Lotus Elan

Hello & Strombergs

PostPost by: 69DHC » Tue Jul 17, 2012 11:23 pm

Hi all,

Back on here after a while, onto my second Elan "George" a 69 DHC S4 SE. What a lovely thing he is too. After owning quite a few serious modern performance cars it's a relief to go back to a proper sportscar! Just had a great drive in my "new" S4 and I still believe no one has made a better sportscar for the road, especially British roads!

Anyway, I've got a couple of questions I hope you can help with. I've been pouring over the archives but can't quite see the answer I'm looking for.

I bought my car fully restored from a specialist and it's in top condition, everything (and I mean everything) has been rebuilt. The car has however only done a couple of hundred miles since then so it needs a shakedown, which is part of the fun eh.

I've had quite a bit of experience tuning various cars from 50's-90's but this is my first look at Strombergs. The car has a set of 175 CD-2's according to the dashpots.

First of all I disconnected the linkages and saw the carbs were out of sync, so out with my trusty SK and they are now perfectly balanced at idle and up to 3000 rpm. The car will now hold a good steady idle at c. 900 rpm and will start from cold ok too. However, the idle is not as good I expect it could be.

So, out with the dual colortunes on 2 and 3 cyl. No. 2 cyl plug was sooty and 3 sooty and wet. The rich condition was confirmed with the colortune showing both were running rich at idle and of course number 3 more rich than 2. Rocket science eh! ;)

Revved up, number 2 leans out and appears to be close to spot on off idle - it goes blue with tinge of yellow at a cruise condition, and yellow with sharp acceleration, quickly settling back to blue shortly after. Good, good.

Number 3 off idle is clearly running too rich as up the rev range it needs leaning out slightly and is mostly yellow.

So in short, at idle both carbs are running rich, but front carb is rich at idle but ok off idle, rear carb is rich at idle and off idle.

This is where I lack the next level of information on how to correct this condition. From what I am reading it doesn't sound like you can adjust these 175 CD2 Stromberg's like an SU. I see there is a tool available to adjust the needle, and I read of these air bleed screws on the RHS of the carb body near the temp compensator, but what is the correct procedure as it seems that mixture adjustment should not be touched, just all parameters base lined ie jet height, needle location, float height - ? There is a diaphragm involved here too?

Do I need to go to the full hog of removing the carbs, checking the jet height, float level etc condsidering the carbs have been rebuilt or is there some way I can make a small correction to address the issues above?

I have two books coming sometime in the next few days which will undoubtedly help, but some advice from the experts on here would be appreciated as of course books don't address specific issues.

Cheers
Attachments
MyElan.jpg and
69DHC
New-tral
 
Posts: 14
Joined: 17 Jul 2012
Location: Goodwood, UK

PostPost by: collins_dan » Wed Jul 18, 2012 2:20 pm

Welcome. Not sure where you are located, but it helps to know as someone may live very close that could help. You may want to check what kind of needles are installed in your stromberg. I changed to B1BT from original fixed needles, either B1G or B1Y, can't remember which, for the very reasons you state. Either too rich at idle to get good mixture at speed, or good at idle, too lean at speed. Here is a post worth reading.
elan-f15/adj-carb-needle-t20300-15.html

All the best, Dan
User avatar
collins_dan
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1156
Joined: 09 Jan 2006
Location: Baltimore, MD

PostPost by: elj221c » Wed Jul 18, 2012 6:06 pm

Silly question time!

Have you checked you have oil in the dashpots?
Roy
'65 S2
User avatar
elj221c
Fourth Gear
Fourth Gear
 
Posts: 633
Joined: 12 Sep 2003
Location: Surrey Hills, England

PostPost by: 69S4 » Wed Jul 18, 2012 7:09 pm

Hello and welcome :D Strombergs are not quite the spawn of the devil but there's probably a bit of the gene pool in there somewhere :lol: Probably the best thing I can do is give you a link to the following site http://www.buckeyetriumphs.org/technical/Carbs/CarbsIII/CarbsIII.htm. It's based on Triumph TR6 Strombergs but a lot of the information carries across. It was probably the single most helpful source (Stromberg users here excepted :roll: ) I had when I was rebuilding mine a few years ago.

