SU HS2 Carburettors ... Spindles

[eddyinfreehold]

Morning everybody. First posting.

I joined up in the Spring at the Practical Classics show and have been enjoying the magazine and friendly approach the Club has ever since. A busy schedule means I don't get out and about much but hopefully that will change soon. I bought a Mk3 1969 Spitfire in excellent condition about 2 years ago and have done about 1000 miles in it since. I bought it because I owned a Mk2 about 40 years ago and had to sell it owing to lack of cash. I have regretted that ever since. If 16 EAM, Wedgewood blue, still exists let me know....

Anyway, to cut to the chase. This is a good solid car, restored about 10 years ago and very original apart from the seats. It had very small niggles that I have been going through one by one.  A badly fitted fuel filter was replaced because of a fuel drip. That led to a pinhole drip in the pipe that leads from the front to rear carb. That was replaced too. A further fuel leak was found on the lid of the front float chamber because one of the screw holes on the chamber lid was broken and the botched repair didn't work. That lid was replaced too (from Burlen) and the fuel line is now secure. It is evident though, because the carbs are very difficult to balance, that the butterfly spindles are worn and drawing air. Next stage will be a full refurb so I bought the kit from Burlen. Before I start I've done some reading. As far as I understand looking at the bagged bits, the kit from Burlen (Rebuild Kit Part No CRK115 replaces CRK248) contains 2 new spindles and a pair of what look like white metal bushes for each which fit neatly . My understanding was that the HS2 carb body ... the twin 1.25" SUs I remember ... doesn't have spindle bushes fitted. The original spindles were designed to wear in the alloy carb body seats. Are these new spindles 'undersize' to allow fitting bushes now or am I barking up the wrong tree? If I do have to fit these bushes will a press be needed or will they push fit if I'm careful with a dowel drift? If so would you use a drop of loctite to hold them? Is there a stop end inside the barrel to prevent them going in too far?

If there's an expert out there who could answer these questions I'd be very grateful. Thank you all.

 

Eddy

[Colin Lindsay]

I've no idea of your carb setup but some kits for specific parts of our cars contain parts for all models, so maybe the bushes are included but not needed for your model of carb? Or is it possible they're included so that you can repair any wear on your carbs by using them now, even if they were never fitted before?

An expert will be along shortly...

[Pete Lewis]

i agree dont think early SU had bushes fitted, you cant fit a bush without very accurate drill/reaming the bore to take the bush

if fitted easy to drift out and tap in place ,  even use some studding to drag the bushes in , but only if originally fitted

in the main the brass spindle wears more than the body so a new spindle will improve air  leaks.

if the body is worn send the carbs to a professional refurb like   http://www.carbex.demon.co.uk/

there are a few places but he is local to me .

good luck 

Pete

 

 

[Mad4classics]

The brass spindles supplied are the same diameter as original and so can replace your existing worn ones. In general it's the brass spindle that wears and not the body; I've found the spindles to be a good fit in the bodies I've done.

You only need to use the bushes if the bodies are worn and in this case it's best to take it to an expert unless you have a lathe.

The burlen servicing and tuning guide descibes boring the bodies to a depth which just takes the bushes without breaking through into the carburetor bore.

David

[eddyinfreehold]

Colin, Pete, David

Many thanks. I will be able to start tomorrow I hope so I'll let you know how it goes along. I'll be glad to get this part done and on with some driving. The refurb kit includes jets but not springs or needles. Still, they can be replaced with the carbs in place I guess if that proves necessary.

Tremendous speedy answers, thanks again gents.

Eddy

[Badwolf]

Hi Eddie. Welcome. Sadly 16EAM does not appear to be listed anywhere so assume the worst in that she has now gone.

[eddyinfreehold]

Thanks for that Badwolf. That's a shame. The car was in poor condition even in 1980 when I sold it to two enthusiasts. I lost touch with them a year or so later. I had some memorable times in that car 😆

[Badwolf]

Look to the future and enjoy your 'new' toy, but don't sell this one.... no matter what.

Look on the bright side though, 16EAM could be in someone's barn off the radar, and just waiting to be re-discovered. Check the dvla site

https://vehicleenquiry.service.gov.uk/

.. occasionally to see if there is any news or get the free app vehiclesmart.

 

[eddyinfreehold]

Well. Rain all this week has delayed progress. That's because of work not the carbs. I'm a cricket groundsman.

