Lotus Elan

Stromberg Rebuild - any advice for a rookie?

PostPost by: SENC » Sun Jan 21, 2018 2:51 pm

Finally had some time yesterday to begin sorting bits and pieces for projects over the next months, and though front anti-sway bushes are next (likely followed by trunnion), one goal of mine is to learn about carbs (never messed with them at any significant level). To that end, I've been collecting spares to experiment with including a pair (unsure whether matching) I got a while ago that had the good luck of coming with a high balance bar intake manifold. My 69 S4 originally had the federal emissions setup, removed by the PO and replaced with a low balance bar setup when he rebuilt the engine about 15 years ago.
20180120_164848.jpg and

The current setup is running fairly well, but given the time since the carbs were last rebuilt it is time for a refresh - so my plan is to rebuild the spare set and do a straight swap. If I screw up, I swap back, so no real downside risk or time pressures. If I get it right, I clean up the current set and prep and store for the future. Mainly I want to learn about rebuilding and setting up the carbs so I can diagnose and resolve problems as they, inevitably, arise - and I would appreciate any wisdom or guidance you can offer.

First - is there any way for me to confirm they are actually matching specs? Identifying markings or serial numbers I should note? Does it matter, since I'm rebuilding to a single spec?

After reading through all of the threads here I could find along with the buckeye triumph articles and burlen site, I'm developing a plan and would value your input:
1 - rebuild to carburettor spec 3296 - this looks to be right for non-emission strombergs for 69 - ordering rebuild kit cdrk68 from burlen - does this kit include diaphragms?
2 - B1Y fixed needles
3 - fixed jets B21582/100

What else am I missing? Any special tools or tricks of the trade I should know? Other needs relative to assembly and mounting of the manifold, balance bar, etc.?

Once I get initial parts and start disassembly I'll plan to update this thread with pictures and questions.

Thanks in advance for your tutelage.
Henry
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PostPost by: oldelanman » Sun Jan 21, 2018 4:36 pm

Henry,
I would be inclined to strip your spare carbs to see what you have before ordering needles and jets. I'm pretty sure that the later non-emission carbs with high level balance pipe would have had top adjustable, spring biased B2AR needles with fixed jets - certainly that's what my UK spec car has. There's no reference to this spec in my workshop manual but it may be in later editions I don't know. Miles Wilkins does make reference to the change in his book. I believe the emission carbs were deliberately made non-adjustable to ensure compliance with emission standards was not compromised in service.
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PostPost by: SENC » Mon Jan 22, 2018 12:41 am

Good call, Roger, and of course you were right about popping them open first. I had some spare time this afternoon after removing and cleaning my sway bar and links, so removed the manifold and popped the tops off the carbs for a peek.

I found 3322F and 3322R stampings on the front and rear carbs, respectively - which does indeed match the burlens site for later nonemission elans and which would suggest B2ARs and fixed jets. On removing the pistons, I found the brass setscrews in both pistons to be locked up tight and the screw heads totally buggered (perhaps this is why I got a decent deal on these carbs), but I was able to pull the needles up just far enough to confirm they are, in fact, B2ARs.

Clearly someone had been in these carburettors as a number of screws are buggered and several mismatched - but I have a few scrap stromberg bodies from which I can borrow most of those things.

Any great ideas on removing the setscrews, or should I just look for some replacement pistons? In one of the old threads here I seem to remember reading that pistons were different formadjusting needles than for fixed - is that accurate? If not, I may be able to pull from my non-lotus stromberg scraps.
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PostPost by: Mike Ostrov » Mon Jan 22, 2018 1:33 am

Hi, Henry. Having re built many Strombergs both fixed and variable needle, the guys will give you excellent advice.

Since you have the European high balance intake manifold, I always weld or braze a fitting on the balance tube in the middle and tap for a NPT barb unit. This way you can use a vacuum gauge, one of the best diagnostic tools for both the TC and my Coventry Climax Lady Godiva engines.Try to find one of the older gauges that have the engine symptoms on the face; ie. late ignition timing , etc. If not the newer models will have an instruction book with all the symptoms in illustration based upon the needle actions.

I think you will enjoy the results.