From the sound of it you're not far off with yours though. Elan's on Strombergs do have a slightly uneven idle which I've heard is due to uneven mixture distribution between the cylinders and not something you can adjust away. There are lots of things that can make it worse though - air leaks either through the spindle seals, the "O" rings or via the vacuum take offs for the headlamp pods or the servo, lack of oil or the wrong viscosity in the dashpots, worn, maladjusted or incorrect needles, broken or stuck temperature compensators, leaky or stuck choke mechanisms bleeding extra fuel or wrong float levels (plus a few others that I haven't thought of). Have a read through the Triumph site though. That should get you up to speed on Stromberg technology.
Stuart Holding
Thame UK / Alpe D'Huez France
69 S4 FHC
Honda GoldWing 1800
Honda CBX1000
Kawasaki H1 500
Yamaha XS2
69S4
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1210
Joined: 23 Sep 2004
Location: nr Oxford UK

PostPost by: 69DHC » Mon Jul 23, 2012 1:05 pm

Thanks for the info guys. I have got my manuals now and typically they don't show the diagrams for the CD2-SE carbs. Bit frustrating!

Can someone simply tell me if this carb has either an adjustable jet or adjustable needle? Getting my hands underneath the rear carb I can feel a slotted round screw (not a hex nut) of course not possible to see properly without removing the carbs and I don't want to do this if I don't have to. It appears there is a Zenith tool perhaps to do this?

http://www.sucarb.co.uk/ProductDetail.aspx?Id=25146

I would have assumed though that the jet in the CD2-SE was not adjustable as it's an emmissions carb, but what do I know. I am guessing it has an adjustable needle for minor alterations.

The idle trim screw does not allow me to lean the carb enough, so it looks like it needs a jet adjustment or a needle adjustment.

If this carb is not adjustable, I guess I will need to check the float levels and jet heights; except reading through the archives on here it seems this is pretty hit and miss and no one appears to have got theirs to stoic from what I can see which is extremely odd.

Not a fan of fiddling with the needle to be honest as can't see how that will help much at idle and would assume/well know it would upset the mixture off idle as well. Most SU needles have the same profile at the idle station within the same range and I assume the Stromberg needles will too.

When I get the time I'm going to weld in my wide band O2 sensor and have a proper look and do some logging. Car is running fine, I'm just a bit of a perfectionist and can tell it's too rich at idle at the moment.

Thanks!
69DHC
New-tral
 
Posts: 14
Joined: 17 Jul 2012
Location: Goodwood, UK

PostPost by: collins_dan » Mon Jul 23, 2012 2:35 pm

The jet is not adjustable, the needle is likely the stock needle which is only minimally adjustable. Running rich at idle and Ok WOT is generally the best you can hope for with the stock needles. That is why many change to some version of adjustable needle. Dan
User avatar
collins_dan
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1156
Joined: 09 Jan 2006
Location: Baltimore, MD

PostPost by: 69S4 » Mon Jul 23, 2012 3:34 pm

69DHC wrote:Thanks for the info guys. I have got my manuals now and typically they don't show the diagrams for the CD2-SE carbs. Bit frustrating!

Can someone simply tell me if this carb has either an adjustable jet or adjustable needle? Getting my hands underneath the rear carb I can feel a slotted round screw (not a hex nut) of course not possible to see properly without removing the carbs and I don't want to do this if I don't have to. It appears there is a Zenith tool perhaps to do this?

http://www.sucarb.co.uk/ProductDetail.aspx?Id=25146


The Strombergs on S4 Elans are adjustable needle and they adjust from the top. You remove the black dashpot damper and there's a tool (a long allen key) that you drop down to locate in the top of the needle adjuster. You can see them at the bottom of this page - http://www.gowerlee.dircon.co.uk/Stromberg.html There's a male and female type (I've got one of each!). Turning clockwise raises (= richer) the needle and if it's been set up properly you've got one turn of adjustment up or down. If the damping oil is vanishing it's probably the "O" ring seal on the needle holder that's damaged.