Finally got them off last night, washed off in paraffin and cleaned. I spent the late afternoon rebuilding the rear carburettor. No particular issues. Yes, there are no spindle bushes to worry about in my case thank goodness. Although the original spindles were badly worn and rattling around in their housing there appeared to be no damage and the new spindles fitted well and very snugly into their alloy housing in the 1.25" carb body.  All the rest of the breakdown and clean was straightforward with various new bits of rubber, jets, springs, float chamber and valve pieces etc.

Pictures attached. Note the extent of the bearing area wear on the old spindle....

[Pete Lewis]

Thats pretty normal  ,

The brass wears more than the soft casting

Good job done , ready for a few more miles 

Pete

[daverclasper]

Hi. Always wondered why the softer metal wears less than the harder?.

Cheers, Dave 

[Pete Lewis]

its all down to whatever , cant remember the metallurgical reason im sure it will be explained 

 

[daverclasper]

So long as it's "whatever", that's good enough. Was just wondering if there was a simple reason.

Dave

[Pete Lewis]

Try Galling

https://en.m.wikipedia.org/wiki/Galling

Pete

[JumpingFrog]

Not sure about galling. Could it be something along the lines of soft things being "abrasive", as they easily embed stuff (in this case probably carbon).

As this is the reason a soft rubber oil seal is able to wear a groove into a steel shaft: https://www.plantengineering.com/articles/repairing-shafts-scored-by-seals/

Just a guess of course, not a metallurgist.

[Unkel Kunkel]

I suspect  the choice of  Al Zn alloys for the carb. body  is more for ease of die casting rather than a choice  based on its bearing  characteristics.

Considering the minimal lubrication, the  lack of any seals,  and the reciprocating half  turn action, It is  surprising these “bearings” function as long as they do.

 

[johny]

From experience I've found that it's not a good idea to put an additional spring pulling on the carb operating mechanism to give more pedal resistance or more positive butterfly closing as the side load wears the spindles much more rapidly☹️

[Pete Lewis]

Agree the twin spring set up on some spits is awful.

Needs a  long spring plenty of extention and stable light loading on  the cable/rod returns not a short high load as some have.

If you want a heavier pedal up the  spring load on the pedal not the carbs.

Pete

[Colin Lindsay]

11 hours ago, Pete Lewis said:

If you want a heavier pedal up the  spring load on the pedal not the carbs.

Pete

That's something I need to do on my GT6, the accelerator pedal is far too light. Now that you've reminded me, I must go look for stronger springs.

[Pete Lewis]

 I  now  have visions of a bungy cord from pedal to sun visor    ha ! 

Pete

 

[eddyinfreehold]

...whooh...just came back to report progress and ask a few questions and I find most have been discussed already. Brilliant.

Right, It's all done now and ready to refit. The only other question I have relates to the last four hours work. Yes four hours ! There are two c. 1/4" spacers or shims that are gasketted between each carb and the inlet manifold. The old gaskets were very tatty and thick and it has taken ages of paraffin soaking and gentle scraping to clean them with a paring knife. I've met similar spacers in many BMC vehicles and a Volvo too. The manual makes no reference to them. As they look a bit like they're made from asbestos I scraped them 'wet' . If anyone says I haven't cleaned them fully The pink residue is just colour. I put a calipers over them and they are of even thickness. Are they designed as heat insulators or are they adding a crucial length to the manifold?

I've also made a short film of the old spindle wobble which I'll post later this week. The front carb was more obviously worn than the rear.

Eddy

[Pete Lewis]

They are just heat insulation ,, will need a gasket each side on refitting

Check the manifold and carb flanges are nice and flat 

Pete

[eddyinfreehold]

Thanks Peter. Bu88ers to clean though. All the gasket stuck to them. The manifold and carb faces/flanges are clean.

Let me try and attach these films of the spindle while I'm at it. Not sure how big the files are...

[Mad4classics]

If they're original they're asbestos as you say; modern replacements are Phenolic.

So care needed when cleaning.

David

[eddyinfreehold]

My bet is they're the latter, they have a bakelite sort of ring to them. Still better safe than sorry. Thanks for that Mad4.

30 mins to reassemble in the car and primed the float chamber with fuel. Started first turn of key. A bit of jet fiddling and we're close. Off to my local garage to balance them properly and check the emission reading. The noise is mostly the wind on this film but it's bubbling nicely at about 950rpm.