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Will HS4 Carbs work on a '67 Midget?

Posted by 67MG 
M McK
Canada   can

I recently purchased a brand new set of HS4 Carburetors, manifold included, to replace the carbs on my 1967 Midget, as they were not far off the price of rebuilding the old ones. However, when I got them home I realized that they are HS4's and my car has HS2's. Everything appears to match up (apart from the throttle linkage, which I will have to acquire) but I wanted to ask around to see if anyone had either had experience or an opinion on this?

Thanks!

Murray
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kuz1 Avatar
Keith Kuzma
Prattville,Alabama, USA   usa

I dont believe they will bolt to your manifold
Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

In reply to a post by kuz1 I dont believe they will bolt to your manifold

That is correct, some 1275 race cars run twin HS4s on an narrowed down MGB intake, very common set up in SCCA and with vintage race cars, but honestly you need some pretty serious mods to get the HS4s to work on a street 1275, putting a bigger than needed set of carbs on your car will do nothing for as in the way of performance and be PITA to get them to even work. Sell the HS4s on the trader section and get the proper HS2s and you'll be much happier.



Hap Waldrop
Acme Speed Shop
864-370-3000
Performance Street/Race engines- modified heads, and DIY engine rebuilt kits
New alloy wheels options for MGBs, see vendors forum for details.
http://www.mgexp.com/phorum/read.php?68,2657584
Be sure to check my engine rebuild kit thread in the Vendors forum for weekly tips. http://www.mgexp.com/phorum/read.php?68,1828263



Edited 1 time(s). Last edit at 04/19/2010 07:15AM by Speedracer.

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eg.midget Avatar
Ed Gerken
Sandusky, Ohio, USA   usa

I'm in the process of rebuilding my HS2 carbs on my '67 Midget. The HS2 stands for Horizontal Short (body). The number 2 is the number of 1/8" increments over 1" of the throat diameter, so the HS2 is 1-1/4" (measured at the manifold end). The HS4 will have a 1-1/2" bore to allow more air and fuel for a larger displacement engine, or for more HP if the engine is appropriately set up and tuned. My opinion is that the HS4 carbs are not likely to work well with your engine without a lot of additional work ($) to make the engine fit the carbs.
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eg.midget Avatar
Ed Gerken
Sandusky, Ohio, USA   usa

Just another bit of free advice/information...if you do opt to buy a pair of HS2s, your '67 uses numbers AUD136F and AUD136R (front & rear). Being the first year of the 1275cc, they used the same carb as the 1098cc engines in both the UK and the US. The number is on a small metal tag attached to one of the float bowl cover screws. After 1968 the UK and US cars used different HS2 models, I suppose to accommodate the different emissions requirements that were evolving in each country at the time. I don't know how interchangeable the different variations of the HS2 are or what the differences are. I found a nice pair of AUD136s on eBay for less than $50 that are very rebuildable and am using the best parts from these and the ones on my car for my rebuild, plus a rebuild kit.

There is great info in the SU Carburetters Tuning Tips and Techniques book by Brooklands. Recommended if you decide to rebuild your own set or if you're an information junkie like me.
M McK
Canada   can

Thanks for the info! With a little more research into these carbs, I am certain that they are actually HS2's, I was thrown off by the throttle linkage. The number on the carb body is AUC870 (MGB?), but the bore is 1-1/4", so I think I am going to try them to see what happens. The only other difference that they have compared to the carbs I have now is that there are what appear to be hose nipples?? on each of the carbs, and this one has an adjustable throttle connection. I have attached a representative photo with these circled in red. Any sugestions? Thanks!
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Attachments:
MG Carb.jpg (30.9 KB) –
MG Carb.jpg

Kerr Avatar
Norm Kerr
Ann Arbor, Mi, USA   usa

those two hose nipples are for connecting the crank case ventilation (they are wyed together to connect to the breather on the front cover).

On a '67, there would have been a PCV valve on the intake manifold and a vented oil filler cap. With these carbs you can ditch the PCV and connect that hose directly to these nipples. Or you can cap these and keep your PCV, all the same either way.

the UK and US HS2s are the same except for a few details that are easy to change: throttle butterflies (pop off versus solid), needles and those breather hose nipples are it, I think.

Norm
kuz1 Avatar
Keith Kuzma
Prattville,Alabama, USA   usa

They should work. Look pretty too.
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Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

Yes those carbs should work on your car, they are a later model than came on your 1967, look on the front carb,just behind the dashpot (the shiney domed top of the carb) they could be a small hose nipple there if so, that is vaccum port ofr your distributor, if not then you should have a vaccum hose nipple on the intake manifold. Another thing, probably stuck in the intake manifold where it mounts to the head on the intake ports, or still stuck inyour hrad at the intake port will be a circulat pice of pipe with a split in them, those pieces positively located the intake to the intake port, if you don't have them get a couple form Moss, etc., they are cheap. Also it's hard to tell looking at the picture, buut you mentioned that the throttle linkage looked different on your other set of carbs, it appears form the picture someone took a MGB throttle linkage bar and cut it down to work on a Midget, if it clears the heat shiedl, then it's more than acceptable to use, you need the throttle stop assembly, I think it like a few dollar, it will bolt ontgo the center section of the throttle linkage bar and have provision in it to secure the throttle cable. When I get to work, I snap photos of the newly finished set of HS2 I just finished rebuilding for a customer and post them.



Hap Waldrop
Acme Speed Shop
864-370-3000
Performance Street/Race engines- modified heads, and DIY engine rebuilt kits
New alloy wheels options for MGBs, see vendors forum for details.
http://www.mgexp.com/phorum/read.php?68,2657584
Be sure to check my engine rebuild kit thread in the Vendors forum for weekly tips. http://www.mgexp.com/phorum/read.php?68,1828263

Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Tech Advice - Alloy wheels for MGB/TR6
mjamgb Avatar
michael anderson
NORTHERN NEVADA, USA   usa

Other than the throttle bell-crank (and the polish!) they look just like the ones on my '74.
Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

Here's a set I just finished and boxed up, they have my Acme/Hilton velocity stacks (Jimmy and I calborated together on these) on them to use with the KN RU-4410 air filters. You'll see the they have the same PVC tube, I used plugs to put there, and the guy is running a filter catch tank for venting the crankcase, I also plugged the intake where the elbow vent tube went.



Hap Waldrop
Acme Speed Shop
864-370-3000
Performance Street/Race engines- modified heads, and DIY engine rebuilt kits
New alloy wheels options for MGBs, see vendors forum for details.
http://www.mgexp.com/phorum/read.php?68,2657584
Be sure to check my engine rebuild kit thread in the Vendors forum for weekly tips. http://www.mgexp.com/phorum/read.php?68,1828263

Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Tech Advice - Alloy wheels for MGB/TR6

Attachments:
acmehs2s.JPG (40.5 KB) –
acmehs2s.JPG

M McK
Canada   can

Thanks for all of the information! I hope to work on these carbs by the weekend!
middie Avatar
warren butler
wyong, NSW Central Coast, Australia   aus

Quick way to tell the difference between a HS2 and a HS4 is to just look at how long the "top" of the carbie is. Long top and it's a HS2, short top and it's a HS4. Don't know about bigger carbies as I only have these two types on my cars.

Attachments:
Carbs.jpg (10.9 KB) –
Carbs.jpg

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