Cheers. Mike, at: 510-232-7764 if you wish to chat. PS: gone for a few days, so, no phone service.
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PostPost by: oldelanman » Mon Jan 22, 2018 1:38 pm

Hi Henry,
It's a shame your carbs have been butchered but they may be salvageable.
My carbs are the earlier version 3296's and I have no idea how they may differ from your later issue ones but I would think that the main components are the same. Pistons for adjustable and fixed needles variants are certainly different and not interchangeable.
I don't know how familiar you are with the adjustable needle set-up but you need to fully remove the grub screw and unscrew the adjuster from the needle carrier before you can remove it from the bottom of the piston. The grub screw has a spring loaded tip which engages with a slot in the needle carrier preventing rotation and removal but allowing vertical movement for adjustment. Unfortunately I don't have any tricks for removal of your damaged screw, really your only option is to carefully drill it out - bear in mind it's hollow with a spring inside ! The adjuster plug is accessed from the top of the piston and you need a long alan key (3mm or 1/8" can't recall which) Turn anticlockwise for removal - only 4 turns or so of thread in total so don't keep winding after that or you may damage the very fine thread. For adjustment in service you need a special tool to prevent the piston rotating and tearing the diaphragm as you turn the adjuster - mine is home made but I think Burlen sell the proper tool.

Another forum member (yvesmontreal) posted a couple of days ago with a similar issue with siezed grub screw
elan-wanted-f4/wanted-stromberg-piston-and-needle-t41114.html
Maybe he will report back if he has any success removing his.

One other tip if not too late - when/if you remove the choke assemblies mark the lever/spindle relationship before you dismantle them, the levers can be fitted 180 deg out and the choke won't work !
Good luck.
carburettor-needle-grub-screw.jpg and
Spring loaded grub screw
carburettor-adjuster-tool-001.jpg and
Stromberg needle adjuster
Roger
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PostPost by: RogerFrench » Mon Jan 22, 2018 2:55 pm

First of all, I'd like to endorse everything t'other Roger has written.
I too had a pair with knackered grub screws, but got one out by soaking for a couple of days with Kroil, followed by heat, from a gun not flame, and there was enough purchase for a screwdriver to work. The other refused, so I started to drill it out. The drill jammed, and luckily in trying to back off the drill, the screw came undone!
One tip I can give you. When removing needle, screw etc., don't bother with trying to pick the bits out of the top. Get a short length of steel brake pipe, put it over the needle, invert the piston on a bit of wood or similar and apply several raps with a small hammer to the brake pipe, driving it all out together. Make sure the adjuster screw is fully in before you do this. Joe Curto gave me this tip, I'm sure he won't mind me passing it on.
Another thing, I bought rebuild kits on eBay from a Triumph specialist that included all screws, washers, diaphragms, gaskets etc., etc. Well worth the money!
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PostPost by: snowyelan » Mon Jan 22, 2018 5:12 pm

If you're going down the drill it out route a 'left hand' or reversed flute drill bit will spin the left over bits in the right (ccw so I guess its left not 'right') direction to back them out of the hole when it finally frees up.
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PostPost by: SENC » Mon Jan 22, 2018 9:47 pm

Is there an easy way to visually distinguish between pistons for adjustable needles and those for fixed needles?
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PostPost by: oldelanman » Tue Jan 23, 2018 9:51 am

SENC wrote:Is there an easy way to visually distinguish between pistons for adjustable needles and those for fixed needles?


The fundamental difference between the two is the adjustable version has a hole right through the centre and the fixed version does not. The simplest way to tell without dismantling the carburetor is to remove the dashpot damper, insert a 1/8" alan key into the top of the guide rod and "feel" for an adjuster nut ..... no adjuster = fixed needle.
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PostPost by: RogerFrench » Tue Jan 23, 2018 11:08 am

oldelanman wrote:
SENC wrote:Is there an easy way to visually distinguish between pistons for adjustable needles and those for fixed needles?


The fundamental difference between the two is the adjustable version has a hole right through the centre and the fixed version does not. The simplest way to tell without dismantling the carburetor is to remove the dashpot damper, insert a 1/8" alan key into the top of the guide rod and "feel" for an adjuster nut ..... no adjuster = fixed needle.