The earlier Strombergs were adjustable jet and that's what the wrench like tool is for. I'm not aware of those being used on Elans though. What you can feel underneath your carbs will be a brass cap that screws over the jet assembly and protrudes through an "O" ring in the float chamber.
Stuart Holding
Thame UK / Alpe D'Huez France
69 S4 FHC
Honda GoldWing 1800
Honda CBX1000
Kawasaki H1 500
Yamaha XS2
69S4
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1210
Joined: 23 Sep 2004
Location: nr Oxford UK

PostPost by: collins_dan » Mon Jul 23, 2012 4:46 pm

Stuart, I'm not sure that you are right about the strombergs on S4's being equipped with adjustable needles, at least not on federal S4's. My impression, and I could be wrong, is that they came with either B1G or B1Y fixed needles. They could be adjusted slightly using the side screw, but that was it. At least this is how my car came and I have gotten the impression over the years, that this is how most came originally. All the best, Dan

edit: just noticed the picture (RHD) and 60DHC's address, so not sure my federal experience is relevant.
User avatar
collins_dan
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1156
Joined: 09 Jan 2006
Location: Baltimore, MD

PostPost by: 69DHC » Mon Jul 23, 2012 7:08 pm

Cheers again, I have the tool for the needles coming so I will try that.

As the front carb mixture is spot on I'm hoping I can get the rear the same with the current needles.
69DHC
New-tral
 
Posts: 14
Joined: 17 Jul 2012
Location: Goodwood, UK

PostPost by: 69S4 » Mon Jul 23, 2012 7:28 pm

collins_dan wrote:Stuart, I'm not sure that you are right about the strombergs on S4's being equipped with adjustable needles, at least not on federal S4's. My impression, and I could be wrong, is that they came with either B1G or B1Y fixed needles. They could be adjusted slightly using the side screw, but that was it. At least this is how my car came and I have gotten the impression over the years, that this is how most came originally. All the best, Dan


Hi Dan. That's interesting; I thought they were all much the same but obviously not if yours are not adjustable. On mine the top of the needle fits into a cylindrical brass holder that's sprung loaded to bias the needle to one side. When you fit that into the piston it screws into a carrier that's fitted into the bottom of the air valve guide rod. The carrier has an o ring seal to keep the oil in and a spring clip on top to stop it moving. The retaining screw at the side fits into the slot in the side of the needle holder but doesn't stop it moving, it just stops it rotating so that turning the carrier with the alan key tool moves the needle up or down by the pitch of the thread. A picture would have explained that a lot easier :lol: but sadly I don't have one to hand :(

Yours, presumably, just push into the bottom of the piston, are fixed there with the side screw and you get whatever the needle profile gives you? That leaves you one step short of twiddler's paradise but probably with better mixture control :lol:
Stuart Holding
Thame UK / Alpe D'Huez France
69 S4 FHC
Honda GoldWing 1800
Honda CBX1000
Kawasaki H1 500
Yamaha XS2
69S4
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1210
Joined: 23 Sep 2004
Location: nr Oxford UK

PostPost by: collins_dan » Mon Jul 23, 2012 8:56 pm

Stuart, Actually, mine is no longer fixed. :lol: I changed out to adjustable, which required both new needles and new pistons, but was well worth it. Cheers, Dan

69DHC, If it ends up, you aren't able to adjust your needles with the tool, what you can do is unscrew the tops and pull out both piston and needle assemblies. Then you can compare the two and see if they are both in the same relative position in the piston, if not, you can loosen the side screw and put the one you are not happy with in the same position as the one that seems good. Good Luck, Dan
User avatar
collins_dan
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1156
Joined: 09 Jan 2006
Location: Baltimore, MD

PostPost by: 69DHC » Tue Jul 24, 2012 3:59 pm

Aha. Well, went on a long-ish drive today, running fine then just stopped like the ignition had been switched off and refused to restart. Conveniently this happened at my restorers place where I was checking out my Healey 100. George must like me otherwise he'd have died somewhere really inconvenient!! ;)

So, bonnet opened and fuel was pouring out near the choke of the front carb. Took the airbox off and petrol has filled up the interior of the air box. Down by the chassis rail was over a pint of petrol! Not a good look. This liquid has been down there for some time so it's clearly been leaking a good while.

