carburettors

[MarkieB]

I think the engine's the original 1972 engine, the carbs have got a kind of oval air box between them; I recently tried making the engine work on petrol, I was told that maybe the Lpg has damaged a part in the carb, making it not work on petrol properly [it basically starved at higher revs/ after a few hundred yards].

What are the original carbs called? I think I gather that SU carbs don't get damaged that way from Lpg, is there a good place to pick them up at a decent price, preferably ready to fit as my knowledge of carbs is very limited as yet?

My other question, is is it possible to put a better fuel pump on an early engine, the clicking noise is worrying enough in itself, although it doesn't seem to slow down either, as it should when supposedly it fills the carbs.

TIA,

[FridgeFreezer]

Markie,

- Carbs are horrible clockwork things and I hate them so this is going to be a bit general

- LPG doesn't lubricate the internals of the carb so parts seize up (needles?)

- The original carbs would be SU or perhaps Zenith?

- Good places to buy anything Land Rover are:

Your local Land Rover club

Sodbury Sortout

eBay

- Fuel pump you can stick an aftermarket Facet one on, most tuning places sell them including RPi, rally design, fuelsystem.co.uk, demon tweeks. The cylindrical ones will tick (they are identical to the standard item but some have more flow)

However, a loudly ticking fuel pump and b*ggered carbs suggests to me that something's stuck, as I thought there was a fuel return line to the tank. If so, and the fuel return is stuck open, you'll never get any fuel pressure, the vehicle won't run, and the pump will go flat out to try and get some pressure up. It could well be a case of giving everything a good clean/service/lubricate as per the Haynes Manual and it'll work again. I've hear it said that those carbs are fairly simple things as they go.

[jwriyadh]

Take off the feed to the first carb and block it. Turn on the ignition and listen to the pump. The fuel often drains back a bit to the tank so the pump starts with a loud ticking and when there is backpressure due to the pipes and carb float chambers being full the ticking reduces in volume.

If the ticking reduces as above it means everything is OK to the needle valves.

If the ticking does not reduce but carries on loudly then it usually means the pump is pulling air instead of fuel. Check all the pipes from the fuel tank and their junctions.

Check the piston dampers have oil in them, they are the plastic screwcaps on the top. Use engine oil. If they are not damped by oil the engine gets no acceleration enrichment and will stutter or die under an opening throttle.

When using LPG with any biased (springloaded) needle carburettor the needles will be dragged, unlubricated, up and down the jet wearing both. This will give over-rich mixture. The needles can be lifted and prevent wear by using the piston lift kit or using plastic locking screws to hold the piston up.

Either SU or Stromberg carbs and their fuel pump are reliable bits of kit and can be fixed easily and cheaply in the field. There is supposed to be a very small advantage in performance with SU, hardly worth the trouble of changing to them.

jw

[MarkieB]

Thanks guys, those are more than a few good pointers; the oil in the dampers was one of the few bits I understood trying to read the relevant part of the workshop manual, so let's hope it's as simple as that

then it's a simple case of wreaking vengeance on whoever sets/implements/benefits from the unreasonably ridiculous artificially high minimum motorway tow fee grrr!

I think Zenith carbs sounds right for what's there for now.

So it sounds as though the SU or Stromberg carbs aren't necessarily much better on the needle valve front, although they are better kit generally. Doesn't the idea of fixing the needle valve open interfere with the proper working of the carb though?

The sound of a different fuel pump to suit the different carbs attracts me, frankly I'd be prepared to put a Saab fuel pump in just so that it would make the reassuring humming noise that I recognise

I suppose I'll have to check all the other suggestions too, pipe junctions, return valves, etcetera, aren't cars a load of work

[jwriyadh]

I think Zenith carbs sounds right for what's there for now.

So it sounds as though the SU or Stromberg carbs aren't necessarily much better on the needle valve front, although they are better kit generally. Doesn't the idea of fixing the needle valve open interfere with the proper working of the carb though?

Markie, just need to clarify, what I call a Stromberg others may call a Zenith.

Fastening the pistons up apparently works fine for LPG. Slacken the screws to use petrol.

jw

[MarkieB]

I've seen a reference, I think it was on RPI's site, to the need to restrict the flow on the return pipes as a matter of course

As I'm thinking of distancing myself from the possibility of instant changeover, the piston lift kits/ the plastic locking screws sound quite a good idea, who should I look to as a stockist?

Cheers