Richard Heath

Hi all An update and further request for advice. Having opened out the manifold, acquired all the relevant parts, fashioned linkages etc I finally put it all together and turned the key. The engine burst into life, and once up to temperature I set about tuning up. However, shortly after that I noticed petrol pouring out of the front carb. I took off the float bowl lid, checked the valve was operating properly, reassembled and started up again..only for the same thing to happen, though this time on the rear carb. Whilst mopping up the spilled fuel, I realised there had also been leakage from the union at the fuel pump. I am obviously keen not to repeat this experience. I am guessing this is an issue of excess fuel pressure - I gather SUs are more sensitive in that respect. Is fitting a spacer between pump and block the way to go? Many thanks

Hi all Thanks to both the advice and the parts found here I have acquired a GT6 manifold, opened out the inlets and mounted the carbs with adapters and spacers. My issue now: how to connect it all! Any advice on the best solution for brackets and linkages? The throttle controls I had previously look like those fitted to the Mk3, but I can't see a way of making the bracket etc work for the SUs. For throttle and choke linkages, is solid steel bar (7.5mm?) the best bet? Thanks.

What's the thickness of the adapters Ian? I haven't sorted filters yet. Would a standard airbox (modified for the SUs) still fit?

Would something like this do the job? https://www.ebay.co.uk/itm/Carbide-burr-12-X-25mm-Pointed-Cone/143028610775?hash=item214d2b66d7:g:MXYAAOSws9dc7UFI Slightly nervous of messing this up, so any advice appreciated!

Clive, Nigel Thanks both for the very comprehensive and helpful replies. Just need to find a GT6 manifold! Here's a picture of the current setup as requested Clive. Given the comments you both make, I am wondering how much of the current running problems are down to the K+N filters sucking in hot air. That might explain why I seem to be able to get it revving OK with the bonnet up, but things going downhill when it's on the road.

Hi I have a Mk2 GT6 with a 2.5 engine and fast road cam. The car has been running on Stromberg 150 carbs, which are clearly not right for the engine, and a V3186 manifold (not sure what that's from). I have acquired a pair of Dolomite Sprint SU HS6 carbs that I intend to fit, but wanted to check a couple of points before making any expensive mistakes! The Strombergs pretty much touch the bonnet, so the SUs wouldn't fit the current manifold without fouling. What is my best option? My understanding is that the standard GT6 manifold would work clearance-wise if adapted to the larger carbs, but I gather they aren't well balanced, and there also don't seem to be many around. Are there other options? Any advice on needles and air filter also gratefully received! Thanks.

Hi Richard Sorry, realise I didn’t say previously - the carbs are CD3’s.

Some answers! I checked cylinder compression and all registered between 150 and 160 (cold), which I believe suggests pretty healthy. I then disassembled the carbs and found the problem: the fuel inlet valve on the rear carb was seized shut, so there was zero fuel going in; I must at some point have tried adjusting them to get the car running - as I said, it has been off the road 10years - and ended up with the front carb feeding the rear cylinders, and completely drowning the front ones. So, a massive improvement and the car should now be at least driveable (once I have attended to brakes etc!). Thanks for all the input. The advice seems to be that getting the car running well on 150s might be challenging, so I’ll consider my options in the longer term. To return to the original topic of my post, the needles are B5DG. Any views on whether those are likely to be the most appropriate?

Hi Thanks everyone for your input. I think the conclusion is that the misfire is unlikely to be down to the carb specs so I need to get to the root of that first (but carb info very useful for later reference). It's likely to be a few weeks before I get the chance, but I'll post an update when I get anywhere.

Hi Thanks for all the replies. Firstly, in answer to the questions... The manifold is a Stanpart V3186. Is that the original? K&N air filters I don't remember choosing the carbs - they were fitted by the Triumph specialist when removing the PI. I suppose it's possible they had forgotten about the other mods. Anyway, I have now had a bit more time to investigate and am wondering whether the needle question might have been a bit of a red herring (or at least not the fundamental issue). Pulling the plugs, I noticed that most were black and sooty, but number 1 was wet. Using a Colourtune, I can see that cylinder 1 is firing very intermittently, and there also seems to be a (not quite so bad) misfire on 3. I had thought the black deposits were just because the engine has only been running for short periods, but now I'm wondering if a chronically rich mixture might also cause the misfire? My thought at the moment is to adjust the carbs to weaken the mixture and see what the effect is; if that doesn't sort, check compression for more sinister problems. Does that sound sensible, and/or any other obvious things to test? Thanks

Hi. I have a Mk II GT6 that has been off the road for about 10 years, and am looking to get it back there for its 50th birthday (September). My issue at the moment is that the engine is running very rough (misfires and very little power). I'm gradually working my way through potential causes (timing, valve clearances, etc) but my suspicion is that the problem is with the carbs, and one thing I want to check is the needles. The issue is complicated by the fact that the previous owner had some modifications done, the relevant ones here being that the engine is stroked out to 2.5 litres and has a Moss fast road cam. There was also fuel injection fitted, but I had that changed back to carbs (Stromberg 150 CD). My questions are (1) does anyone know what the correct needles would be for this setup, and (2) if the current needles were incorrect, would that alone be sufficient to cause the problems I am experiencing? Thanks