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MG MGB GT V8 Factory Originals Technical - Dangerous bodge?
|Hi V8 folk|
I'd like to solicit the group's opinion on the following:
My, recently purchased, V8 conversion has a pair of SUs mounted in the usual (for an MGB) position, but they are the variety with a separate float chamber. This has required the converter to mount the float chamber on the end of a rod such that the carbs are 'in the Vee' and the float chambers are 'outside the rocker covers'. This seems to work OK. The problem is that he has lengthened the fuel pipes (the ones between the float chambers and the carbs) by cutting them and gluing in a another piece of pipe. Well, on the right hand carb the glue had softend enough to cause a leak (this is how I found out about it - the whole sorry mess was disguised (the builder would probably say 'protected') by a length of 'spiral wrap' as used in wiring looms). The pipes pulled apart easily while I was investigating.
(If it makes any difference there is a little tag attached to one carb "AUD 270 P")
The questions I have are:
1) Is it OK to mount the float chambers remotely like this? (I'm pretty stuck if the answer is no.)
2) Is it normal practice to glue fuel delivery tubes together? (I'm not a classic car guy).
3) How do I fix this properly? - Obviously get a longer piece of pipe. But how is it attached to the carb and to the float chamber? It seems to go into a brass fitting on the plastic part of the bottom of the carb with no obvious means of detaching it. And on the float chamber end, there is a brass nut through which it emerges, but a gentle tug pulled it out.
It seems you have older types SU with the seperate float chamber and the way the converter fitted these is not good. Just glue the pipes together is not a proper way of connecting. I even would not consider to
fit longer pipes because this makes things weaker and increases the possibility of a fire. I would advise to fit a pair of SDI carbs. The only diffeculty is the linkages but i think these are available again these days.
|Peter van de Velde|
I've got a spare pair of HIF6 carbs in my shed if you'd like them (Horizontal Integral Float 1 3/4") They came off an SD1 engine which I bought for the cylinder heads. A tenner for the pair? This might solve your leaks problem and get your float chambers further away from your exhaust manifolds and HT leads.
I know i shouldn't advertise on the BB but this is more like doing a favour for another V8 owner, which is why we're all here isn't it?
|The answer to Q3 answers 1 and 2. Junk what you have before the leaks drip all over a hot exhaust and the vapours are ignited by some leaking HT current from one of the leads in the same area. An underbonnet fire will spoil your day!!|
Take up Phillip's offer and if there are any other parts you are short of then contact Clive Wheatley, a spares secretary of the MGCC V8 Register, who has created many correct pattern SU carb set ups for the V8.
I have contacted Philip and arranged to get his carbs. I'm sure there will be fun and games getting them to work, though, as the car's constructor has not used a replica factory V8 manifold. Instead, he has duplicated the system shown in Roger Williams' book where the stock Rover manifold is retained but with the 'arms' reaching back instead of sideways. (If that makes any sense.) This results in the carbs being significantly further apart than the factory V8. I'll have to make linkages etc. (A pity I don't still have a Mechano set!)
Thanks to all who replied - and I'm sure I'll be along again soon with more questions!
You have the earlier HS type of carb,probably from the original donor Rover P6 . I had his problem of loose jet tubes on my original 1950 cc conversion-and it was the reason amongst others that I then fitted a set of HIF 6 carbs.The original jet tube is a clear plastic tube with a spiral wound wire sleeve.The float chamber end has a brass ferrule inserted internally and the little brass union is meant to compress the rubber washer to act as a compression fitting.I found that the heat and vibration of my well tuned engine (and your V8)would cause this joint to leak-I think that possibly modern petrol and high under bonnet temps do not help.The jet end is again a factory formed compression joint forced together by the external brass ferrule. DO NOT use glue when continuous exposure to a solvent like petrol is involved.
I use HIF SUs on my own V8 conversion (See pics on the V8 site -add /v8_conversions to this site name).
Having built my own manifold and linkage you want to aware of the the following:
I dont know whether you have a bonnet bulge-you may need to have the dashpots shortened as per the factory V8-the SD1 brass fuel;overflow spigots are in the wrong places and need plugging and new spigots made from brass tubes and pressed into new drillings in the carb bodies.A new linkage will also have to be fabricated.
Whilst I am a SU man -I am hearing very good reports about the down draft weber carb and manifold setup(see also the RPI site).I have heard that this setup is a copy of the carter 9410-no doubt sombody from the US will correct me on this one. MY good friend BobP would be offended if I didnt put a good word for a double pumper Holley Carb plus nanifold,bendix pump et al.
When you work out the price of the mods to the SUs,new top manifold and bottom manifold you might find that these are economical alternatives....
The route i went with my conversion is use the standard manifold, cut off the standard carb mountings, buy the original v8 plenum, weld the manifold up so that the plenum can be fitted (it has to be machined flat after welding). The linkages and the connections between both carbs i made from the standard linkages. I also shortened the dashpots my self. There are at least 2 different kind of plastic dashpot caps which vary a lot in height. You should take the shortest which has only a height of approx 3-4 mm over the dashpots. I also polished the manifold, the plenum and the carbs and it really looks smashing.
The route i went is time consuming and you need to have some contacts to do the welding and machining of the manifold. If you have some contacts it sure is a very cheap route.
|Peter van de Velde|
Thanks for your detailed reply. The information about how the pipe is joined at both ends was exacly what I wanted. I'm getting a pair of long pipes made which should make the car drivable while I sort out the HIF 6s. (Though this is not so important at the moment as a wheel bearing has just failed - see MGB Technical.)
I'm hoping to put the HIF 6 carbs on the existing manifold, thus keeping the cost down. I agree that if I have to buy V8 replica manifold and adapter, then I should look at other setups.
The current carbs have the 'chimney' machined off the dashpot and have extremely thin black plastic tops (I'd say even thinner than the ones Peter van de Velde mentions). This allows them to fit without bonnet modification (though there are a pair of indents in the sound deadening!).
I don't understand about the overflows being in the wrong place. Why can't I just attach the overflow pipes?
PS. Great pictures!
This thread was discussed between 26/07/2000 and 30/07/2000
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