Iain T Posted February 13, 2020 Report Share Posted February 13, 2020 As I am playing about with the air intake on my Mk2 Vitesse I couldn't resist these stub stacks on the Rimmer website pt no RL1396ALT. By all accounts stub stacks will smooth and increase the airflow into a carburetor and as I don't have the facilities to make a pair I thought I would give them a try. They are £46.50 + vat for the pair. As to size they are made for SU HS4 carbs but as you can see the i/d is the same as a Stromberg 150 and the mounting holes are only 3mm different in pitch so I am just going to elongate the holes to suit. The two smaller holes are virtually in line so I may leave them or increase diameter by 1mm. I just need to drill new holes for the damper piston and Bob's yer uncle! They are 100mm o/d, 36.0 i/d and 16mm high, the profile resembles half a teardrop. According to my measurements that should leave about 32mm from the top of the stub to the inside of the airbox. Whether they will make any appreciable difference I don't know but 'every little helps'. Iain PS, they don't qualify as 'bling' 'cos you can't see them on the car! Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 13, 2020 Report Share Posted February 13, 2020 you need to machine the air piston vent !!!!!! for use on strombergs i fitted some on the Vit6 by cutting the filter disc and add spacers to hold all in place if you get the gist i reckon it made a difference, but my 1600 was a right hairy thing anyway pete Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2020 Author Report Share Posted February 13, 2020 Pete, I did say I needed to drill holes, ok machine a slot, in them for the damper (air) piston! I will be using an external trunked air filter and selling the K&N pancakes. CTM Performance will be doing the head and intake manifold mods, matching etc so I need to get more cold air in but I'm not going for a hairy dragster but as much torque as I can reasonably get. To that end I will probably choose Chris Witor's 3021 camshaft. Iain Link to comment Share on other sites More sharing options...
daverclasper Posted February 13, 2020 Report Share Posted February 13, 2020 2 hours ago, Pete Lewis said: i reckon it made a difference, but my 1600 was a right hairy thing anyway Hi Pete. Is this maybe?, almost?, "a must have"?. 😅 Dave Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 13, 2020 Report Share Posted February 13, 2020 well it should smooth /help the air velocity in through a normally sharp edged entry only a must have if you wish to twiddle , in most normal every day driving its not a must have as fitting is a fiddle if you use a std filter element as you can see Pete Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2020 Author Report Share Posted February 13, 2020 True, you really need to junk the original filters to correctly fit the stacks. I'm on the hunt for an external filter and how the mount and trunk it to the air box. I'm mindful to protect the filter from getting wet. Iain Link to comment Share on other sites More sharing options...
trigolf Posted February 13, 2020 Report Share Posted February 13, 2020 Slight thread drift - but I've always wondered why the standard air filter box has a cutout in the bottom edge, under the rear air filter, which then gets dirty twice as quick and also must suck in warm air from the engine compartment ? Someone please explain ! Gav Link to comment Share on other sites More sharing options...
Nigel Clark Posted February 13, 2020 Report Share Posted February 13, 2020 3 hours ago, Iain T said: To that end I will probably choose Chris Witor's 3021 camshaft. Iain I've fitted the CW3021 in the 2.5 litre engine in my GT6. It gives plenty of extra go at the top end without sacrificing low end torque. In my opinion, it's the best 6 cylinder cam for road use. Nigel Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2020 Author Report Share Posted February 13, 2020 I believe someone at Triumph realised air flow to the rear carb could be compromised by the front filter hence the simplistic fix. Yes it does mean hot air is drawn in, I will be blanking mine off. Iain Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2020 Author Report Share Posted February 13, 2020 Nigel, the crazy lifts and lap overs on some cams are not required unless you circuit race. The same with over strong valve springs. Iain Link to comment Share on other sites More sharing options...
Peter Truman Posted February 13, 2020 Report Share Posted February 13, 2020 Just looked at the Chris Witor webpage look at the Technical Page, Inlet Manifold Comparison, Other Notes, it shows the Stromberg 150's as is at 84CFM and with Stubs at 91, ie a 8% increase. Some interesting info there Peter T Link to comment Share on other sites More sharing options...
Iain T Posted February 14, 2020 Author Report Share Posted February 14, 2020 I am certainly hoping for an increase in get up and go. When I finish the engine mods and put it on a rolling road I might try it with and without the stub stacks to see what the variance is and report back. Problem is I will have to armed with needle options I have 6AC in the carbs now and 7B to try out anybody know of a inbetweeny number? Pete, I have mohair headlining does that qualify my Mk2 as 'hairy'??? Iain Link to comment Share on other sites More sharing options...
JohnD Posted February 14, 2020 Report Share Posted February 14, 2020 Yiou might think that somethink as shiny and neat as that must have a beneficial effect. But I have anold article from that doyen of engine tuners, Dave Walker, (Auntie Flow, CCC June 1994, p.70-72) (Yes I know I'm a hoarder!) Dave was flow testing his mods to a cylinder head and fitted stub stacks. On Webers, 1" stacks made no difference at all to the flow, even at WoT! John Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 14, 2020 Report Share Posted February 14, 2020 Ian any spare hair is needed down here yes she had a few changes we applied but it was a flier she would leave mates TR7 in the dust , no hair just a tin top, you could really upset some BM egotistical drivers great fun now its pipe and slipper cruising in the 2000 pete Link to comment Share on other sites More sharing options...
Iain T Posted February 14, 2020 Author Report Share Posted February 14, 2020 John, Webers are Italian 🍷the same rules don't apply to British Zenith-Strombergs!?!🍺 Iain Link to comment Share on other sites More sharing options...
Nick Jones Posted February 14, 2020 Report Share Posted February 14, 2020 On 13/02/2020 at 19:57, Iain T said: True, you really need to junk the original filters to correctly fit the stacks. I'm on the hunt for an external filter and how the mount and trunk it to the air box. I'm mindful to protect the filter from getting wet. Iain No easy task in a Vitesse engine bay. On my FI setup I have the throttle body on the end of the plenum facing forward and a conical filter on the end of that pointing between the wheel tub (bonnet down) and the radiator. It’s partly boxed to try and keep the heat out. Works well enough when moving (I can monitor the inlet air temp) but at very low speed in traffic it creeps up and up. Nick Link to comment Share on other sites More sharing options...
Iain T Posted February 15, 2020 Author Report Share Posted February 15, 2020 Yes requires some thought how and where to mount (the side valance seems a good option) and the correct sized/flow filter. I've seen what Chris Witor has done with a forward facing cone filter but that is still in the hot air flow from the radiator fan so not ideal. What ever position the filter is mounted it must not get wet so it's going to be a compromise. Iain Link to comment Share on other sites More sharing options...
Iain T Posted March 3, 2020 Author Report Share Posted March 3, 2020 Finally got round to modifying the stubs, I may just countersink the small holes to fully align with the carbs. I machined out the back of the stub instead of a slot in the face so as not to disturb the airflow. Iain Link to comment Share on other sites More sharing options...
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