Or if you have it apart look at the needle where it fits in the air valve. The adjustable is quite a bit bigger, about 8mm diameter vs 5mm.
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PostPost by: SENC » Mon Nov 26, 2018 3:52 am

Finally got back on this project this weekend after a spring and summer of work on the suspension. Found some replacement pistons from Chatsworth Motors, which gave me the confidence to go at the frozen grub screws with a drill bit. Got one out successfully, but the 2nd piston is totally buggered.

First carb is disassembled and cleaned and ready for reassembly. Hope to get it back together one evening this week and get to work on the other next weekend.
Attachments
20181125_224506.jpg and
Stromberg 175CD2SE ready for reassembly
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PostPost by: Mike Ostrov » Mon Nov 26, 2018 4:24 am

Hi, Henry. I have many 175 Stromberg parts if needed. Cheers. Mike.
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PostPost by: 69S4 » Mon Nov 26, 2018 3:34 pm

Well you've got the Haynes Stromberg book which is a good start. :lol:

A lot of the rebuild is just thought, care and deliberation. Take your time and double check everything as you go. There are a few areas where the Haynes book glosses over the procedure though. When I last rebuilt mine the list of stuff I wish I'd paid more attention to was something like:

Change the spindle seals. It's not as hard to do as you might think but makes a difference to idle / low speed running.

The float height is supposed to be 17mm with the float tang meeting the needle at right angles. On mine 'right angles' and '17mm' are nowhere near each other even with washers under the valve. The 17mm bit is the more important of the two.

It's possible/ easy to reasssemble the choke components backwards. The cable still moves the arm but the car won't start.

The temp compensators are important for hot restarting so don't just screw them up tight like some 'authorities' advise. I've not found any published data on their operating temperatures for Elans (Haynes just say don't touch it) but years of fiddling with mine suggests something a little lower than the Buckeye TR6 info. Mine are set to just open at 40C and are substantially open by 50C. I've measured heat soaked carb body temperatures of 55C with an infra red thermometer when parked from hot for 30 mins or so in the summer. The idle trimming screw should be tight shut. It's not meant to do anything under normal conditions. They (the compensators and the trimming screw) work not so much by the extra air directly weakening the mixture as reducing the vacuum. With less vacuum the needle isn't raised as far so it passes less fuel.

Needles - I've always used B1Y needles with a 'natural' colour spring but B2AR are often mentioned as an alternative. When I looked at the profile data there didn't seem a lot between them. Whichever one you use I'd strongly suggest you change the jet at the same time if they're the originals (the carbs look like adjustable needle ones from the photo). My old jets came out with a distinct 'groove' where the needle bias had caused rubbing. That was part of my running rich problem.

The jet needs to be pressed out through the bottom of the body and a new one pressed in but it doesn't need that much pressure - it's not like wishbone bushes. The drop from the inside of the body to the top of the new jet is important but again, Haynes don't give it. 3mm (.120") to the centre part of the jet is what works for me with the needle shoulder level with the bottom of the piston. If your jet is up or down a bit you'll need to 'compensate' with the needle position to get to a zero point for tuning.

When it comes to tuning the carbs on the car I've given up with the Allen key tool down through the damping chamber. Instead I take the pistons out, adjust the needle up or down in 10 thou increments on the bench, put them back and drive the car for a while to see whether it's worse / better etc. For me at the moment that 120 thou needle shoulder to jet centre gap is about right.
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PostPost by: The Veg » Mon Nov 26, 2018 7:46 pm

If you're new to this, only dismantle one carb at a time- that way the other can serve as a 'road map' if you get lost on the re-assembly.

Rebuild kits containing most or all of the seals and gaskets are available.
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PostPost by: SENC » Tue Nov 27, 2018 1:42 am

Thanks, Gents. Got a bit of the first one back together this evening, though struggled getting the new jet in place (bent the lower shaft on the first one rather severely in the press even though it was straight and centered and I'd lubed it). Polished the second one a bit and took it very slow and got it seated. I did replace the spindle seals as recommended - used the spindle as a guide and a small socket to tap them to get them started. No time tomorrow night, but hope to finish it Wednesday or Friday evening then on to #2. I do plan to try to balance the temp compensators as mentioned in the buckeye article, so thanks for your observation about having them open a bit earlier.
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