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1 1/2" H4 SU carburettor
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Fri Oct 08, 2021 10:53 pm    Post subject: 1 1/2" H4 SU carburettor Reply with quote

I have been looking for a new or refurbished SU carb; in particular the H4... but Burlen, my first port of call, seems to be out of stock and I have had no luck in searching the 'net at all.

I want to find a single 1 1/2" H4 with the original style choke and a banjo type fitting to the float chamber.

The reason I am looking for this particular carb is that the Eaton M45 supercharger that I have fitted to the MG TC has a 1 3/4" H6 which, at the time , I was advised by the supplier would be ideal for my engine.

I have since discovered that for a 1300cc engine - even modified with the fast road cam and tuned head with bigger inlet valves, like mine - the 1 1/2" carb - which it would normally have had - would still be the better option.

What concerns me is that I have been told by a hot rod supercharger guy in the States that the bigger carb could both reduce torque and MPG... but I don't know if that is the case or not.

I thought perhaps if I had a choice of carbs and experimented with different needles I might stand a chance of getting optimum performance from the engine.

Any ideas??
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lowdrag



Joined: 10 Apr 2009
Posts: 1600
Location: Le Mans

PostPosted: Sat Oct 09, 2021 3:19 am    Post subject: Reply with quote

Not sure if this is exactly what you seek but I found it on Google:-

https://www.ebay.co.uk/itm/NEW-H4-SU-CARBURETTOR-MINI-COOPER-SEBRING-SPRITE-MG-/353645646614?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=CjwKCAjw2P-KBhByEiwADBYWCrLLVyt3umodOOG4FYDDvv9nOY6b6tdJ2TXSl4jUc3lAyyX53I2GVxoCnfgQAvD_BwE
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sat Oct 09, 2021 9:48 am    Post subject: Reply with quote

I looked at that one. It's quite close but I think that would be a HS4 rather than an H4. I don't know what it does (presumably it must do something) but there is an extension built in to the design.



If the HS4 is a direct replacement then I expect the one you have suggested would polish up O.K.

(Unlike some on here, I prefer shiny.... but I wouldn't be put off by it's tarnished condition!)

Thanks for trying.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1763
Location: Above the snow line in old Monmouthshire

PostPosted: Sat Oct 09, 2021 11:34 am    Post subject: Reply with quote

I'm no expert at all but I think the HS carbs were simply updated versions of the H models - essentially advances in materials had made it possible to simplify the jet and its feed from the float chamber, which could be a source of trouble on the older models.
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peter scott



Joined: 18 Dec 2007
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PostPosted: Sat Oct 09, 2021 1:52 pm    Post subject: Reply with quote

I don't know but does the S mean sloping? The eBay one is canted at an angle but I think you want a vertical one. I think the canted ones just have a twisted "bracket" on the bottom of the float bowel. I suspect there is no difference in the main carb body.

Apart from Burlen the other major supplier is Midel in Australia but looking at their website they don't appear to have H4 or HS4 in stock either.

Peter
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sat Oct 09, 2021 2:44 pm    Post subject: Reply with quote

Bitumen Boy wrote:
I'm no expert at all but I think the HS carbs were simply updated versions of the H models - essentially advances in materials had made it possible to simplify the jet and its feed from the float chamber, which could be a source of trouble on the older models.


Thank you for your advise. Yes, I am pretty sure you are right about the "S". I have also read that the earlier carbs could make cold starting troublesome.


Last edited by Ray White on Sat Oct 09, 2021 3:17 pm; edited 1 time in total
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sat Oct 09, 2021 2:54 pm    Post subject: Reply with quote

peter scott wrote:
I don't know but does the S mean sloping? The eBay one is canted at an angle but I think you want a vertical one. I think the canted ones just have a twisted "bracket" on the bottom of the float bowel. I suspect there is no difference in the main carb body.

Apart from Burlen the other major supplier is Midel in Australia but looking at their website they don't appear to have H4 or HS4 in stock either.

Peter


Good to have your input Peter. You are right that I want (if I can find it) a vertical one; a slightly smaller version of what is already fitted. The body on my carb extends sideways and I don't know what difference it might make to the running. What I do know is that a carb with a shorter body will cause me difficulties in positioning the choke cable; it would need to be changed and I am fast running out of options..

As the supercharger is a modern design and specifically adapted for the XPAG engine, I can only imagine the H4 carb was chosen as the best option available.

( I wonder if the reason the supplier enthused about the HS6 was a shortage of the correct carbs? ) Confused
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1763
Location: Above the snow line in old Monmouthshire

PostPosted: Sat Oct 09, 2021 10:13 pm    Post subject: Reply with quote

I rather think that where SU carbs are mounted at an angle it's down to the manifold rather than the carb flanges. Seem to recall that uneven wear can be a problem when they're mounted that way, and it's probably just a dodge for squeezing them into a cramped engine bay.
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sat Oct 09, 2021 11:05 pm    Post subject: Reply with quote

Bitumen Boy wrote:
I rather think that where SU carbs are mounted at an angle it's down to the manifold rather than the carb flanges. Seem to recall that uneven wear can be a problem when they're mounted that way, and it's probably just a dodge for squeezing them into a cramped engine bay.


