Piglet Posted July 21, 2022 Report Share Posted July 21, 2022 How can I tell what carbs are on my MK3 Spit? Seems there are two types... Alex Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 21, 2022 Report Share Posted July 21, 2022 should be SU HS2 but a photo would help are there no brass tag numbers on the float top cover screws?? Burlen gives you the SU specs but has youres been molested to something non standard List Vehicles - SU Carburetters Link to comment Share on other sites More sharing options...
Piglet Posted July 21, 2022 Author Report Share Posted July 21, 2022 Not the best pic but I can get more tomorrow...thanks Pete. Alex Link to comment Share on other sites More sharing options...
NonMember Posted July 22, 2022 Report Share Posted July 22, 2022 Those look like HS4s from a 1500, although you still have the Mk3 throttle linkage and they've had the waxstat removal conversion. Link to comment Share on other sites More sharing options...
DanMi Posted July 22, 2022 Report Share Posted July 22, 2022 they look like HS2 to me with the bolts to the manifold in a vertical alignment, HS4 are angled (but hard to see!). They are the later type though with the crankcase breathing to the carbs as in MK4 rather than having the crankcase breath to a valve on the manifold. They also may have a valve in the throttle butterfly and a sprung needle as in the MK4. I think that they are a set of MK4 carbs Link to comment Share on other sites More sharing options...
Josef Posted July 22, 2022 Report Share Posted July 22, 2022 As Alex has an apparently standard Mk3 airbox fitted, then they’re going to be HS2 rather than HS4. But as Dan says, from a MkIV rather than Mk3 cause of the breather arrangement. The only major difference is the needles, BO for Mk3 and AAN (I think?) for the MkIV. Mk3 spec on my Mk3 - note no tube between the carbs MkIV spec on my Herald (with switch of the fuel line to the rear of the engine) Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 22, 2022 Report Share Posted July 22, 2022 and HS2 is 1.25" venturi the HS4 is 1.5" so thats an easy check getting HS4 to run well on a 1296 is going to be an ongoing headache i have a local one and its a nightmare of faffing around big is not better Pete Link to comment Share on other sites More sharing options...
chrishawley Posted July 22, 2022 Report Share Posted July 22, 2022 I was going to contribute as below but not sure was very helpful so have greyed it out. But going back to the top, for clarification: What's the issue or problem seeking a solution? Perhaps parts are required? Or an originality/athenticity question? Any further guidance in this respect would be good. ---- Just trawling through the SU book. It appears that were two variations of the HS2 for Spit3; to wit AUD257 and AUD275. The only difference I can find between AUD257 and AUD275 is BO needle as opposed to DD needle. If Spit4 HS2s are in the equation then there were two variations AUD 441 and AUD 580 which appear to differ from each other only in the throttle disc. ----. Link to comment Share on other sites More sharing options...
Piglet Posted July 22, 2022 Author Report Share Posted July 22, 2022 Chris I need to know so I can get the correct size filters. I measured and it's 1.25". Almost measured in mm lol. The number seems to read LB2 57F. Managed to clean up the connecting pipe okay but it's clearly not for these carbs as the left hand side has been bent to fit! I also changed the small rubber hoses as they looked like they'd been there since, oooh, 1967. And new Jubilee clips too. Alex Link to comment Share on other sites More sharing options...
Clive Posted July 22, 2022 Report Share Posted July 22, 2022 AUD257F I reckon. But just buy for HS2 carbs if fitting aftermarket filters Link to comment Share on other sites More sharing options...
Piglet Posted July 22, 2022 Author Report Share Posted July 22, 2022 Thanks Clive, I will make a note! Alex Link to comment Share on other sites More sharing options...
Josef Posted July 22, 2022 Report Share Posted July 22, 2022 The standard ones are GFE1037 if that helps. Link to comment Share on other sites More sharing options...
Piglet Posted July 22, 2022 Author Report Share Posted July 22, 2022 Thank you! Alex Link to comment Share on other sites More sharing options...
Nigel Clark Posted July 22, 2022 Report Share Posted July 22, 2022 Those are certainly SU HS2s but appear to have the breather hoses as per Mk4 Spitfire. Nigel Link to comment Share on other sites More sharing options...
Clive Posted July 23, 2022 Report Share Posted July 23, 2022 9 hours ago, Piglet said: Thanks Clive, I will make a note! Alex But don't rely on the tag, easy to swap between carbs. The ones you have, as others have said, are from a later car, I presume you don't have the flying saucer PCV valve in teh manifold either? The main difference will be needles. Fixed on a mk3, but spring biased on the later carbs. BUT it is possible somebody has made a pair of bitsa carbs, using the late bodies but earlier pistons. You need to take the tops off the carbs, see if the needles are slightly sprung. None of that affects the filters you need. Link to comment Share on other sites More sharing options...
Wagger Posted July 23, 2022 Report Share Posted July 23, 2022 Nothig to do with the carbs. Why is your road spring distorted? Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 23, 2022 Report Share Posted July 23, 2022 Wagger good spot . thats a bit Zebedee Pete Link to comment Share on other sites More sharing options...
Piglet Posted July 23, 2022 Author Report Share Posted July 23, 2022 I did mention that before a while back on the build thread and someone said it's normal. But clearly that's not the case... Alex Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 24, 2022 Report Share Posted July 24, 2022 any coil spring can have a bit of a torsional set but being banana is not so good , if only that the spring rate wont be very linear this may be down to the spring ends not seating well on the shocker or top plate Pete Link to comment Share on other sites More sharing options...
Colin Lindsay Posted July 24, 2022 Report Share Posted July 24, 2022 https://sucarb.co.uk/carbspec/carburettor/essentials/id/2405/ AUD257F (F for front, the other should be R for rear) are standard fitting for the MK3 from 1967 - 1968, according to the SU Carb site linked above. Great site for spare parts. Link to comment Share on other sites More sharing options...
Clive Posted July 24, 2022 Report Share Posted July 24, 2022 1 hour ago, Colin Lindsay said: https://sucarb.co.uk/carbspec/carburettor/essentials/id/2405/ AUD257F (F for front, the other should be R for rear) are standard fitting for the MK3 from 1967 - 1968, according to the SU Carb site linked above. Great site for spare parts. But the issue her is that teh carb bodies, maybe the whole carb, are from a later spitfire. So the tab number cannot be trusted. Link to comment Share on other sites More sharing options...
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