The car still has the mechanical pump but has a Filter King fitted inline. I will need to check the pressure of that I'm sure. 2.5 or 1.5 psi - ? SU's like 1.5 psi, what about Strombergs? Webers I think run 2.5 - ? Hopefully this isn't the cause of the problem.. EDIT: can't be, they didn't have pressure regulators inline from stock and the mechnical pump can't pump too hard right.

Well, anyway, this is going to mean the carbs have to come off now, so I will rebuild them myself to ensure they are correct. I've ordered a kit from Southern Carbs which will include an adjustable jet.

I do find it pretty weird how the rear carb was running rich, but the front carb is doing the leaking. Oh well I'm sure an engineering type could explain that one!

Got to love these little cars... :roll: :mrgreen:
69DHC
New-tral
 
Posts: 14
Joined: 17 Jul 2012
Location: Goodwood, UK

PostPost by: 69S4 » Tue Jul 24, 2012 5:02 pm

Far as I'm aware it's also 1.5psi for Strombergs but that just comes from the back of my mind so it could well be wrong. I've also got a Filter King fitted just before the carbs to control the pressure from an electric pump but I've never managed to work out what pressure it's regulating to. Over the years I've wound the adjuster in and out almost at random but never noticed it making much difference.
Stuart Holding
Thame UK / Alpe D'Huez France
69 S4 FHC
Honda GoldWing 1800
Honda CBX1000
Kawasaki H1 500
Yamaha XS2
69S4
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1210
Joined: 23 Sep 2004
Location: nr Oxford UK

PostPost by: oldelanman » Tue Jul 24, 2012 5:48 pm

69S4 wrote:Hi Dan. That's interesting; I thought they were all much the same but obviously not if yours are not adjustable. On mine the top of the needle fits into a cylindrical brass holder that's sprung loaded to bias the needle to one side. When you fit that into the piston it screws into a carrier that's fitted into the bottom of the air valve guide rod. The carrier has an o ring seal to keep the oil in and a spring clip on top to stop it moving. The retaining screw at the side fits into the slot in the side of the needle holder but doesn't stop it moving, it just stops it rotating so that turning the carrier with the alan key tool moves the needle up or down by the pitch of the thread. A picture would have explained that a lot easier :lol: but sadly I don't have one to hand :(


Is this any help ?
Carburettor overhaul 006.jpg and
Carburettor overhaul 013.jpg and


69DHC wrote:I have got my manuals now and typically they don't show the diagrams for the CD2-SE carbs.

I would suggest you get yourself a copy of the Workshop Manual. It has 15 pages on the standard Stromberg (CD2-S) including diagrams and drawings and a further 5 pages on the emission version (CD2-SE) which may help you understand exactly what you have. That said the manual only shows the fixed needle and fixed jet set-up, no mention of the adjustable needle which was I believe introduced towards the end of Stromberg usage for domestic market - not for federal emission cars which I believe always had fixed needles.
69DHC wrote:Down by the chassis rail was over a pint of petrol!

There should be a large drain hole in the bottom of that well underneath the carbs - maybe it's been glassed over.
Roger
S4 DHC
oldelanman
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1676
Joined: 02 Jan 2008
Location: Dorset UK

PostPost by: ricarbo » Tue Jul 24, 2012 6:11 pm

Just because the fuel pump looks original does not mean it delivers the right pressure. Someone might have rebuilt it with wrong bits. I'd get a low pressure gauge and check it. Leaking sounds like a float valve problem, though.
Richard
ricarbo
Third Gear
Third Gear
 
Posts: 271
Joined: 14 Apr 2010
Location: Hove, East Sussex, England
Next

Total Online:

Users browsing this forum: No registered users and 6 guests