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Swapping SU Carb parts
Posted: Wed Mar 03, 2021 7:45 am
by Andymoor94
Hi everyone,
Just a quick one, is it possible to interchange parts of SU carbs? The tag on top of my float chamber seems to be that of a H1 but the body itself is bigger.
Is it possible that the body could've been swapped?
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 7:59 am
by philthehill
Anything is possible.
Could you please quote the tag details and attach a photo of the carb.
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 9:22 am
by Andymoor94
philthehill wrote: ↑Wed Mar 03, 2021 7:59 am
Anything is possible.
Could you please quote the tag details and attach a photo of the carb.
Will do tonight, absolutely.
So are they interchangeable by design? Bolt on, bolt off? Because if so, I can sort all of the issues I've had with this bloody carb spacer sooner rather than later.
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 10:00 am
by philthehill
If I remember correctly the H1 and H2 are not interchangeable as regards bolting to the inlet manifold. The bolt centres are different.
The H1 is very restrictive and I would use as a minimum the H2 carb. The H series carbs come with different size float chambers.
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 11:37 am
by Andymoor94
philthehill wrote: ↑Wed Mar 03, 2021 10:00 am
If I remember correctly the H1 and H2 are not interchangeable as regards bolting to the inlet manifold. The bolt centres are different.
The H1 is very restrictive and I would use as a minimum the H2 carb. The H series carbs come with different size float chambers.
Yes, the previous owner made this god awful adapter to fit this seemingly H2 carb to the original manifold. Given the carb freezing issues I had in the winter, and also with the welds of the flange breaking at one point too, I would much rather the restrictive H1 carb body over this ridiculous setup!
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 11:51 am
by philthehill
That is a bit of a mess.
If you are getting freeze up I would change the inlet manifold and retain the H2 carb.
Here is a suitable manifold. It is open to offers.
https://www.ebay.co.uk/itm/MORRIS-MINOR ... SwbIxfJURw
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 12:16 pm
by StillGotMy1stCar
Before you place an offer on the manifold in Phil's link above, the manifold is broken.
See photo
- s-l1600.jpg (375.35 KiB) Viewed 1347 times
Edit: Apologies Phil, after posting I realised the alloy inlet can be removed.
Regards John
Re: Swapping SU Carb parts
Posted: Wed Mar 03, 2021 6:07 pm
by Andymoor94
I appreciate the ongoing help in the matter. A mess it certainly is.
Tag on the float chamber, AUC738, of one H1 carb.
32mm bore on the body however, plus AUC6060 stamping, H2 body.
That sorts it! Now the options I have.
I'm not a spirited driver and though the H2 would definitely be the better carb to keep, as long as I have the 803cc engine, I would prefer to keep the correct factory carb, so I'll be buying the H1 body online, which I've found. I can at least irradicate the god awful adapter. The manifold would have been an absolutely perfect purchase if I was intending to keep the 803cc engine, however I am intending to upgrade later down the line. I'm sure a purist seeking an 803cc would appreciate the correct carb to accompany.
That said, the H2 body is not going in the bin. Should I change my mind, I want to be able to revert in case!
Re: Swapping SU Carb parts
Posted: Thu Mar 18, 2021 6:13 pm
by Andymoor94
So I bought a H1 body, started swapping the pieces and then of course came across the obstacles I never stopped to think of. The piston won't fit, nor will the throttle butterfly.
Out of pure luck, a piston came up on eBay for dirt cheap!
So what would be the best way for me to clean this bad boy?
Re: Swapping SU Carb parts
Posted: Sat Mar 20, 2021 11:27 am
by mogbob
Hmmm ! That piston has been sitting around for some time.
The operation of the SU piston is to slide up and down the chamber. With the cleaned / new piston in the
chamber with spring , invert it , so that the piston falls to the top. Placing a finger over the hole ( where the damper is screwed in ) to stop air entering , put the chamber right way up. With second hand , get ready to catch the piston , as it falls inside the chamber. It should take 5 / 7 seconds to travel and drop out.
There must be some resistance. The " fit " cannot be ; - either too tight or too loose for this to happen.
If you " go completely mad " with abrasive material on the internals .i.e wire brush in the drill / angle grinder , emery paper , sand paper , file , sharp knife , etc. etc. you will end up with a very clean ( but totally useless
piston ). It will fail the " drop test " because you will have removed too much material from the friction surfaces !
You can use a petrol moistened rag , Mentholated Spirits , White Spirit , etc but the most convenient "weapon "
is spray Carburettor cleaner. Use outside or in a well ventilated area , with no source of ignition present in the area.
Use an old metal baking tray or similar and an old toothbrush / nylon brush to agitate the spray. I estimate it
will take several applications. RESIST all temptation to use the abrasive methods.
Bob
Re: Swapping SU Carb parts
Posted: Sun Mar 21, 2021 8:24 am
by Andymoor94
mogbob wrote: ↑Sat Mar 20, 2021 11:27 am
Hmmm ! That piston has been sitting around for some time.
The operation of the SU piston is to slide up and down the chamber. With the cleaned / new piston in the
chamber with spring , invert it , so that the piston falls to the top. Placing a finger over the hole ( where the damper is screwed in ) to stop air entering , put the chamber right way up. With second hand , get ready to catch the piston , as it falls inside the chamber. It should take 5 / 7 seconds to travel and drop out.
There must be some resistance. The " fit " cannot be ; - either too tight or too loose for this to happen.
If you " go completely mad " with abrasive material on the internals .i.e wire brush in the drill / angle grinder , emery paper , sand paper , file , sharp knife , etc. etc.
you will end up with a very clean ( but totally useless
piston ). It will fail the
" drop test " because you will have removed too much material from the friction surfaces !
You can use a petrol moistened rag , Mentholated Spirits , White Spirit , etc but the most convenient "weapon "
is spray Carburettor cleaner. Use outside or in a well ventilated area , with no source of ignition present in the area.
Use an old metal baking tray or similar and an old toothbrush / nylon brush to agitate the spray. I estimate it
will take several applications. RESIST all temptation to use the abrasive methods.
Bob
Thanks Bob. As someone who is all too happy to grab his wire brush, you've potentially saved me haha