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MG MGB GT V8 Factory Originals Technical - Using standard SD1 carbs and manifold

Anyone used the standard SD1 carbs and manifold on their conversion ?
How much do they protude through the bonnet level ?
What sort of bonnet bulge or scoop have people used ?
Any links ot web photo's of MGB's with such bonnet bulges or scoops ?

I know everyone will say use a Holley / Weber, original type inlet manifold (/ Clive Wheatley adapter) or fuel injection but that's not what I'm asking.

At the worst I'll make my own alloy adapters to turn the carbs throught 90 degrees as per the car at -

I doing an ecomony conversion. At present, after buying a good MGB GT, another rough MGB GT for parts & a SD1 then selling the surplus, I have most of the parts (including original V8 exhaust manifolds) to convert. The NET result is that I have made enough profit overall to pay for the good MGB GT and all the parts with approx 400 cash in hand and still have loads to sell ! Buying an expensive carb set up defeats my aim of buying and getting a converted MGB GT on the road for NOTHING.

This is an expercise to prove to myself that you don't have to have loads of money to have fun with a car if you are prepared to do the work.
Paul Humphries

I believe that the MK I costello conversions used the twin SU intake as found on early rovers. heres a (not the greatest quality) picture of the setup and a costello bonnet bulge. Hope this helps.
the MK II costello conversions used a side draft weber with an adapter, facing rearward.

Thanks Jake.

The bulge needed isn't as big as I'd expected.

I wonder if Stromberg carbs would give even better clearance ?

Anyone know of a link to a photo of a MKII Costello manifold as the idea of a rear facing Weber intrigues.
Paul Humphries

I've only seen one picture of one in a magazine once. I do have a pic of a homemade adapter that copies the setup, its on a GT6 with an Olds 215. Its under the carburation section of my webpage.
Hope this helps.

Paul...that bulge is about 1" higher than th stock fulge on an MGC hood! I've tried it...right now, I'm working with one of Clive Wheatley's OE V8 intake knock-offs but the carbs are an issue...I've got an original Rover 'high hat' intake with carbs...but, the carbs on the Clive Wheatley intake sit too close together for linkage to work...
...what type carbs did the factory MGB GT use? Certainly not the same as the Rover 3500! take a look at my project go to >>
anthony barnhill

the factory carbs are a special HIF6 with shorter dashpots to clear the underside of the bonnet. as to the linkage, if you want to try and imitate it, i can snap a couple of close up shots of mine, i have a factory set up, not a repro, plus theyre not on the car yet so i could pull the linkage off and take measurements too if you need that. overall the carbs seem pretty standard with the exception of one or two special linkage pieces, and of course the shorter tops.

I went with the Clive Wheatley plenum and modified my own inlet manifold and it is working well.

You can fit the HIF6 carburettors to Clives manifold even though they are taller than the factory dashpots.

The real difference between the dashpots I have and the factory V8 ones is only 1/8". Yes, that little! I had the loan of a factory setup to copy the airbox from and throttle linkage. The lower dashpots would be nice to have but not essential.

I made my own linkage with provision for balance etc. It was tricky, but some of the smaller parts tig welded together can be made to form a reasonably professional looking system. Clive Wheatley has the original linkage reproduced, but would not sell me the parts unless they were fitted to a carburettor also purchased from him. If he changes his mind can someone let me know please.

I have a photo of my engine bay, but do not know how to do show it on the net. I can email it to anyone interested.

Have you seen the other thread near this one where Jake gives a link of a V8 with 2" SUs??

Ian G Buckley

Ian...please email me a photo (
Jake...I'll take your photos & dimensions also, please...
...think I'm using HS-6's & when they're on the plenum, there's not more than an inch between them...also, they're real close to my heater box - maybe 2"...

...hopefully, the 2 photos below will show some detail (if they appear):



anthony barnhill

Wel, apparently you can't put photos directly on the are their links:
anthony barnhill

from your photos, your carbs appear to be HIF6's. those SU carbs with the Internal Float are designated IF. you could always have the tops machined down along with the top tube in the piston for the damper. just a thought, if you need dimensions for this i can get those too. ill try and get some engineering drawings done this weekend of the linkage setup. my engine appears to sit further forward than yours, i have more than enough room for the airbox behind the carbs. heres a pic of when i test fitted the engine and tranny a month ago.
i may have to make a new set of mounting brackets to get the engine to sit 1/2" back, there isnt much clearance between the water pump pulley and the radiator, and the shifter sits a little forward of MGB stock position.


I have sent you my photos. You can put them on display somewhere if you like.

I have now opened your photos and they are HIF6 carburettors, same as I have and those dashpots will fit, if your engine is low enough.

Here is the test:

Your MG rocker covers are the same as mine. Place a straight edge across the vertical lips where the mudguards bolt on. Directly above the foremost flat part of each rocker cover.

The measurement should be 2" .


Ian G Buckley

The GT6, with a homemade inlet for a Weber carb, shown on Jakes web site seems to be made from steel rather than alloy.
This has got me thinking !
What material is the original and the Clive Wheatley manifold adapters made from - I assumed alloy but as they are painted I wonder if it's cast iron ?
Can anyone givce me a valid reason why I shouldn't make a homemade adapter out of steel tube ?
I was going to use the original alloy carb to air filter housing bends as a basis if I needed to make adapters but steel is a lot easier to weld etc.

Paul Humphries hood goes on easily with my carbs as I have my engine snugged down real problm is 2-fold:
1) my engine is pretty far to the rear & I don't think I have enough room for air cleaner...
2) I don't have linkage expertise to figure out how to make them work...

Jake...if I owe you anything for the drawings, let me know...they'll probably solve problem #2 above...

...I can redo my motor mounts & move engine forward if needed....
anthony barnhill

my pleasure to help, i know ive needed more than my fair share and have almost always gotten it. plus i need the practice at drawing them up on the computer. what ill do is render some 3D models and save the pics, take some real pics of the actual linkage and whip up some eng. drawings, all of which i will post to my website and relay the address here. check back on saturday or sunday for the link.

oh and if you need drawings to fabricate new motor mount brackets, i have those too. im in the habit of making up models and drawings of parts that i have to buy but that i know i could make.


The airbox you can see in the photo of my car only misses the nose of the heater motor by about 1/8".

It also has a cut out to allow space for the heater hose to be vertical from the heater outlet on the left side of the car.

I think my motor is 1/2" further back than most.
Ian G Buckley

the original and wheatley manifold adapters are alloy but i dont see any reason not to make one up out of steel, fabrication sure would be easier. good luck.

This thread was discussed between 23/01/2003 and 25/01/2003

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