It is the float chamber on HS carbs is at an angle or "slope" to the main body of the carb not the manifold.

You are right about some cars having the carb mounted at an angle. On a mini or 1100 the carb is at an angle and the piston can sometimes stick up in the dash pot. I remember once replacing a valve in a friend's mini and on completion the car wouldn't start. It was late and I was tired. Eventually I twigged what had happed and it was quickly remedied. Mad
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1763
Location: Above the snow line in old Monmouthshire

PostPosted: Sun Oct 10, 2021 1:34 am    Post subject: Reply with quote

Ray White wrote:
Bitumen Boy wrote:
I rather think that where SU carbs are mounted at an angle it's down to the manifold rather than the carb flanges. Seem to recall that uneven wear can be a problem when they're mounted that way, and it's probably just a dodge for squeezing them into a cramped engine bay.


It is the float chamber on HS carbs is at an angle or "slope" to the main body of the carb not the manifold.

You are right about some cars having the carb mounted at an angle. On a mini or 1100 the carb is at an angle and the piston can sometimes stick up in the dash pot. I remember once replacing a valve in a friend's mini and on completion the car wouldn't start. It was late and I was tired. Eventually I twigged what had happed and it was quickly remedied. Mad


The angled float chamber is the thing that I just couldn't quite remember earlier Laughing it's a long long time since I had a car so equipped. Are those angled float chambers interchangeable with the horizontal type..? I don't know that they are but it would make sense if they were made that way so that only one main body casting was needed to cover all possible installations.

I see the ebay carb is being sold by Andrew Turner; I bought the carbs for my Herald conversion job a few years back from him. Why not give him a ring? I did because I wanted different float chamber lids to standard to route the fuel line away from the hot engine, a quick chat and I was sorted, parts swapped over for no extra cost. Those carbs worked straight out of the box with no messing around... Smile
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sun Oct 10, 2021 9:58 am    Post subject: Reply with quote

There is certainly no harm is giving the guy a call. It's the wrong carb for my supercharger but like you say he may be able to help.
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alastairq



Joined: 14 Oct 2016
Posts: 2120
Location: East Yorkshire

PostPosted: Sun Oct 10, 2021 11:19 am    Post subject: Reply with quote

http://sucarb.co.uk/float-chambers-spares/float-bowl-chambers.html

The Old H-type float chambers coul dbe had in angled[either plane] or vertical.
Plus with a choice of 'angles'....[20 & 30 degree, I think?}
The HS types had the flexible fuel supply pipe.
With The H-type, I think care needs to be taken with the material used for the top hat grommets [rubber gaskets] used on the banjo under the jet?
In today's fuel-age, it may be prudent to buy guaranteed ethanol-resistant material, eh?
Burlen were non-committal about the materials they used regarding ethanol, when I emailed them not long ago.

Of course, if used with a blower, then I doubt 95 octane petrol of any description will be the fuel of choice, eh?
More likely needing to use 98 octane [which, at the worst, is currently E5]...??
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sun Oct 10, 2021 12:00 pm    Post subject: Reply with quote

All the information is gradually coming together. Thanks, Alastair. That the f/c angle could be adjusted would account for some of the spare parts that I have seen advertised.

Burlen is no longer stocking ANY grommets!

(At least that is what their website says)

As to petrol.... Who knows what will be available by the time I have finished this car ?. I sometimes wonder if it will EVER get done and that's despite doing something almost every day. Sad
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alastairq



Joined: 14 Oct 2016
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Location: East Yorkshire

PostPosted: Sun Oct 10, 2021 12:15 pm    Post subject: Reply with quote

Quote:
Burlen is no longer stocking ANY grommets!

(At least that is what their website says)


RAy, do you mean these?

http://sucarb.co.uk/float-chambers-spares/grommets/grommet.html
_________________
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Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Ray White



Joined: 02 Dec 2014
Posts: 7111
Location: Derby

PostPosted: Sun Oct 10, 2021 4:08 pm    Post subject: Reply with quote

alastairq wrote:
Quote:
Burlen is no longer stocking ANY grommets!

(At least that is what their website says)


RAy, do you mean these?

http://sucarb.co.uk/float-chambers-spares/grommets/grommet.html


AHHH! So they DO have them!!.

I presume these are the ones that disintegrate in ethanol petrol?

As a desperate measure I looked into getting a rebuild kit and they were temporarily out of stock . (The kits include grommets).

As it happens, I was amused to learn the carb body has no fewer than 4 different thread forms!!!
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