The Triumph Dolomite Club - Discussion Forum

Am I right in thinking that the circled pipe is the fuel overflow pipe and that it (and its counterpart on the other carb) should have a pipe leading down away from the hot elements of the engine?

Thanks

Yes yes.

Jeroen

Only ever seen the overflow pipe fitted to the front carb

Lucky that the engine is a crossflow design and the exhaust is on the other side.
The theory is that it will never overflow , but of course they do sometimes.
The "other" dolomite types that run lumps of iron do not enjoy a crossflow engine and the carb sits on top of the "Exhaust maniflowed, oh the joy of the flamey flame, and the burny burn, much joy, car in cinders". That is if the owner/mechanic of the said car has removed the metal shield, which many have.
That was my tribute to the late Stanley Unwin.

Thanks guys

There was an item on the old top gear or fifth gear, I think it was one of those, showing that petrol doesn't catch fire when dropped onto a hot exhaust manifold (unless there's a loose spark), but older hydraulic fluids would flash every time. I assume it's because the latent heat of petrol vaporization is so high, it keeps the vapor below its flash temp, but that is only a hypothesis. Don't think I'd want to try it with a car I liked though.

Graham

I had one of those float chamber needle valves that was a ball bearing on my 1300, the thing would leak out of the over flow and drip on to my hot exhaust manifold, it didn't catch fire, just evaporated.

I now have a proper SU needle valve and all is good which is also peace of mind.

Yes, these rubber cone tipped ones seem to be okay again. The brass tipped ones were fine till they were worn when they leaked. But I've had a few problems with the ones with a rubber insert into a brass tip. Last set started sticking to the valve seats and starving the engine of fuel.

Graham

Yes petrol is an interesting fluid and I expect leaking petrol might not catch fire but just like Graham I would not want to test the theory too much.
When I was a teenager I put a small pot of petrol on a fire and it did not burst into flames but the top did catch fire ..........however when spilt and turned to a gas it virtually exploded. All good fun when your young and stupid, however now I am old and stupid

trackerjack wrote:I put a small pot of petrol on a fire

I put a loose Jetex rocket engine on the fire when I was 9 and managed, finally, to get the fuse to light the propellant - first time I ever did. That was fun - almost. They go quite quick when they're not pushing anything along. Ended up as a little red hot lump burning a hole in the lino under the kitchen sofa.

But I do make sure I keep one of those overflow pipes on the front carb, to keep any petrol out of the alternator. Again, I'm not sure it would necessarily catch fire, but then again (again) I'm not necessarily sure it won't.

Graham

GrahamFountain wrote:

trackerjack wrote:I put a small pot of petrol on a fire

I put a loose Jetex rocket engine on the fire when I was 9 and managed, finally, to get the fuse to light the propellant - first time I ever did. That was fun - almost. They go quite quick when they're not pushing anything along. Ended up as a little red hot lump burning a hole in the lino under the kitchen sofa.

But I do make sure I keep one of those overflow pipes on the front carb, to keep any petrol out of the alternator. Again, I'm not sure it would necessarily catch fire, but then again (again) I'm not necessarily sure it won't.

Graham

When we were kids we used to put a small hole in the bottom of a used empty can of beans and also a small hole in the side. This was put over the gas hob and filled with gas and placed in a bowl of water that did not cover the hole in the side, then we lit the top hole which burnt like a candle with the flame getting smaller and smaller, until BOOM the gas inside ignited, sending the can skyward.
My mother never did find out how those dents and marks in the ceiling got there

I used to do this in the garden - a bigger tin and more custard, it's pretty impressive.
https://www.youtube.com/watch?v=aGBT5pwxThU

Over the years my 1500cc dolomite's have suffered a number times where the rear carb's have overflowed and petrol has been dripping onto the hot exhaust. It is most off putting but thankfully it has never ignited and from about 1980 the later cars that I own have plastic overflow pipes.