakens the mixture? If this is the case, would it not be better to be sourcing the intake air from outside the engine bay? I'm also running HS6s and I would observe that the car is terribly lumpy when cold, runs very smoothly at operating temperature, but becomes fractious when the temperature rises and a low-rev misfire creepes in under load until the temperature drops back down again. I have K&N pancakes and I was wondering whether it would make sense to go back to the original box filter and connect the intake via a pipe to a hole through the radiator shroud. I remember reading that the Strombergs don't like any kind of forced air intake (and, presumably, a ram effect is likely if the air comes from immediately behind the grille), but would you see a similar risk with the HS6s? Cheers Paul Quote Link to post Share on other sites
johnny250 Posted May 29, 2014 Report Share Posted May 29, 2014 No problems, works well with HS6....... Quote Link to post Share on other sites
PaulAA Posted May 29, 2014 Report Share Posted May 29, 2014 John Superb - thanks. Not an off-the-shelf item, I assume..? Paul Quote Link to post Share on other sites
Peter Cobbold Posted May 29, 2014 Report Share Posted May 29, 2014 Paul, The hotter the air going into the carb the less dense the mixture entering the engine. That alone will lower power a bit. It might not change the mixture, not sure. The lower density of the air will reduce the 'suction' at a given volume flow, so fuel flow will also drop, a bit. But they may be close to cancelling out, leaving mixture moreorless unchanged. For cold weather operation more recent carb set ups have a hot air intake from around the exhaust manifold, with a thermostatically operated flap valve. eg TR7, BGTV8. The hot air improves warm-up running. For cold weather lumpiness that sort of mod might well help. It probably works by helping fuel droplets evaporate in the inch or so after the jet so ensuring mixture distribution is optimal between cylinder. The hot spot does the same for liquid fuel running down the floor of the manifold. A remote filter and cold air duct will be better for power running when engine is up to temperature - like johnny250's. That with a TR7 thermovalve might be a cure for Poland-cold running. Not certain what causes low rpm+load misfire in hot underbonnet temperatures (??). Fuel evaporation after the jet should be good, so I'd not suspect distribution issues. It might be fuel bubbling in the tube from float chamber to jet. Its very close to the exhaust manifold so might be too hot in static air. It would be worst when fuel flow is low. Its a good idea to have a heat reflector plate between the inlet and exhaust manifolds to stop the inlet heating up. Thin ali is fine. Failing that, try wrapping the fuel tube to the jet in aluminium foil - see it it makes a difference. The ram air effect is miniscule unless you are driving at 100+mph. And a fliter tucked behind the front valence wont see it. I think HS6s take the atmospheric air to lift the piston from the filtered supply, so any tiny rise in ram pressure would cancel out across the piston. cheers Peter Quote Link to post Share on other sites
PaulAA Posted May 30, 2014 Report Share Posted May 30, 2014 Peter Thanks, as always. Genuinely cold starting is not a real problem - the car lives in an underground garage, which, even in winter, rarely drops below 5deg. I therefore have the luxury of doing a couple of circuits before tackling the ramp and outside temperatures. That said, I'll investigate the TR7 thermovalve, to see whether it would make a difference. I'll also investigate insulation of the fuel pipe. I installed a heat deflector between the maifold and carbs, but the throttle linkage obstructed the snug fit and I ended up rotating them 90deg, thus exposing the bowl to the heat of the exhaust and rather defeating the object of having them... Cheers Paul Quote Link to post Share on other sites
tr6wilts Posted May 30, 2014 Report Share Posted May 30, 2014 (edited) What jets do you have, I had HS6's with waxstat jets that caused these exact issues, I swapped them out for standard jets, and no more issues... I could have replaced the wax capsule with 2 one pence pieces (cheap fix) but the jets seemed in poor shape. Rich Edited May 31, 2014 by tr6wilts Quote Link to post Share on other sites
Tim D. Posted May 30, 2014 Report Share Posted May 30, 2014 I guess you meant 2 X 1p pieces Quote Link to post Share on other sites
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