The V8 Owners Forum -

sick of the usual efi electronic problems and the engine running like a bag of spanners all the time so time for change back to simple and effective!
i have a disco 3.9 efi, lucas dizzy, with brc "just" lpg, and aquired a straight from the box weber 500, but jetted/setup for 4.6.

i'm planning to fit a plenum type top and running an inlet hose with k and n on the end instead of the pancake filter, this will let me fit the existing lpg mixer in the line.
i'll also fit an inline facet type pump hopefully running through the existing, disconnected in tank pump, even if i have to gut it.
what rods/jets are best for the 3.9 setup, i am also planning to decat the exhausts but keep the lambdas in for the brc lpg.
does this sound feasable?
any weird s***t i'm likely to come across?

I doubt that you will get your car through the MOT emissions test with the carb fitted.

Anyway the 3.5 settings that I have used on a few engines seem to work well enough on the 3.9 The out of the box setting will be too rich but you've stated that it's already been fiddled with anyway.

I'd start with an 86 primary jet (standard)
67-55 rod
silver rod springs
secondary jets in the mid 80's.
The pilots will be somewhere around 1.5 to 2.5 turns

Having said that it is always difficult to predict how each engine will respond to the carb due to the cam, inlet manifold and the exhaust system.

With regards to the primary circuit, other jet and rod combo's can give the same actual AFR as the setting above. For example 83 primary, 63-47 rod.

The 500 carb does not work too well with the Lucas vac advance system.

I'd run the timing around 12-14 static 34 all in at 2750-3000 RPM with no vac system fitted at all. Sorting out the timing can make a BIG difference to the BHP figure!

sidecar wrote:I doubt that you will get your car through the MOT emissions test with the carb fitted.
!

Why so?
A carburettor should be able to get down to reasonable emissions at idle which is where the test is done.

Ian

Ian Anderson wrote:

sidecar wrote:I doubt that you will get your car through the MOT emissions test with the carb fitted.
!

Why so?
A carburettor should be able to get down to reasonable emissions at idle which is where the test is done.

Ian

A carb'd engine will get down to a reasonable CO level but I would have though that this engine will be expected to get to a much lower CO level. , EFI manages to achieve this level but a carb never will. That's one of the reasons that no manufacturers use a carb anymore.

not too worried about the emissions, it'll go in on lpg.

the mot was brought in many years ago to make sure all cars were at a safe minimum standard to be on the road, so tell me what the hell have emissions got to do with safety and in what way does your car become dangerous on the road cause its emissions are slightly high? eco madness!

thanks for the advice, the weber will also be mated to a eddy performer manifold, heard good things of this set up so fingers crossed.

chuggernought wrote:not too worried about the emissions, it'll go in on lpg.

the mot was brought in many years ago to make sure all cars were at a safe minimum standard to be on the road, so tell me what the hell have emissions got to do with safety and in what way does your car become dangerous on the road cause its emissions are slightly high? eco madness!

Safety for other people? You can be killed in other ways than being hit by an unsafe car.

There's no real reason not to have your vehicle produce reasonable emissions at idle and part load speeds. Full throttle operation is different.

DaveEFI wrote:

chuggernought wrote:not too worried about the emissions, it'll go in on lpg.

the mot was brought in many years ago to make sure all cars were at a safe minimum standard to be on the road, so tell me what the hell have emissions got to do with safety and in what way does your car become dangerous on the road cause its emissions are slightly high? eco madness!

Safety for other people? You can be killed in other ways than being hit by an unsafe car.

There's no real reason not to have your vehicle produce reasonable emissions at idle and part load speeds. Full throttle operation is different.

Also if you get the mixture wrong at idle and at cruise you will knacker the rings and the bores in no time. The Eddy 500 is very good at doing this! Not because its a crap carb, its just way too rich on cruise for most RV8 lumps. Real steel don't like these carbs for this reason. (I like them because they can be sorted out quite easily!)