Stromberg CD3 needles

[rogerguzzi]

Hello All

              I am working on the carbs and have decided to fit new spindles and discs.

I have several needles but I can not find a chart anywhere!

I have 5BW (fitted) 5CE and 5DK.

So does anyone have a chart of sizes or recommendations for a Mk1 2Lt with a 25/65/65/25 cam with 0.030" extra lift on both lobes  and a gas flowed Chris Witor inlet manifold.

I have ported the the head as best I can and cut 3 angle valve seats and the backs of the valves as the tuning book says.

I shall be running Megajolt so can adjust ignition to suit.

The engine is fully balanced and plus 0.040" O/S plus I upgraded the head studs to 7/16" UNF

I have refitted the standard exhaust manifold as I do not want the heat or noise and a standard S/S exhaust system(maybe change back pipe to semi sports?)

I know I will loose some power but it should be quickish but better for touring along with the O/D gearbox and 3.63 diff?

so any Ideas?

Roger

[Nick Jones]

Roger,

I mailed you a couple of Stromberg manuals.  One has needle tables in the back.  I'd start with the standard Mk2 needles and matching springs - don't think they'll be all that far off.  Did you keep the wideband?

Nick

[rogerguzzi]

Hello Nick

                 Thanks' for that but I had read those and still unsure!

I sold the new dual wideband kit to Phil but I do have a single one kicking about somewhere? (I will get a threaded collar fitted in the front pipe to take a sensor) When I get it?

plus one I took off Spitty that was a bit slow starting up but could play with! (or sod it and buy another one?) then sell more stuff? (engine ,gearbox, bonnet, etc plus a car or motorcycle!)

still we have to watch the pennies ! not sure why at at my age? the kids will soon spend it!

The carbs started as I decided to fit some small u/j's to the cross link!(then it snow balled again!)still they look nice?(will post a photo when the B*ggers are back on!)

Roger

ps have ordered the stuff from Chris Witor may give him a ring for advise?

then there is the remote air cleaner to sort as no room inside the filter housing as I am fitting some re machined ram thingy's! for cool air

Will it ever stop?

[rogerguzzi]

Hello All

              After having another good look through Alan's files I have found the needle graph (loads of them) and managed to edit it and put a standard 2000 needle on (5BU)

So at the moment there are no needles fitted now as I have fitted new spindles , discs, and diaphragms and 6mm u/j's to cross shaft!

I am thinking of fitting the 5DK needle as it looks about the same on the first 4 station then just gets a bit richer over the rest of the range!

Now seeing as the car will have a ported inlet manifold(Witor) radiused ram pipes, A Witor cam with extra lift on both lobes, A ported head(by Me?) 3 angle valve seats and valves.(also by me!)

I will fit a remote free airflow air filter.

I know I am refitting the standard Exhaust manifold (but the car will be leading a bit different life now! Touring) but hopefully will still be quick ish ?

I think on the carb u/j's I will put flats under the grub screws front carb and joining shaft and machine a groove in the rear carb fitting to take the grub screw(so that one will be left slack while setting up then clamped!

Roger

ps I know I get side tracked to easily!

 

 

 

 

 

[Nick Jones]

Like the ujs 

Suggest Vitesse /GT6 Mk2 needles might be better than anything from a mk 1 as the cam timing is a better match?

[rogerguzzi]

Hello Nick

                 You probably right? but now I have found all the needle spec its mind bending

Plus I have had a quick look at Vit/GT6 ones and they all seem to go lean at top end?

The needle I suggested was very similar until big throttle openings (and how often will I be there ?)

Still no rush all the wiring is still out plus trim and dash board etc! Still Spitty is ready to go when things are better! (not sure if our trip to Spain will happen this year?) that's if they want us and if we are comfortable to go because if all the bars and tavernas are not open what would be the point?

Roger

ps still got lots of trip planed for the local group or just me and the Memsahib if they can not be bothered all will involve nice roads and in my case Cake and nice Coffee!(not one for the big fry up!)

[Radioactive Man]

9 hours ago, rogerguzzi said:

ps still got lots of trip planed for the local group or just me and the Memsahib if they can not be bothered all will involve nice roads and in my case Cake and nice Coffee!(not one for the big fry up!)

Cake and coffee sounds good to me.  Just give me some notice so I can try and book time off work.

[Nick Jones]

Needle selection is a bit of a black art as there are more factors in play than meet the eye. Piston weights and springs also play a part as they set the working flow range.

The lean ends to the Vitesse/GT6 Mk2 needles may be a consequence of the 150CDs being nearly maxed out leading to an increase in vacuum at the jet under high rpm full throttle conditions causing a tendency to go rich.  I know Alan spent a lot of time and effort trying to deal with this (including auxiliary air devices). He had some success but eventually bit the bullet, moved up a class and fitted 175s.

[rogerguzzi]

Hello Nick

                 I am swayed by your better judgement and have ordered 2 NOS off Fleabay for £20 (good price compared to Burlen about £40 with p&p!)

I have gone for the B5AJ which I think was fitted to GT6 plus before they started leaning them off!

The first 3 needles are what Triumph fitted as they got leaner and the other 3 is what I have already.

I think this way I will have a fighting chance of getting it running as there is the Megajolt to rewire as well plus the different camshaft and manifold etc!

Roger

[rogerguzzi]

Hello All

              I have finally got my welded up ram pipes back and re machined them and drilled accurately!

I just have to strip the old paint off and re paint the air box

Its a pity they will not be seen!(Perspex front?) 

Roger

[PeterC]

Trumpets will make the piston run lower for the same mass air flow. The stock carb mouth, as SU, creates a small depression that means the piston runs higher to satisfy its "constant depression" operation. Hence fitting a trumpet abolishes the entry pressure drop and makes the piston run lower. The cruise mixture will weaken, but impossible to predict.

It is easier to see if the mouth pressure drop is increased (eg with a choke plate) then the piston lifts lots to give a rich starting mixture

At butterlfy openings >30 deg the pulses of flow from each iv opening are no longer choked by sonic flow past the disc, and act on the jet to create a richer mixure even at the same needle position. Trumpets will weaken this mixture too. Only way to find how rich is with a UEGO.  There is a lot more going on in  these carbs than meets the eye !!

.

 

[rogerguzzi]

Hello  Peter

                   That has educated me a bit more (I think)

So I think I will go for B5AJ if I ever get it all together again!

Plus I have 3 richer needles so I would be able try them at no extra cost and with AFR meter I should be able to get it something like?

Roger