ARRGGHHH!! Carb Issues???

[Rangi246]

Hi everyone

I have a real issue with the car at the moment (65 Vit 1600). I recently got a set of very shiney, fully reconditioned Stromberg CD150 carbs for the car from Andrew Turner, put them on and balanced them up.  

As soon as I fired up the car the front carb hosed fuel out the air filter on idle so it was promptly switched off and the carb thoroughly cleaned. This solved the idle problem but I noticed that when it was revved up in neutral the engine now has a nasty vibration that shakes/vibrates the whole car.

I then took it for a drive and it seems to go ok at 30-40mph but as soon as it gets to about 50mph the engine splutters, shakes and loses power, almost like 3 cylinders are no longer working. The revs slowly decline and the car wont pull away.

After pulling over and checking to make sure the front carb wasn't stuck again and thinking the car was running lean, I richened up the mixture a little to see if that would help. After letting the car idle/rest for about 10 minutes (and still noticing that vibration from the engine when revved up, I took off again and it did exactly the same thing after about 2 miles. I managed to get the car home but only just.

So far i've checked and cleaned the points, made sure there was oil in the dashposts, checked the plugs and leads, checked the inline fuel filter and needless to say i'm scratching my head now. While the old carbs leaked oil from the dashpot overflow all the time and the front one had a loose(ish) throttle shaft, it ran a whole lot better than its currently doing.

Any suggestions?

Cheers
Mark

[esxefi]

sounds like the front carb needle valve was stuck open.

uneven running and vibration possibly from flooding and fouled plugs never to return.replace them.

[Encom]

Have you re-centred the jets? Sounds like one needle is off centre and hence isn't letting the piston rise and fall smoothly. Might also want to check needles are both inserted into the piston the correct amount (shoulder flush to the base of the piston) and the same amount. If you take them out check the needles are also the same type and that they are not bent.

[heraldcoupe]

The symptoms are very similar to when a diaphragm becomes porous, or develops a small leak. Shouldn't be the case with rebuilt carbs, but worth checking carefully in case,

Cheers,
Bill.

[mazfg]

Are you sure it's firing on all cylinders?  I had similar symptoms after head rebuild....when increasing the throttle in neutral, engine revs but could feel a vibration, in use, loss of power...especially up hill. Turned out no.3 was firing intermittently due to plug lead not properly connected at distributor. Having 6 cylinders means the engine can sounds ok at idle, which mine did, but no power when applying throttle.

[herald948]

I agree with all of the above as possible causes, and I will add (based on *cough* personal experience) that it is worth double-checking firing order. Swapping two leads on a Triumph six can do some strange things!

[Pete Lewis]

yes 153624 anti clockwise on the cap.

messing with fuel lines can cause a well documented gremlin,  as you insert the bundy into the rubber hose you sliver off a peice of rubber ,this floats back and forth in the supply lines and will block the back of the float needle valve,  so one carb gets a block and your down to only 3 cyl and a balamce pipe ..

    Pete

[Rangi246]

Thanks everyone. I'll check the firing sequence first and the plug leads again. If no luck there it'll be a strip down of the carbs to make sure all is well.

Mark