5 replies to this topic

[hfolguera]

Hi all!
First of all, congratulations for this awsome forum! I've learnt a lot reading topics!

I'm writing from Barcelona and I'm currently restoring an Austin MK3 from 1973 with an 998 engine.

 

I would really like to mount some 12" wheels (in fact, I would like a 13" sportpack) but I have been told they're too much for my engine, so I'm thinking about give a Stage 1 kit to my mini (SU HS4 carb and an RC40 exhaust).

 

My question is about the HS4 carb; diving into several shops, a single SU HS4 costs around 750€ (new) or 400€ (used). I think it's quite pricey!

 

I've found some used SU HS4 carbs on ebay and local used parts apps for around 80€. Of course they are full of dirt and must be rebuild. The idea is do a deep cleaning and buy a rebuild kit (around 100€) which would sum up around 200€, half the price!

 

 

My questions are...

Is it worth buying the 80€ carb and rebuild it?
Do you see any problems in doing that?

Any specific part which I MUST replace?
Why is there such a difference in the price?

Any other advice?

 

Thanks in advance!

[Ethel]

There's not much that can wear & they are pretty serviceable.

 

If you can get one cheap enough it'll likely be worth it, if only as a source of spares. They used to be little more than scrap metal as they usually outlasted the rest of the car.

 

Floats, jets & needles are near enough service items that can just be replaced. The next likely issue is wear causing an air leak through the throttle spindle, new spindle bushes can be fitted with a little extra effort. The only terminal fault would be wear between the dashpot & piston. You can easily assess that with a "drop test" & the parts are interchangeable between carbs of the same size.

[stuart bowes]

don't know if it's of any interest to you but I recently rebuilt a pair of HS2's (smaller version) and there are some pics here:

 

https://www.theminif...-998/?p=3771635

 

I found the strip down and rebuild relatively straight forward but I did watch a few vids first to make that easier.  the hardest (fiddly) bit was getting the choke return spring back on, but that was just a case of patience, a bit of dexterity with a couple of small screwdrivers and a few choice swearwords

 

I spent a bit of time on the buffing wheel to get them nice and shiny as well, a bit more work to do on that but they're pretty much done, it basically makes them look new again with minimal effort

 

the spindle as Ethel mentioned, mine was a little looser than I liked as well, the correct answer most likely is get them re-bushed, but the wear on mine seemed to be mostly on the spindle itself instead of the body of the carb,  I chose to replace the spindles and actually found some manufactured with rubber O rings to help seal.  now whether that is a good long term solution or not I'm sure others can advise but I will say I was only happy to do that because there was fairly minimal play to start with, it was more of a 'just to be sure' than a 'fix'

 

getting the jet lined up with the needle takes a few attempts and some patience, assuming no physical fault or damage to the piston and carb body though it wasn't really all that difficult.  plenty of guides and videos around to help

 

be cafeful when you connect up the jet pipe to the float bowl, it would be easy to put a kink in the inner plastic tubing, and that won't help flow, the outer metal spring like casing will help protect it but only so much

 

one thing i found an issue was various cars used the A series engine with that carb so you might find if it comes with a manifold it might be the wrong angle for mini fitting.  other manifolds are easy to find and not hugely expensive, you would also need a different float bowl adaptor to sit at the right angle.  but if it was listed as taken from a mini, you're probably fine (I think mine came from a sprite maybe)

Edited by stuart bowes, Yesterday, 01:09 PM.

[Ethel]

It's the linkages for the choke & throttle that tend to vary a bit between models - and where some secondhand spares can be handiest.

Float angles shouldn't matter too much, or cars wouldn't cope with going up & down hills. A level float might resist wear on its pivot for longer though & if you can use a file you can likely fettle the float chamber mounting.

 

Another think to watch out for are waxstat jets. They're neither good or bad particularly, but the choke linkage is different, so a carb that matches the one it's replacing will be a bit more useful.

[stuart bowes]

Why is there such a difference in the price?

 

 

I guess the answer to this is, because you're paying for someone to do an engineering job for a number of hours to rebuild it for you, if they charge £80 an hour, even £300 doesn't cover 4 hours work, and it takes longer than that, I was at it for a good 6-8 hours on and off, then again I'm not someone who's done it a hundred times before and has all the right tools laid out and the knack of doing each part

 

as with a lot of things, do it yourself, save the cost

[timmy850]

If you’ve seen some of AC Dodds posts you’ll see things like the throttle spindle bushes being out of spec in the rebuild kits. Custom machining bushes to proper tolerance takes time and money but will give a proper functioning carb

If you were inexperienced and did the job yourself assuming all the new parts were good you may end up with a worse result than when you started.